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
  84         /* Packet reception metadata */
  85         int ifindex;
  86         int family, ipproto;
  87         union in_addr_union sender, destination;
  88         uint16_t sender_port, destination_port;
  89         uint32_t ttl;
  90
  91         bool on_stack:1;
  92         bool extracted:1;
  93         bool refuse_compression:1;
  94         bool canonical_form:1;
  95 };
  96
  97 static inline uint8_t* DNS_PACKET_DATA(DnsPacket *p) {
  98         if (_unlikely_(!p))
  99                 return NULL;
 100
 101         if (p->_data)
 102                 return p->_data;
 103
 104         return ((uint8_t*) p) + ALIGN(sizeof(DnsPacket));
 105 }
 106
 107 #define DNS_PACKET_HEADER(p) ((DnsPacketHeader*) DNS_PACKET_DATA(p))
 108 #define DNS_PACKET_ID(p) DNS_PACKET_HEADER(p)->id
 109 #define DNS_PACKET_QR(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 15) & 1)
 110 #define DNS_PACKET_OPCODE(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 11) & 15)
 111 #define DNS_PACKET_AA(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 10) & 1)
 112 #define DNS_PACKET_TC(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 9) & 1)
 113 #define DNS_PACKET_RD(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 8) & 1)
 114 #define DNS_PACKET_RA(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 7) & 1)
 115 #define DNS_PACKET_AD(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 5) & 1)
 116 #define DNS_PACKET_CD(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 4) & 1)
 117 #define DNS_PACKET_RCODE(p) (be16toh(DNS_PACKET_HEADER(p)->flags) & 15)
 118
 119 /* LLMNR defines some bits differently */
 120 #define DNS_PACKET_LLMNR_C(p) DNS_PACKET_AA(p)
 121 #define DNS_PACKET_LLMNR_T(p) DNS_PACKET_RD(p)
 122
 123 #define DNS_PACKET_QDCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->qdcount)
 124 #define DNS_PACKET_ANCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->ancount)
 125 #define DNS_PACKET_NSCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->nscount)
 126 #define DNS_PACKET_ARCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->arcount)
 127
 128 #define DNS_PACKET_MAKE_FLAGS(qr, opcode, aa, tc, rd, ra, ad, cd, rcode) \
 129         (((uint16_t) !!(qr) << 15) |                                    \
 130          ((uint16_t) ((opcode) & 15) << 11) |                           \
 131          ((uint16_t) !!(aa) << 10) |                /* on LLMNR: c */   \
 132          ((uint16_t) !!(tc) << 9) |                                     \
 133          ((uint16_t) !!(rd) << 8) |                 /* on LLMNR: t */   \
 134          ((uint16_t) !!(ra) << 7) |                                     \
 135          ((uint16_t) !!(ad) << 5) |                                     \
 136          ((uint16_t) !!(cd) << 4) |                                     \
 137          ((uint16_t) ((rcode) & 15)))
 138
 139 static inline unsigned DNS_PACKET_RRCOUNT(DnsPacket *p) {
 140         return
 141                 (unsigned) DNS_PACKET_ANCOUNT(p) +
 142                 (unsigned) DNS_PACKET_NSCOUNT(p) +
 143                 (unsigned) DNS_PACKET_ARCOUNT(p);
 144 }
 145
 146 int dns_packet_new(DnsPacket **p, DnsProtocol protocol, size_t mtu);
 147 int dns_packet_new_query(DnsPacket **p, DnsProtocol protocol, size_t mtu, bool dnssec_checking_disabled);
 148
 149 DnsPacket *dns_packet_ref(DnsPacket *p);
 150 DnsPacket *dns_packet_unref(DnsPacket *p);
 151
 152 DEFINE_TRIVIAL_CLEANUP_FUNC(DnsPacket*, dns_packet_unref);
 153
 154 int dns_packet_validate(DnsPacket *p);
 155 int dns_packet_validate_reply(DnsPacket *p);
 156 int dns_packet_validate_query(DnsPacket *p);
 157
 158 int dns_packet_append_blob(DnsPacket *p, const void *d, size_t sz, size_t *start);
 159 int dns_packet_append_uint8(DnsPacket *p, uint8_t v, size_t *start);
 160 int dns_packet_append_uint16(DnsPacket *p, uint16_t v, size_t *start);
 161 int dns_packet_append_uint32(DnsPacket *p, uint32_t v, size_t *start);
