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Diffstat (limited to 'src/resolve/resolved-dns-packet.h')
| -rw-r--r-- | src/resolve/resolved-dns-packet.h | 349 |
1 files changed, 349 insertions, 0 deletions
diff --git a/src/resolve/resolved-dns-packet.h b/src/resolve/resolved-dns-packet.h new file mode 100644 index 0000000..a6af44c --- /dev/null +++ b/src/resolve/resolved-dns-packet.h @@ -0,0 +1,349 @@ +/* SPDX-License-Identifier: LGPL-2.1-or-later */ +#pragma once + +#include <netinet/ip.h> +#include <netinet/ip6.h> +#include <netinet/udp.h> + +#include "hashmap.h" +#include "in-addr-util.h" +#include "macro.h" +#include "sparse-endian.h" + +typedef struct DnsPacketHeader DnsPacketHeader; +typedef struct DnsPacket DnsPacket; + +#include "resolved-def.h" +#include "resolved-dns-answer.h" +#include "resolved-dns-question.h" +#include "resolved-dns-rr.h" + +typedef enum DnsProtocol { + DNS_PROTOCOL_DNS, + DNS_PROTOCOL_MDNS, + DNS_PROTOCOL_LLMNR, + _DNS_PROTOCOL_MAX, + _DNS_PROTOCOL_INVALID = -EINVAL, +} DnsProtocol; + +struct DnsPacketHeader { + uint16_t id; + be16_t flags; + be16_t qdcount; + be16_t ancount; + be16_t nscount; + be16_t arcount; +} _packed_; + +#define DNS_PACKET_HEADER_SIZE sizeof(DnsPacketHeader) +#define UDP4_PACKET_HEADER_SIZE (sizeof(struct iphdr) + sizeof(struct udphdr)) +#define UDP6_PACKET_HEADER_SIZE (sizeof(struct ip6_hdr) + sizeof(struct udphdr)) + +assert_cc(sizeof(struct ip6_hdr) == 40); +assert_cc(sizeof(struct iphdr) == 20); +assert_cc(sizeof(struct udphdr) == 8); +assert_cc(sizeof(DnsPacketHeader) == 12); + +/* The various DNS protocols deviate in how large a packet can grow, but the TCP transport has a 16-bit size + * field, hence that appears to be the absolute maximum. */ +#define DNS_PACKET_SIZE_MAX 0xFFFFu + +/* The default size to use for allocation when we don't know how large + * the packet will turn out to be. */ +#define DNS_PACKET_SIZE_START 512u + +/* RFC 1035 say 512 is the maximum, for classic unicast DNS */ +#define DNS_PACKET_UNICAST_SIZE_MAX 512u + +/* With EDNS0 we can use larger packets, default to 1232, which is what is commonly used */ +#define DNS_PACKET_UNICAST_SIZE_LARGE_MAX 1232u + +struct DnsPacket { + unsigned n_ref; + DnsProtocol protocol; + size_t size, allocated, rindex, max_size, fragsize; + void *_data; /* don't access directly, use DNS_PACKET_DATA()! */ + Hashmap *names; /* For name compression */ + size_t opt_start, opt_size; + + /* Parsed data */ + DnsQuestion *question; + DnsAnswer *answer; + DnsResourceRecord *opt; + + /* For support of truncated packets */ + DnsPacket *more; + + /* Packet reception metadata */ + usec_t timestamp; /* CLOCK_BOOTTIME (or CLOCK_MONOTONIC if the former doesn't exist) */ + int ifindex; + int family, ipproto; + union in_addr_union sender, destination; + uint16_t sender_port, destination_port; + uint32_t ttl; + + bool on_stack; + bool extracted; + bool refuse_compression; + bool canonical_form; + + /* Note: fields should be ordered to minimize alignment gaps. Use pahole! */ +}; + +static inline uint8_t* DNS_PACKET_DATA(const DnsPacket *p) { + if (_unlikely_(!p)) + return NULL; + + if (p->_data) + return p->_data; + + return ((uint8_t*) p) + ALIGN(sizeof(DnsPacket)); +} + +#define