435 lines
14 KiB
C
435 lines
14 KiB
C
/* SPDX-License-Identifier: LGPL-2.1+ */
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#include "alloc-util.h"
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#include "hostname-util.h"
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#include "local-addresses.h"
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#include "missing_network.h"
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#include "resolved-dns-synthesize.h"
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int dns_synthesize_ifindex(int ifindex) {
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/* When the caller asked for resolving on a specific
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* interface, we synthesize the answer for that
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* interface. However, if nothing specific was claimed and we
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* only return localhost RRs, we synthesize the answer for
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* localhost. */
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if (ifindex > 0)
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return ifindex;
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return LOOPBACK_IFINDEX;
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}
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int dns_synthesize_family(uint64_t flags) {
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/* Picks an address family depending on set flags. This is
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* purely for synthesized answers, where the family we return
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* for the reply should match what was requested in the
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* question, even though we are synthesizing the answer
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* here. */
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if (!(flags & SD_RESOLVED_DNS)) {
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if (flags & (SD_RESOLVED_LLMNR_IPV4|SD_RESOLVED_MDNS_IPV4))
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return AF_INET;
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if (flags & (SD_RESOLVED_LLMNR_IPV6|SD_RESOLVED_MDNS_IPV6))
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return AF_INET6;
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}
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return AF_UNSPEC;
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}
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DnsProtocol dns_synthesize_protocol(uint64_t flags) {
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/* Similar as dns_synthesize_family() but does this for the
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* protocol. If resolving via DNS was requested, we claim it
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* was DNS. Similar, if nothing specific was
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* requested. However, if only resolving via LLMNR was
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* requested we return that. */
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if (flags & SD_RESOLVED_DNS)
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return DNS_PROTOCOL_DNS;
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if (flags & SD_RESOLVED_LLMNR)
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return DNS_PROTOCOL_LLMNR;
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if (flags & SD_RESOLVED_MDNS)
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return DNS_PROTOCOL_MDNS;
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return DNS_PROTOCOL_DNS;
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}
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static int synthesize_localhost_rr(Manager *m, const DnsResourceKey *key, int ifindex, DnsAnswer **answer) {
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int r;
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assert(m);
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assert(key);
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assert(answer);
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r = dns_answer_reserve(answer, 2);
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if (r < 0)
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return r;
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if (IN_SET(key->type, DNS_TYPE_A, DNS_TYPE_ANY)) {
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_cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL;
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rr = dns_resource_record_new_full(DNS_CLASS_IN, DNS_TYPE_A, dns_resource_key_name(key));
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if (!rr)
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return -ENOMEM;
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rr->a.in_addr.s_addr = htobe32(INADDR_LOOPBACK);
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r = dns_answer_add(*answer, rr, dns_synthesize_ifindex(ifindex), DNS_ANSWER_AUTHENTICATED);
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if (r < 0)
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return r;
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}
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if (IN_SET(key->type, DNS_TYPE_AAAA, DNS_TYPE_ANY)) {
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_cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL;
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rr = dns_resource_record_new_full(DNS_CLASS_IN, DNS_TYPE_AAAA, dns_resource_key_name(key));
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if (!rr)
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return -ENOMEM;
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rr->aaaa.in6_addr = in6addr_loopback;
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r = dns_answer_add(*answer, rr, dns_synthesize_ifindex(ifindex), DNS_ANSWER_AUTHENTICATED);
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if (r < 0)
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return r;
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}
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return 0;
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}
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static int answer_add_ptr(DnsAnswer **answer, const char *from, const char *to, int ifindex, DnsAnswerFlags flags) {
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_cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL;
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rr = dns_resource_record_new_full(DNS_CLASS_IN, DNS_TYPE_PTR, from);
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if (!rr)
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return -ENOMEM;
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rr->ptr.name = strdup(to);
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if (!rr->ptr.name)
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return -ENOMEM;
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return dns_answer_add(*answer, rr, ifindex, flags);
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}
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static int synthesize_localhost_ptr(Manager *m, const DnsResourceKey *key, int ifindex, DnsAnswer **answer) {
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int r;
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assert(m);
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assert(key);
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assert(answer);
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if (IN_SET(key->type, DNS_TYPE_PTR, DNS_TYPE_ANY)) {
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r = dns_answer_reserve(answer, 1);
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if (r < 0)
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return r;
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r = answer_add_ptr(answer, dns_resource_key_name(key), "localhost", dns_synthesize_ifindex(ifindex), DNS_ANSWER_AUTHENTICATED);
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if (r < 0)
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return r;
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}
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return 0;
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}
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static int answer_add_addresses_rr(
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DnsAnswer **answer,
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const char *name,
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struct local_address *addresses,
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unsigned n_addresses) {
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unsigned j;
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int r;
