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Diffstat (limited to '')
| -rw-r--r-- | libevent/evdns.c | 4847 |
1 files changed, 4847 insertions, 0 deletions
diff --git a/libevent/evdns.c b/libevent/evdns.c new file mode 100644 index 0000000..a5b31a3 --- /dev/null +++ b/libevent/evdns.c @@ -0,0 +1,4847 @@ +/* Copyright 2006-2007 Niels Provos + * Copyright 2007-2012 Nick Mathewson and Niels Provos + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * 3. The name of the author may not be used to endorse or promote products + * derived from this software without specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR + * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES + * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. + * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, + * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT + * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, + * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY + * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT + * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF + * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + */ + +/* Based on software by Adam Langly. Adam's original message: + * + * Async DNS Library + * Adam Langley <agl@imperialviolet.org> + * http://www.imperialviolet.org/eventdns.html + * Public Domain code + * + * This software is Public Domain. To view a copy of the public domain dedication, + * visit http://creativecommons.org/licenses/publicdomain/ or send a letter to + * Creative Commons, 559 Nathan Abbott Way, Stanford, California 94305, USA. + * + * I ask and expect, but do not require, that all derivative works contain an + * attribution similar to: + * Parts developed by Adam Langley <agl@imperialviolet.org> + * + * You may wish to replace the word "Parts" with something else depending on + * the amount of original code. + * + * (Derivative works does not include programs which link against, run or include + * the source verbatim in their source distributions) + * + * Version: 0.1b + */ + +#include "event2/event-config.h" +#include "evconfig-private.h" + +#include <sys/types.h> + +#ifndef _FORTIFY_SOURCE +#define _FORTIFY_SOURCE 3 +#endif + +#include <string.h> +#include <fcntl.h> +#ifdef EVENT__HAVE_SYS_TIME_H +#include <sys/time.h> +#endif +#ifdef EVENT__HAVE_STDINT_H +#include <stdint.h> +#endif +#include <stdlib.h> +#include <string.h> +#include <errno.h> +#ifdef EVENT__HAVE_UNISTD_H +#include <unistd.h> +#endif +#include <limits.h> +#include <sys/stat.h> +#include <stdio.h> +#include <stdarg.h> +#ifdef _WIN32 +#include <winsock2.h> +#include <winerror.h> +#include <ws2tcpip.h> +#ifndef _WIN32_IE +#define _WIN32_IE 0x400 +#endif +#include <shlobj.h> +#endif + +#include "event2/dns.h" +#include "event2/dns_struct.h" +#include "event2/dns_compat.h" +#include "event2/util.h" +#include "event2/event.h" +#include "event2/event_struct.h" +#include "event2/thread.h" + +#include "defer-internal.h" +#include "log-internal.h" +#include "mm-internal.h" +#include "strlcpy-internal.h" +#include "ipv6-internal.h" +#include "util-internal.h" +#include "evthread-internal.h" +#ifdef _WIN32 +#include <ctype.h> +#include <winsock2.h> +#include <windows.h> +#include <iphlpapi.h> +#include <io.h> +#else +#include <sys/socket.h> +#include <netinet/in.h> +#include <arpa/inet.h> +#endif + +#ifdef EVENT__HAVE_NETINET_IN6_H +#include <netinet/in6.h> +#endif + +#define EVDNS_LOG_DEBUG EVENT_LOG_DEBUG +#define EVDNS_LOG_WARN EVENT_LOG_WARN +#define EVDNS_LOG_MSG EVENT_LOG_MSG + +#ifndef HOST_NAME_MAX +#define HOST_NAME_MAX 255 +#endif + +#include <stdio.h> + +#undef MIN +#define MIN(a,b) ((a)<(b)?(a):(b)) + +#define ASSERT_VALID_REQUEST(req) \ + EVUTIL_ASSERT((req)->handle && (req)->handle->current_req == (req)) + +#define u64 ev_uint64_t +#define u32 ev_uint32_t +#define u16 ev_uint16_t +#define u8 ev_uint8_t + +/* maximum number of addresses from a single packet */ +/* that we bother recording */ +#define MAX_V4_ADDRS 32 +#define MAX_V6_ADDRS 32 + + +#define TYPE_A EVDNS_TYPE_A +#define TYPE_CNAME 5 +#define TYPE_PTR EVDNS_TYPE_PTR +#define TYPE_SOA EVDNS_TYPE_SOA +#define TYPE_AAAA EVDNS_TYPE_AAAA + +#define CLASS_INET EVDNS_CLASS_INET + +/* Persistent handle. We keep this separate from 'struct request' since we + * need some object to last for as long as an evdns_request is outstanding so + * that it can be canceled, whereas a search request can lead to multiple + * 'struct request' instances being created over its lifetime. */ +struct evdns_request { + struct request *current_req; + struct evdns_base *base; + + int pending_cb; /* Waiting for its callback to be invoked; not + * owned by event base any more. */ + + /* elements used by the searching code */ + int search_index; + struct search_state *search_state; + char *search_origname; /* needs to be free()ed */ + int search_flags; +}; + +struct request { + u8 *request; /* the dns packet data */ + u8 request_type; /* TYPE_PTR or TYPE_A or TYPE_AAAA */ + unsigned int request_len; + int reissue_count; + int tx_count; /* the number of times that this packet has been sent */ + void *user_pointer; /* the pointer given to us for this request */ + evdns_callback_type user_callback; + struct nameserver *ns; /* the server which we last sent it */ + + /* these objects are kept in a circular list */ + /* XXX We could turn this into a CIRCLEQ. */ + struct request *next, *prev; + + struct event timeout_event; + + u16 trans_id; /* the transaction id */ + unsigned request_appended :1; /* true if the request pointer is data which follows this struct */ + unsigned transmit_me :1; /* needs to be transmitted */ + + /* XXXX This is a horrible hack. */ + char **put_cname_in_ptr; /* store the cname here if we get one. */ + + struct evdns_base *base; + + struct evdns_request *handle; +}; + +struct reply { + unsigned int type; + unsigned int have_answer : 1; + union { + struct { + u32 addrcount; + u32 addresses[MAX_V4_ADDRS]; + } a; + struct { + u32 addrcount; + struct in6_addr addresses[MAX_V6_ADDRS]; + } aaaa; + struct { + char name[HOST_NAME_MAX]; + } ptr; + } data; +}; + +struct nameserver { + evutil_socket_t socket; /* a connected UDP socket */ + struct sockaddr_storage address; + ev_socklen_t addrlen; + int failed_times; /* number of times which we have given this server a chance */ + int timedout; /* number of times in a row a request has timed out */ + struct event event; + /* these objects are kept in a circular list */ + struct nameserver *next, *prev; + struct event timeout_event; /* used to keep the timeout for */ + /* when we next probe this server. */ + /* Valid if state == 0 */ + /* Outstanding probe request for this nameserver, if any */ + struct evdns_request *probe_request; + char state; /* zero if we think that this server is down */ + char choked; /* true if we have an EAGAIN from this server's socket */ + char write_waiting; /* true if we are waiting for EV_WRITE events */ + struct evdns_base *base; + + /* Number of currently inflight requests: used + * to track when we should add/del the event. */ + int requests_inflight; +}; + + +/* Represents a local port where we're listening for DNS requests. Right now, */ +/* only UDP is supported. */ +struct evdns_server_port { + evutil_socket_t socket; /* socket we use to read queries and write replies. */ + int refcnt; /* reference count. */ + char choked; /* Are we currently blocked from writing? */ + char closing; /* Are we trying to close this port, pending writes? */ + evdns_request_callback_fn_type user_callback; /* Fn to handle requests */ + void *user_data; /* Opaque pointer passed to user_callback */ + struct event event; /* Read/write event */ + /* circular list of replies that we want to write. */ + struct server_request *pending_replies; + struct event_base *event_base; + +#ifndef EVENT__DISABLE_THREAD_SUPPORT + void *lock; +#endif +}; + +/* Represents part of a reply being built. (That is, a single RR.) */ +struct server_reply_item { + struct server_reply_item *next; /* next item in sequence. */ + char *name; /* name part of the RR */ + u16 type; /* The RR type */ + u16 class; /* The RR class (usually CLASS_INET) */ + u32 ttl; /* The RR TTL */ + char is_name; /* True iff data is a label */ + u16 datalen; /* Length of data; -1 if data is a label */ + void *data; /* The contents of the RR */ +}; + +/* Represents a request that we've received as a DNS server, and holds */ +/* the components of the reply as we're constructing it. */ +struct server_request { + /* Pointers to the next and previous entries on the list of replies */ + /* that we're waiting to write. Only set if we have tried to respond */ + /* and gotten EAGAIN. */ + struct server_request *next_pending; + struct server_request *prev_pending; + + u16 trans_id; /* Transaction id. */ + struct evdns_server_port *port; /* Which port received this request on? */ + struct sockaddr_storage addr; /* Where to send the response */ + ev_socklen_t addrlen; /* length of addr */ + + int n_answer; /* how many answer RRs have been set? */ + int n_authority; /* how many authority RRs have been set? */ + int n_additional; /* how many additional RRs have been set? */ + + struct server_reply_item *answer; /* linked list of answer RRs */ + struct server_reply_item *authority; /* linked list of authority RRs */ + struct server_reply_item *additional; /* linked list of additional RRs */ + + /* Constructed response. Only set once we're ready to send a reply. */ + /* Once this is set, the RR fields are cleared, and no more should be set. */ + char *response; + size_t response_len; + + /* Caller-visible fields: flags, questions. */ + struct evdns_server_request base; +}; + +struct evdns_base { + /* An array of n_req_heads circular lists for inflight requests. + * Each inflight request req is in req_heads[req->trans_id % n_req_heads]. + */ + struct request **req_heads; + /* A circular list of requests that we're waiting to send, but haven't + * sent yet because there are too many requests inflight */ + struct request *req_waiting_head; + /* A circular list of nameservers. */ + struct nameserver *server_head; + int n_req_heads; + + struct event_base *event_base; + + /* The number of good nameservers that we have */ + int global_good_nameservers; + + /* inflight requests are contained in the req_head list */ + /* and are actually going out across the network */ + int global_requests_inflight; + /* requests which aren't inflight are in the waiting list */ + /* and are counted here */ + int global_requests_waiting; + + int global_max_requests_inflight; + + struct timeval global_timeout; /* 5 seconds by default */ + int global_max_reissues; /* a reissue occurs when we get some errors from the server */ + int global_max_retransmits; /* number of times we'll retransmit a request which timed out */ + /* number of timeouts in a row before we consider this server to be down */ + int global_max_nameserver_timeout; + /* true iff we will use the 0x20 hack to prevent poisoning attacks. */ + int global_randomize_case; + + /* The first time that a nameserver fails, how long do we wait before + * probing to see if it has returned? */ + struct timeval global_nameserver_probe_initial_timeout; + + /** Port to bind to for outgoing DNS packets. */ + struct sockaddr_storage global_outgoing_address; + /** ev_socklen_t for global_outgoing_address. 0 if it isn't set. */ + ev_socklen_t global_outgoing_addrlen; + + struct timeval global_getaddrinfo_allow_skew; + + int so_rcvbuf; + int so_sndbuf; + + int getaddrinfo_ipv4_timeouts; + int getaddrinfo_ipv6_timeouts; + int getaddrinfo_ipv4_answered; + int getaddrinfo_ipv6_answered; + + struct search_state *global_search_state; + + TAILQ_HEAD(hosts_list, hosts_entry) hostsdb; + +#ifndef EVENT__DISABLE_THREAD_SUPPORT + void *lock; +#endif + + int disable_when_inactive; +}; + +struct hosts_entry { + TAILQ_ENTRY(hosts_entry) next; + union { + struct sockaddr sa; + struct sockaddr_in sin; + struct sockaddr_in6 sin6; + } addr; + int addrlen; + char hostname[1]; +}; + +static struct evdns_base *current_base = NULL; + +struct evdns_base * +evdns_get_global_base(void) +{ + return current_base; +} + +/* Given a pointer to an evdns_server_request, get the corresponding */ +/* server_request. */ +#define TO_SERVER_REQUEST(base_ptr) \ + ((struct server_request*) \ + (((char*)(base_ptr) - evutil_offsetof(struct server_request, base)))) + +#define REQ_HEAD(base, id) ((base)->req_heads[id % (base)->n_req_heads]) + +static struct nameserver *nameserver_pick(struct evdns_base *base); +static void evdns_request_insert(struct request *req, struct request **head); +static void evdns_request_remove(struct request *req, struct request **head); +static void nameserver_ready_callback(evutil_socket_t fd, short events, void *arg); +static int evdns_transmit(struct evdns_base *base); +static int evdns_request_transmit(struct request *req); +static void nameserver_send_probe(struct nameserver *const ns); +static void search_request_finished(struct evdns_request *const); +static int search_try_next(struct evdns_request *const req); +static struct request *search_request_new(struct evdns_base *base, struct evdns_request *handle, int type, const char *const name, int flags, evdns_callback_type user_callback, void *user_arg); +static void evdns_requests_pump_waiting_queue(struct evdns_base *base); +static u16 transaction_id_pick(struct evdns_base *base); +static struct request *request_new(struct evdns_base *base, struct evdns_request *handle, int type, const char *name, int flags, evdns_callback_type callback, void *ptr); +static void request_submit(struct request *const req); + +static int server_request_free(struct server_request *req); +static void server_request_free_answers(struct server_request *req); +static void server_port_free(struct evdns_server_port *port); +static void server_port_ready_callback(evutil_socket_t fd, short events, void *arg); +static int evdns_base_resolv_conf_parse_impl(struct evdns_base *base, int flags, const char *const filename); +static int evdns_base_set_option_impl(struct evdns_base *base, + const char *option, const char *val, int flags); +static void evdns_base_free_and_unlock(struct evdns_base *base, int fail_requests); +static void evdns_request_timeout_callback(evutil_socket_t fd, short events, void *arg); + +static int strtoint(const char *const str); + +#ifdef EVENT__DISABLE_THREAD_SUPPORT +#define EVDNS_LOCK(base) EVUTIL_NIL_STMT_ +#define EVDNS_UNLOCK(base) EVUTIL_NIL_STMT_ +#define ASSERT_LOCKED(base) EVUTIL_NIL_STMT_ +#else +#define EVDNS_LOCK(base) \ + EVLOCK_LOCK((base)->lock, 0) +#define EVDNS_UNLOCK(base) \ + EVLOCK_UNLOCK((base)->lock, 0) +#define ASSERT_LOCKED(base) \ + EVLOCK_ASSERT_LOCKED((base)->lock) +#endif + +static evdns_debug_log_fn_type evdns_log_fn = NULL; + +void +evdns_set_log_fn(evdns_debug_log_fn_type fn) +{ + evdns_log_fn = fn; +} + +#ifdef __GNUC__ +#define EVDNS_LOG_CHECK __attribute__ ((format(printf, 2, 3))) +#else +#define EVDNS_LOG_CHECK +#endif + +static void evdns_log_(int severity, const char *fmt, ...) EVDNS_LOG_CHECK; +static void +evdns_log_(int severity, const char *fmt, ...) +{ + va_list args; + va_start(args,fmt); + if (evdns_log_fn) { + char buf[512]; + int is_warn = (severity == EVDNS_LOG_WARN); + evutil_vsnprintf(buf, sizeof(buf), fmt, args); + evdns_log_fn(is_warn, buf); + } else { + event_logv_(severity, NULL, fmt, args); + } + va_end(args); +} + +#define log evdns_log_ + +/* This walks the list of inflight requests to find the */ +/* one with a matching transaction id. Returns NULL on */ +/* failure */ +static struct request * +request_find_from_trans_id(struct evdns_base *base, u16 trans_id) { + struct request *req = REQ_HEAD(base, trans_id); + struct request *const started_at = req; + + ASSERT_LOCKED(base); + + if (req) { + do { + if (req->trans_id == trans_id) return req; + req = req->next; + } while (req != started_at); + } + + return NULL; +} + +/* a libevent callback function which is called when a nameserver */ +/* has gone down and we want to test if it has came back to life yet */ +static void +nameserver_prod_callback(evutil_socket_t fd, short events, void *arg) { + struct nameserver *const ns = (struct nameserver *) arg; + (void)fd; + (void)events; + + EVDNS_LOCK(ns->base); + nameserver_send_probe(ns); + EVDNS_UNLOCK(ns->base); +} + +/* a libevent callback which is called when a nameserver probe (to see if */ +/* it has come back to life) times out. We increment the count of failed_times */ +/* and wait longer to send the next probe packet. */ +static void +nameserver_probe_failed(struct nameserver *const ns) { + struct timeval timeout; + int