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         /* For support of truncated packets */
  92         DnsPacket *more;
  93
  94         bool on_stack:1;
  95         bool extracted:1;
  96         bool refuse_compression:1;
  97         bool canonical_form:1;
  98 };
  99
 100 static inline uint8_t* DNS_PACKET_DATA(DnsPacket *p) {
 101         if (_unlikely_(!p))
 102                 return NULL;
 103
 104         if (p->_data)
 105                 return p->_data;
 106
 107         return ((uint8_t*) p) + ALIGN(sizeof(DnsPacket));
 108 }
 109
 110 #define DNS_PACKET_HEADER(p) ((DnsPacketHeader*) DNS_PACKET_DATA(p))
 111 #define DNS_PACKET_ID(p) DNS_PACKET_HEADER(p)->id
 112 #define DNS_PACKET_QR(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 15) & 1)
 113 #define DNS_PACKET_OPCODE(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 11) & 15)
 114 #define DNS_PACKET_AA(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 10) & 1)
 115 #define DNS_PACKET_TC(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 9) & 1)
 116 #define DNS_PACKET_RD(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 8) & 1)
 117 #define DNS_PACKET_RA(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 7) & 1)
 118 #define DNS_PACKET_AD(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 5) & 1)
 119 #define DNS_PACKET_CD(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 4) & 1)
 120 #define DNS_PACKET_RCODE(p) (be16toh(DNS_PACKET_HEADER(p)->flags) & 15)
 121
 122 /* LLMNR defines some bits differently */
 123 #define DNS_PACKET_LLMNR_C(p) DNS_PACKET_AA(p)
 124 #define DNS_PACKET_LLMNR_T(p) DNS_PACKET_RD(p)
 125
 126 #define DNS_PACKET_QDCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->qdcount)
 127 #define DNS_PACKET_ANCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->ancount)
 128 #define DNS_PACKET_NSCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->nscount)
 129 #define DNS_PACKET_ARCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->arcount)
 130
 131 #define DNS_PACKET_MAKE_FLAGS(qr, opcode, aa, tc, rd, ra, ad, cd, rcode) \
 132         (((uint16_t) !!(qr) << 15) |                                    \
 133          ((uint16_t) ((opcode) & 15) << 11) |                           \
 134          ((uint16_t) !!(aa) << 10) |                /* on LLMNR: c */   \
 135          ((uint16_t) !!(tc) << 9) |                                     \
 136          ((uint16_t) !!(rd) << 8) |                 /* on LLMNR: t */   \
 137          ((uint16_t) !!(ra) << 7) |                                     \
 138          ((uint16_t) !!(ad) << 5) |                                     \
 139          ((uint16_t) !!(cd) << 4) |                                     \
 140          ((uint16_t) ((rcode) & 15)))
 141
 142 static inline unsigned DNS_PACKET_RRCOUNT(DnsPacket *p) {
 143         return
 144                 (unsigned) DNS_PACKET_ANCOUNT(p) +
 145                 (unsigned) DNS_PACKET_NSCOUNT(p) +
 146                 (unsigned) DNS_PACKET_ARCOUNT(p);
 147 }
 148
 149 int dns_packet_new(DnsPacket **p, DnsProtocol protocol, size_t mtu);
 150 int dns_packet_new_query(DnsPacket **p, DnsProtocol protocol, size_t mtu, bool dnssec_checking_disabled);
 151
 152 void dns_packet_set_flags(DnsPacket *p, bool dnssec_checking_disabled, bool truncated);
 153
 154 DnsPacket *dns_packet_ref(DnsPacket *p);
 155 DnsPacket *dns_packet_unref(DnsPacket *p);
 156
 157 DEFINE_TRIVIAL_CLEANUP_FUNC(DnsPacket*, dns_packet_unref);
 158
 159 int dns_packet_validate(DnsPacket *p);
 160 int dns_packet_validate_reply(DnsPacket *p);
 161 int dns_packet_validate_query(DnsPacket *p);
 162
 163 int dns_packet_append_blob(DnsPacket *p, const void *d, size_t sz, size_t *start);
 164 int dns_packet_append_uint8(DnsPacket *p, uint8_t v, size_t *start);
 165 int dns_packet_append_uint16(DnsPacket *p, uint16_t v, size_t *start);
 166 int dns_packet_append_uint32(DnsPacket *p, uint32_t v, size_t *start);
 167 int dns_packet_append_string(DnsPacket *p, const char *s, size_t *start);
 168 int dns_packet_append_raw_string(DnsPacket *p, const void *s, size_t size, size_t *start);