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assert(answer);
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assert(name);
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r = dns_answer_reserve(answer, n_addresses);
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if (r < 0)
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return r;
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for (j = 0; j < n_addresses; j++) {
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_cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL;
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r = dns_resource_record_new_address(&rr, addresses[j].family, &addresses[j].address, name);
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if (r < 0)
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return r;
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r = dns_answer_add(*answer, rr, addresses[j].ifindex, DNS_ANSWER_AUTHENTICATED);
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if (r < 0)
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return r;
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}
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return 0;
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}
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static int answer_add_addresses_ptr(
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DnsAnswer **answer,
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const char *name,
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struct local_address *addresses,
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unsigned n_addresses,
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int af, const union in_addr_union *match) {
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bool added = false;
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unsigned j;
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int r;
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assert(answer);
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assert(name);
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for (j = 0; j < n_addresses; j++) {
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_cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL;
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if (af != AF_UNSPEC) {
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if (addresses[j].family != af)
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continue;
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if (match && !in_addr_equal(af, match, &addresses[j].address))
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continue;
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}
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r = dns_answer_reserve(answer, 1);
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if (r < 0)
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return r;
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r = dns_resource_record_new_reverse(&rr, addresses[j].family, &addresses[j].address, name);
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if (r < 0)
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return r;
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r = dns_answer_add(*answer, rr, addresses[j].ifindex, DNS_ANSWER_AUTHENTICATED);
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if (r < 0)
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return r;
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added = true;
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}
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return added;
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}
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static int synthesize_system_hostname_rr(Manager *m, const DnsResourceKey *key, int ifindex, DnsAnswer **answer) {
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_cleanup_free_ struct local_address *addresses = NULL;
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int n = 0, af;
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assert(m);
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assert(key);
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assert(answer);
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af = dns_type_to_af(key->type);
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if (af >= 0) {
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n = local_addresses(m->rtnl, ifindex, af, &addresses);
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if (n < 0)
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return n;
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if (n == 0) {
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struct local_address buffer[2];
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/* If we have no local addresses then use ::1
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* and 127.0.0.2 as local ones. */
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if (IN_SET(af, AF_INET, AF_UNSPEC))
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buffer[n++] = (struct local_address) {
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.family = AF_INET,
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.ifindex = dns_synthesize_ifindex(ifindex),
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.address.in.s_addr = htobe32(0x7F000002),
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};
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if (IN_SET(af, AF_INET6, AF_UNSPEC))
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buffer[n++] = (struct local_address) {
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.family = AF_INET6,
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.ifindex = dns_synthesize_ifindex(ifindex),
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.address.in6 = in6addr_loopback,
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};
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return answer_add_addresses_rr(answer,
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dns_resource_key_name(key),
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buffer, n);
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}
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}
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return answer_add_addresses_rr(answer, dns_resource_key_name(key), addresses, n);
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}
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static int synthesize_system_hostname_ptr(Manager *m, int af, const union in_addr_union *address, int ifindex, DnsAnswer **answer) {
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_cleanup_free_ struct local_address *addresses = NULL;
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bool added = false;
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int n, r;
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assert(m);
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assert(address);
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assert(answer);
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if (af == AF_INET && address->in.s_addr == htobe32(0x7F000002)) {
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/* Always map the IPv4 address 127.0.0.2 to the local hostname, in addition to "localhost": */
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r = dns_answer_reserve(answer, 4);
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if (r < 0)
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return r;
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r = answer_add_ptr(answer, "2.0.0.127.in-addr.arpa", m->full_hostname, dns_synthesize_ifindex(ifindex), DNS_ANSWER_AUTHENTICATED);
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if (r < 0)
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return r;
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r = answer_add_ptr(answer, "2.0.0.127.in-addr.arpa", m->llmnr_hostname, dns_synthesize_ifindex(ifindex), DNS_ANSWER_AUTHENTICATED);
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if (r < 0)
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return r;
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r = answer_add_ptr(answer, "2.0.0.127.in-addr.arpa", m->mdns_hostname, dns_synthesize_ifindex(ifindex), DNS_ANSWER_AUTHENTICATED);
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if (r < 0)
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return r;
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r = answer_add_ptr(answer, "2.0.0.127.in-addr.arpa", "localhost", dns_synthesize_ifindex(ifindex), DNS_ANSWER_AUTHENTICATED);
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if (r < 0)
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return r;
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return 1;
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}
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n = local_addresses(m->rtnl, ifindex, af, &addresses);
