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#pragma once
/***
This file is part of systemd.
Copyright 2014 Lennart Poettering
systemd is free software; you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version.
systemd is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with systemd; If not, see <http://www.gnu.org/licenses/>.
***/
#include <netinet/ip.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 = -1
} DnsProtocol;
struct DnsPacketHeader {
uint16_t id;
be16_t flags;
be16_t qdcount;
be16_t ancount;
be16_t nscount;
be16_t arcount;
};
#define DNS_PACKET_HEADER_SIZE sizeof(DnsPacketHeader)
#define UDP_PACKET_HEADER_SIZE (sizeof(struct iphdr) + sizeof(struct udphdr))
/* The various DNS protocols deviate in how large a packet can grow,
but the TCP transport has a 16bit size field, hence that appears to
be the absolute maximum. */
#define DNS_PACKET_SIZE_MAX 0xFFFF
/* RFC 1035 say 512 is the maximum, for classic unicast DNS */
#define DNS_PACKET_UNICAST_SIZE_MAX 512
/* With EDNS0 we can use larger packets, default to 4096, which is what is commonly used */
#define DNS_PACKET_UNICAST_SIZE_LARGE_MAX 4096
#define DNS_PACKET_SIZE_START 512
struct DnsPacket {
int n_ref;
DnsProtocol protocol;
size_t size, allocated, rindex;
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;
/* Packet reception metadata */
int ifindex;
int family, ipproto;
union in_addr_union sender, destination;
uint16_t sender_port, destination_port;
uint32_t ttl;
/* For support of truncated packets */
DnsPacket *more;
bool on_stack:1;
bool extracted:1;
bool refuse_compression:1;
bool canonical_form:1;
};
static inline uint8_t* DNS_PACKET_DATA(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)
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) & 15);
}
/* 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 mtu);
int dns_packet_new_query(DnsPacket **p, DnsProtocol protocol, size_t mtu, bool dnssec_checking_disabled);
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);
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, size_t *start);
int dns_packet_append_rr(DnsPacket *p, const DnsResourceRecord *rr, size_t *start, size_t *rdata_start);
int dns_packet_append_opt(DnsPacket *p, uint16_t max_udp_size, bool edns0_do, size_t *start);
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, 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);
static inline bool DNS_PACKET_SHALL_CACHE(DnsPacket *p) {
/* Never cache data originating from localhost, under the
* assumption, that it's coming from a locally DNS forwarder
* or server, that is caching on its own. */
return in_addr_is_localhost(p->family, &p->sender) == 0;
}
/* 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_MAX_DEFINED
};
const char* dns_rcode_to_string(int i) _const_;
int dns_rcode_from_string(const char *s) _pure_;
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 } })
static inline uint64_t SD_RESOLVED_FLAGS_MAKE(DnsProtocol protocol, int family, bool authenticated) {
uint64_t f;
/* Converts a protocol + family into a flags field as used in queries and responses */
f = authenticated ? SD_RESOLVED_AUTHENTICATED : 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 family == AF_INET6 ? SD_RESOLVED_MDNS_IPV6 : SD_RESOLVED_MDNS_IPV4;
default:
break;
}
return 0;
}
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