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Diffstat (limited to '')
| -rw-r--r-- | libcli/dns/dns_lookup.c | 374 |
1 files changed, 374 insertions, 0 deletions
diff --git a/libcli/dns/dns_lookup.c b/libcli/dns/dns_lookup.c new file mode 100644 index 0000000..cb0ede8 --- /dev/null +++ b/libcli/dns/dns_lookup.c @@ -0,0 +1,374 @@ +/* + * Unix SMB/CIFS implementation. + * Internal DNS query structures + * Copyright (C) Volker Lendecke 2018 + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 3 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, see <http://www.gnu.org/licenses/>. + */ + +#include "replace.h" +#include "libcli/dns/dns_lookup.h" +#include "libcli/dns/resolvconf.h" +#include "libcli/dns/libdns.h" +#include "lib/util/tevent_unix.h" +#include "lib/util/samba_util.h" +#include "lib/util/debug.h" + +struct dns_lookup_state { + struct tevent_context *ev; + const char *name; + enum dns_qclass qclass; + enum dns_qtype qtype; + + char **nameservers; + size_t num_nameservers; + size_t num_sent; + + struct tevent_req **dns_subreqs; + struct tevent_req *wait_subreq; + + struct dns_name_packet *reply; +}; + +static int dns_lookup_send_next(struct tevent_req *req); + +static void dns_lookup_done(struct tevent_req *subreq); +static void dns_lookup_waited(struct tevent_req *subreq); + +struct tevent_req *dns_lookup_send(TALLOC_CTX *mem_ctx, + struct tevent_context *ev, + FILE *resolv_conf_fp, + const char *name, + enum dns_qclass qclass, + enum dns_qtype qtype) +{ + struct tevent_req *req; + struct dns_lookup_state *state; + FILE *fp = resolv_conf_fp; + int ret; + + req = tevent_req_create(mem_ctx, &state, struct dns_lookup_state); + if (req == NULL) { + return NULL; + } + state->ev = ev; + state->name = name; + state->qclass = qclass; + state->qtype = qtype; + + if (resolv_conf_fp == NULL) { + const char *resolvconf = "/etc/resolv.conf"; + +#ifdef ENABLE_SELFTEST + { + const char *envvar = getenv("RESOLV_CONF"); + if (envvar != NULL) { + resolvconf = envvar; + } + } +#endif + + fp = fopen(resolvconf, "r"); + if (fp == NULL) { + tevent_req_error(req, errno); + return tevent_req_post(req, ev); + } + } + + ret = parse_resolvconf_fp( + fp, + state, + &state->nameservers, + &state->num_nameservers); + + if (resolv_conf_fp == NULL) { + fclose(fp); + } + + if (ret != 0) { + tevent_req_error(req, ret); + return tevent_req_post(req, ev); + } + + if (state->num_nameservers == 0) { + /* + * glibc's getaddrinfo returns EAI_AGAIN when no + * nameservers are configured. EAGAIN seems closest. + */ + tevent_req_error(req, EAGAIN); + return tevent_req_post(req, ev); + } + + state->dns_subreqs = talloc_zero_array( + state, + struct tevent_req *, + state->num_nameservers); + + if (tevent_req_nomem(state->dns_subreqs, req)) { + return tevent_req_post(req, ev); + } + + ret = dns_lookup_send_next(req); + if (tevent_req_error(req, ret)) { + return tevent_req_post(req, ev); + } + + return req; +} + +static int dns_lookup_send_next(struct tevent_req *req) +{ + struct dns_lookup_state *state = tevent_req_data( + req, struct dns_lookup_state); + + DBG_DEBUG("Sending DNS request #%zu to %s\n", + state->num_sent, + state->nameservers[state->num_sent]); + + state->dns_subreqs[state->num_sent] = dns_cli_request_send( + state->dns_subreqs, + state->ev, + state->nameservers[state->num_sent], + state->name, + state->qclass, + state->qtype); + + if (state->dns_subreqs[state->num_sent] == NULL) { + return ENOMEM; + } + tevent_req_set_callback(state->dns_subreqs[state->num_sent], + dns_lookup_done, + req); + state->num_sent += 1; + + if (state->num_sent == state->num_nameservers) { + /* + * No more nameservers left + */ + DBG_DEBUG("cancelling wait_subreq\n"); + TALLOC_FREE(state->wait_subreq); + return 0; + } + + if (state->wait_subreq != NULL) { + /* + * This can happen if we fire the next request upon + * dns_cli_request returning a network-level error + */ + return 0; + } + + state->wait_subreq = tevent_wakeup_send( + state, + state->ev, + tevent_timeval_current_ofs(1, 0)); + if (state->wait_subreq == NULL) { + return