 162 int dns_packet_append_string(DnsPacket *p, const char *s, size_t *start);
 163 int dns_packet_append_raw_string(DnsPacket *p, const void *s, size_t size, size_t *start);
 164 int dns_packet_append_label(DnsPacket *p, const char *s, size_t l, size_t *start);
 165 int dns_packet_append_name(DnsPacket *p, const char *name, bool allow_compression, size_t *start);
 166 int dns_packet_append_key(DnsPacket *p, const DnsResourceKey *key, size_t *start);
 167 int dns_packet_append_rr(DnsPacket *p, const DnsResourceRecord *rr, size_t *start, size_t *rdata_start);
 168 int dns_packet_append_opt_rr(DnsPacket *p, uint16_t max_udp_size, bool edns0_do, size_t *start);
 169
 170 void dns_packet_truncate(DnsPacket *p, size_t sz);
 171
 172 int dns_packet_read(DnsPacket *p, size_t sz, const void **ret, size_t *start);
 173 int dns_packet_read_blob(DnsPacket *p, void *d, size_t sz, size_t *start);
 174 int dns_packet_read_uint8(DnsPacket *p, uint8_t *ret, size_t *start);
 175 int dns_packet_read_uint16(DnsPacket *p, uint16_t *ret, size_t *start);
 176 int dns_packet_read_uint32(DnsPacket *p, uint32_t *ret, size_t *start);
 177 int dns_packet_read_string(DnsPacket *p, char **ret, size_t *start);
 178 int dns_packet_read_raw_string(DnsPacket *p, const void **ret, size_t *size, size_t *start);
 179 int dns_packet_read_name(DnsPacket *p, char **ret, bool allow_compression, size_t *start);
 180 int dns_packet_read_key(DnsPacket *p, DnsResourceKey **ret, size_t *start);
 181 int dns_packet_read_rr(DnsPacket *p, DnsResourceRecord **ret, size_t *start);
 182
 183 void dns_packet_rewind(DnsPacket *p, size_t idx);
 184
 185 int dns_packet_skip_question(DnsPacket *p);
 186 int dns_packet_extract(DnsPacket *p);
 187
 188 static inline bool DNS_PACKET_SHALL_CACHE(DnsPacket *p) {
 189         /* Never cache data originating from localhost, under the
 190          * assumption, that it's coming from a locally DNS forwarder
 191          * or server, that is caching on its own. */
 192
 193         return in_addr_is_localhost(p->family, &p->sender) == 0;
 194 }
 195
 196 enum {
 197         DNS_RCODE_SUCCESS = 0,
 198         DNS_RCODE_FORMERR = 1,
 199         DNS_RCODE_SERVFAIL = 2,
 200         DNS_RCODE_NXDOMAIN = 3,
 201         DNS_RCODE_NOTIMP = 4,
 202         DNS_RCODE_REFUSED = 5,
 203         DNS_RCODE_YXDOMAIN = 6,
 204         DNS_RCODE_YXRRSET = 7,
 205         DNS_RCODE_NXRRSET = 8,
 206         DNS_RCODE_NOTAUTH = 9,
 207         DNS_RCODE_NOTZONE = 10,
 208         DNS_RCODE_BADVERS = 16,
 209         DNS_RCODE_BADSIG = 16, /* duplicate value! */
 210         DNS_RCODE_BADKEY = 17,
 211         DNS_RCODE_BADTIME = 18,
 212         DNS_RCODE_BADMODE = 19,
 213         DNS_RCODE_BADNAME = 20,
 214         DNS_RCODE_BADALG = 21,
 215         DNS_RCODE_BADTRUNC = 22,
 216         _DNS_RCODE_MAX_DEFINED
 217 };
 218
 219 const char* dns_rcode_to_string(int i) _const_;
 220 int dns_rcode_from_string(const char *s) _pure_;
 221
 222 const char* dns_protocol_to_string(DnsProtocol p) _const_;
 223 DnsProtocol dns_protocol_from_string(const char *s) _pure_;
 224
 225 #define LLMNR_MULTICAST_IPV4_ADDRESS ((struct in_addr) { .s_addr = htobe32(224U << 24 | 252U) })
 226 #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 } })
 227
 228 static inline uint64_t SD_RESOLVED_FLAGS_MAKE(DnsProtocol protocol, int family, bool authenticated) {
 229         uint64_t f;
 230
 231         /* Converts a protocol + family into a flags field as used in queries and responses */
 232
 233         f = authenticated ? SD_RESOLVED_AUTHENTICATED : 0;
 234
 235         switch (protocol) {
 236         case DNS_PROTOCOL_DNS:
 237                 return f|SD_RESOLVED_DNS;
 238
 239         case DNS_PROTOCOL_LLMNR:
 240                 return f|(family == AF_INET6 ? SD_RESOLVED_LLMNR_IPV6 : SD_RESOLVED_LLMNR_IPV4);
 241
 242         case DNS_PROTOCOL_MDNS:
 243                 return family == AF_INET6 ? SD_RESOLVED_MDNS_IPV6 : SD_RESOLVED_MDNS_IPV4;
 244
 245         default:
 246                 break;
 247         }
 248
 249         return 0;
 250 }