DNS_PACKET_HEADER(p) ((DnsPacketHeader*) DNS_PACKET_DATA(p)) +#define DNS_PACKET_ID(p) DNS_PACKET_HEADER(p)->id +#define DNS_PACKET_QR(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 15) & 1) +#define DNS_PACKET_OPCODE(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 11) & 15) +#define DNS_PACKET_AA(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 10) & 1) +#define DNS_PACKET_TC(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 9) & 1) +#define DNS_PACKET_RD(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 8) & 1) +#define DNS_PACKET_RA(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 7) & 1) +#define DNS_PACKET_AD(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 5) & 1) +#define DNS_PACKET_CD(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 4) & 1) + +#define DNS_PACKET_FLAG_TC (UINT16_C(1) << 9) + +static inline uint16_t DNS_PACKET_RCODE(DnsPacket *p) { + uint16_t rcode; + + if (p->opt) + rcode = (uint16_t) (p->opt->ttl >> 24); + else + rcode = 0; + + return rcode | (be16toh(DNS_PACKET_HEADER(p)->flags) & 0xF); +} + +static inline uint16_t DNS_PACKET_PAYLOAD_SIZE_MAX(DnsPacket *p) { + + /* Returns the advertised maximum size for replies, or the DNS default if there's nothing defined. */ + + if (p->ipproto == IPPROTO_TCP) /* we ignore EDNS(0) size data on TCP, like everybody else */ + return DNS_PACKET_SIZE_MAX; + + if (p->opt) + return MAX(DNS_PACKET_UNICAST_SIZE_MAX, p->opt->key->class); + + return DNS_PACKET_UNICAST_SIZE_MAX; +} + +static inline bool DNS_PACKET_DO(DnsPacket *p) { + if (!p->opt) + return false; + + return !!(p->opt->ttl & (1U << 15)); +} + +static inline bool DNS_PACKET_VERSION_SUPPORTED(DnsPacket *p) { + /* Returns true if this packet is in a version we support. Which means either non-EDNS or EDNS(0), but not EDNS + * of any newer versions */ + + if (!p->opt) + return true; + + return DNS_RESOURCE_RECORD_OPT_VERSION_SUPPORTED(p->opt); +} + +static inline bool DNS_PACKET_IS_FRAGMENTED(DnsPacket *p) { + assert(p); + + /* For ingress packets: was this packet fragmented according to our knowledge? */ + + return p->fragsize != 0; +} + +/* LLMNR defines some bits differently */ +#define DNS_PACKET_LLMNR_C(p) DNS_PACKET_AA(p) +#define DNS_PACKET_LLMNR_T(p) DNS_PACKET_RD(p) + +#define DNS_PACKET_QDCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->qdcount) +#define DNS_PACKET_ANCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->ancount) +#define DNS_PACKET_NSCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->nscount) +#define DNS_PACKET_ARCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->arcount) + +#define DNS_PACKET_MAKE_FLAGS(qr, opcode, aa, tc, rd, ra, ad, cd, rcode) \ + (((uint16_t) !!(qr) << 15) | \ + ((uint16_t) ((opcode) & 15) << 11) | \ + ((uint16_t) !!(aa) << 10) | /* on LLMNR: c */ \ + ((uint16_t) !!(tc) << 9) | \ + ((uint16_t) !!(rd) << 8) | /* on LLMNR: t */ \ + ((uint16_t) !!(ra) << 7) | \ + ((uint16_t) !!(ad) << 5) | \ + ((uint16_t) !!