 169 int dns_packet_append_label(DnsPacket *p, const char *s, size_t l, size_t *start);
 170 int dns_packet_append_name(DnsPacket *p, const char *name, bool allow_compression, size_t *start);
 171 int dns_packet_append_key(DnsPacket *p, const DnsResourceKey *key, size_t *start);
 172 int dns_packet_append_rr(DnsPacket *p, const DnsResourceRecord *rr, size_t *start, size_t *rdata_start);
 173 int dns_packet_append_opt_rr(DnsPacket *p, uint16_t max_udp_size, bool edns0_do, size_t *start);
 174
 175 void dns_packet_truncate(DnsPacket *p, size_t sz);
 176
 177 int dns_packet_read(DnsPacket *p, size_t sz, const void **ret, size_t *start);
 178 int dns_packet_read_blob(DnsPacket *p, void *d, size_t sz, size_t *start);
 179 int dns_packet_read_uint8(DnsPacket *p, uint8_t *ret, size_t *start);
 180 int dns_packet_read_uint16(DnsPacket *p, uint16_t *ret, size_t *start);
 181 int dns_packet_read_uint32(DnsPacket *p, uint32_t *ret, size_t *start);
 182 int dns_packet_read_string(DnsPacket *p, char **ret, size_t *start);
 183 int dns_packet_read_raw_string(DnsPacket *p, const void **ret, size_t *size, size_t *start);
 184 int dns_packet_read_name(DnsPacket *p, char **ret, bool allow_compression, size_t *start);
 185 int dns_packet_read_key(DnsPacket *p, DnsResourceKey **ret, size_t *start);
 186 int dns_packet_read_rr(DnsPacket *p, DnsResourceRecord **ret, size_t *start);
 187
 188 void dns_packet_rewind(DnsPacket *p, size_t idx);
 189
 190 int dns_packet_skip_question(DnsPacket *p);
 191 int dns_packet_extract(DnsPacket *p);
 192
 193 static inline bool DNS_PACKET_SHALL_CACHE(DnsPacket *p) {
 194         /* Never cache data originating from localhost, under the
 195          * assumption, that it's coming from a locally DNS forwarder
 196          * or server, that is caching on its own. */
 197
 198         return in_addr_is_localhost(p->family, &p->sender) == 0;
 199 }
 200
 201 enum {
 202         DNS_RCODE_SUCCESS = 0,
 203         DNS_RCODE_FORMERR = 1,
 204         DNS_RCODE_SERVFAIL = 2,
 205         DNS_RCODE_NXDOMAIN = 3,
 206         DNS_RCODE_NOTIMP = 4,
 207         DNS_RCODE_REFUSED = 5,
 208         DNS_RCODE_YXDOMAIN = 6,
 209         DNS_RCODE_YXRRSET = 7,
 210         DNS_RCODE_NXRRSET = 8,
 211         DNS_RCODE_NOTAUTH = 9,
 212         DNS_RCODE_NOTZONE = 10,
 213         DNS_RCODE_BADVERS = 16,
 214         DNS_RCODE_BADSIG = 16, /* duplicate value! */
 215         DNS_RCODE_BADKEY = 17,
 216         DNS_RCODE_BADTIME = 18,
 217         DNS_RCODE_BADMODE = 19,
 218         DNS_RCODE_BADNAME = 20,
 219         DNS_RCODE_BADALG = 21,
 220         DNS_RCODE_BADTRUNC = 22,
 221         _DNS_RCODE_MAX_DEFINED
 222 };
 223
 224 const char* dns_rcode_to_string(int i) _const_;
 225 int dns_rcode_from_string(const char *s) _pure_;
 226
 227 const char* dns_protocol_to_string(DnsProtocol p) _const_;
 228 DnsProtocol dns_protocol_from_string(const char *s) _pure_;
 229
 230 #define LLMNR_MULTICAST_IPV4_ADDRESS ((struct in_addr) { .s_addr = htobe32(224U << 24 | 252U) })
 231 #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 } })
 232
 233 #define MDNS_MULTICAST_IPV4_ADDRESS  ((struct in_addr) { .s_addr = htobe32(224U << 24 | 251U) })
 234 #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 } })
 235
 236 static inline uint64_t SD_RESOLVED_FLAGS_MAKE(DnsProtocol protocol, int family, bool authenticated) {
 237         uint64_t f;
 238
 239         /* Converts a protocol + family into a flags field as used in queries and responses */
 240
 241         f = authenticated ? SD_RESOLVED_AUTHENTICATED : 0;
 242
 243         switch (protocol) {
 244         case DNS_PROTOCOL_DNS:
 245                 return f|SD_RESOLVED_DNS;
 246
 247         case DNS_PROTOCOL_LLMNR:
 248                 return f|(family == AF_INET6 ? SD_RESOLVED_LLMNR_IPV6 : SD_RESOLVED_LLMNR_IPV4);
 249
 250         case DNS_PROTOCOL_MDNS:
 251                 return family == AF_INET6 ? SD_RESOLVED_MDNS_IPV6 : SD_RESOLVED_MDNS_IPV4;
 252
 253         default:
 254                 break;
 255         }
 256
 257         return 0;
 258 }