i; + + ASSERT_LOCKED(ns->base); + (void) evtimer_del(&ns->timeout_event); + if (ns->state == 1) { + /* This can happen if the nameserver acts in a way which makes us mark */ + /* it as bad and then starts sending good replies. */ + return; + } + +#define MAX_PROBE_TIMEOUT 3600 +#define TIMEOUT_BACKOFF_FACTOR 3 + + memcpy(&timeout, &ns->base->global_nameserver_probe_initial_timeout, + sizeof(struct timeval)); + for (i=ns->failed_times; i > 0 && timeout.tv_sec < MAX_PROBE_TIMEOUT; --i) { + timeout.tv_sec *= TIMEOUT_BACKOFF_FACTOR; + timeout.tv_usec *= TIMEOUT_BACKOFF_FACTOR; + if (timeout.tv_usec > 1000000) { + timeout.tv_sec += timeout.tv_usec / 1000000; + timeout.tv_usec %= 1000000; + } + } + if (timeout.tv_sec > MAX_PROBE_TIMEOUT) { + timeout.tv_sec = MAX_PROBE_TIMEOUT; + timeout.tv_usec = 0; + } + + ns->failed_times++; + + if (evtimer_add(&ns->timeout_event, &timeout) < 0) { + char addrbuf[128]; + log(EVDNS_LOG_WARN, + "Error from libevent when adding timer event for %s", + evutil_format_sockaddr_port_( + (struct sockaddr *)&ns->address, + addrbuf, sizeof(addrbuf))); + } +} + +static void +request_swap_ns(struct request *req, struct nameserver *ns) { + if (ns && req->ns != ns) { + EVUTIL_ASSERT(req->ns->requests_inflight > 0); + req->ns->requests_inflight--; + ns->requests_inflight++; + + req->ns = ns; + } +} + +/* called when a nameserver has been deemed to have failed. For example, too */ +/* many packets have timed out etc */ +static void +nameserver_failed(struct nameserver *const ns, const char *msg) { + struct request *req, *started_at; + struct evdns_base *base = ns->base; + int i; + char addrbuf[128]; + + ASSERT_LOCKED(base); + /* if this nameserver has already been marked as failed */ + /* then don't do anything */ + if (!ns->state) return; + + log(EVDNS_LOG_MSG, "Nameserver %s has failed: %s", + evutil_format_sockaddr_port_( + (struct sockaddr *)&ns->address, + addrbuf, sizeof(addrbuf)), + msg); + + base->global_good_nameservers--; + EVUTIL_ASSERT(base->global_good_nameservers >= 0); + if (base->global_good_nameservers == 0) { + log(EVDNS_LOG_MSG, "All nameservers have failed"); + } + + ns->state = 0; + ns->failed_times = 1; + + if (evtimer_add(&ns->timeout_event, + &base->global_nameserver_probe_initial_timeout) < 0) { + log(EVDNS_LOG_WARN, + "Error from libevent when adding timer event for %s", + evutil_format_sockaddr_port_( + (struct sockaddr *)&ns->address, + addrbuf, sizeof(addrbuf))); + /* ???? Do more? */ + } + + /* walk the list of inflight requests to see if any can be reassigned to */ + /* a different server. Requests in the waiting queue don't have a */ + /* nameserver assigned yet */ + + /* if we don't have *any* good nameservers then there's no point */ + /* trying to reassign requests to one */ + if (!base->global_good_nameservers) return; + + for (i = 0; i < base->n_req_heads; ++i) { + req = started_at = base->req_heads[i]; + if (req) { + do { + if (req->tx_count == 0 && req->ns == ns) { + /* still waiting to go out, can be moved */ + /* to another server */ + request_swap_ns(req, nameserver_pick(base)); + } + req = req->next; + } while (req != started_at); + } + } +} + +static void +nameserver_up(struct nameserver *const ns) +{ + char addrbuf[128]; + ASSERT_LOCKED(ns->base); + if (ns->state) return; + log(EVDNS_LOG_MSG, "Nameserver %s is back up", + evutil_format_sockaddr_port_( + (struct sockaddr *)&ns->address, + addrbuf, sizeof(addrbuf))); + evtimer_del(&ns->timeout_event); + if (ns->probe_request) { + evdns_cancel_request(ns->base, ns->probe_request); + ns->probe_request = NULL; + } + ns->state = 1; + ns->failed_times = 0; + ns->timedout = 0; + ns->base->global_good_nameservers++; +} + +static void +request_trans_id_set(struct request *const req, const u16 trans_id) { + req->trans_id = trans_id; + *((u16 *) req->request) = htons(trans_id); +} + +/* Called to remove a request from a list and dealloc it. */ +/* head is a pointer to the head of the list it should be */ +/* removed from or NULL if the request isn't in a list. */ +/* when free_handle is one, free the handle as well. */ +static void +request_finished(struct request *const req, struct request **head, int free_handle) { + struct evdns_base *base = req->base; + int was_inflight = (head != &base->req_waiting_head); + EVDNS_LOCK(base); + ASSERT_VALID_REQUEST(req); + + if (head) + evdns_request_remove(req, head); + + log(EVDNS_LOG_DEBUG, "Removing timeout for request %p", req); + if (was_inflight) { + evtimer_del(&req->timeout_event); + base->global_requests_inflight--; + req->ns->requests_inflight--; + } else { + base->global_requests_waiting--; + } + /* it was initialized during request_new / evtimer_assign */ + event_debug_unassign(&req->timeout_event); + + if (req->ns && + req->ns->requests_inflight == 0 && + req->base->disable_when_inactive) { + event_del(&req->ns->event); + evtimer_del(&req->ns->timeout_event); + } + + if (!req->request_appended) { + /* need to free the request data on it's own */ + mm_free(req->request); + } else { + /* the request data is appended onto the header */ + /* so everything gets free()ed when we: */ + } + + if (req->handle) { + EVUTIL_ASSERT(req->handle->current_req == req); + + if (free_handle) { + search_request_finished(req->handle); + req->handle->current_req = NULL; + if (! req->handle->pending_cb) { + /* If we're planning to run the callback, + * don't free the handle until later. */ + mm_free(req->handle); + } + req->handle = NULL; /* If we have a bug, let's crash + * early */ + } else { + req->handle->current_req = NULL; + } + } + + mm_free(req); + + evdns_requests_pump_waiting_queue(base); + EVDNS_UNLOCK(base); +} + +/* This is called when a server returns a funny error code. */ +/* We try the request again with another server. */ +/* */ +/* return: */ +/* 0 ok */ +/* 1 failed/reissue is pointless */ +static int +request_reissue(struct request *req) { + const struct nameserver *const last_ns = req->ns; + ASSERT_LOCKED(req->base); + ASSERT_VALID_REQUEST(req); + /* the last nameserver should have been marked as failing */ + /* by the caller of this function, therefore pick will try */ + /* not to return it */ + request_swap_ns(req, nameserver_pick(req->base)); + if (req->ns == last_ns) { + /* ... but pick did return it */ + /* not a lot of point in trying again with the */ + /* same server */ + return 1; + } + + req->reissue_count++; + req->tx_count = 0; + req->transmit_me = 1; + + return 0; +} + +/* this function looks for space on the inflight queue and promotes */ +/* requests from the waiting queue if it can. */ +/* */ +/* TODO: */ +/* add return code, see at nameserver_pick() and other functions. */ +static void +evdns_requests_pump_waiting_queue(struct evdns_base *base) { + ASSERT_LOCKED(base); + while (base->global_requests_inflight < base->global_max_requests_inflight && + base->global_requests_waiting) { + struct request *req; + + EVUTIL_ASSERT(base->req_waiting_head); + req = base->req_waiting_head; + + req->ns = nameserver_pick(base); + if (!req->ns) + return; + + /* move a request from the waiting queue to the inflight queue */ + req->ns->requests_inflight++; + + evdns_request_remove(req, &base->req_waiting_head); + + base->global_requests_waiting--; + base->global_requests_inflight++; + + request_trans_id_set(req, transaction_id_pick(base)); + + evdns_request_insert(req, &REQ_HEAD(base, req->trans_id)); + evdns_request_transmit(req); + evdns_transmit(base); + } +} + +/* TODO(nickm) document */ +struct deferred_reply_callback { + struct event_callback deferred; + struct evdns_request *handle; + u8 request_type; + u8 have_reply; + u32 ttl; + u32 err; + evdns_callback_type user_callback; + struct reply reply; +}; + +static void +reply_run_callback(struct event_callback *d, void *user_pointer) +{ + struct deferred_reply_callback *cb = + EVUTIL_UPCAST(d, struct deferred_reply_callback, deferred); + + switch (cb->request_type) { + case TYPE_A: + if (cb->have_reply) + cb->user_callback(DNS_ERR_NONE, DNS_IPv4_A, + cb->reply.data.a.addrcount, cb->ttl, + cb->reply.data.a.addresses, + user_pointer); + else + cb->user_callback(cb->err, 0, 0, cb->ttl, NULL, user_pointer); + break; + case TYPE_PTR: + if (cb->have_reply) { + char *name = cb->reply.data.ptr.name; + cb->user_callback(DNS_ERR_NONE, DNS_PTR, 1, cb->ttl, + &name, user_pointer); + } else { + cb->user_callback(cb->err, 0, 0, cb->ttl, NULL, user_pointer); + } + break; + case TYPE_AAAA: + if (cb->have_reply) + cb->user_callback(DNS_ERR_NONE, DNS_IPv6_AAAA, + cb->reply.data.aaaa.addrcount, cb->ttl, + cb->reply.data.aaaa.addresses, + user_pointer); + else + cb->user_callback(cb->err, 0, 0, cb->ttl, NULL, user_pointer); + break; + default: + EVUTIL_ASSERT(0); + } + + if (cb->handle && cb->handle->pending_cb) { + mm_free(cb->handle); + } + + mm_free(cb); +} + +static void +reply_schedule_callback(struct request *const req, u32 ttl, u32 err, struct reply *reply) +{ + struct deferred_reply_callback *d = mm_calloc(1, sizeof(*d)); + + if (!d) { + event_warn("%s: Couldn't allocate space for deferred callback.", + __func__); + return; + } + + ASSERT_LOCKED(req->base); + + d->request_type = req->request_type; + d->user_callback = req->user_callback; + d->ttl = ttl; + d->err = err; + if (reply) { + d->have_reply = 1; + memcpy(&d->reply, reply, sizeof(struct reply)); + } + + if (req->handle) { + req->handle->pending_cb = 1; + d->handle = req->handle; + } + + event_deferred_cb_init_( + &d->deferred, + event_get_priority(&req->timeout_event), + reply_run_callback, + req->user_pointer); + event_deferred_cb_schedule_( + req->base->event_base, + &d->deferred); +} + + +#define _QR_MASK 0x8000U +#define _OP_MASK 0x7800U +#define _AA_MASK 0x0400U +#define _TC_MASK 0x0200U +#define _RD_MASK 0x0100U +#define _RA_MASK 0x0080U +#define _Z_MASK 0x0040U +#define _AD_MASK 0x0020U +#define _CD_MASK 0x0010U +#define _RCODE_MASK 0x000fU +#define _Z_MASK_DEPRECATED 0x0070U + +/* this processes a parsed reply packet */ +static void +reply_handle(struct request *const req, u16 flags, u32 ttl, struct reply *reply) { + int error; + char addrbuf[128]; + static const int error_codes[] = { + DNS_ERR_FORMAT, DNS_ERR_SERVERFAILED, DNS_ERR_NOTEXIST, + DNS_ERR_NOTIMPL, DNS_ERR_REFUSED + }; + + ASSERT_LOCKED(req->base); + ASSERT_VALID_REQUEST(req); + + if (flags & (_RCODE_MASK | _TC_MASK) || !reply || !reply->have_answer) { + /* there was an error */ + if (flags & _TC_MASK) { + error = DNS_ERR_TRUNCATED; + } else if (flags & _RCODE_MASK) { + u16 error_code = (flags & _RCODE_MASK) - 1; + if (error_code > 4) { + error = DNS_ERR_UNKNOWN; + } else { + error = error_codes[error_code]; + } + } else if (reply && !reply->have_answer) { + error = DNS_ERR_NODATA; + } else { + error = DNS_ERR_UNKNOWN; + } + + switch (error) { + case DNS_ERR_NOTIMPL: + case DNS_ERR_REFUSED: + /* we regard these errors as marking a bad nameserver */ + if (req->reissue_count < req->base->global_max_reissues) { + char msg[64]; + evutil_snprintf(msg, sizeof(msg), "Bad response %d (%s)", + error, evdns_err_to_string(error)); + nameserver_failed(req->ns, msg); + if (!request_reissue(req)) return; + } + break; + case DNS_ERR_SERVERFAILED: + /* rcode 2 (servfailed) sometimes means "we + * are broken" and sometimes (with some binds) + * means "that request was very confusing." + * Treat this as a timeout, not a failure. + */ + log(EVDNS_LOG_DEBUG, "Got a SERVERFAILED from nameserver" + "at %s; will allow the request to time out.", + evutil_format_sockaddr_port_( + (struct sockaddr *)&req->ns->address, + addrbuf, sizeof(addrbuf))); + /* Call the timeout function */ + evdns_request_timeout_callback(0, 0, req); + return; + default: + /* we got a good reply from the nameserver: it is up. */ + if (req->handle == req->ns->probe_request) { + /* Avoid double-free */ + req->ns->probe_request = NULL; + } + + nameserver_up(req->ns); + } + + if (req->handle->search_state && + req->request_type != TYPE_PTR) { + /* if we have a list of domains to search in, + * try the next one */ + if (!search_try_next(req->handle)) { + /* a new request was issued so this + * request is finished and */ + /* the user callback will be made when + * that request (or a */ + /* child of it) finishes. */ + return; + } + } + + /* all else failed. Pass the failure up */ + reply_schedule_callback(req, ttl, error, NULL); + request_finished(req, &REQ_HEAD(req->base, req->trans_id), 1); + } else { + /* all ok, tell the user */ + reply_schedule_callback(req, ttl, 0, reply); + if (req->handle == req->ns->probe_request) + req->ns->probe_request = NULL; /* Avoid double-free */ + nameserver_up(req->ns); + request_finished(req, &REQ_HEAD(req->base, req->trans_id), 1); + } +} + +static int +name_parse(u8 *packet, int length, int *idx, char *name_out, int name_out_len) { + int name_end = -1; + int j = *idx; + int ptr_count = 0; +#define GET32(x) do { if (j + 4 > length) goto err; memcpy(&t32_, packet + j, 4); j += 4; x = ntohl(t32_); } while (0) +#define GET16(x) do { if (j + 2 > length) goto err; memcpy(&t_, packet + j, 2); j += 2; x = ntohs(t_); } while (0) +#define GET8(x) do { if (j >= length) goto err; x = packet[j++]; } while (0) + + char *cp = name_out; + const char *const end = name_out + name_out_len; + + /* Normally, names are a series of length prefixed strings terminated */ + /* with a length of 0 (the lengths are u8's < 63). */ + /* However, the length can start with a pair of 1 bits and that */ + /* means that the next 14 bits are a pointer within the current */ + /* packet. */ + + for (;;) { + u8 label_len; + GET8(label_len); + if (!label_len) break; + if (label_len & 0xc0) { + u8 ptr_low; + GET8(ptr_low); + if (name_end < 0) name_end = j; + j = (((int)label_len & 0x3f) << 8) + ptr_low; + /* Make sure that the target offset is in-bounds. */ + if (j < 0 || j >= length) return -1; + /* If we've jumped more times than there are characters in the + * message, we must have a loop. */ + if (++ptr_count > length) return -1; + continue; + } + if (label_len > 63) return -1; + if (cp != name_out) { + if (cp + 1 >= end) return -1; + *cp++ = '.'; + } + if (cp + label_len >= end) return -1; + if (j + label_len > length) return -1; + memcpy(cp, packet + j, label_len); + cp += label_len; + j += label_len; + } + if (cp >= end) return -1; + *cp = '\0'; + if (name_end < 0) + *idx = j; + else + *idx = name_end; + return 0; + err: + return -1; +} + +/* parses a raw request from a nameserver */ +static int +reply_parse(struct evdns_base *base, u8 *packet, int length) { + int j = 0, k = 0; /* index into packet */ + u16 t_; /* used by the macros */ + u32 t32_; /* used by the macros */ + char tmp_name[256], cmp_name[256]; /* used by the macros */ + int name_matches = 0; + + u16 trans_id, questions, answers, authority, additional, datalength; + u16 flags = 0; + u32 ttl, ttl_r = 0xffffffff; + struct reply reply; + struct request *req = NULL; + unsigned int i; + + ASSERT_LOCKED(base); + + GET16(trans_id); + GET16(flags); + GET16(questions); + GET16(answers); + GET16(authority); + GET16(additional); + (void) authority; /* suppress "unused variable" warnings. */ + (void) additional; /* suppress "unused variable" warnings. */ + + req = request_find_from_trans_id(base, trans_id); + if (!req) return -1; + EVUTIL_ASSERT(req->base == base); + + memset(&reply, 0, sizeof(reply)); + + /* If it's not an answer, it doesn't correspond to any request. */ + if (!(flags & _QR_MASK)) return -1; /* must be an answer */ + if ((flags & (_RCODE_MASK|_TC_MASK)) && (flags & (_RCODE_MASK|_TC_MASK)) != DNS_ERR_NOTEXIST) { + /* there was an error and it's not NXDOMAIN */ + goto err; + } + /* if (!answers) return; */ /* must have an answer of some form */ + + /* This macro skips a name in the DNS reply. */ +#define SKIP_NAME \ + do { tmp_name[0] = '\0'; \ + if (name_parse(packet, length, &j, tmp_name, \ + sizeof(tmp_name))<0) \ + goto err; \ + } while (0) + + reply.type = req->request_type; + + /* skip over each question in the reply */ + for (i = 0; i < questions; ++i) { + /* the question looks like + * <label:name><u16:type><u16:class> + */ + tmp_name[0] = '\0'; + cmp_name[0] = '\0'; + k = j; + if (name_parse(packet, length, &j, tmp_name, sizeof(tmp_name)) < 0) + goto err; + if (name_parse(req->request, req->request_len, &k, + cmp_name, sizeof(cmp_name))<0) + goto err; + if (!base->global_randomize_case) { + if (strcmp(tmp_name, cmp_name) == 0) + name_matches = 1; + } else { + if (evutil_ascii_strcasecmp(tmp_name, cmp_name) == 0) + name_matches = 1; + } + + j += 4; + if (j > length) + goto err; + } + + if (!name_matches) + goto err; + + /* now we have the answer section which looks like + * <label:name><u16:type><u16:class><u32:ttl><u16:len><data...