(cd) << 4) | \ + ((uint16_t) ((rcode) & 15))) + +static inline unsigned DNS_PACKET_RRCOUNT(DnsPacket *p) { + return + (unsigned) DNS_PACKET_ANCOUNT(p) + + (unsigned) DNS_PACKET_NSCOUNT(p) + + (unsigned) DNS_PACKET_ARCOUNT(p); +} + +int dns_packet_new(DnsPacket **p, DnsProtocol protocol, size_t min_alloc_dsize, size_t max_size); +int dns_packet_new_query(DnsPacket **p, DnsProtocol protocol, size_t min_alloc_dsize, bool dnssec_checking_disabled); + +int dns_packet_dup(DnsPacket **ret, DnsPacket *p); + +void dns_packet_set_flags(DnsPacket *p, bool dnssec_checking_disabled, bool truncated); + +DnsPacket *dns_packet_ref(DnsPacket *p); +DnsPacket *dns_packet_unref(DnsPacket *p); + +DEFINE_TRIVIAL_CLEANUP_FUNC(DnsPacket*, dns_packet_unref); + +#define DNS_PACKET_REPLACE(a, b) \ + do { \ + typeof(a)* _a = &(a); \ + typeof(b) _b = (b); \ + dns_packet_unref(*_a); \ + *_a = _b; \ + } while(0) + +int dns_packet_validate(DnsPacket *p); +int dns_packet_validate_reply(DnsPacket *p); +int dns_packet_validate_query(DnsPacket *p); + +int dns_packet_is_reply_for(DnsPacket *p, const DnsResourceKey *key); + +int dns_packet_append_blob(DnsPacket *p, const void *d, size_t sz, size_t *start); +int dns_packet_append_uint8(DnsPacket *p, uint8_t v, size_t *start); +int dns_packet_append_uint16(DnsPacket *p, uint16_t v, size_t *start); +int dns_packet_append_uint32(DnsPacket *p, uint32_t v, size_t *start); +int dns_packet_append_string(DnsPacket *p, const char *s, size_t *start); +int dns_packet_append_raw_string(DnsPacket *p, const void *s, size_t size, size_t *start); +int dns_packet_append_label(DnsPacket *p, const char *s, size_t l, bool canonical_candidate, size_t *start); +int dns_packet_append_name(DnsPacket *p, const char *name, bool allow_compression, bool canonical_candidate, size_t *start); +int dns_packet_append_key(DnsPacket *p, const DnsResourceKey *key, const DnsAnswerFlags flags, size_t *start); +int dns_packet_append_rr(DnsPacket *p, const DnsResourceRecord *rr, const DnsAnswerFlags flags, size_t *start, size_t *rdata_start); +int dns_packet_append_opt(DnsPacket *p, uint16_t max_udp_size, bool edns0_do, bool include_rfc6975, const char *nsid, int rcode, size_t *ret_start); +int dns_packet_append_question(DnsPacket *p, DnsQuestion *q); +int dns_packet_append_answer(DnsPacket *p, DnsAnswer *a, unsigned *completed); + +int dns_packet_patch_max_udp_size(DnsPacket *p, uint16_t max_udp_size); +int dns_packet_patch_ttls(DnsPacket *p, usec_t timestamp); + +void dns_packet_truncate(DnsPacket *p, size_t sz); +int dns_packet_truncate_opt(DnsPacket *p); + +int dns_packet_read(DnsPacket *p, size_t sz, const void **ret, size_t *start); +int dns_packet_read_blob(DnsPacket *p, void *d, size_t sz, size_t *start); +int dns_packet_read_uint8(DnsPacket *p, uint8_t *ret, size_t *start); +int dns_packet_read_uint16(DnsPacket *p, uint16_t *ret, size_t *start); +int dns_packet_read_uint32(DnsPacket *p, uint32_t *ret, size_t *start); +int dns_packet_read_string(DnsPacket *p, char **ret, size_t *start); +int dns_packet_read_raw_string(DnsPacket *p, const void **ret, size_t *size, size_t *start); +int dns_packet_read_name(DnsPacket *p, char **ret, bool allow_compression, size_t *start); +int dns_packet_read_key(DnsPacket *p, DnsResourceKey **ret, bool *ret_cache_flush_or_qu, size_t *start); +int dns_packet_read_rr(DnsPacket *p, DnsResourceRecord **ret, bool *ret_cache_flush, size_t *start); + +void dns_packet_rewind(DnsPacket *p, size_t idx); + +int