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if (n <= 0)
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return n;
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r = answer_add_addresses_ptr(answer, m->full_hostname, addresses, n, af, address);
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if (r < 0)
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return r;
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if (r > 0)
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added = true;
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r = answer_add_addresses_ptr(answer, m->llmnr_hostname, addresses, n, af, address);
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if (r < 0)
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return r;
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if (r > 0)
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added = true;
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r = answer_add_addresses_ptr(answer, m->mdns_hostname, addresses, n, af, address);
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if (r < 0)
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return r;
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if (r > 0)
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added = true;
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return added;
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}
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static int synthesize_gateway_rr(Manager *m, const DnsResourceKey *key, int ifindex, DnsAnswer **answer) {
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_cleanup_free_ struct local_address *addresses = NULL;
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int n = 0, af, r;
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assert(m);
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assert(key);
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assert(answer);
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af = dns_type_to_af(key->type);
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if (af >= 0) {
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n = local_gateways(m->rtnl, ifindex, af, &addresses);
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if (n <= 0)
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return n; /* < 0 means: error; == 0 means we have no gateway */
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}
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r = answer_add_addresses_rr(answer, dns_resource_key_name(key), addresses, n);
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if (r < 0)
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return r;
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return 1; /* > 0 means: we have some gateway */
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}
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static int synthesize_gateway_ptr(Manager *m, int af, const union in_addr_union *address, int ifindex, DnsAnswer **answer) {
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_cleanup_free_ struct local_address *addresses = NULL;
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int n;
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assert(m);
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assert(address);
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assert(answer);
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n = local_gateways(m->rtnl, ifindex, af, &addresses);
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if (n <= 0)
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return n;
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return answer_add_addresses_ptr(answer, "_gateway", addresses, n, af, address);
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}
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int dns_synthesize_answer(
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Manager *m,
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DnsQuestion *q,
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int ifindex,
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DnsAnswer **ret) {
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_cleanup_(dns_answer_unrefp) DnsAnswer *answer = NULL;
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DnsResourceKey *key;
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bool found = false, nxdomain = false;
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int r;
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assert(m);
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assert(q);
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DNS_QUESTION_FOREACH(key, q) {
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union in_addr_union address;
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const char *name;
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int af;
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if (!IN_SET(key->class, DNS_CLASS_IN, DNS_CLASS_ANY))
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continue;
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name = dns_resource_key_name(key);
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if (is_localhost(name)) {
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r = synthesize_localhost_rr(m, key, ifindex, &answer);
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if (r < 0)
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return log_error_errno(r, "Failed to synthesize localhost RRs: %m");
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} else if (manager_is_own_hostname(m, name)) {
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r = synthesize_system_hostname_rr(m, key, ifindex, &answer);
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if (r < 0)
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return log_error_errno(r, "Failed to synthesize system hostname RRs: %m");
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} else if (is_gateway_hostname(name)) {
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r = synthesize_gateway_rr(m, key, ifindex, &answer);
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if (r < 0)
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return log_error_errno(r, "Failed to synthesize gateway RRs: %m");
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if (r == 0) { /* if we have no gateway return NXDOMAIN */
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nxdomain = true;
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continue;
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}
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} else if ((dns_name_endswith(name, "127.in-addr.arpa") > 0 && dns_name_equal(name, "2.0.0.127.in-addr.arpa") == 0) ||
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dns_name_equal(name, "1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa") > 0) {
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r = synthesize_localhost_ptr(m, key, ifindex, &answer);
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if (r < 0)
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return log_error_errno(r, "Failed to synthesize localhost PTR RRs: %m");
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} else if (dns_name_address(name, &af, &address) > 0) {
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int v, w;
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v = synthesize_system_hostname_ptr(m, af, &address, ifindex, &answer);
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if (v < 0)
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return log_error_errno(v, "Failed to synthesize system hostname PTR RR: %m");
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w = synthesize_gateway_ptr(m, af, &address, ifindex, &answer);
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if (w < 0)
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return log_error_errno(w, "Failed to synthesize gateway hostname PTR RR: %m");
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if (v == 0 && w == 0) /* This IP address is neither a local one nor a gateway */
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continue;
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} else
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continue;
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found = true;
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}
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if (found) {
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if (ret)
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*ret = TAKE_PTR(answer);
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return 1;
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} else if (nxdomain)
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return -ENXIO;
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return 0;
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}
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