/* SPDX-License-Identifier: LGPL-2.1-or-later */ #pragma once #include #include #include #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_AD (UINT16_C(1) << 5) #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 >> 20) & 0xFF0); 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);