src/resolve/resolved-dns-packet.h

   1 /*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
   2
   3 #pragma once
   4
   5 /***
   6   This file is part of systemd.
   7
   8   Copyright 2014 Lennart Poettering
   9
  10   systemd is free software; you can redistribute it and/or modify it
  11   under the terms of the GNU Lesser General Public License as published by
  12   the Free Software Foundation; either version 2.1 of the License, or
  13   (at your option) any later version.
  14
  15   systemd is distributed in the hope that it will be useful, but
  16   WITHOUT ANY WARRANTY; without even the implied warranty of
  17   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  18   Lesser General Public License for more details.
  19
  20   You should have received a copy of the GNU Lesser General Public License
  21   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  22  ***/
  23
  24 #include <netinet/ip.h>
  25 #include <netinet/udp.h>
  26
  27 #include "hashmap.h"
  28 #include "in-addr-util.h"
  29 #include "macro.h"
  30 #include "sparse-endian.h"
  31
  32 typedef struct DnsPacketHeader DnsPacketHeader;
  33 typedef struct DnsPacket DnsPacket;
  34
  35 #include "resolved-def.h"
  36 #include "resolved-dns-answer.h"
  37 #include "resolved-dns-question.h"
  38 #include "resolved-dns-rr.h"
  39
  40 typedef enum DnsProtocol {
  41         DNS_PROTOCOL_DNS,
  42         DNS_PROTOCOL_MDNS,
  43         DNS_PROTOCOL_LLMNR,
  44         _DNS_PROTOCOL_MAX,
  45         _DNS_PROTOCOL_INVALID = -1
  46 } DnsProtocol;
  47
  48 struct DnsPacketHeader {
  49         uint16_t id;
  50         be16_t flags;
  51         be16_t qdcount;
  52         be16_t ancount;
  53         be16_t nscount;
  54         be16_t arcount;
  55 };
  56
  57 #define DNS_PACKET_HEADER_SIZE sizeof(DnsPacketHeader)
  58 #define UDP_PACKET_HEADER_SIZE (sizeof(struct iphdr) + sizeof(struct udphdr))
  59
  60 /* The various DNS protocols deviate in how large a packet can grow,
  61    but the TCP transport has a 16bit size field, hence that appears to
  62    be the absolute maximum. */
  63 #define DNS_PACKET_SIZE_MAX 0xFFFF
  64
  65 /* RFC 1035 say 512 is the maximum, for classic unicast DNS */
  66 #define DNS_PACKET_UNICAST_SIZE_MAX 512
  67
  68 /* With EDNS0 we can use larger packets, default to 4096, which is what is commonly used */
  69 #define DNS_PACKET_UNICAST_SIZE_LARGE_MAX 4096
  70
  71 #define DNS_PACKET_SIZE_START 512
  72
  73 struct DnsPacket {
  74         int n_ref;
  75         DnsProtocol protocol;
  76         size_t size, allocated, rindex;
  77         void *_data; /* don't access directly, use DNS_PACKET_DATA()! */
  78         Hashmap *names; /* For name compression */
  79
  80         /* Parsed data */
  81         DnsQuestion *question;
  82         DnsAnswer *answer;
  83         DnsResourceRecord *opt;
  84
  85         /* Packet reception metadata */
  86         int ifindex;
  87         int family, ipproto;
  88         union in_addr_union sender, destination;
  89         uint16_t sender_port, destination_port;
  90         uint32_t ttl;
  91
  92         /* For support of truncated packets */
  93         DnsPacket *more;
  94
  95         bool on_stack:1;
  96         bool extracted:1;
  97         bool refuse_compression:1;
  98         bool canonical_form:1;
  99 };
 100
 101 static inline uint8_t* DNS_PACKET_DATA(DnsPacket *p) {
 102         if (_unlikely_(!p))
 103                 return NULL;
 104
 105         if (p->_data)
 106                 return p->_data;
 107
 108         return ((uint8_t*) p) + ALIGN(sizeof(DnsPacket));
 109 }
 110
 111 #define DNS_PACKET_HEADER(p) ((DnsPacketHeader*) DNS_PACKET_DATA(p))
 112 #define DNS_PACKET_ID(p) DNS_PACKET_HEADER(p)->id
 113 #define DNS_PACKET_QR(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 15) & 1)