dns_packet_skip_question(DnsPacket *p); +int dns_packet_extract(DnsPacket *p); + +bool dns_packet_equal(const DnsPacket *a, const DnsPacket *b); + +int dns_packet_has_nsid_request(DnsPacket *p); + +/* https://www.iana.org/assignments/dns-parameters/dns-parameters.xhtml#dns-parameters-6 */ +enum { + DNS_RCODE_SUCCESS = 0, + DNS_RCODE_FORMERR = 1, + DNS_RCODE_SERVFAIL = 2, + DNS_RCODE_NXDOMAIN = 3, + DNS_RCODE_NOTIMP = 4, + DNS_RCODE_REFUSED = 5, + DNS_RCODE_YXDOMAIN = 6, + DNS_RCODE_YXRRSET = 7, + DNS_RCODE_NXRRSET = 8, + DNS_RCODE_NOTAUTH = 9, + DNS_RCODE_NOTZONE = 10, + DNS_RCODE_BADVERS = 16, + DNS_RCODE_BADSIG = 16, /* duplicate value! */ + DNS_RCODE_BADKEY = 17, + DNS_RCODE_BADTIME = 18, + DNS_RCODE_BADMODE = 19, + DNS_RCODE_BADNAME = 20, + DNS_RCODE_BADALG = 21, + DNS_RCODE_BADTRUNC = 22, + DNS_RCODE_BADCOOKIE = 23, + _DNS_RCODE_MAX_DEFINED, + _DNS_RCODE_MAX = 4095 /* 4 bit rcode in the header plus 8 bit rcode in OPT, makes 12 bit */ +}; + +const char* dns_rcode_to_string(int i) _const_; +int dns_rcode_from_string(const char *s) _pure_; +const char *format_dns_rcode(int i, char buf[static DECIMAL_STR_MAX(int)]); +#define FORMAT_DNS_RCODE(i) format_dns_rcode(i, (char [DECIMAL_STR_MAX(int)]) {}) + +const char* dns_protocol_to_string(DnsProtocol p) _const_; +DnsProtocol dns_protocol_from_string(const char *s) _pure_; + +#define LLMNR_MULTICAST_IPV4_ADDRESS ((struct in_addr) { .s_addr = htobe32(224U << 24 | 252U) }) +#define LLMNR_MULTICAST_IPV6_ADDRESS ((struct in6_addr) { .s6_addr = { 0xFF, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x03 } }) + +#define MDNS_MULTICAST_IPV4_ADDRESS ((struct in_addr) { .s_addr = htobe32(224U << 24 | 251U) }) +#define MDNS_MULTICAST_IPV6_ADDRESS ((struct in6_addr) { .s6_addr = { 0xFF, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xfb } }) + +extern const struct hash_ops dns_packet_hash_ops; + +static inline uint64_t SD_RESOLVED_FLAGS_MAKE( + DnsProtocol protocol, + int family, + bool authenticated, + bool confidential) { + uint64_t f; + + /* Converts a protocol + family into a flags field as used in queries and responses */ + + f = (authenticated ? SD_RESOLVED_AUTHENTICATED : 0) | + (confidential ? SD_RESOLVED_CONFIDENTIAL : 0); + + switch (protocol) { + case DNS_PROTOCOL_DNS: + return f|SD_RESOLVED_DNS; + + case DNS_PROTOCOL_LLMNR: + return f|(family == AF_INET6 ? SD_RESOLVED_LLMNR_IPV6 : SD_RESOLVED_LLMNR_IPV4); + + case DNS_PROTOCOL_MDNS: + return f|(family == AF_INET6 ? SD_RESOLVED_MDNS_IPV6 : SD_RESOLVED_MDNS_IPV4); + + default: + return f; + } +} + +static inline size_t dns_packet_size_max(DnsPacket *p) { + assert(p); + + /* Why not insist on a fully initialized max_size during DnsPacket construction? Well, this way it's easy to + * allocate a transient, throw-away DnsPacket on the stack by simple zero initialization, without having to + * deal with explicit field initialization. */ + + return p->max_size != 0 ? p->max_size : DNS_PACKET_SIZE_MAX; +} + +static inline size_t udp_header_size(int af) { + + switch (af) { + case AF_INET: + return UDP4_PACKET_HEADER_SIZE; + case AF_INET6: + return UDP6_PACKET_HEADER_SIZE; + default: + assert_not_reached(); + } +} + +size_t dns_packet_size_unfragmented(DnsPacket *p); |