> + */ + + for (i = 0; i < answers; ++i) { + u16 type, class; + + SKIP_NAME; + GET16(type); + GET16(class); + GET32(ttl); + GET16(datalength); + + if (type == TYPE_A && class == CLASS_INET) { + int addrcount, addrtocopy; + if (req->request_type != TYPE_A) { + j += datalength; continue; + } + if ((datalength & 3) != 0) /* not an even number of As. */ + goto err; + addrcount = datalength >> 2; + addrtocopy = MIN(MAX_V4_ADDRS - reply.data.a.addrcount, (unsigned)addrcount); + + ttl_r = MIN(ttl_r, ttl); + /* we only bother with the first four addresses. */ + if (j + 4*addrtocopy > length) goto err; + memcpy(&reply.data.a.addresses[reply.data.a.addrcount], + packet + j, 4*addrtocopy); + j += 4*addrtocopy; + reply.data.a.addrcount += addrtocopy; + reply.have_answer = 1; + if (reply.data.a.addrcount == MAX_V4_ADDRS) break; + } else if (type == TYPE_PTR && class == CLASS_INET) { + if (req->request_type != TYPE_PTR) { + j += datalength; continue; + } + if (name_parse(packet, length, &j, reply.data.ptr.name, + sizeof(reply.data.ptr.name))<0) + goto err; + ttl_r = MIN(ttl_r, ttl); + reply.have_answer = 1; + break; + } else if (type == TYPE_CNAME) { + char cname[HOST_NAME_MAX]; + if (!req->put_cname_in_ptr || *req->put_cname_in_ptr) { + j += datalength; continue; + } + if (name_parse(packet, length, &j, cname, + sizeof(cname))<0) + goto err; + *req->put_cname_in_ptr = mm_strdup(cname); + } else if (type == TYPE_AAAA && class == CLASS_INET) { + int addrcount, addrtocopy; + if (req->request_type != TYPE_AAAA) { + j += datalength; continue; + } + if ((datalength & 15) != 0) /* not an even number of AAAAs. */ + goto err; + addrcount = datalength >> 4; /* each address is 16 bytes long */ + addrtocopy = MIN(MAX_V6_ADDRS - reply.data.aaaa.addrcount, (unsigned)addrcount); + ttl_r = MIN(ttl_r, ttl); + + /* we only bother with the first four addresses. */ + if (j + 16*addrtocopy > length) goto err; + memcpy(&reply.data.aaaa.addresses[reply.data.aaaa.addrcount], + packet + j, 16*addrtocopy); + reply.data.aaaa.addrcount += addrtocopy; + j += 16*addrtocopy; + reply.have_answer = 1; + if (reply.data.aaaa.addrcount == MAX_V6_ADDRS) break; + } else { + /* skip over any other type of resource */ + j += datalength; + } + } + + if (!reply.have_answer) { + for (i = 0; i < authority; ++i) { + u16 type, class; + SKIP_NAME; + GET16(type); + GET16(class); + GET32(ttl); + GET16(datalength); + if (type == TYPE_SOA && class == CLASS_INET) { + u32 serial, refresh, retry, expire, minimum; + SKIP_NAME; + SKIP_NAME; + GET32(serial); + GET32(refresh); + GET32(retry); + GET32(expire); + GET32(minimum); + (void)expire; + (void)retry; + (void)refresh; + (void)serial; + ttl_r = MIN(ttl_r, ttl); + ttl_r = MIN(ttl_r, minimum); + } else { + /* skip over any other type of resource */ + j += datalength; + } + } + } + + if (ttl_r == 0xffffffff) + ttl_r = 0; + + reply_handle(req, flags, ttl_r, &reply); + return 0; + err: + if (req) + reply_handle(req, flags, 0, NULL); + return -1; +} + +/* Parse a raw request (packet,length) sent to a nameserver port (port) from */ +/* a DNS client (addr,addrlen), and if it's well-formed, call the corresponding */ +/* callback. */ +static int +request_parse(u8 *packet, int length, struct evdns_server_port *port, struct sockaddr *addr, ev_socklen_t addrlen) +{ + int j = 0; /* index into packet */ + u16 t_; /* used by the macros */ + char tmp_name[256]; /* used by the macros */ + + int i; + u16 trans_id, flags, questions, answers, authority, additional; + struct server_request *server_req = NULL; + + ASSERT_LOCKED(port); + + /* Get the header fields */ + GET16(trans_id); + GET16(flags); + GET16(questions); + GET16(answers); + GET16(authority); + GET16(additional); + (void)answers; + (void)additional; + (void)authority; + + if (flags & _QR_MASK) return -1; /* Must not be an answer. */ + flags &= (_RD_MASK|_CD_MASK); /* Only RD and CD get preserved. */ + + server_req = mm_malloc(sizeof(struct server_request)); + if (server_req == NULL) return -1; + memset(server_req, 0, sizeof(struct server_request)); + + server_req->trans_id = trans_id; + memcpy(&server_req->addr, addr, addrlen); + server_req->addrlen = addrlen; + + server_req->base.flags = flags; + server_req->base.nquestions = 0; + server_req->base.questions = mm_calloc(sizeof(struct evdns_server_question *), questions); + if (server_req->base.questions == NULL) + goto err; + + for (i = 0; i < questions; ++i) { + u16 type, class; + struct evdns_server_question *q; + int namelen; + if (name_parse(packet, length, &j, tmp_name, sizeof(tmp_name))<0) + goto err; + GET16(type); + GET16(class); + namelen = (int)strlen(tmp_name); + q = mm_malloc(sizeof(struct evdns_server_question) + namelen); + if (!q) + goto err; + q->type = type; + q->dns_question_class = class; + memcpy(q->name, tmp_name, namelen+1); + server_req->base.questions[server_req->base.nquestions++] = q; + } + + /* Ignore answers, authority, and additional. */ + + server_req->port = port; + port->refcnt++; + + /* Only standard queries are supported. */ + if (flags & _OP_MASK) { + evdns_server_request_respond(&(server_req->base), DNS_ERR_NOTIMPL); + return -1; + } + + port->user_callback(&(server_req->base), port->user_data); + + return 0; +err: + if (server_req->base.questions) { + for (i = 0; i < server_req->base.nquestions; ++i) + mm_free(server_req->base.questions[i]); + mm_free(server_req->base.questions); + } + mm_free(server_req); + return -1; + +#undef SKIP_NAME +#undef GET32 +#undef GET16 +#undef GET8 +} + + +void +evdns_set_transaction_id_fn(ev_uint16_t (*fn)(void)) +{ +} + +void +evdns_set_random_bytes_fn(void (*fn)(char *, size_t)) +{ +} + +/* Try to choose a strong transaction id which isn't already in flight */ +static u16 +transaction_id_pick(struct evdns_base *base) { + ASSERT_LOCKED(base); + for (;;) { + u16 trans_id; + evutil_secure_rng_get_bytes(&trans_id, sizeof(trans_id)); + + if (trans_id == 0xffff) continue; + /* now check to see if that id is already inflight */ + if (request_find_from_trans_id(base, trans_id) == NULL) + return trans_id; + } +} + +/* choose a namesever to use. This function will try to ignore */ +/* nameservers which we think are down and load balance across the rest */ +/* by updating the server_head global each time. */ +static struct nameserver * +nameserver_pick(struct evdns_base *base) { + struct nameserver *started_at = base->server_head, *picked; + ASSERT_LOCKED(base); + if (!base->server_head) return NULL; + + /* if we don't have any good nameservers then there's no */ + /* point in trying to find one. */ + if (!base->global_good_nameservers) { + base->server_head = base->server_head->next; + return base->server_head; + } + + /* remember that nameservers are in a circular list */ + for (;;) { + if (base->server_head->state) { + /* we think this server is currently good */ + picked = base->server_head; + base->server_head = base->server_head->next; + return picked; + } + + base->server_head = base->server_head->next; + if (base->server_head == started_at) { + /* all the nameservers seem to be down */ + /* so we just return this one and hope for the */ + /* best */ + EVUTIL_ASSERT(base->global_good_nameservers == 0); + picked = base->server_head; + base->server_head = base->server_head->next; + return picked; + } + } +} + +/* this is called when a namesever socket is ready for reading */ +static void +nameserver_read(struct nameserver *ns) { + struct sockaddr_storage ss; + ev_socklen_t addrlen = sizeof(ss); + u8 packet[1500]; + char addrbuf[128]; + ASSERT_LOCKED(ns->base); + + for (;;) { + const int r = recvfrom(ns->socket, (void*)packet, + sizeof(packet), 0, + (struct sockaddr*)&ss, &addrlen); + if (r < 0) { + int err = evutil_socket_geterror(ns->socket); + if (EVUTIL_ERR_RW_RETRIABLE(err)) + return; + nameserver_failed(ns, + evutil_socket_error_to_string(err)); + return; + } + if (evutil_sockaddr_cmp((struct sockaddr*)&ss, + (struct sockaddr*)&ns->address, 0)) { + log(EVDNS_LOG_WARN, "Address mismatch on received " + "DNS packet. Apparent source was %s", + evutil_format_sockaddr_port_( + (struct sockaddr *)&ss, + addrbuf, sizeof(addrbuf))); + return; + } + + ns->timedout = 0; + reply_parse(ns->base, packet, r); + } +} + +/* Read a packet from a DNS client on a server port s, parse it, and */ +/* act accordingly. */ +static void +server_port_read(struct evdns_server_port *s) { + u8 packet[1500]; + struct sockaddr_storage addr; + ev_socklen_t addrlen; + int r; + ASSERT_LOCKED(s); + + for (;;) { + addrlen = sizeof(struct sockaddr_storage); + r = recvfrom(s->socket, (void*)packet, sizeof(packet), 0, + (struct sockaddr*) &addr, &addrlen); + if (r < 0) { + int err = evutil_socket_geterror(s->socket); + if (EVUTIL_ERR_RW_RETRIABLE(err)) + return; + log(EVDNS_LOG_WARN, + "Error %s (%d) while reading request.", + evutil_socket_error_to_string(err), err); + return; + } + request_parse(packet, r, s, (struct sockaddr*) &addr, addrlen); + } +} + +/* Try to write all pending replies on a given DNS server port. */ +static void +server_port_flush(struct evdns_server_port *port) +{ + struct server_request *req = port->pending_replies; + ASSERT_LOCKED(port); + while (req) { + int r = sendto(port->socket, req->response, (int)req->response_len, 0, + (struct sockaddr*) &req->addr, (ev_socklen_t)req->addrlen); + if (r < 0) { + int err = evutil_socket_geterror(port->socket); + if (EVUTIL_ERR_RW_RETRIABLE(err)) + return; + log(EVDNS_LOG_WARN, "Error %s (%d) while writing response to port; dropping", evutil_socket_error_to_string(err), err); + } + if (server_request_free(req)) { + /* we released the last reference to req->port. */ + return; + } else { + EVUTIL_ASSERT(req != port->pending_replies); + req = port->pending_replies; + } + } + + /* We have no more pending requests; stop listening for 'writeable' events. */ + (void) event_del(&port->event); + event_assign(&port->event, port->event_base, + port->socket, EV_READ | EV_PERSIST, + server_port_ready_callback, port); + + if (event_add(&port->event, NULL) < 0) { + log(EVDNS_LOG_WARN, "Error from libevent when adding event for DNS server."); + /* ???? Do more? */ + } +} + +/* set if we are waiting for the ability to write to this server. */ +/* if waiting is true then we ask libevent for EV_WRITE events, otherwise */ +/* we stop these events. */ +static void +nameserver_write_waiting(struct nameserver *ns, char waiting) { + ASSERT_LOCKED(ns->base); + if (ns->write_waiting == waiting) return; + + ns->write_waiting = waiting; + (void) event_del(&ns->event); + event_assign(&ns->event, ns->base->event_base, + ns->socket, EV_READ | (waiting ? EV_WRITE : 0) | EV_PERSIST, + nameserver_ready_callback, ns); + if (event_add(&ns->event, NULL) < 0) { + char addrbuf[128]; + log(EVDNS_LOG_WARN, "Error from libevent when adding event for %s", + evutil_format_sockaddr_port_( + (struct sockaddr *)&ns->address, + addrbuf, sizeof(addrbuf))); + /* ???? Do more? */ + } +} + +/* a callback function. Called by libevent when the kernel says that */ +/* a nameserver socket is ready for writing or reading */ +static void +nameserver_ready_callback(evutil_socket_t fd, short events, void *arg) { + struct nameserver *ns = (struct nameserver *) arg; + (void)fd; + + EVDNS_LOCK(ns->base); + if (events & EV_WRITE) { + ns->choked = 0; + if (!evdns_transmit(ns->base)) { + nameserver_write_waiting(ns, 0); + } + } + if (events & EV_READ) { + nameserver_read(ns); + } + EVDNS_UNLOCK(ns->base); +} + +/* a callback function. Called by libevent when the kernel says that */ +/* a server socket is ready for writing or reading. */ +static void +server_port_ready_callback(evutil_socket_t fd, short events, void *arg) { + struct evdns_server_port *port = (struct evdns_server_port *) arg; + (void) fd; + + EVDNS_LOCK(port); + if (events & EV_WRITE) { + port->choked = 0; + server_port_flush(port); + } + if (events & EV_READ) { + server_port_read(port); + } + EVDNS_UNLOCK(port); +} + +/* This is an inefficient representation; only use it via the dnslabel_table_* + * functions, so that is can be safely replaced with something smarter later. */ +#define MAX_LABELS 128 +/* Structures used to implement name compression */ +struct dnslabel_entry { char *v; off_t pos; }; +struct dnslabel_table { + int n_labels; /* number of current entries */ + /* map from name to position in message */ + struct dnslabel_entry labels[MAX_LABELS]; +}; + +/* Initialize dnslabel_table. */ +static void +dnslabel_table_init(struct dnslabel_table *table) +{ + table->n_labels = 0; +} + +/* Free all storage held by table, but not the table itself. */ +static void +dnslabel_clear(struct dnslabel_table *table) +{ + int i; + for (i = 0; i < table->n_labels; ++i) + mm_free(table->labels[i].v); + table->n_labels = 0; +} + +/* return the position of the label in the current message, or -1 if the label */ +/* hasn't been used yet. */ +static int +dnslabel_table_get_pos(const struct dnslabel_table *table, const char *label) +{ + int i; + for (i = 0; i < table->n_labels; ++i) { + if (!strcmp(label, table->labels[i].v)) + return table->labels[i].pos; + } + return -1; +} + +/* remember that we've used the label at position pos */ +static int +dnslabel_table_add(struct dnslabel_table *table, const char *label, off_t pos) +{ + char *v; + int p; + if (table->n_labels == MAX_LABELS) + return (-1); + v = mm_strdup(label); + if (v == NULL) + return (-1); + p = table->n_labels++; + table->labels[p].v = v; + table->labels[p].pos = pos; + + return (0); +} + +/* Converts a string to a length-prefixed set of DNS labels, starting */ +/* at buf[j]. name and buf must not overlap. name_len should be the length */ +/* of name. table is optional, and is used for compression. */ +/* */ +/* Input: abc.def */ +/* Output: <3>abc<3>def<0> */ +/* */ +/* Returns the first index after the encoded name, or negative on error. */ +/* -1 label was > 63 bytes */ +/* -2 name too long to fit in buffer. */ +/* */ +static off_t +dnsname_to_labels(u8 *const buf, size_t buf_len, off_t j, + const char *name, const size_t name_len, + struct dnslabel_table *table) { + const char *end = name + name_len; + int ref = 0; + u16 t_; + +#define APPEND16(x) do { \ + if (j + 2 > (off_t)buf_len) \ + goto overflow; \ + t_ = htons(x); \ + memcpy(buf + j, &t_, 2); \ + j += 2; \ + } while (0) +#define APPEND32(x) do { \ + if (j + 4 > (off_t)buf_len) \ + goto overflow; \ + t32_ = htonl(x); \ + memcpy(buf + j, &t32_, 4); \ + j += 4; \ + } while (0) + + if (name_len > 255) return -2; + + for (;;) { + const char *const start = name; + if (table && (ref = dnslabel_table_get_pos(table, name)) >= 0) { + APPEND16(ref | 0xc000); + return j; + } + name = strchr(name, '.'); + if (!name) { + const size_t label_len = end - start; + if (label_len > 63) return -1; + if ((size_t)(j+label_len+1) > buf_len) return -2; + if (table) dnslabel_table_add(table, start, j); + buf[j++] = (ev_uint8_t)label_len; + + memcpy(buf + j, start, label_len); + j += (int) label_len; + break; + } else { + /* append length of the label. */ + const size_t label_len = name - start; + if (label_len > 63) return -1; + if ((size_t)(j+label_len+1) > buf_len) return -2; + if (table) dnslabel_table_add(table, start, j); + buf[j++] = (ev_uint8_t)label_len; + + memcpy(buf + j, start, label_len); + j += (int) label_len; + /* hop over the '.' */ + name++; + } + } + + /* the labels must be terminated by a 0. */ + /* It's possible that the name ended in a . */ + /* in which case the zero is already there */ + if (!j || buf[j-1]) buf[j++] = 0; + return j; + overflow: + return (-2); +} + +/* Finds the length of a dns request for a DNS name of the given */ +/* length. The actual request may be smaller than the value returned */ +/* here */ +static size_t +evdns_request_len(const size_t name_len) { + return 96 + /* length of the DNS standard header */ + name_len + 2 + + 4; /* space for the resource type */ +} + +/* build a dns request packet into buf. buf should be at least as long */ +/* as evdns_request_len told you it should be. */ +/* */ +/* Returns the amount of space used. Negative on error. */ +static int +evdns_request_data_build(const char *const name, const size_t name_len, + const u16 trans_id, const u16 type, const u16 class, + u8 *const buf, size_t buf_len) { + off_t j = 0; /* current offset into buf */ + u16 t_; /* used by the macros */ + + APPEND16(trans_id); + APPEND16(0x0100); /* standard query, recusion needed */ + APPEND16(1); /* one question */ + APPEND16(0); /* no answers */ + APPEND16(0); /* no authority */ + APPEND16(0); /* no additional */ + + j = dnsname_to_labels(buf, buf_len, j, name, name_len, NULL); + if (j < 0) { + return (int)j; + } + + APPEND16(type); + APPEND16(class); + + return (int)j; + overflow: + return (-1); +} + +/* exported function */ +struct evdns_server_port * +evdns_add_server_port_with_base(struct event_base *base, evutil_socket_t socket, int flags, evdns_request_callback_fn_type cb, void *user_data) +{ + struct evdns_server_port *port; + if (flags) + return NULL; /* flags not yet implemented */ + if (!