-/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
-
+/* SPDX-License-Identifier: LGPL-2.1+ */
#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>
#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
+ * 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 512
+#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 4096
-
-#define DNS_PACKET_SIZE_START 512
+#define DNS_PACKET_UNICAST_SIZE_LARGE_MAX 4096u
struct DnsPacket {
- int n_ref;
+ unsigned n_ref;
DnsProtocol protocol;
- size_t size, allocated, rindex;
+ 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;
#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;
else
rcode = 0;
- return rcode | (be16toh(DNS_PACKET_HEADER(p)->flags) & 15);
+ 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 */
(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);
+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);
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);
+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, 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);
DNS_RCODE_BADNAME = 20,
DNS_RCODE_BADALG = 21,
DNS_RCODE_BADTRUNC = 22,
- _DNS_RCODE_MAX_DEFINED
+ 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_;
#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;
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;
+ return f|(family == AF_INET6 ? SD_RESOLVED_MDNS_IPV6 : SD_RESOLVED_MDNS_IPV4);
default:
- break;
+ 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 0;
+ return p->max_size != 0 ? p->max_size : DNS_PACKET_SIZE_MAX;
}
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