 114 #define DNS_PACKET_OPCODE(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 11) & 15)
 115 #define DNS_PACKET_AA(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 10) & 1)
 116 #define DNS_PACKET_TC(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 9) & 1)
 117 #define DNS_PACKET_RD(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 8) & 1)
 118 #define DNS_PACKET_RA(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 7) & 1)
 119 #define DNS_PACKET_AD(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 5) & 1)
 120 #define DNS_PACKET_CD(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 4) & 1)
 121 #define DNS_PACKET_RCODE(p) (be16toh(DNS_PACKET_HEADER(p)->flags) & 15)
 122
 123 /* LLMNR defines some bits differently */
 124 #define DNS_PACKET_LLMNR_C(p) DNS_PACKET_AA(p)
 125 #define DNS_PACKET_LLMNR_T(p) DNS_PACKET_RD(p)
 126
 127 #define DNS_PACKET_QDCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->qdcount)
 128 #define DNS_PACKET_ANCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->ancount)
 129 #define DNS_PACKET_NSCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->nscount)
 130 #define DNS_PACKET_ARCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->arcount)
 131
 132 #define DNS_PACKET_MAKE_FLAGS(qr, opcode, aa, tc, rd, ra, ad, cd, rcode) \
 133         (((uint16_t) !!(qr) << 15) |                                    \
 134          ((uint16_t) ((opcode) & 15) << 11) |                           \
 135          ((uint16_t) !!(aa) << 10) |                /* on LLMNR: c */   \
 136          ((uint16_t) !!(tc) << 9) |                                     \
 137          ((uint16_t) !!(rd) << 8) |                 /* on LLMNR: t */   \
 138          ((uint16_t) !!(ra) << 7) |                                     \
 139          ((uint16_t) !!(ad) << 5) |                                     \
 140          ((uint16_t) !!(cd) << 4) |                                     \
 141          ((uint16_t) ((rcode) & 15)))
 142
 143 static inline unsigned DNS_PACKET_RRCOUNT(DnsPacket *p) {
 144         return
 145                 (unsigned) DNS_PACKET_ANCOUNT(p) +
 146                 (unsigned) DNS_PACKET_NSCOUNT(p) +
 147                 (unsigned) DNS_PACKET_ARCOUNT(p);
 148 }
 149
 150 int dns_packet_new(DnsPacket **p, DnsProtocol protocol, size_t mtu);
 151 int dns_packet_new_query(DnsPacket **p, DnsProtocol protocol, size_t mtu, bool dnssec_checking_disabled);
 152
 153 void dns_packet_set_flags(DnsPacket *p, bool dnssec_checking_disabled, bool truncated);
 154
 155 DnsPacket *dns_packet_ref(DnsPacket *p);
 156 DnsPacket *dns_packet_unref(DnsPacket *p);
 157
 158 DEFINE_TRIVIAL_CLEANUP_FUNC(DnsPacket*, dns_packet_unref);
 159
 160 int dns_packet_validate(DnsPacket *p);
 161 int dns_packet_validate_reply(DnsPacket *p);
 162 int dns_packet_validate_query(DnsPacket *p);
 163
 164 int dns_packet_is_reply_for(DnsPacket *p, const DnsResourceKey *key);
 165
 166 int dns_packet_append_blob(DnsPacket *p, const void *d, size_t sz, size_t *start);
 167 int dns_packet_append_uint8(DnsPacket *p, uint8_t v, size_t *start);
 168 int dns_packet_append_uint16(DnsPacket *p, uint16_t v, size_t *start);
 169 int dns_packet_append_uint32(DnsPacket *p, uint32_t v, size_t *start);
 170 int dns_packet_append_string(DnsPacket *p, const char *s, size_t *start);
 171 int dns_packet_append_raw_string(DnsPacket *p, const void *s, size_t size, size_t *start);
 172 int dns_packet_append_label(DnsPacket *p, const char *s, size_t l, size_t *start);
 173 int dns_packet_append_name(DnsPacket *p, const char *name, bool allow_compression, size_t *start);
 174 int dns_packet_append_key(DnsPacket *p, const DnsResourceKey *key, size_t *start);
 175 int dns_packet_append_rr(DnsPacket *p, const DnsResourceRecord *rr, size_t *start, size_t *rdata_start);