ENOMEM; + } + tevent_req_set_callback(state->wait_subreq, dns_lookup_waited, req); + + return 0; +} + +static void dns_lookup_done(struct tevent_req *subreq) +{ + struct tevent_req *req = tevent_req_callback_data( + subreq, struct tevent_req); + struct dns_lookup_state *state = tevent_req_data( + req, struct dns_lookup_state); + int dns_cli_request_ret; + size_t i; + + dns_cli_request_ret = dns_cli_request_recv( + subreq, + state, + &state->reply); + + for (i = 0; i < state->num_nameservers; i++) { + if (state->dns_subreqs[i] == subreq) { + break; + } + } + + TALLOC_FREE(subreq); + + if (i == state->num_nameservers) { + /* should never happen */ + DBG_WARNING("Failed to find subreq"); + tevent_req_error(req, EINVAL); + return; + } + state->dns_subreqs[i] = NULL; + + if (dns_cli_request_ret == 0) { + /* + * Success, cancel everything else + */ + TALLOC_FREE(state->dns_subreqs); + TALLOC_FREE(state->wait_subreq); + tevent_req_done(req); + return; + } + + DBG_DEBUG("dns_cli_request[%zu] returned %s\n", i, + strerror(dns_cli_request_ret)); + + if (state->num_sent < state->num_nameservers) { + /* + * We have a nameserver left to try + */ + int ret; + + ret = dns_lookup_send_next(req); + if (tevent_req_error(req, ret)) { + return; + } + } + + DBG_DEBUG("looking for outstanding requests\n"); + + for (i = 0; i<state->num_nameservers; i++) { + if (state->dns_subreqs[i] != NULL) { + break; + } + } + + DBG_DEBUG("i=%zu, num_nameservers=%zu\n", + i, state->num_nameservers); + + if (i == state->num_nameservers) { + /* + * Report the lower-level error if we have nothing + * outstanding anymore + */ + tevent_req_error(req, dns_cli_request_ret); + return; + } + + /* + * Do nothing: We have other nameservers that might come back + * with something good. + */ +} + +static void dns_lookup_waited(struct tevent_req *subreq) +{ + struct tevent_req *req = tevent_req_callback_data( + subreq, struct tevent_req); + struct dns_lookup_state *state = tevent_req_data( + req, struct dns_lookup_state); + int ret; + bool ok; + + DBG_DEBUG("waited\n"); + + ok = tevent_wakeup_recv(subreq); + TALLOC_FREE(subreq); + if (!ok) { + tevent_req_oom(req); + return; + } + state->wait_subreq = NULL; + + ret = dns_lookup_send_next(req); + if (tevent_req_error(req, ret)) { + return; + } + + /* + * dns_lookup_send_next() has already triggered the next wakeup + */ +} + +int dns_lookup_recv(struct tevent_req *req, TALLOC_CTX *mem_ctx, + struct dns_name_packet **reply) +{ + struct dns_lookup_state *state = tevent_req_data( + req, struct dns_lookup_state); + int err; + + if (tevent_req_is_unix_error(req, &err)) { + return err; + } + + *reply = talloc_move(mem_ctx, &state->reply); + + tevent_req_received(req); + return 0; +} + +int dns_lookup(FILE *resolv_conf_fp, + const char *name, + enum dns_qclass qclass, + enum dns_qtype qtype, + TALLOC_CTX *mem_ctx, + struct dns_name_packet **reply) +{ + struct tevent_context *ev; + struct tevent_req *req; + int ret = ENOMEM; + + ev = samba_tevent_context_init(mem_ctx); + if (ev == NULL) { + goto fail; + } + req = dns_lookup_send(ev, ev, resolv_conf_fp, name, qclass, qtype); + if (req == NULL) { + goto fail; + } + if (!tevent_req_poll_unix(req, ev, &ret)) { + goto fail; + } + ret = dns_lookup_recv(req, mem_ctx, reply); +fail: + TALLOC_FREE(ev); + return ret; +} + +bool dns_res_rec_get_sockaddr(const struct dns_res_rec *rec, + struct sockaddr_storage *addr) +{ + sa_family_t family; + const char *src; + void *dst; + int ret; + + switch (rec->rr_type) { + case DNS_QTYPE_A: + family = AF_INET; + src = rec->rdata.ipv4_record; + dst = &(((struct sockaddr_in *)addr)->sin_addr); + break; +#ifdef HAVE_IPV6 + case DNS_QTYPE_AAAA: + family = AF_INET6; + src = rec->rdata.ipv6_record; + dst = &(((struct sockaddr_in6 *)addr)->sin6_addr); + break; +#endif + default: + /* We only care about IP addresses */ + return false; + } + + *addr = (struct sockaddr_storage) { .ss_family = family }; + + ret = inet_pton(family, src, dst); + if (ret != 1) { + DBG_DEBUG("inet_pton(%s) failed\n", src); + return false; + } + + return true; +} |