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-rw-r--r--src/resolve/resolved-dns-packet.h302
1 files changed, 302 insertions, 0 deletions
diff --git a/src/resolve/resolved-dns-packet.h b/src/resolve/resolved-dns-packet.h
new file mode 100644
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--- /dev/null
+++ b/src/resolve/resolved-dns-packet.h
@@ -0,0 +1,302 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+#pragma once
+
+#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 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 4096, which is what is commonly used */
+#define DNS_PACKET_UNICAST_SIZE_LARGE_MAX 4096u
+
+struct DnsPacket {
+ unsigned n_ref;
+ DnsProtocol protocol;
+ size_t size, allocated, rindex, max_size;
+ 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)
+
+#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 >> 24);
+ 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);
+}
+
+/* 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);
+
+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, 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, int rcode, size_t *start);
+int dns_packet_append_question(DnsPacket *p, DnsQuestion *q);
+int dns_packet_append_answer(DnsPacket *p, DnsAnswer *a);
+
+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_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* 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) {
+ 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 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;
+}
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