 176 int dns_packet_append_opt_rr(DnsPacket *p, uint16_t max_udp_size, bool edns0_do, size_t *start);
 177
 178 void dns_packet_truncate(DnsPacket *p, size_t sz);
 179
 180 int dns_packet_read(DnsPacket *p, size_t sz, const void **ret, size_t *start);
 181 int dns_packet_read_blob(DnsPacket *p, void *d, size_t sz, size_t *start);
 182 int dns_packet_read_uint8(DnsPacket *p, uint8_t *ret, size_t *start);
 183 int dns_packet_read_uint16(DnsPacket *p, uint16_t *ret, size_t *start);
 184 int dns_packet_read_uint32(DnsPacket *p, uint32_t *ret, size_t *start);
 185 int dns_packet_read_string(DnsPacket *p, char **ret, size_t *start);
 186 int dns_packet_read_raw_string(DnsPacket *p, const void **ret, size_t *size, size_t *start);
 187 int dns_packet_read_name(DnsPacket *p, char **ret, bool allow_compression, size_t *start);
 188 int dns_packet_read_key(DnsPacket *p, DnsResourceKey **ret, size_t *start);
 189 int dns_packet_read_rr(DnsPacket *p, DnsResourceRecord **ret, size_t *start);
 190
 191 void dns_packet_rewind(DnsPacket *p, size_t idx);
 192
 193 int dns_packet_skip_question(DnsPacket *p);
 194 int dns_packet_extract(DnsPacket *p);
 195
 196 static inline bool DNS_PACKET_SHALL_CACHE(DnsPacket *p) {
 197         /* Never cache data originating from localhost, under the
 198          * assumption, that it's coming from a locally DNS forwarder
 199          * or server, that is caching on its own. */
 200
 201         return in_addr_is_localhost(p->family, &p->sender) == 0;
 202 }
 203
 204 enum {
 205         DNS_RCODE_SUCCESS = 0,
 206         DNS_RCODE_FORMERR = 1,
 207         DNS_RCODE_SERVFAIL = 2,
 208         DNS_RCODE_NXDOMAIN = 3,
 209         DNS_RCODE_NOTIMP = 4,
 210         DNS_RCODE_REFUSED = 5,
 211         DNS_RCODE_YXDOMAIN = 6,
 212         DNS_RCODE_YXRRSET = 7,
 213         DNS_RCODE_NXRRSET = 8,
 214         DNS_RCODE_NOTAUTH = 9,
 215         DNS_RCODE_NOTZONE = 10,
 216         DNS_RCODE_BADVERS = 16,
 217         DNS_RCODE_BADSIG = 16, /* duplicate value! */
 218         DNS_RCODE_BADKEY = 17,
 219         DNS_RCODE_BADTIME = 18,
 220         DNS_RCODE_BADMODE = 19,
 221         DNS_RCODE_BADNAME = 20,
 222         DNS_RCODE_BADALG = 21,
 223         DNS_RCODE_BADTRUNC = 22,
 224         _DNS_RCODE_MAX_DEFINED
 225 };
 226
 227 const char* dns_rcode_to_string(int i) _const_;
 228 int dns_rcode_from_string(const char *s) _pure_;
 229
 230 const char* dns_protocol_to_string(DnsProtocol p) _const_;
 231 DnsProtocol dns_protocol_from_string(const char *s) _pure_;
 232
 233 #define LLMNR_MULTICAST_IPV4_ADDRESS ((struct in_addr) { .s_addr = htobe32(224U << 24 | 252U) })
 234 #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 } })
 235
 236 #define MDNS_MULTICAST_IPV4_ADDRESS  ((struct in_addr) { .s_addr = htobe32(224U << 24 | 251U) })
 237 #define MDNS_MULTICAST_IPV6_ADDRESS  ((struct in6_addr) { .s6_addr = { 0xFF, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0xfb } })
 238
 239 static inline uint64_t SD_RESOLVED_FLAGS_MAKE(DnsProtocol protocol, int family, bool authenticated) {
 240         uint64_t f;
 241
 242         /* Converts a protocol + family into a flags field as used in queries and responses */
 243
 244         f = authenticated ? SD_RESOLVED_AUTHENTICATED : 0;
 245
 246         switch (protocol) {
 247         case DNS_PROTOCOL_DNS:
 248                 return f|SD_RESOLVED_DNS;
 249
 250         case DNS_PROTOCOL_LLMNR:
 251                 return f|(family == AF_INET6 ? SD_RESOLVED_LLMNR_IPV6 : SD_RESOLVED_LLMNR_IPV4);
 252
 253         case DNS_PROTOCOL_MDNS:
 254                 return family == AF_INET6 ? SD_RESOLVED_MDNS_IPV6 : SD_RESOLVED_MDNS_IPV4;
 255
 256         default:
 257                 break;
 258         }
 259
 260         return 0;
 261 }