(port = mm_malloc(sizeof(struct evdns_server_port)))) + return NULL; + memset(port, 0, sizeof(struct evdns_server_port)); + + + port->socket = socket; + port->refcnt = 1; + port->choked = 0; + port->closing = 0; + port->user_callback = cb; + port->user_data = user_data; + port->pending_replies = NULL; + port->event_base = base; + + event_assign(&port->event, port->event_base, + port->socket, EV_READ | EV_PERSIST, + server_port_ready_callback, port); + if (event_add(&port->event, NULL) < 0) { + mm_free(port); + return NULL; + } + EVTHREAD_ALLOC_LOCK(port->lock, EVTHREAD_LOCKTYPE_RECURSIVE); + return port; +} + +struct evdns_server_port * +evdns_add_server_port(evutil_socket_t socket, int flags, evdns_request_callback_fn_type cb, void *user_data) +{ + return evdns_add_server_port_with_base(NULL, socket, flags, cb, user_data); +} + +/* exported function */ +void +evdns_close_server_port(struct evdns_server_port *port) +{ + EVDNS_LOCK(port); + if (--port->refcnt == 0) { + EVDNS_UNLOCK(port); + server_port_free(port); + } else { + port->closing = 1; + EVDNS_UNLOCK(port); + } +} + +/* exported function */ +int +evdns_server_request_add_reply(struct evdns_server_request *req_, int section, const char *name, int type, int class, int ttl, int datalen, int is_name, const char *data) +{ + struct server_request *req = TO_SERVER_REQUEST(req_); + struct server_reply_item **itemp, *item; + int *countp; + int result = -1; + + EVDNS_LOCK(req->port); + if (req->response) /* have we already answered? */ + goto done; + + switch (section) { + case EVDNS_ANSWER_SECTION: + itemp = &req->answer; + countp = &req->n_answer; + break; + case EVDNS_AUTHORITY_SECTION: + itemp = &req->authority; + countp = &req->n_authority; + break; + case EVDNS_ADDITIONAL_SECTION: + itemp = &req->additional; + countp = &req->n_additional; + break; + default: + goto done; + } + while (*itemp) { + itemp = &((*itemp)->next); + } + item = mm_malloc(sizeof(struct server_reply_item)); + if (!item) + goto done; + item->next = NULL; + if (!(item->name = mm_strdup(name))) { + mm_free(item); + goto done; + } + item->type = type; + item->dns_question_class = class; + item->ttl = ttl; + item->is_name = is_name != 0; + item->datalen = 0; + item->data = NULL; + if (data) { + if (item->is_name) { + if (!(item->data = mm_strdup(data))) { + mm_free(item->name); + mm_free(item); + goto done; + } + item->datalen = (u16)-1; + } else { + if (!(item->data = mm_malloc(datalen))) { + mm_free(item->name); + mm_free(item); + goto done; + } + item->datalen = datalen; + memcpy(item->data, data, datalen); + } + } + + *itemp = item; + ++(*countp); + result = 0; +done: + EVDNS_UNLOCK(req->port); + return result; +} + +/* exported function */ +int +evdns_server_request_add_a_reply(struct evdns_server_request *req, const char *name, int n, const void *addrs, int ttl) +{ + return evdns_server_request_add_reply( + req, EVDNS_ANSWER_SECTION, name, TYPE_A, CLASS_INET, + ttl, n*4, 0, addrs); +} + +/* exported function */ +int +evdns_server_request_add_aaaa_reply(struct evdns_server_request *req, const char *name, int n, const void *addrs, int ttl) +{ + return evdns_server_request_add_reply( + req, EVDNS_ANSWER_SECTION, name, TYPE_AAAA, CLASS_INET, + ttl, n*16, 0, addrs); +} + +/* exported function */ +int +evdns_server_request_add_ptr_reply(struct evdns_server_request *req, struct in_addr *in, const char *inaddr_name, const char *hostname, int ttl) +{ + u32 a; + char buf[32]; + if (in && inaddr_name) + return -1; + else if (!in && !inaddr_name) + return -1; + if (in) { + a = ntohl(in->s_addr); + evutil_snprintf(buf, sizeof(buf), "%d.%d.%d.%d.in-addr.arpa", + (int)(u8)((a )&0xff), + (int)(u8)((a>>8 )&0xff), + (int)(u8)((a>>16)&0xff), + (int)(u8)((a>>24)&0xff)); + inaddr_name = buf; + } + return evdns_server_request_add_reply( + req, EVDNS_ANSWER_SECTION, inaddr_name, TYPE_PTR, CLASS_INET, + ttl, -1, 1, hostname); +} + +/* exported function */ +int +evdns_server_request_add_cname_reply(struct evdns_server_request *req, const char *name, const char *cname, int ttl) +{ + return evdns_server_request_add_reply( + req, EVDNS_ANSWER_SECTION, name, TYPE_CNAME, CLASS_INET, + ttl, -1, 1, cname); +} + +/* exported function */ +void +evdns_server_request_set_flags(struct evdns_server_request *exreq, int flags) +{ + struct server_request *req = TO_SERVER_REQUEST(exreq); + req->base.flags &= ~(EVDNS_FLAGS_AA|EVDNS_FLAGS_RD); + req->base.flags |= flags; +} + +static int +evdns_server_request_format_response(struct server_request *req, int err) +{ + unsigned char buf[1500]; + size_t buf_len = sizeof(buf); + off_t j = 0, r; + u16 t_; + u32 t32_; + int i; + u16 flags; + struct dnslabel_table table; + + if (err < 0 || err > 15) return -1; + + /* Set response bit and error code; copy OPCODE and RD fields from + * question; copy RA and AA if set by caller. */ + flags = req->base.flags; + flags |= (_QR_MASK | err); + + dnslabel_table_init(&table); + APPEND16(req->trans_id); + APPEND16(flags); + APPEND16(req->base.nquestions); + APPEND16(req->n_answer); + APPEND16(req->n_authority); + APPEND16(req->n_additional); + + /* Add questions. */ + for (i=0; i < req->base.nquestions; ++i) { + const char *s = req->base.questions[i]->name; + j = dnsname_to_labels(buf, buf_len, j, s, strlen(s), &table); + if (j < 0) { + dnslabel_clear(&table); + return (int) j; + } + APPEND16(req->base.questions[i]->type); + APPEND16(req->base.questions[i]->dns_question_class); + } + + /* Add answer, authority, and additional sections. */ + for (i=0; i<3; ++i) { + struct server_reply_item *item; + if (i==0) + item = req->answer; + else if (i==1) + item = req->authority; + else + item = req->additional; + while (item) { + r = dnsname_to_labels(buf, buf_len, j, item->name, strlen(item->name), &table); + if (r < 0) + goto overflow; + j = r; + + APPEND16(item->type); + APPEND16(item->dns_question_class); + APPEND32(item->ttl); + if (item->is_name) { + off_t len_idx = j, name_start; + j += 2; + name_start = j; + r = dnsname_to_labels(buf, buf_len, j, item->data, strlen(item->data), &table); + if (r < 0) + goto overflow; + j = r; + t_ = htons( (short) (j-name_start) ); + memcpy(buf+len_idx, &t_, 2); + } else { + APPEND16(item->datalen); + if (j+item->datalen > (off_t)buf_len) + goto overflow; + memcpy(buf+j, item->data, item->datalen); + j += item->datalen; + } + item = item->next; + } + } + + if (j > 512) { +overflow: + j = 512; + buf[2] |= 0x02; /* set the truncated bit. */ + } + + req->response_len = j; + + if (!(req->response = mm_malloc(req->response_len))) { + server_request_free_answers(req); + dnslabel_clear(&table); + return (-1); + } + memcpy(req->response, buf, req->response_len); + server_request_free_answers(req); + dnslabel_clear(&table); + return (0); +} + +/* exported function */ +int +evdns_server_request_respond(struct evdns_server_request *req_, int err) +{ + struct server_request *req = TO_SERVER_REQUEST(req_); + struct evdns_server_port *port = req->port; + int r = -1; + + EVDNS_LOCK(port); + if (!req->response) { + if ((r = evdns_server_request_format_response(req, err))<0) + goto done; + } + + r = sendto(port->socket, req->response, (int)req->response_len, 0, + (struct sockaddr*) &req->addr, (ev_socklen_t)req->addrlen); + if (r<0) { + int sock_err = evutil_socket_geterror(port->socket); + if (EVUTIL_ERR_RW_RETRIABLE(sock_err)) + goto done; + + if (port->pending_replies) { + req->prev_pending = port->pending_replies->prev_pending; + req->next_pending = port->pending_replies; + req->prev_pending->next_pending = + req->next_pending->prev_pending = req; + } else { + req->prev_pending = req->next_pending = req; + port->pending_replies = req; + port->choked = 1; + + (void) event_del(&port->event); + event_assign(&port->event, port->event_base, port->socket, (port->closing?0:EV_READ) | EV_WRITE | EV_PERSIST, server_port_ready_callback, port); + + if (event_add(&port->event, NULL) < 0) { + log(EVDNS_LOG_WARN, "Error from libevent when adding event for DNS server"); + } + + } + + r = 1; + goto done; + } + if (server_request_free(req)) { + r = 0; + goto done; + } + + if (port->pending_replies) + server_port_flush(port); + + r = 0; +done: + EVDNS_UNLOCK(port); + return r; +} + +/* Free all storage held by RRs in req. */ +static void +server_request_free_answers(struct server_request *req) +{ + struct server_reply_item *victim, *next, **list; + int i; + for (i = 0; i < 3; ++i) { + if (i==0) + list = &req->answer; + else if (i==1) + list = &req->authority; + else + list = &req->additional; + + victim = *list; + while (victim) { + next = victim->next; + mm_free(victim->name); + if (victim->data) + mm_free(victim->data); + mm_free(victim); + victim = next; + } + *list = NULL; + } +} + +/* Free all storage held by req, and remove links to it. */ +/* return true iff we just wound up freeing the server_port. */ +static int +server_request_free(struct server_request *req) +{ + int i, rc=1, lock=0; + if (req->base.questions) { + for (i = 0; i < req->base.nquestions; ++i) + mm_free(req->base.questions[i]); + mm_free(req->base.questions); + } + + if (req->port) { + EVDNS_LOCK(req->port); + lock=1; + if (req->port->pending_replies == req) { + if (req->next_pending && req->next_pending != req) + req->port->pending_replies = req->next_pending; + else + req->port->pending_replies = NULL; + } + rc = --req->port->refcnt; + } + + if (req->response) { + mm_free(req->response); + } + + server_request_free_answers(req); + + if (req->next_pending && req->next_pending != req) { + req->next_pending->prev_pending = req->prev_pending; + req->prev_pending->next_pending = req->next_pending; + } + + if (rc == 0) { + EVDNS_UNLOCK(req->port); /* ????? nickm */ + server_port_free(req->port); + mm_free(req); + return (1); + } + if (lock) + EVDNS_UNLOCK(req->port); + mm_free(req); + return (0); +} + +/* Free all storage held by an evdns_server_port. Only called when */ +static void +server_port_free(struct evdns_server_port *port) +{ + EVUTIL_ASSERT(port); + EVUTIL_ASSERT(!port->refcnt); + EVUTIL_ASSERT(!port->pending_replies); + if (port->socket > 0) { + evutil_closesocket(port->socket); + port->socket = -1; + } + (void) event_del(&port->event); + event_debug_unassign(&port->event); + EVTHREAD_FREE_LOCK(port->lock, EVTHREAD_LOCKTYPE_RECURSIVE); + mm_free(port); +} + +/* exported function */ +int +evdns_server_request_drop(struct evdns_server_request *req_) +{ + struct server_request *req = TO_SERVER_REQUEST(req_); + server_request_free(req); + return 0; +} + +/* exported function */ +int +evdns_server_request_get_requesting_addr(struct evdns_server_request *req_, struct sockaddr *sa, int addr_len) +{ + struct server_request *req = TO_SERVER_REQUEST(req_); + if (addr_len < (int)req->addrlen) + return -1; + memcpy(sa, &(req->addr), req->addrlen); + return req->addrlen; +} + +#undef APPEND16 +#undef APPEND32 + +/* this is a libevent callback function which is called when a request */ +/* has timed out. */ +static void +evdns_request_timeout_callback(evutil_socket_t fd, short events, void *arg) { + struct request *const req = (struct request *) arg; + struct evdns_base *base = req->base; + + (void) fd; + (void) events; + + log(EVDNS_LOG_DEBUG, "Request %p timed out", arg); + EVDNS_LOCK(base); + + if (req->tx_count >= req->base->global_max_retransmits) { + struct nameserver *ns = req->ns; + /* this request has failed */ + log(EVDNS_LOG_DEBUG, "Giving up on request %p; tx_count==%d", + arg, req->tx_count); + reply_schedule_callback(req, 0, DNS_ERR_TIMEOUT, NULL); + + request_finished(req, &REQ_HEAD(req->base, req->trans_id), 1); + nameserver_failed(ns, "request timed out."); + } else { + /* retransmit it */ + log(EVDNS_LOG_DEBUG, "Retransmitting request %p; tx_count==%d", + arg, req->tx_count); + (void) evtimer_del(&req->timeout_event); + request_swap_ns(req, nameserver_pick(base)); + evdns_request_transmit(req); + + req->ns->timedout++; + if (req->ns->timedout > req->base->global_max_nameserver_timeout) { + req->ns->timedout = 0; + nameserver_failed(req->ns, "request timed out."); + } + } + + EVDNS_UNLOCK(base); +} + +/* try to send a request to a given server. */ +/* */ +/* return: */ +/* 0 ok */ +/* 1 temporary failure */ +/* 2 other failure */ +static int +evdns_request_transmit_to(struct request *req, struct nameserver *server) { + int r; + ASSERT_LOCKED(req->base); + ASSERT_VALID_REQUEST(req); + + if (server->requests_inflight == 1 && + req->base->disable_when_inactive && + event_add(&server->event, NULL) < 0) { + return 1; + } + + r = sendto(server->socket, (void*)req->request, req->request_len, 0, + (struct sockaddr *)&server->address, server->addrlen); + if (r < 0) { + int err = evutil_socket_geterror(server->socket); + if (EVUTIL_ERR_RW_RETRIABLE(err)) + return 1; + nameserver_failed(req->ns, evutil_socket_error_to_string(err)); + return 2; + } else if (r != (int)req->request_len) { + return 1; /* short write */ + } else { + return 0; + } +} + +/* try to send a request, updating the fields of the request */ +/* as needed */ +/* */ +/* return: */ +/* 0 ok */ +/* 1 failed */ +static int +evdns_request_transmit(struct request *req) { + int retcode = 0, r; + + ASSERT_LOCKED(req->base); + ASSERT_VALID_REQUEST(req); + /* if we fail to send this packet then this flag marks it */ + /* for evdns_transmit */ + req->transmit_me = 1; + EVUTIL_ASSERT(req->trans_id != 0xffff); + + if (!req->ns) + { + /* unable to transmit request if no nameservers */ + return 1; + } + + if (req->ns->choked) { + /* don't bother trying to write to a socket */ + /* which we have had EAGAIN from */ + return 1; + } + + r = evdns_request_transmit_to(req, req->ns); + switch (r) { + case 1: + /* temp failure */ + req->ns->choked = 1; + nameserver_write_waiting(req->ns, 1); + return 1; + case 2: + /* failed to transmit the request entirely. we can fallthrough since + * we'll set a timeout, which will time out, and make us retransmit the + * request anyway. */ + retcode = 1; + EVUTIL_FALLTHROUGH; + default: + /* all ok */ + log(EVDNS_LOG_DEBUG, + "Setting timeout for request %p, sent to nameserver %p", req, req->ns); + if (evtimer_add(&req->timeout_event, &req->base->global_timeout) < 0) { + log(EVDNS_LOG_WARN, + "Error from libevent when adding timer for request %p", + req); + /* ???? Do more? */ + } + req->tx_count++; + req->transmit_me = 0; + return retcode; + } +} + +static void +nameserver_probe_callback(int result, char type, int count, int ttl, void *addresses, void *arg) { + struct nameserver *const ns = (struct nameserver *) arg; + (void) type; + (void) count; + (void) ttl; + (void) addresses; + + if (result == DNS_ERR_CANCEL) { + /* We canceled this request because the nameserver came up + * for some other reason. Do not change our opinion about + * the nameserver. */ + return; + } + + EVDNS_LOCK(ns->base); + ns->probe_request = NULL; + if (result == DNS_ERR_NONE || result == DNS_ERR_NOTEXIST) { + /* this is a good reply */ + nameserver_up(ns); + } else { + nameserver_probe_failed(ns); + } + EVDNS_UNLOCK(ns->base); +} + +static void +nameserver_send_probe(struct nameserver *const ns) { + struct evdns_request *handle; + struct request *req; + char addrbuf[128]; + /* here we need to send a probe to a given nameserver */ + /* in the hope that it is up now. */ + + ASSERT_LOCKED(ns->base); + log(EVDNS_LOG_DEBUG, "Sending probe to %s", + evutil_format_sockaddr_port_( + (struct sockaddr *)&ns->address, + addrbuf, sizeof(addrbuf))); + handle = mm_calloc(1, sizeof(*handle)); + if (!handle) return; + req = request_new(ns->base, handle, TYPE_A, "google.com", DNS_QUERY_NO_SEARCH, nameserver_probe_callback, ns); + if (!req) { + mm_free(handle); + return; + } + ns->probe_request = handle; + /* we force this into the inflight queue no matter what */ + request_trans_id_set(req, transaction_id_pick(ns->base)); + req->ns = ns; + request_submit(req); +} + +/* returns: */ +/* 0 didn't try to transmit anything */ +/* 1 tried to transmit something */ +static int +evdns_transmit(struct evdns_base *base) { + char did_try_to_transmit = 0; + int i; + + ASSERT_LOCKED(base); + for (i = 0; i < base->n_req_heads; ++i) { + if (base->req_heads[i]) { + struct request *const started_at = base->req_heads[i], *req = started_at; + /* first transmit all the requests which are currently waiting */ + do { + if (req->transmit_me) { + did_try_to_transmit = 1; + evdns_request_transmit(req); + } + + req = req->next; + } while (req != started_at); + } + } + + return did_try_to_transmit; +} + +/* exported function */ +int +evdns_base_count_nameservers(struct evdns_base *base) +{ + const struct nameserver *server; + int n = 0; + + EVDNS_LOCK(base); + server = base->server_head; + if (!server) + goto done; + do { + ++n; + server = server->next; + } while (server != base->server_head); +done: + EVDNS_UNLOCK(base); + return n; +} + +int +evdns_count_nameservers(void) +{ + return evdns_base_count_nameservers(current_base); +} + +/* exported function */ +int +evdns_base_clear_nameservers_and_suspend(struct evdns_base *base) +{ + struct nameserver *server, *started_at; + int i; + + EVDNS_LOCK(base); + server = base->server_head; + started_at = base->server_head; + if (!server) { + EVDNS_UNLOCK(base); + return 0; + } + while (1) { + struct nameserver *next = server->next; + (void) event_del(&server->event); + if (evtimer_initialized(&server->timeout_event)) + (void) evtimer_del(&server->timeout_event); + if (server->probe_request) { + evdns_cancel_request(server->base, server->probe_request); + server->probe_request = NULL; + } + if (server->socket >= 0) + evutil_closesocket(server->socket); + mm_free(server); + if (next == started_at) + break; + server = next; + } + base->server_head = NULL; + base->global_good_nameservers = 0; + + for (i = 0; i < base->n_req_heads; ++i) { + struct request *req, *req_started_at; + req = req_started_at = base->req_heads[i]; + while (req) { + struct request *next = req->next; + req->tx_count = req->reissue_count = 0; + req->ns = NULL; + /* ???? What to do about searches? */ + (void) evtimer_del(&req->timeout_event); + req->trans_id = 0; + req->transmit_me = 0; + + base->global_requests_waiting++; + evdns_request_insert(req, &base->req_waiting_head); + /* We want to insert these suspended elements at the front of + * the waiting queue, since they were pending before any of + * the waiting entries were added. This is a circular list, + * so we can just shift the start back by one.*/ + base->req_waiting_head = base->req_waiting_head->prev; + + if (next == req_started_at) + break; + req = next; + } + base->req_heads[i] = NULL; + } + + base->global_requests_inflight = 0; + + EVDNS_UNLOCK(base); + return 0; +} + +int +evdns_clear_nameservers_and_suspend(void) +{ + return evdns_base_clear_nameservers_and_suspend(current_base); +} + + +/* exported function */ +int +evdns_base_resume(struct evdns_base *base) +{ + EVDNS_LOCK(base); + evdns_requests_pump_waiting_queue(base); + EVDNS_UNLOCK(base); + + return 0; +} + +int +evdns_resume(void) +{ + return evdns_base_resume(current_base); +} + +static int +evdns_nameserver_add_impl_(struct evdns_base *base, const struct sockaddr *address, int addrlen) { + /* first check to see if we already have this nameserver */ + + const struct nameserver *server = base->server_head, *const started_at = base->server_head; + struct nameserver *ns; + int err = 0; + char addrbuf[128]; + + ASSERT_LOCKED(base); + if (server) { + do { + if (!evutil_sockaddr_cmp((struct sockaddr*)&server->address, address, 1)) return 3; + server = server->next; + } while (server != started_at); + } + if (addrlen > (int)sizeof(ns->address)) { + log(EVDNS_LOG_DEBUG, "Addrlen %d too long.", (int)addrlen); + return 2; + } + + ns = (struct nameserver *) mm_malloc(sizeof(struct nameserver)); + if (!ns) return -1; + + memset(ns, 0, sizeof(struct nameserver)); + ns->base = base; + + evtimer_assign(&ns->timeout_event, ns->base->event_base, nameserver_prod_callback, ns); + + ns->socket = evutil_socket_(address->sa_family, + SOCK_DGRAM|EVUTIL_SOCK_NONBLOCK|EVUTIL_SOCK_CLOEXEC, 0); + if (ns->socket < 0) { err = 1; goto out1; } + + if (base->global_outgoing_addrlen && + !evutil_sockaddr_is_loopback_(address)) { + if (bind(ns->socket, + (struct sockaddr*)&base->global_outgoing_address, + base->global_outgoing_addrlen) < 0) { + log(EVDNS_LOG_WARN,"Couldn't bind to outgoing address"); + err = 2; + goto out2; + } + } + + if (base->so_rcvbuf) { + if (setsockopt(ns->socket, SOL_SOCKET, SO_RCVBUF, + (void *)&base->so_rcvbuf, sizeof(base->so_rcvbuf))) { + log(EVDNS_LOG_WARN, "Couldn't set SO_RCVBUF to %i", base->so_rcvbuf); + err = -SO_RCVBUF; + goto out2; + } + } + if (base->so_sndbuf) { + if (setsockopt(ns->socket, SOL_SOCKET, SO_SNDBUF, + (void *)&base->so_sndbuf, sizeof(base->so_sndbuf))) { + log(EVDNS_LOG_WARN, "Couldn't set SO_SNDBUF to %i", base->so_sndbuf); + err = -SO_SNDBUF; + goto out2; + } + } + + memcpy(&ns->address, address, addrlen); + ns->addrlen = addrlen; + ns->state = 1; + event_assign(&ns->event, ns->base->event_base, ns->socket, + EV_READ | EV_PERSIST, nameserver_ready_callback, ns); + if (!base->disable_when_inactive && event_add(&ns->event, NULL) < 0) { + err = 2; + goto out2; + } + + log(EVDNS_LOG_DEBUG, "Added nameserver %s as %p", + evutil_format_sockaddr_port_(address, addrbuf, sizeof(addrbuf)), ns); + + /* insert this nameserver into the list of them */ + if (!base->server_head) { + ns->next = ns->prev = ns; + base->server_head = ns; + } else { + ns->next = base->server_head->next; + ns->prev = base->server_head; + base->server_head->next = ns; + ns->next->prev = ns; + } + + base->global_good_nameservers++; + + return 0; + +out2: + evutil_closesocket(ns->socket); +out1: + event_debug_unassign(&ns->event); + mm_free(ns); + log(EVDNS_LOG_WARN, "Unable to add nameserver %s: error %d", + evutil_format_sockaddr_port_(address, addrbuf, sizeof(addrbuf)), err); + return err; +} + +/* exported function */ +int +evdns_base_nameserver_add(struct evdns_base *base, unsigned long int address) +{ + struct sockaddr_in sin; + int res; + memset(&sin, 0, sizeof(sin)); + sin.sin_addr.s_addr = address; + sin.sin_port = htons(53); + sin.sin_family = AF_INET; + EVDNS_LOCK(base); + res = evdns_nameserver_add_impl_(base, (struct sockaddr*)&sin, sizeof(sin)); + EVDNS_UNLOCK(base); + return res; +} + +int +evdns_nameserver_add(unsigned long int address) { + if (!current_base) + current_base = evdns_base_new(NULL, 0); + return evdns_base_nameserver_add(current_base, address); +} + +static void +sockaddr_setport(struct sockaddr *sa, ev_uint16_t port) +{ + if (sa->sa_family == AF_INET) { + ((struct sockaddr_in *)sa)->sin_port = htons(port); + } else if (sa->sa_family == AF_INET6) { + ((struct sockaddr_in6 *)sa)->sin6_port = htons(port); + } +} + +static ev_uint16_t +sockaddr_getport(struct sockaddr *sa) +{ + if (sa->sa_family == AF_INET) { + return ntohs(((struct sockaddr_in *)sa)->sin_port); + } else if (sa->sa_family == AF_INET6) { + return ntohs(((struct sockaddr_in6 *)sa)->sin6_port); + } else { + return 0; + } +} + +/* exported function */ +int +evdns_base_nameserver_ip_add(struct evdns_base *base, const char *ip_as_string) { + struct sockaddr_storage ss; + struct sockaddr *sa; + int len = sizeof(ss); + int res; + if (evutil_parse_sockaddr_port(ip_as_string, (struct sockaddr *)&ss, + &len)) { + log(EVDNS_LOG_WARN, "Unable to parse nameserver address %s", + ip_as_string); + return 4; + } + sa = (struct sockaddr *) &ss; + if (sockaddr_getport(sa) == 0) + sockaddr_setport(sa, 53); + + EVDNS_LOCK(base); + res = evdns_nameserver_add_impl_(base, sa, len); + EVDNS_UNLOCK(base); + return res; +} + +int +evdns_nameserver_ip_add(const char *ip_as_string) { + if (!current_base) + current_base = evdns_base_new(NULL, 0); + return evdns_base_nameserver_ip_add(current_base, ip_as_string); +} + +int +evdns_base_nameserver_sockaddr_add(struct evdns_base *base, + const struct sockaddr *sa, ev_socklen_t len, unsigned flags) +{ + int res; + EVUTIL_ASSERT(base); + EVDNS_LOCK(base); + res = evdns_nameserver_add_impl_(base, sa, len); + EVDNS_UNLOCK(base); + return res; +} + +int +evdns_base_get_nameserver_addr(struct evdns_base *base, int idx, + struct sockaddr *sa, ev_socklen_t len) +{ + int result = -1; + int i; + struct nameserver *server; + EVDNS_LOCK(base); + server = base->server_head; + for (i = 0; i < idx && server; ++i, server = server->next) { + if (server->next == base->server_head) + goto done; + } + if (! server) + goto done; + + if (server->addrlen > len) { + result = (int) server->addrlen; + goto done; + } + + memcpy(sa, &server->address, server->addrlen); + result = (int) server->addrlen; +done: + EVDNS_UNLOCK(base); + return result; +} + +/* remove from the queue */ +static void +evdns_request_remove(struct request *req, struct request **head) +{ + ASSERT_LOCKED(req->base); + ASSERT_VALID_REQUEST(req); + +#if 0 + { + struct request *ptr; + int found = 0; + EVUTIL_ASSERT(*head != NULL); + + ptr = *head; + do { + if (ptr == req) { + found = 1; + break; + } + ptr = ptr->next; + } while (ptr != *head); + EVUTIL_ASSERT(found); + + EVUTIL_ASSERT(req->next); + } +#endif + + if (req->next == req) { + /* only item in the list */ + *head = NULL; + } else { + req->next->prev = req->prev; + req->prev->next = req->next; + if (*head == req) *head = req->next; + } + req->next = req->prev = NULL; +} + +/* insert into the tail of the queue */ +static void +evdns_request_insert(struct request *req, struct request **head) { + ASSERT_LOCKED(req->base); + ASSERT_VALID_REQUEST(req); + if (!*head) { + *head = req; + req->next = req->prev = req; + return; + } + + req->prev = (*head)->prev; + req->prev->next = req; + req->next = *head; + (*head)->prev = req; +} + +static int +string_num_dots(const char *s) { + int count = 0; + while ((s = strchr(s, '.'))) { + s++; + count++; + } + return count; +} + +static struct request * +request_new(struct evdns_base *base, struct evdns_request *handle, int type, + const char *name, int flags, evdns_callback_type callback, + void *user_ptr) { + + const char issuing_now = + (base->global_requests_inflight < base->global_max_requests_inflight) ? 1 : 0; + + const size_t name_len = strlen(name); + const size_t request_max_len = evdns_request_len(name_len); + const u16 trans_id = issuing_now ? transaction_id_pick(base) : 0xffff; + /* the request data is alloced in a single block with the header */ + struct request *const req = + mm_malloc(sizeof(struct request) + request_max_len); + int rlen; + char namebuf[256]; + (void) flags; + + ASSERT_LOCKED(base); + + if (!req) return NULL; + + if (name_len >= sizeof(namebuf)) { + mm_free(req); + return NULL; + } + + memset(req, 0, sizeof(struct request)); + req->base = base; + + evtimer_assign(&req->timeout_event, req->base->event_base, evdns_request_timeout_callback, req); + + if (base->global_randomize_case) { + unsigned i; + char randbits[(sizeof(namebuf)+7)/8]; + strlcpy(namebuf, name, sizeof(namebuf)); + evutil_secure_rng_get_bytes(randbits, (name_len+7)/8); + for (i = 0; i < name_len; ++i) { + if (EVUTIL_ISALPHA_(namebuf[i])) { + if ((randbits[i >> 3] & (1<<(i & 7)))) + namebuf[i] |= 0x20; + else + namebuf[i] &= ~0x20; + } + } + name = namebuf; + } + + /* request data lives just after the header */ + req->request = ((u8 *) req) + sizeof(struct request); + /* denotes that the request data shouldn't be free()ed */ + req->request_appended = 1; + rlen = evdns_request_data_build(name, name_len, trans_id, + type, CLASS_INET, req->request, request_max_len); + if (rlen < 0) + goto err1; + + req->request_len = rlen; + req->trans_id = trans_id; + req->tx_count = 0; + req->request_type = type; + req->user_pointer = user_ptr; + req->user_callback = callback; + req->ns = issuing_now ? nameserver_pick(base) : NULL; + req->next = req->prev = NULL; + req->handle = handle; + if (handle) { + handle->current_req = req; + handle->base = base; + } + + return req; +err1: + mm_free(req); + return NULL; +} + +static void +request_submit(struct request *const req) { + struct evdns_base *base = req->base; + ASSERT_LOCKED(base); + ASSERT_VALID_REQUEST(req); + if (req->ns) { + /* if it has a nameserver assigned then this is going */ + /* straight into the inflight queue */ + evdns_request_insert(req, &REQ_HEAD(base, req->trans_id)); + + base->global_requests_inflight++; + req->ns->requests_inflight++; + + evdns_request_transmit(req); + } else { + evdns_request_insert(req, &base->req_waiting_head); + base->global_requests_waiting++; + } +} + +/* exported function */ +void +evdns_cancel_request(struct evdns_base *base, struct evdns_request *handle) +{ + struct request *req; + + if (!handle->current_req) + return; + + if (!base) { + /* This redundancy is silly; can we fix it? (Not for 2.0) XXXX */ + base = handle->base; + if (!base) + base = handle->current_req->base; + } + + EVDNS_LOCK(base); + if (handle->pending_cb) { + EVDNS_UNLOCK(base); + return; + } + + req = handle->current_req; + ASSERT_VALID_REQUEST(req); + + reply_schedule_callback(req, 0, DNS_ERR_CANCEL, NULL); + if (req->ns) { + /* remove from inflight queue */ + request_finished(req, &REQ_HEAD(base, req->trans_id), 1); + } else { + /* remove from global_waiting head */ + request_finished(req, &base->req_waiting_head, 1); + } + EVDNS_UNLOCK(base); +} + +/* exported function */ +struct evdns_request * +evdns_base_resolve_ipv4(struct evdns_base *base, const char *name, int flags, + evdns_callback_type callback, void *ptr) { + struct evdns_request *handle; + struct request *req; + log(EVDNS_LOG_DEBUG, "Resolve requested for %s", name); + handle = mm_calloc(1, sizeof(*handle)); + if (handle == NULL) + return NULL; + EVDNS_LOCK(base); + if (flags & DNS_QUERY_NO_SEARCH) { + req = + request_new(base, handle, TYPE_A, name, flags, + callback, ptr); + if (req) + request_submit(req); + } else { + search_request_new(base, handle, TYPE_A, name, flags, + callback, ptr); + } + if (handle->current_req == NULL) { + mm_free(handle); + handle = NULL; + } + EVDNS_UNLOCK(base); + return handle; +} + +int evdns_resolve_ipv4(const char *name, int flags, + evdns_callback_type callback, void *ptr) +{ + return evdns_base_resolve_ipv4(current_base, name, flags, callback, ptr) + ? 0 : -1; +} + + +/* exported function */ +struct evdns_request * +evdns_base_resolve_ipv6(struct evdns_base *base, + const char *name, int flags, + evdns_callback_type callback, void *ptr) +{ + struct evdns_request *handle; + struct request *req; + log(EVDNS_LOG_DEBUG, "Resolve requested for %s", name); + handle = mm_calloc(1, sizeof(*handle)); + if (handle == NULL) + return NULL; + EVDNS_LOCK(base); + if (flags & DNS_QUERY_NO_SEARCH) { + req = request_new(base, handle, TYPE_AAAA, name, flags, + callback, ptr); + if (req) + request_submit(req); + } else { + search_request_new(base, handle, TYPE_AAAA, name, flags, + callback, ptr); + } + if (handle->current_req == NULL) { + mm_free(handle); + handle = NULL; + } + EVDNS_UNLOCK(base); + return handle; +} + +int evdns_resolve_ipv6(const char *name, int flags, + evdns_callback_type callback, void *ptr) { + return evdns_base_resolve_ipv6(current_base, name, flags, callback, ptr) + ? 0 : -1; +} + +struct evdns_request * +evdns_base_resolve_reverse(struct evdns_base *base, const struct in_addr *in, int flags, evdns_callback_type callback, void *ptr) { + char buf[32]; + struct evdns_request *handle; + struct request *req; + u32 a; + EVUTIL_ASSERT(in); + a = ntohl(in->s_addr); + evutil_snprintf(buf, sizeof(buf), "%d.%d.%d.%d.in-addr.arpa", + (int)(u8)((a )&0xff), + (int)(u8)((a>>8 )&0xff), + (int)(u8)((a>>16)&0xff), + (int)(u8)((a>>24)&0xff)); + handle = mm_calloc(1, sizeof(*handle)); + if (handle == NULL) + return NULL; + log(EVDNS_LOG_DEBUG, "Resolve requested for %s (reverse)", buf); + EVDNS_LOCK(base); + req = request_new(base, handle, TYPE_PTR, buf, flags, callback, ptr); + if (req) + request_submit(req); + if (handle->current_req == NULL) { + mm_free(handle); + handle = NULL; + } + EVDNS_UNLOCK(base); + return (handle); +} + +int evdns_resolve_reverse(const struct in_addr *in, int flags, evdns_callback_type callback, void *ptr) { + return evdns_base_resolve_reverse(current_base, in, flags, callback, ptr) + ? 0 : -1; +} + +struct evdns_request * +evdns_base_resolve_reverse_ipv6(struct evdns_base *base, const struct in6_addr *in, int flags, evdns_callback_type callback, void *ptr) { + /* 32 nybbles, 32 periods, "ip6.arpa", NUL. */ + char buf[73]; + char *cp; + struct evdns_request *handle; + struct request *req; + int i; + EVUTIL_ASSERT(in); + cp = buf; + for (i=15; i >= 0; --i) { + u8 byte = in->s6_addr[i]; + *cp++ = "0123456789abcdef"[byte & 0x0f]; + *cp++ = '.'; + *cp++ = "0123456789abcdef"[byte >> 4]; + *cp++ = '.'; + } + EVUTIL_ASSERT(cp + strlen("ip6.arpa") < buf+sizeof(buf)); + memcpy(cp, "ip6.arpa", strlen("ip6.arpa")+1); + handle = mm_calloc(1, sizeof(*handle)); + if (handle == NULL) + return NULL; + log(EVDNS_LOG_DEBUG, "Resolve requested for %s (reverse)", buf); + EVDNS_LOCK(base); + req = request_new(base, handle, TYPE_PTR, buf, flags, callback, ptr); + if (req) + request_submit(req); + if (handle->current_req == NULL) { + mm_free(handle); + handle = NULL; + } + EVDNS_UNLOCK(base); + return (handle); +} + +int evdns_resolve_reverse_ipv6(const struct in6_addr *in, int flags, evdns_callback_type callback, void *ptr) { + return evdns_base_resolve_reverse_ipv6(current_base, in, flags, callback, ptr) + ? 0 : -1; +} + +/* ================================================================= */ +/* Search support */ +/* */ +/* the libc resolver has support for searching a number of domains */ +/* to find a name. If nothing else then it takes the single domain */ +/* from the gethostname() call. */ +/* */ +/* It can also be configured via the domain and search options in a */ +/* resolv.conf. */ +/* */ +/* The ndots option controls how many dots it takes for the resolver */ +/* to decide that a name is non-local and so try a raw lookup first. */ + +struct search_domain { + int len; + struct search_domain *next; + /* the text string is appended to this structure */ +}; + +struct search_state { + int refcount; + int ndots; + int num_domains; + struct search_domain *head; +}; + +static void +search_state_decref(struct search_state *const state) { + if (!state) return; + state->refcount--; + if (!state->refcount) { + struct search_domain *next, *dom; + for (dom = state->head; dom; dom = next) { + next = dom->next; + mm_free(dom); + } + mm_free(state); + } +} + +static struct search_state * +search_state_new(void) { + struct search_state *state = (struct search_state *) mm_malloc(sizeof(struct search_state)); + if (!state) return NULL; + memset(state, 0, sizeof(struct search_state)); + state->refcount = 1; + state->ndots = 1; + + return state; +} + +static void +search_postfix_clear(struct evdns_base *base) { + search_state_decref(base->global_search_state); + + base->global_search_state = search_state_new(); +} + +/* exported function */ +void +evdns_base_search_clear(struct evdns_base *base) +{ + EVDNS_LOCK(base); + search_postfix_clear(base); + EVDNS_UNLOCK(base); +} + +void +evdns_search_clear(void) { + evdns_base_search_clear(current_base); +} + +static void +search_postfix_add(struct evdns_base *base, const char *domain) { + size_t domain_len; + struct search_domain *sdomain; + while (domain[0] == '.') domain++; + domain_len = strlen(domain); + + ASSERT_LOCKED(base); + if (!base->global_search_state) base->global_search_state = search_state_new(); + if (!base->global_search_state) return; + base->global_search_state->num_domains++; + + sdomain = (struct search_domain *) mm_malloc(sizeof(struct search_domain) + domain_len); + if (!sdomain) return; + memcpy( ((u8 *) sdomain) + sizeof(struct search_domain), domain, domain_len); + sdomain->next = base->global_search_state->head; + sdomain->len = (int) domain_len; + + base->global_search_state->head = sdomain; +} + +/* reverse the order of members in the postfix list. This is needed because, */ +/* when parsing resolv.conf we push elements in the wrong order */ +static void +search_reverse(struct evdns_base *base) { + struct search_domain *cur, *prev = NULL, *next; + ASSERT_LOCKED(base); + cur = base->global_search_state->head; + while (cur) { + next = cur->next; + cur->next = prev; + prev = cur; + cur = next; + } + + base->global_search_state->head = prev; +} + +/* exported function */ +void +evdns_base_search_add(struct evdns_base *base, const char *domain) { + EVDNS_LOCK(base); + search_postfix_add(base, domain); + EVDNS_UNLOCK(base); +} +void +evdns_search_add(const char *domain) { + evdns_base_search_add(current_base, domain); +} + +/* exported function */ +void +evdns_base_search_ndots_set(struct evdns_base *base, const int ndots) { + EVDNS_LOCK(base); + if (!base->global_search_state) base->global_search_state = search_state_new(); + if (base->global_search_state) + base->global_search_state->ndots = ndots; + EVDNS_UNLOCK(base); +} +void +evdns_search_ndots_set(const int ndots) { + evdns_base_search_ndots_set(current_base, ndots); +} + +static void +search_set_from_hostname(struct evdns_base *base) { + char hostname[HOST_NAME_MAX + 1], *domainname; + + ASSERT_LOCKED(base); + search_postfix_clear(base); + if (gethostname(hostname, sizeof(hostname))) return; + domainname = strchr(hostname, '.'); + if (!domainname) return; + search_postfix_add(base, domainname); +} + +/* warning: returns malloced string */ +static char * +search_make_new(const struct search_state *const state, int n, const char *const base_name) { + const size_t base_len = strlen(base_name); + char need_to_append_dot; + struct search_domain *dom; + + if (!base_len) return NULL; + need_to_append_dot = base_name[base_len - 1] == '.' ? 0 : 1; + + for (dom = state->head; dom; dom = dom->next) { + if (!n--) { + /* this is the postfix we want */ + /* the actual postfix string is kept at the end of the structure */ + const u8 *const postfix = ((u8 *) dom) + sizeof(struct search_domain); + const int postfix_len = dom->len; + char *const newname = (char *) mm_malloc(base_len + need_to_append_dot + postfix_len + 1); + if (!newname) return NULL; + memcpy(newname, base_name, base_len); + if (need_to_append_dot) newname[base_len] = '.'; + memcpy(newname + base_len + need_to_append_dot, postfix, postfix_len); + newname[base_len + need_to_append_dot + postfix_len] = 0; + return newname; + } + } + + /* we ran off the end of the list and still didn't find the requested string */ + EVUTIL_ASSERT(0); + return NULL; /* unreachable; stops warnings in some compilers. */ +} + +static struct request * +search_request_new(struct evdns_base *base, struct evdns_request *handle, + int type, const char *const name, int flags, + evdns_callback_type user_callback, void *user_arg) { + ASSERT_LOCKED(base); + EVUTIL_ASSERT(type == TYPE_A || type == TYPE_AAAA); + EVUTIL_ASSERT(handle->current_req == NULL); + if ( ((flags & DNS_QUERY_NO_SEARCH) == 0) && + base->global_search_state && + base->global_search_state->num_domains) { + /* we have some domains to search */ + struct request *req; + if (string_num_dots(name) >= base->global_search_state->ndots) { + req = request_new(base, handle, type, name, flags, user_callback, user_arg); + if (!req) return NULL; + handle->search_index = -1; + } else { + char *const new_name = search_make_new(base->global_search_state, 0, name); + if (!new_name) return NULL; + req = request_new(base, handle, type, new_name, flags, user_callback, user_arg); + mm_free(new_name); + if (!req) return NULL; + handle->search_index = 0; + } + EVUTIL_ASSERT(handle->search_origname == NULL); + handle->search_origname = mm_strdup(name); + if (handle->search_origname == NULL) { + /* XXX Should we dealloc req? If yes, how? */ + if (req) + mm_free(req); + return NULL; + } + handle->search_state = base->global_search_state; + handle->search_flags = flags; + base->global_search_state->refcount++; + request_submit(req); + return req; + } else { + struct request *const req = request_new(base, handle, type, name, flags, user_callback, user_arg); + if (!req) return NULL; + request_submit(req); + return req; + } +} + +/* this is called when a request has failed to find a name. We need to check */ +/* if it is part of a search and, if so, try the next name in the list */ +/* returns: */ +/* 0 another request has been submitted */ +/* 1 no more requests needed */ +static int +search_try_next(struct evdns_request *const handle) { + struct request *req = handle->current_req; + struct evdns_base *base = req->base; + struct request *newreq; + ASSERT_LOCKED(base); + if (handle->search_state) { + /* it is part of a search */ + char *new_name; + handle->search_index++; + if (handle->search_index >= handle->search_state->num_domains) { + /* no more postfixes to try, however we may need to try */ + /* this name without a postfix */ + if (string_num_dots(handle->search_origname) < handle->search_state->ndots) { + /* yep, we need to try it raw */ + newreq = request_new(base, NULL, req->request_type, handle->search_origname, handle->search_flags, req->user_callback, req->user_pointer); + log(EVDNS_LOG_DEBUG, "Search: trying raw query %s", handle->search_origname); + if (newreq) { + search_request_finished(handle); + goto submit_next; + } + } + return 1; + } + + new_name = search_make_new(handle->search_state, handle->search_index, handle->search_origname); + if (!new_name) return 1; + log(EVDNS_LOG_DEBUG, "Search: now trying %s (%d)", new_name, handle->search_index); + newreq = request_new(base, NULL, req->request_type, new_name, handle->search_flags, req->user_callback, req->user_pointer); + mm_free(new_name); + if (!newreq) return 1; + goto submit_next; + } + return 1; + +submit_next: + request_finished(req, &REQ_HEAD(req->base, req->trans_id), 0); + handle->current_req = newreq; + newreq->handle = handle; + request_submit(newreq); + return 0; +} + +static void +search_request_finished(struct evdns_request *const handle) { + ASSERT_LOCKED(handle->current_req->base); + if (handle->search_state) { + search_state_decref(handle->search_state); + handle->search_state = NULL; + } + if (handle->search_origname) { + mm_free(handle->search_origname); + handle->search_origname = NULL; + } +} + +/* ================================================================= */ +/* Parsing resolv.conf files */ + +static void +evdns_resolv_set_defaults(struct evdns_base *base, int flags) { + int add_default = flags & DNS_OPTION_NAMESERVERS; + if (flags & DNS_OPTION_NAMESERVERS_NO_DEFAULT) + add_default = 0; + + /* if the file isn't found then we assume a local resolver */ + ASSERT_LOCKED(base); + if (flags & DNS_OPTION_SEARCH) + search_set_from_hostname(base); + if (add_default) + evdns_base_nameserver_ip_add(base, "127.0.0.1"); +} + +#ifndef EVENT__HAVE_STRTOK_R +static char * +strtok_r(char *s, const char *delim, char **state) { + char *cp, *start; + start = cp = s ? s : *state; + if (!cp) + return NULL; + while (*cp && !strchr(delim, *cp)) + ++cp; + if (!*cp) { + if (cp == start) + return NULL; + *state = NULL; + return start; + } else { + *cp++ = '\0'; + *state = cp; + return start; + } +} +#endif + +/* helper version of atoi which returns -1 on error */ +static int +strtoint(const char *const str) +{ + char *endptr; + const int r = strtol(str, &endptr, 10); + if (*endptr) return -1; + return r; +} + +/* Parse a number of seconds into a timeval; return -1 on error. */ +static int +evdns_strtotimeval(const char *const str, struct timeval *out) +{ + double d; + char *endptr; + d = strtod(str, &endptr); + if (*endptr) return -1; + if (d < 0) return -1; + out->tv_sec = (int) d; + out->tv_usec = (int) ((d - (int) d)*1000000); + if (out->tv_sec == 0 && out->tv_usec < 1000) /* less than 1 msec */ + return -1; + return 0; +} + +/* helper version of atoi that returns -1 on error and clips to bounds. */ +static int +strtoint_clipped(const char *const str, int min, int max) +{ + int r = strtoint(str); + if (r == -1) + return r; + else if (r<min) + return min; + else if (r>max) + return max; + else + return r; +} + +static int +evdns_base_set_max_requests_inflight(struct evdns_base *base, int maxinflight) +{ + int old_n_heads = base->n_req_heads, n_heads; + struct request **old_heads = base->req_heads, **new_heads, *req; + int i; + + ASSERT_LOCKED(base); + if (maxinflight < 1) + maxinflight = 1; + n_heads = (maxinflight+4) / 5; + EVUTIL_ASSERT(n_heads > 0); + new_heads = mm_calloc(n_heads, sizeof(struct request*)); + if (!new_heads) + return (-1); + if (old_heads) { + for (i = 0; i < old_n_heads; ++i) { + while (old_heads[i]) { + req = old_heads[i]; + evdns_request_remove(req, &old_heads[i]); + evdns_request_insert(req, &new_heads[req->trans_id % n_heads]); + } + } + mm_free(old_heads); + } + base->req_heads = new_heads; + base->n_req_heads = n_heads; + base->global_max_requests_inflight = maxinflight; + return (0); +} + +/* exported function */ +int +evdns_base_set_option(struct evdns_base *base, + const char *option, const char *val) +{ + int res; + EVDNS_LOCK(base); + res = evdns_base_set_option_impl(base, option, val, DNS_OPTIONS_ALL); + EVDNS_UNLOCK(base); + return res; +} + +static inline int +str_matches_option(const char *s1, const char *optionname) +{ + /* Option names are given as "option:" We accept either 'option' in + * s1, or 'option:randomjunk'. The latter form is to implement the + * resolv.conf parser. */ + size_t optlen = strlen(optionname); + size_t slen = strlen(s1); + if (slen == optlen || slen == optlen - 1) + return !strncmp(s1, optionname, slen); + else if (slen > optlen) + return !strncmp(s1, optionname, optlen); + else + return 0; +} + +static int +evdns_base_set_option_impl(struct evdns_base *base, + const char *option, const char *val, int flags) +{ + ASSERT_LOCKED(base); + if (str_matches_option(option, "ndots:")) { + const int ndots = strtoint(val); + if (ndots == -1) return -1; + if (!(flags & DNS_OPTION_SEARCH)) return 0; + log(EVDNS_LOG_DEBUG, "Setting ndots to %d", ndots); + if (!base->global_search_state) base->global_search_state = search_state_new(); + if (!base->global_search_state) return -1; + base->global_search_state->ndots = ndots; + } else if (str_matches_option(option, "timeout:")) { + struct timeval tv; + if (evdns_strtotimeval(val, &tv) == -1) return -1; + if (!(flags & DNS_OPTION_MISC)) return 0; + log(EVDNS_LOG_DEBUG, "Setting timeout to %s", val); + memcpy(&base->global_timeout, &tv, sizeof(struct timeval)); + } else if (str_matches_option(option, "getaddrinfo-allow-skew:")) { + struct timeval tv; + if (evdns_strtotimeval(val, &tv) == -1) return -1; + if (!(flags & DNS_OPTION_MISC)) return 0; + log(EVDNS_LOG_DEBUG, "Setting getaddrinfo-allow-skew to %s", + val); + memcpy(&base->global_getaddrinfo_allow_skew, &tv, + sizeof(struct timeval)); + } else if (str_matches_option(option, "max-timeouts:")) { + const int maxtimeout = strtoint_clipped(val, 1, 255); + if (maxtimeout == -1) return -1; + if (!(flags & DNS_OPTION_MISC)) return 0; + log(EVDNS_LOG_DEBUG, "Setting maximum allowed timeouts to %d", + maxtimeout); + base->global_max_nameserver_timeout = maxtimeout; + } else if (str_matches_option(option, "max-inflight:")) { + const int maxinflight = strtoint_clipped(val, 1, 65000); + if (maxinflight == -1) return -1; + if (!(flags & DNS_OPTION_MISC)) return 0; + log(EVDNS_LOG_DEBUG, "Setting maximum inflight requests to %d", + maxinflight); + evdns_base_set_max_requests_inflight(base, maxinflight); + } else if (str_matches_option(option, "attempts:")) { + int retries = strtoint(val); + if (retries == -1) return -1; + if (retries > 255) retries = 255; + if (!(flags & DNS_OPTION_MISC)) return 0; + log(EVDNS_LOG_DEBUG, "Setting retries to %d", retries); + base->global_max_retransmits = retries; + } else if (str_matches_option(option, "randomize-case:")) { + int randcase = strtoint(val); + if (randcase == -1) return -1; + if (!(flags & DNS_OPTION_MISC)) return 0; + base->global_randomize_case = randcase; + } else if (str_matches_option(option, "bind-to:")) { + /* XXX This only applies to successive nameservers, not + * to already-configured ones. We might want to fix that. */ + int len = sizeof(base->global_outgoing_address); + if (!(flags & DNS_OPTION_NAMESERVERS)) return 0; + if (evutil_parse_sockaddr_port(val, + (struct sockaddr*)&base->global_outgoing_address, &len)) + return -1; + base->global_outgoing_addrlen = len; + } else if (str_matches_option(option, "initial-probe-timeout:")) { + struct timeval tv; + if (evdns_strtotimeval(val, &tv) == -1) return -1; + if (tv.tv_sec > 3600) + tv.tv_sec = 3600; + if (!(flags & DNS_OPTION_MISC)) return 0; + log(EVDNS_LOG_DEBUG, "Setting initial probe timeout to %s", + val); + memcpy(&base->global_nameserver_probe_initial_timeout, &tv, + sizeof(tv)); + } else if (str_matches_option(option, "so-rcvbuf:")) { + int buf = strtoint(val); + if (buf == -1) return -1; + if (!(flags & DNS_OPTION_MISC)) return 0; + log(EVDNS_LOG_DEBUG, "Setting SO_RCVBUF to %s", val); + base->so_rcvbuf = buf; + } else if (str_matches_option(option, "so-sndbuf:")) { + int buf = strtoint(val); + if (buf == -1) return -1; + if (!(flags & DNS_OPTION_MISC)) return 0; + log(EVDNS_LOG_DEBUG, "Setting SO_SNDBUF to %s", val); + base->so_sndbuf = buf; + } + return 0; +} + +int +evdns_set_option(const char *option, const char *val, int flags) +{ + if (!current_base) + current_base = evdns_base_new(NULL, 0); + return evdns_base_set_option(current_base, option, val); +} + +static void +resolv_conf_parse_line(struct evdns_base *base, char *const start, int flags) { + char *strtok_state; + static const char *const delims = " \t"; +#define NEXT_TOKEN strtok_r(NULL, delims, &strtok_state) + + + char *const first_token = strtok_r(start, delims, &strtok_state); + ASSERT_LOCKED(base); + if (!first_token) return; + + if (!strcmp(first_token, "nameserver") && (flags & DNS_OPTION_NAMESERVERS)) { + const char *const nameserver = NEXT_TOKEN; + + if (nameserver) + evdns_base_nameserver_ip_add(base, nameserver); + } else if (!strcmp(first_token, "domain") && (flags & DNS_OPTION_SEARCH)) { + const char *const domain = NEXT_TOKEN; + if (domain) { + search_postfix_clear(base); + search_postfix_add(base, domain); + } + } else if (!strcmp(first_token, "search") && (flags & DNS_OPTION_SEARCH)) { + const char *domain; + search_postfix_clear(base); + + while ((domain = NEXT_TOKEN)) { + search_postfix_add(base, domain); + } + search_reverse(base); + } else if (!strcmp(first_token, "options")) { + const char *option; + while ((option = NEXT_TOKEN)) { + const char *val = strchr(option, ':'); + evdns_base_set_option_impl(base, option, val ? val+1 : "", flags); + } + } +#undef NEXT_TOKEN +} + +/* exported function */ +/* returns: */ +/* 0 no errors */ +/* 1 failed to open file */ +/* 2 failed to stat file */ +/* 3 file too large */ +/* 4 out of memory */ +/* 5 short read from file */ +int +evdns_base_resolv_conf_parse(struct evdns_base *base, int flags, const char *const filename) { + int res; + EVDNS_LOCK(base); + res = evdns_base_resolv_conf_parse_impl(base, flags, filename); + EVDNS_UNLOCK(base); + return res; +} + +static char * +evdns_get_default_hosts_filename(void) +{ +#ifdef _WIN32 + /* Windows is a little coy about where it puts its configuration + * files. Sure, they're _usually_ in C:\windows\system32, but + * there's no reason in principle they couldn't be in + * W:\hoboken chicken emergency\ + */ + char path[MAX_PATH+1]; + static const char hostfile[] = "\\drivers\\etc\\hosts"; + char *path_out; + size_t len_out; + + if (! SHGetSpecialFolderPathA(NULL, path, CSIDL_SYSTEM, 0)) + return NULL; + len_out = strlen(path)+strlen(hostfile)+1; + path_out = mm_malloc(len_out); + evutil_snprintf(path_out, len_out, "%s%s", path, hostfile); + return path_out; +#else + return mm_strdup("/etc/hosts"); +#endif +} + +static int +evdns_base_resolv_conf_parse_impl(struct evdns_base *base, int flags, const char *const filename) { + size_t n; + char *resolv; + char *start; + int err = 0; + int add_default; + + log(EVDNS_LOG_DEBUG, "Parsing resolv.conf file %s", filename); + + add_default = flags & DNS_OPTION_NAMESERVERS; + if (flags & DNS_OPTION_NAMESERVERS_NO_DEFAULT) + add_default = 0; + + if (flags & DNS_OPTION_HOSTSFILE) { + char *fname = evdns_get_default_hosts_filename(); + evdns_base_load_hosts(base, fname); + if (fname) + mm_free(fname); + } + + if (!filename) { + evdns_resolv_set_defaults(base, flags); + return 1; + } + + if ((err = evutil_read_file_(filename, &resolv, &n, 0)) < 0) { + if (err == -1) { + /* No file. */ + evdns_resolv_set_defaults(base, flags); + return 1; + } else { + return 2; + } + } + + start = resolv; + for (;;) { + char *const newline = strchr(start, '\n'); + if (!newline) { + resolv_conf_parse_line(base, start, flags); + break; + } else { + *newline = 0; + resolv_conf_parse_line(base, start, flags); + start = newline + 1; + } + } + + if (!base->server_head && add_default) { + /* no nameservers were configured. */ + evdns_base_nameserver_ip_add(base, "127.0.0.1"); + err = 6; + } + if (flags & DNS_OPTION_SEARCH && (!base->global_search_state || base->global_search_state->num_domains == 0)) { + search_set_from_hostname(base); + } + + mm_free(resolv); + return err; +} + +int +evdns_resolv_conf_parse(int flags, const char *const filename) { + if (!current_base) + current_base = evdns_base_new(NULL, 0); + return evdns_base_resolv_conf_parse(current_base, flags, filename); +} + + +#ifdef _WIN32 +/* Add multiple nameservers from a space-or-comma-separated list. */ +static int +evdns_nameserver_ip_add_line(struct evdns_base *base, const char *ips) { + const char *addr; + char *buf; + int r; + ASSERT_LOCKED(base); + while (*ips) { + while (isspace(*ips) || *ips == ',' || *ips == '\t') + ++ips; + addr = ips; + while (isdigit(*ips) || *ips == '.' || *ips == ':' || + *ips=='[' || *ips==']') + ++ips; + buf = mm_malloc(ips-addr+1); + if (!buf) return 4; + memcpy(buf, addr, ips-addr); + buf[ips-addr] = '\0'; + r = evdns_base_nameserver_ip_add(base, buf); + mm_free(buf); + if (r) return r; + } + return 0; +} + +typedef DWORD(WINAPI *GetNetworkParams_fn_t)(FIXED_INFO *, DWORD*); + +/* Use the windows GetNetworkParams interface in iphlpapi.dll to */ +/* figure out what our nameservers are. */ +static int +load_nameservers_with_getnetworkparams(struct evdns_base *base) +{ + /* Based on MSDN examples and inspection of c-ares code. */ + FIXED_INFO *fixed; + HMODULE handle = 0; + ULONG size = sizeof(FIXED_INFO); + void *buf = NULL; + int status = 0, r, added_any; + IP_ADDR_STRING *ns; + GetNetworkParams_fn_t fn; + + ASSERT_LOCKED(base); + if (!(handle = evutil_load_windows_system_library_( + TEXT("iphlpapi.dll")))) { + log(EVDNS_LOG_WARN, "Could not open iphlpapi.dll"); + status = -1; + goto done; + } + if (!(fn = (GetNetworkParams_fn_t) GetProcAddress(handle, "GetNetworkParams"))) { + log(EVDNS_LOG_WARN, "Could not get address of function."); + status = -1; + goto done; + } + + buf = mm_malloc(size); + if (!buf) { status = 4; goto done; } + fixed = buf; + r = fn(fixed, &size); + if (r != ERROR_SUCCESS && r != ERROR_BUFFER_OVERFLOW) { + status = -1; + goto done; + } + if (r != ERROR_SUCCESS) { + mm_free(buf); + buf = mm_malloc(size); + if (!buf) { status = 4; goto done; } + fixed = buf; + r = fn(fixed, &size); + if (r != ERROR_SUCCESS) { + log(EVDNS_LOG_DEBUG, "fn() failed."); + status = -1; + goto done; + } + } + + EVUTIL_ASSERT(fixed); + added_any = 0; + ns = &(fixed->DnsServerList); + while (ns) { + r = evdns_nameserver_ip_add_line(base, ns->IpAddress.String); + if (r) { + log(EVDNS_LOG_DEBUG,"Could not add nameserver %s to list,error: %d", + (ns->IpAddress.String),(int)GetLastError()); + status = r; + } else { + ++added_any; + log(EVDNS_LOG_DEBUG,"Successfully added %s as nameserver",ns->IpAddress.String); + } + + ns = ns->Next; + } + + if (!added_any) { + log(EVDNS_LOG_DEBUG, "No nameservers added."); + if (status == 0) + status = -1; + } else { + status = 0; + } + + done: + if (buf) + mm_free(buf); + if (handle) + FreeLibrary(handle); + return status; +} + +static int +config_nameserver_from_reg_key(struct evdns_base *base, HKEY key, const TCHAR *subkey) +{ + char *buf; + DWORD bufsz = 0, type = 0; + int status = 0; + + ASSERT_LOCKED(base); + if (RegQueryValueEx(key, subkey, 0, &type, NULL, &bufsz) + != ERROR_MORE_DATA) + return -1; + if (!(buf = mm_malloc(bufsz))) + return -1; + + if (RegQueryValueEx(key, subkey, 0, &type, (LPBYTE)buf, &bufsz) + == ERROR_SUCCESS && bufsz > 1) { + status = evdns_nameserver_ip_add_line(base,buf); + } + + mm_free(buf); + return status; +} + +#define SERVICES_KEY TEXT("System\\CurrentControlSet\\Services\\") +#define WIN_NS_9X_KEY SERVICES_KEY TEXT("VxD\\MSTCP") +#define WIN_NS_NT_KEY SERVICES_KEY TEXT("Tcpip\\Parameters") + +static int +load_nameservers_from_registry(struct evdns_base *base) +{ + int found = 0; + int r; +#define TRY(k, name) \ + if (!found && config_nameserver_from_reg_key(base,k,TEXT(name)) == 0) { \ + log(EVDNS_LOG_DEBUG,"Found nameservers in %s/%s",#k,name); \ + found = 1; \ + } else if (!found) { \ + log(EVDNS_LOG_DEBUG,"Didn't find nameservers in %s/%s", \ + #k,#name); \ + } + + ASSERT_LOCKED(base); + + if (((int)GetVersion()) > 0) { /* NT */ + HKEY nt_key = 0, interfaces_key = 0; + + if (RegOpenKeyEx(HKEY_LOCAL_MACHINE, WIN_NS_NT_KEY, 0, + KEY_READ, &nt_key) != ERROR_SUCCESS) { + log(EVDNS_LOG_DEBUG,"Couldn't open nt key, %d",(int)GetLastError()); + return -1; + } + r = RegOpenKeyEx(nt_key, TEXT("Interfaces"), 0, + KEY_QUERY_VALUE|KEY_ENUMERATE_SUB_KEYS, + &interfaces_key); + if (r != ERROR_SUCCESS) { + log(EVDNS_LOG_DEBUG,"Couldn't open interfaces key, %d",(int)GetLastError()); + return -1; + } + TRY(nt_key, "NameServer"); + TRY(nt_key, "DhcpNameServer"); + TRY(interfaces_key, "NameServer"); + TRY(interfaces_key, "DhcpNameServer"); + RegCloseKey(interfaces_key); + RegCloseKey(nt_key); + } else { + HKEY win_key = 0; + if (RegOpenKeyEx(HKEY_LOCAL_MACHINE, WIN_NS_9X_KEY, 0, + KEY_READ, &win_key) != ERROR_SUCCESS) { + log(EVDNS_LOG_DEBUG, "Couldn't open registry key, %d", (int)GetLastError()); + return -1; + } + TRY(win_key, "NameServer"); + RegCloseKey(win_key); + } + + if (found == 0) { + log(EVDNS_LOG_WARN,"Didn't find any nameservers."); + } + + return found ? 0 : -1; +#undef TRY +} + +int +evdns_base_config_windows_nameservers(struct evdns_base *base) +{ + int r; + char *fname; + if (base == NULL) + base = current_base; + if (base == NULL) + return -1; + EVDNS_LOCK(base); + fname = evdns_get_default_hosts_filename(); + log(EVDNS_LOG_DEBUG, "Loading hosts entries from %s", fname); + evdns_base_load_hosts(base, fname); + if (fname) + mm_free(fname); + + if (load_nameservers_with_getnetworkparams(base) == 0) { + EVDNS_UNLOCK(base); + return 0; + } + r = load_nameservers_from_registry(base); + + EVDNS_UNLOCK(base); + return r; +} + +int +evdns_config_windows_nameservers(void) +{ + if (!current_base) { + current_base = evdns_base_new(NULL, 1); + return current_base == NULL ? -1 : 0; + } else { + return evdns_base_config_windows_nameservers(current_base); + } +} +#endif + +struct evdns_base * +evdns_base_new(struct event_base *event_base, int flags) +{ + struct evdns_base *base; + + if (evutil_secure_rng_init() < 0) { + log(EVDNS_LOG_WARN, "Unable to seed random number generator; " + "DNS can't run."); + return NULL; + } + + /* Give the evutil library a hook into its evdns-enabled + * functionality. We can't just call evdns_getaddrinfo directly or + * else libevent-core will depend on libevent-extras. */ + evutil_set_evdns_getaddrinfo_fn_(evdns_getaddrinfo); + evutil_set_evdns_getaddrinfo_cancel_fn_(evdns_getaddrinfo_cancel); + + base = mm_malloc(sizeof(struct evdns_base)); + if (base == NULL) + return (NULL); + memset(base, 0, sizeof(struct evdns_base)); + base->req_waiting_head = NULL; + + EVTHREAD_ALLOC_LOCK(base->lock, EVTHREAD_LOCKTYPE_RECURSIVE); + EVDNS_LOCK(base); + + /* Set max requests inflight and allocate req_heads. */ + base->req_heads = NULL; + + evdns_base_set_max_requests_inflight(base, 64); + + base->server_head = NULL; + base->event_base = event_base; + base->global_good_nameservers = base->global_requests_inflight = + base->global_requests_waiting = 0; + + base->global_timeout.tv_sec = 5; + base->global_timeout.tv_usec = 0; + base->global_max_reissues = 1; + base->global_max_retransmits = 3; + base->global_max_nameserver_timeout = 3; + base->global_search_state = NULL; + base->global_randomize_case = 1; + base->global_getaddrinfo_allow_skew.tv_sec = 3; + base->global_getaddrinfo_allow_skew.tv_usec = 0; + base->global_nameserver_probe_initial_timeout.tv_sec = 10; + base->global_nameserver_probe_initial_timeout.tv_usec = 0; + + TAILQ_INIT(&base->hostsdb); + +#define EVDNS_BASE_ALL_FLAGS ( \ + EVDNS_BASE_INITIALIZE_NAMESERVERS | \ + EVDNS_BASE_DISABLE_WHEN_INACTIVE | \ + EVDNS_BASE_NAMESERVERS_NO_DEFAULT | \ + 0) + + if (flags & ~EVDNS_BASE_ALL_FLAGS) { + flags = EVDNS_BASE_INITIALIZE_NAMESERVERS; + log(EVDNS_LOG_WARN, + "Unrecognized flag passed to evdns_base_new(). Assuming " + "you meant EVDNS_BASE_INITIALIZE_NAMESERVERS."); + } +#undef EVDNS_BASE_ALL_FLAGS + + if (flags & EVDNS_BASE_INITIALIZE_NAMESERVERS) { + int r; + int opts = DNS_OPTIONS_ALL; + if (flags & EVDNS_BASE_NAMESERVERS_NO_DEFAULT) { + opts |= DNS_OPTION_NAMESERVERS_NO_DEFAULT; + } + +#ifdef _WIN32 + r = evdns_base_config_windows_nameservers(base); +#else + r = evdns_base_resolv_conf_parse(base, opts, "/etc/resolv.conf"); +#endif + if (r) { + evdns_base_free_and_unlock(base, 0); + return NULL; + } + } + if (flags & EVDNS_BASE_DISABLE_WHEN_INACTIVE) { + base->disable_when_inactive = 1; + } + + EVDNS_UNLOCK(base); + return base; +} + +int +evdns_init(void) +{ + struct evdns_base *base = evdns_base_new(NULL, 1); + if (base) { + current_base = base; + return 0; + } else { + return -1; + } +} + +const char * +evdns_err_to_string(int err) +{ + switch (err) { + case DNS_ERR_NONE: return "no error"; + case DNS_ERR_FORMAT: return "misformatted query"; + case DNS_ERR_SERVERFAILED: return "server failed"; + case DNS_ERR_NOTEXIST: return "name does not exist"; + case DNS_ERR_NOTIMPL: return "query not implemented"; + case DNS_ERR_REFUSED: return "refused"; + + case DNS_ERR_TRUNCATED: return "reply truncated or ill-formed"; + case DNS_ERR_UNKNOWN: return "unknown"; + case DNS_ERR_TIMEOUT: return "request timed out"; + case DNS_ERR_SHUTDOWN: return "dns subsystem shut down"; + case DNS_ERR_CANCEL: return "dns request canceled"; + case DNS_ERR_NODATA: return "no records in the reply"; + default: return "[Unknown error code]"; + } +} + +static void +evdns_nameserver_free(struct nameserver *server) +{ + if (server->socket >= 0) + evutil_closesocket(server->socket); + (void) event_del(&server->event); + event_debug_unassign(&server->event); + if (server->state == 0) + (void) event_del(&server->timeout_event); + if (server->probe_request) { + evdns_cancel_request(server->base, server->probe_request); + server->probe_request = NULL; + } + event_debug_unassign(&server->timeout_event); + mm_free(server); +} + +static void +evdns_base_free_and_unlock(struct evdns_base *base, int fail_requests) +{ + struct nameserver *server, *server_next; + struct search_domain *dom, *dom_next; + int i; + + /* Requires that we hold the lock. */ + + /* TODO(nickm) we might need to refcount here. */ + + while (base->req_waiting_head) { + if (fail_requests) + reply_schedule_callback(base->req_waiting_head, 0, DNS_ERR_SHUTDOWN, NULL); + request_finished(base->req_waiting_head, &base->req_waiting_head, 1); + } + for (i = 0; i < base->n_req_heads; ++i) { + while (base->req_heads[i]) { + if (fail_requests) + reply_schedule_callback(base->req_heads[i], 0, DNS_ERR_SHUTDOWN, NULL); + request_finished(base->req_heads[i], &REQ_HEAD(base, base->req_heads[i]->trans_id), 1); + } + } + base->global_requests_inflight = base->global_requests_waiting = 0; + + for (server = base->server_head; server; server = server_next) { + server_next = server->next; + /** already done something before */ + server->probe_request = NULL; + evdns_nameserver_free(server); + if (server_next == base->server_head) + break; + } + base->server_head = NULL; + base->global_good_nameservers = 0; + + if (base->global_search_state) { + for (dom = base->global_search_state->head; dom; dom = dom_next) { + dom_next = dom->next; + mm_free(dom); + } + mm_free(base->global_search_state); + base->global_search_state = NULL; + } + + { + struct hosts_entry *victim; + while ((victim = TAILQ_FIRST(&base->hostsdb))) { + TAILQ_REMOVE(&base->hostsdb, victim, next); + mm_free(victim); + } + } + + mm_free(base->req_heads); + + EVDNS_UNLOCK(base); + EVTHREAD_FREE_LOCK(base->lock, EVTHREAD_LOCKTYPE_RECURSIVE); + + mm_free(base); +} + +void +evdns_base_free(struct evdns_base *base, int fail_requests) +{ + EVDNS_LOCK(base); + evdns_base_free_and_unlock(base, fail_requests); +} + +void +evdns_base_clear_host_addresses(struct evdns_base *base) +{ + struct hosts_entry *victim; + EVDNS_LOCK(base); + while ((victim = TAILQ_FIRST(&base->hostsdb))) { + TAILQ_REMOVE(&base->hostsdb, victim, next); + mm_free(victim); + } + EVDNS_UNLOCK(base); +} + +void +evdns_shutdown(int fail_requests) +{ + if (current_base) { + struct evdns_base *b = current_base; + current_base = NULL; + evdns_base_free(b, fail_requests); + } + evdns_log_fn = NULL; +} + +static int +evdns_base_parse_hosts_line(struct evdns_base *base, char *line) +{ + char *strtok_state; + static const char *const delims = " \t"; + char *const addr = strtok_r(line, delims, &strtok_state); + char *hostname, *hash; + struct sockaddr_storage ss; + int socklen = sizeof(ss); + ASSERT_LOCKED(base); + +#define NEXT_TOKEN strtok_r(NULL, delims, &strtok_state) + + if (!addr || *addr == '#') + return 0; + + memset(&ss, 0, sizeof(ss)); + if (evutil_parse_sockaddr_port(addr, (struct sockaddr*)&ss, &socklen)<0) + return -1; + if (socklen > (int)sizeof(struct sockaddr_in6)) + return -1; + + if (sockaddr_getport((struct sockaddr*)&ss)) + return -1; + + while ((hostname = NEXT_TOKEN)) { + struct hosts_entry *he; + size_t namelen; + if ((hash = strchr(hostname, '#'))) { + if (hash == hostname) + return 0; + *hash = '\0'; + } + + namelen = strlen(hostname); + + he = mm_calloc(1, sizeof(struct hosts_entry)+namelen); + if (!he) + return -1; + EVUTIL_ASSERT(socklen <= (int)sizeof(he->addr)); + memcpy(&he->addr, &ss, socklen); + memcpy(he->hostname, hostname, namelen+1); + he->addrlen = socklen; + + TAILQ_INSERT_TAIL(&base->hostsdb, he, next); + + if (hash) + return 0; + } + + return 0; +#undef NEXT_TOKEN +} + +static int +evdns_base_load_hosts_impl(struct evdns_base *base, const char *hosts_fname) +{ + char *str=NULL, *cp, *eol; + size_t len; + int err=0; + + ASSERT_LOCKED(base); + + if (hosts_fname == NULL || + (err = evutil_read_file_(hosts_fname, &str, &len, 0)) < 0) { + char tmp[64]; + strlcpy(tmp, "127.0.0.1 localhost", sizeof(tmp)); + evdns_base_parse_hosts_line(base, tmp); + strlcpy(tmp, "::1 localhost", sizeof(tmp)); + evdns_base_parse_hosts_line(base, tmp); + return err ? -1 : 0; + } + + /* This will break early if there is a NUL in the hosts file. + * Probably not a problem.*/ + cp = str; + for (;;) { + eol = strchr(cp, '\n'); + + if (eol) { + *eol = '\0'; + evdns_base_parse_hosts_line(base, cp); + cp = eol+1; + } else { + evdns_base_parse_hosts_line(base, cp); + break; + } + } + + mm_free(str); + return 0; +} + +int +evdns_base_load_hosts(struct evdns_base *base, const char *hosts_fname) +{ + int res; + if (!base) + base = current_base; + EVDNS_LOCK(base); + res = evdns_base_load_hosts_impl(base, hosts_fname); + EVDNS_UNLOCK(base); + return res; +} + +/* A single request for a getaddrinfo, either v4 or v6. */ +struct getaddrinfo_subrequest { + struct evdns_request *r; + ev_uint32_t type; +}; + +/* State data used to implement an in-progress getaddrinfo. */ +struct evdns_getaddrinfo_request { + struct evdns_base *evdns_base; + /* Copy of the modified 'hints' data that we'll use to build + * answers. */ + struct evutil_addrinfo hints; + /* The callback to invoke when we're done */ + evdns_getaddrinfo_cb user_cb; + /* User-supplied data to give to the callback. */ + void *user_data; + /* The port to use when building sockaddrs. */ + ev_uint16_t port; + /* The sub_request for an A record (if any) */ + struct getaddrinfo_subrequest ipv4_request; + /* The sub_request for an AAAA record (if any) */ + struct getaddrinfo_subrequest ipv6_request; + + /* The cname result that we were told (if any) */ + char *cname_result; + + /* If we have one request answered and one request still inflight, + * then this field holds the answer from the first request... */ + struct evutil_addrinfo *pending_result; + /* And this event is a timeout that will tell us to cancel the second + * request if it's taking a long time. */ + struct event timeout; + + /* And this field holds the error code from the first request... */ + int pending_error; + /* If this is set, the user canceled this request. */ + unsigned user_canceled : 1; + /* If this is set, the user can no longer cancel this request; we're + * just waiting for the free. */ + unsigned request_done : 1; +}; + +/* Convert an evdns errors to the equivalent getaddrinfo error. */ +static int +evdns_err_to_getaddrinfo_err(int e1) +{ + /* XXX Do this better! */ + if (e1 == DNS_ERR_NONE) + return 0; + else if (e1 == DNS_ERR_NOTEXIST) + return EVUTIL_EAI_NONAME; + else + return EVUTIL_EAI_FAIL; +} + +/* Return the more informative of two getaddrinfo errors. */ +static int +getaddrinfo_merge_err(int e1, int e2) +{ + /* XXXX be cleverer here. */ + if (e1 == 0) + return e2; + else + return e1; +} + +static void +free_getaddrinfo_request(struct evdns_getaddrinfo_request *data) +{ + /* DO NOT CALL this if either of the requests is pending. Only once + * both callbacks have been invoked is it safe to free the request */ + if (data->pending_result) + evutil_freeaddrinfo(data->pending_result); + if (data->cname_result) + mm_free(data->cname_result); + event_del(&data->timeout); + mm_free(data); + return; +} + +static void +add_cname_to_reply(struct evdns_getaddrinfo_request *data, + struct evutil_addrinfo *ai) +{ + if (data->cname_result && ai) { + ai->ai_canonname = data->cname_result; + data->cname_result = NULL; + } +} + +/* Callback: invoked when one request in a mixed-format A/AAAA getaddrinfo + * request has finished, but the other one took too long to answer. Pass + * along the answer we got, and cancel the other request. + */ +static void +evdns_getaddrinfo_timeout_cb(evutil_socket_t fd, short what, void *ptr) +{ + int v4_timedout = 0, v6_timedout = 0; + struct evdns_getaddrinfo_request *data = ptr; + + /* Cancel any pending requests, and note which one */ + if (data->ipv4_request.r) { + /* XXXX This does nothing if the request's callback is already + * running (pending_cb is set). */ + evdns_cancel_request(NULL, data->ipv4_request.r); + v4_timedout = 1; + EVDNS_LOCK(data->evdns_base); + ++data->evdns_base->getaddrinfo_ipv4_timeouts; + EVDNS_UNLOCK(data->evdns_base); + } + if (data->ipv6_request.r) { + /* XXXX This does nothing if the request's callback is already + * running (pending_cb is set). */ + evdns_cancel_request(NULL, data->ipv6_request.r); + v6_timedout = 1; + EVDNS_LOCK(data->evdns_base); + ++data->evdns_base->getaddrinfo_ipv6_timeouts; + EVDNS_UNLOCK(data->evdns_base); + } + + /* We only use this timeout callback when we have an answer for + * one address. */ + EVUTIL_ASSERT(!v4_timedout || !v6_timedout); + + /* Report the outcome of the other request that didn't time out. */ + if (data->pending_result) { + add_cname_to_reply(data, data->pending_result); + data->user_cb(0, data->pending_result, data->user_data); + data->pending_result = NULL; + } else { + int e = data->pending_error; + if (!e) + e = EVUTIL_EAI_AGAIN; + data->user_cb(e, NULL, data->user_data); + } + + data->user_cb = NULL; /* prevent double-call if evdns callbacks are + * in-progress. XXXX It would be better if this + * weren't necessary. */ + + if (!v4_timedout && !v6_timedout) { + /* should be impossible? XXXX */ + free_getaddrinfo_request(data); + } +} + +static int +evdns_getaddrinfo_set_timeout(struct evdns_base *evdns_base, + struct evdns_getaddrinfo_request *data) +{ + return event_add(&data->timeout, &evdns_base->global_getaddrinfo_allow_skew); +} + +static inline int +evdns_result_is_answer(int result) +{ + return (result != DNS_ERR_NOTIMPL && result != DNS_ERR_REFUSED && + result != DNS_ERR_SERVERFAILED && result != DNS_ERR_CANCEL); +} + +static void +evdns_getaddrinfo_gotresolve(int result, char type, int count, + int ttl, void *addresses, void *arg) +{ + int i; + struct getaddrinfo_subrequest *req = arg; + struct getaddrinfo_subrequest *other_req; + struct evdns_getaddrinfo_request *data; + + struct evutil_addrinfo *res; + + struct sockaddr_in sin; + struct sockaddr_in6 sin6; + struct sockaddr *sa; + int socklen, addrlen; + void *addrp; + int err; + int user_canceled; + + EVUTIL_ASSERT(req->type == DNS_IPv4_A || req->type == DNS_IPv6_AAAA); + if (req->type == DNS_IPv4_A) { + data = EVUTIL_UPCAST(req, struct evdns_getaddrinfo_request, ipv4_request); + other_req = &data->ipv6_request; + } else { + data = EVUTIL_UPCAST(req, struct evdns_getaddrinfo_request, ipv6_request); + other_req = &data->ipv4_request; + } + + /** Called from evdns_base_free() with @fail_requests == 1 */ + if (result != DNS_ERR_SHUTDOWN) { + EVDNS_LOCK(data->evdns_base); + if (evdns_result_is_answer(result)) { + if (req->type == DNS_IPv4_A) + ++data->evdns_base->getaddrinfo_ipv4_answered; + else + ++data->evdns_base->getaddrinfo_ipv6_answered; + } + user_canceled = data->user_canceled; + if (other_req->r == NULL) + data->request_done = 1; + EVDNS_UNLOCK(data->evdns_base); + } else { + data->evdns_base = NULL; + user_canceled = data->user_canceled; + } + + req->r = NULL; + + if (result == DNS_ERR_CANCEL && ! user_canceled) { + /* Internal cancel request from timeout or internal error. + * we already answered the user. */ + if (other_req->r == NULL) + free_getaddrinfo_request(data); + return; + } + + if (data->user_cb == NULL) { + /* We already answered. XXXX This shouldn't be needed; see + * comments in evdns_getaddrinfo_timeout_cb */ + free_getaddrinfo_request(data); + return; + } + + if (result == DNS_ERR_NONE) { + if (count == 0) + err = EVUTIL_EAI_NODATA; + else + err = 0; + } else { + err = evdns_err_to_getaddrinfo_err(result); + } + + if (err) { + /* Looks like we got an error. */ + if (other_req->r) { + /* The other request is still working; maybe it will + * succeed. */ + /* XXXX handle failure from set_timeout */ + if (result != DNS_ERR_SHUTDOWN) { + evdns_getaddrinfo_set_timeout(data->evdns_base, data); + } + data->pending_error = err; + return; + } + + if (user_canceled) { + data->user_cb(EVUTIL_EAI_CANCEL, NULL, data->user_data); + } else if (data->pending_result) { + /* If we have an answer waiting, and we weren't + * canceled, ignore this error. */ + add_cname_to_reply(data, data->pending_result); + data->user_cb(0, data->pending_result, data->user_data); + data->pending_result = NULL; + } else { + if (data->pending_error) + err = getaddrinfo_merge_err(err, + data->pending_error); + data->user_cb(err, NULL, data->user_data); + } + free_getaddrinfo_request(data); + return; + } else if (user_canceled) { + if (other_req->r) { + /* The other request is still working; let it hit this + * callback with EVUTIL_EAI_CANCEL callback and report + * the failure. */ + return; + } + data->user_cb(EVUTIL_EAI_CANCEL, NULL, data->user_data); + free_getaddrinfo_request(data); + return; + } + + /* Looks like we got some answers. We should turn them into addrinfos + * and then either queue those or return them all. */ + EVUTIL_ASSERT(type == DNS_IPv4_A || type == DNS_IPv6_AAAA); + + if (type == DNS_IPv4_A) { + memset(&sin, 0, sizeof(sin)); + sin.sin_family = AF_INET; + sin.sin_port = htons(data->port); + + sa = (struct sockaddr *)&sin; + socklen = sizeof(sin); + addrlen = 4; + addrp = &sin.sin_addr.s_addr; + } else { + memset(&sin6, 0, sizeof(sin6)); + sin6.sin6_family = AF_INET6; + sin6.sin6_port = htons(data->port); + + sa = (struct sockaddr *)&sin6; + socklen = sizeof(sin6); + addrlen = 16; + addrp = &sin6.sin6_addr.s6_addr; + } + + res = NULL; + for (i=0; i < count; ++i) { + struct evutil_addrinfo *ai; + memcpy(addrp, ((char*)addresses)+i*addrlen, addrlen); + ai = evutil_new_addrinfo_(sa, socklen, &data->hints); + if (!ai) { + if (other_req->r) { + evdns_cancel_request(NULL, other_req->r); + } + data->user_cb(EVUTIL_EAI_MEMORY, NULL, data->user_data); + if (res) + evutil_freeaddrinfo(res); + + if (other_req->r == NULL) + free_getaddrinfo_request(data); + return; + } + res = evutil_addrinfo_append_(res, ai); + } + + if (other_req->r) { + /* The other request is still in progress; wait for it */ + /* XXXX handle failure from set_timeout */ + evdns_getaddrinfo_set_timeout(data->evdns_base, data); + data->pending_result = res; + return; + } else { + /* The other request is done or never started; append its + * results (if any) and return them. */ + if (data->pending_result) { + if (req->type == DNS_IPv4_A) + res = evutil_addrinfo_append_(res, + data->pending_result); + else + res = evutil_addrinfo_append_( + data->pending_result, res); + data->pending_result = NULL; + } + + /* Call the user callback. */ + add_cname_to_reply(data, res); + data->user_cb(0, res, data->user_data); + + /* Free data. */ + free_getaddrinfo_request(data); + } +} + +static struct hosts_entry * +find_hosts_entry(struct evdns_base *base, const char *hostname, + struct hosts_entry *find_after) +{ + struct hosts_entry *e; + + if (find_after) + e = TAILQ_NEXT(find_after, next); + else + e = TAILQ_FIRST(&base->hostsdb); + + for (; e; e = TAILQ_NEXT(e, next)) { + if (!evutil_ascii_strcasecmp(e->hostname, hostname)) + return e; + } + return NULL; +} + +static int +evdns_getaddrinfo_fromhosts(struct evdns_base *base, + const char *nodename, struct evutil_addrinfo *hints, ev_uint16_t port, + struct evutil_addrinfo **res) +{ + int n_found = 0; + struct hosts_entry *e; + struct evutil_addrinfo *ai=NULL; + int f = hints->ai_family; + + EVDNS_LOCK(base); + for (e = find_hosts_entry(base, nodename, NULL); e; + e = find_hosts_entry(base, nodename, e)) { + struct evutil_addrinfo *ai_new; + ++n_found; + if ((e->addr.sa.sa_family == AF_INET && f == PF_INET6) || + (e->addr.sa.sa_family == AF_INET6 && f == PF_INET)) + continue; + ai_new = evutil_new_addrinfo_(&e->addr.sa, e->addrlen, hints); + if (!ai_new) { + n_found = 0; + goto out; + } + sockaddr_setport(ai_new->ai_addr, port); + ai = evutil_addrinfo_append_(ai, ai_new); + } + EVDNS_UNLOCK(base); +out: + if (n_found) { + /* Note that we return an empty answer if we found entries for + * this hostname but none were of the right address type. */ + *res = ai; + return 0; + } else { + if (ai) + evutil_freeaddrinfo(ai); + return -1; + } +} + +struct evdns_getaddrinfo_request * +evdns_getaddrinfo(struct evdns_base *dns_base, + const char *nodename, const char *servname, + const struct evutil_addrinfo *hints_in, + evdns_getaddrinfo_cb cb, void *arg) +{ + struct evdns_getaddrinfo_request *data; + struct evutil_addrinfo hints; + struct evutil_addrinfo *res = NULL; + int err; + int port = 0; + int want_cname = 0; + int started = 0; + + if (!dns_base) { + dns_base = current_base; + if (!dns_base) { + log(EVDNS_LOG_WARN, + "Call to getaddrinfo_async with no " + "evdns_base configured."); + cb(EVUTIL_EAI_FAIL, NULL, arg); /* ??? better error? */ + return NULL; + } + } + + /* If we _must_ answer this immediately, do so. */ + if ((hints_in && (hints_in->ai_flags & EVUTIL_AI_NUMERICHOST))) { + res = NULL; + err = evutil_getaddrinfo(nodename, servname, hints_in, &res); + cb(err, res, arg); + return NULL; + } + + if (hints_in) { + memcpy(&hints, hints_in, sizeof(hints)); + } else { + memset(&hints, 0, sizeof(hints)); + hints.ai_family = PF_UNSPEC; + } + + evutil_adjust_hints_for_addrconfig_(&hints); + + /* Now try to see if we _can_ answer immediately. */ + /* (It would be nice to do this by calling getaddrinfo directly, with + * AI_NUMERICHOST, on plaforms that have it, but we can't: there isn't + * a reliable way to distinguish the "that wasn't a numeric host!" case + * from any other EAI_NONAME cases.) */ + err = evutil_getaddrinfo_common_(nodename, servname, &hints, &res, &port); + if (err != EVUTIL_EAI_NEED_RESOLVE) { + cb(err, res, arg); + return NULL; + } + + /* If there is an entry in the hosts file, we should give it now. */ + if (!evdns_getaddrinfo_fromhosts(dns_base, nodename, &hints, port, &res)) { + cb(0, res, arg); + return NULL; + } + + /* Okay, things are serious now. We're going to need to actually + * launch a request. + */ + data = mm_calloc(1,sizeof(struct evdns_getaddrinfo_request)); + if (!data) { + cb(EVUTIL_EAI_MEMORY, NULL, arg); + return NULL; + } + + memcpy(&data->hints, &hints, sizeof(data->hints)); + data->port = (ev_uint16_t)port; + data->ipv4_request.type = DNS_IPv4_A; + data->ipv6_request.type = DNS_IPv6_AAAA; + data->user_cb = cb; + data->user_data = arg; + data->evdns_base = dns_base; + + want_cname = (hints.ai_flags & EVUTIL_AI_CANONNAME); + + /* If we are asked for a PF_UNSPEC address, we launch two requests in + * parallel: one for an A address and one for an AAAA address. We + * can't send just one request, since many servers only answer one + * question per DNS request. + * + * Once we have the answer to one request, we allow for a short + * timeout before we report it, to see if the other one arrives. If + * they both show up in time, then we report both the answers. + * + * If too many addresses of one type time out or fail, we should stop + * launching those requests. (XXX we don't do that yet.) + */ + + EVDNS_LOCK(dns_base); + + if (hints.ai_family != PF_INET6) { + log(EVDNS_LOG_DEBUG, "Sending request for %s on ipv4 as %p", + nodename, &data->ipv4_request); + + data->ipv4_request.r = evdns_base_resolve_ipv4(dns_base, + nodename, 0, evdns_getaddrinfo_gotresolve, + &data->ipv4_request); + if (want_cname && data->ipv4_request.r) + data->ipv4_request.r->current_req->put_cname_in_ptr = + &data->cname_result; + } + if (hints.ai_family != PF_INET) { + log(EVDNS_LOG_DEBUG, "Sending request for %s on ipv6 as %p", + nodename, &data->ipv6_request); + + data->ipv6_request.r = evdns_base_resolve_ipv6(dns_base, + nodename, 0, evdns_getaddrinfo_gotresolve, + &data->ipv6_request); + if (want_cname && data->ipv6_request.r) + data->ipv6_request.r->current_req->put_cname_in_ptr = + &data->cname_result; + } + + evtimer_assign(&data->timeout, dns_base->event_base, + evdns_getaddrinfo_timeout_cb, data); + + started = (data->ipv4_request.r || data->ipv6_request.r); + + EVDNS_UNLOCK(dns_base); + + if (started) { + return data; + } else { + mm_free(data); + cb(EVUTIL_EAI_FAIL, NULL, arg); + return NULL; + } +} + +void +evdns_getaddrinfo_cancel(struct evdns_getaddrinfo_request *data) +{ + EVDNS_LOCK(data->evdns_base); + if (data->request_done) { + EVDNS_UNLOCK(data->evdns_base); + return; + } + event_del(&data->timeout); + data->user_canceled = 1; + if (data->ipv4_request.r) + evdns_cancel_request(data->evdns_base, data->ipv4_request.r); + if (data->ipv6_request.r) + evdns_cancel_request(data->evdns_base, data->ipv6_request.r); + EVDNS_UNLOCK(data->evdns_base); +} |