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-rw-r--r--src/resolve/resolved-dns-synthesize.c418
1 files changed, 418 insertions, 0 deletions
diff --git a/src/resolve/resolved-dns-synthesize.c b/src/resolve/resolved-dns-synthesize.c
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+++ b/src/resolve/resolved-dns-synthesize.c
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+/***
+ 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 "alloc-util.h"
+#include "hostname-util.h"
+#include "local-addresses.h"
+#include "resolved-dns-synthesize.h"
+
+static int SYNTHESIZE_IFINDEX(int ifindex) {
+
+ /* When the caller asked for resolving on a specific
+ * interface, we synthesize the answer for that
+ * interface. However, if nothing specific was claimed and we
+ * only return localhost RRs, we synthesize the answer for
+ * localhost. */
+
+ if (ifindex > 0)
+ return ifindex;
+
+ return LOOPBACK_IFINDEX;
+}
+
+static int SYNTHESIZE_FAMILY(uint64_t flags) {
+
+ /* Picks an address family depending on set flags. This is
+ * purely for synthesized answers, where the family we return
+ * for the reply should match what was requested in the
+ * question, even though we are synthesizing the answer
+ * here. */
+
+ if (!(flags & SD_RESOLVED_DNS)) {
+ if (flags & (SD_RESOLVED_LLMNR_IPV4|SD_RESOLVED_MDNS_IPV4))
+ return AF_INET;
+ if (flags & (SD_RESOLVED_LLMNR_IPV6|SD_RESOLVED_MDNS_IPV6))
+ return AF_INET6;
+ }
+
+ return AF_UNSPEC;
+}
+
+static DnsProtocol SYNTHESIZE_PROTOCOL(uint64_t flags) {
+
+ /* Similar as SYNTHESIZE_FAMILY() but does this for the
+ * protocol. If resolving via DNS was requested, we claim it
+ * was DNS. Similar, if nothing specific was
+ * requested. However, if only resolving via LLMNR was
+ * requested we return that. */
+
+ if (flags & SD_RESOLVED_DNS)
+ return DNS_PROTOCOL_DNS;
+ if (flags & SD_RESOLVED_LLMNR)
+ return DNS_PROTOCOL_LLMNR;
+ if (flags & SD_RESOLVED_MDNS)
+ return DNS_PROTOCOL_MDNS;
+
+ return DNS_PROTOCOL_DNS;
+}
+
+static int synthesize_localhost_rr(Manager *m, const DnsResourceKey *key, int ifindex, DnsAnswer **answer) {
+ int r;
+
+ assert(m);
+ assert(key);
+ assert(answer);
+
+ r = dns_answer_reserve(answer, 2);
+ if (r < 0)
+ return r;
+
+ if (IN_SET(key->type, DNS_TYPE_A, DNS_TYPE_ANY)) {
+ _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL;
+
+ rr = dns_resource_record_new_full(DNS_CLASS_IN, DNS_TYPE_A, DNS_RESOURCE_KEY_NAME(key));
+ if (!rr)
+ return -ENOMEM;
+
+ rr->a.in_addr.s_addr = htobe32(INADDR_LOOPBACK);
+
+ r = dns_answer_add(*answer, rr, SYNTHESIZE_IFINDEX(ifindex), DNS_ANSWER_AUTHENTICATED);
+ if (r < 0)
+ return r;
+ }
+
+ if (IN_SET(key->type, DNS_TYPE_AAAA, DNS_TYPE_ANY)) {
+ _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL;
+
+ rr = dns_resource_record_new_full(DNS_CLASS_IN, DNS_TYPE_AAAA, DNS_RESOURCE_KEY_NAME(key));
+ if (!rr)
+ return -ENOMEM;
+
+ rr->aaaa.in6_addr = in6addr_loopback;
+
+ r = dns_answer_add(*answer, rr, SYNTHESIZE_IFINDEX(ifindex), DNS_ANSWER_AUTHENTICATED);
+ if (r < 0)
+ return r;
+ }
+
+ return 0;
+}
+
+static int answer_add_ptr(DnsAnswer **answer, const char *from, const char *to, int ifindex, DnsAnswerFlags flags) {
+ _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL;
+
+ rr = dns_resource_record_new_full(DNS_CLASS_IN, DNS_TYPE_PTR, from);
+ if (!rr)
+ return -ENOMEM;
+
+ rr->ptr.name = strdup(to);
+ if (!rr->ptr.name)
+ return -ENOMEM;
+
+ return dns_answer_add(*answer, rr, ifindex, flags);
+}
+
+static int synthesize_localhost_ptr(Manager *m, const DnsResourceKey *key, int ifindex, DnsAnswer **answer) {
+ int r;
+
+ assert(m);
+ assert(key);
+ assert(answer);
+
+ if (IN_SET(key->type, DNS_TYPE_PTR, DNS_TYPE_ANY)) {
+ r = dns_answer_reserve(answer, 1);
+ if (r < 0)
+ return r;
+
+ r = answer_add_ptr(answer, DNS_RESOURCE_KEY_NAME(key), "localhost", SYNTHESIZE_IFINDEX(ifindex), DNS_ANSWER_AUTHENTICATED);
+ if (r < 0)
+ return r;
+ }
+
+ return 0;
+}
+
+static int answer_add_addresses_rr(
+ DnsAnswer **answer,
+ const char *name,
+ struct local_address *addresses,
+ unsigned n_addresses) {
+
+ unsigned j;
+ int r;
+
+ assert(answer);
+ assert(name);
+
+ r = dns_answer_reserve(answer, n_addresses);
+ if (r < 0)
+ return r;
+
+ for (j = 0; j < n_addresses; j++) {
+ _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL;
+
+ r = dns_resource_record_new_address(&rr, addresses[j].family, &addresses[j].address, name);
+ if (r < 0)
+ return r;
+
+ r = dns_answer_add(*answer, rr, addresses[j].ifindex, DNS_ANSWER_AUTHENTICATED);
+ if (r < 0)
+ return r;
+ }
+
+ return 0;
+}
+
+static int answer_add_addresses_ptr(
+ DnsAnswer **answer,
+ const char *name,
+ struct local_address *addresses,
+ unsigned n_addresses,
+ int af, const union in_addr_union *match) {
+
+ unsigned j;
+ int r;
+
+ assert(answer);
+ assert(name);
+
+ for (j = 0; j < n_addresses; j++) {
+ _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL;
+
+ if (af != AF_UNSPEC) {
+
+ if (addresses[j].family != af)
+ continue;
+
+ if (match && !in_addr_equal(af, match, &addresses[j].address))
+ continue;
+ }
+
+ r = dns_answer_reserve(answer, 1);
+ if (r < 0)
+ return r;
+
+ r = dns_resource_record_new_reverse(&rr, addresses[j].family, &addresses[j].address, name);
+ if (r < 0)
+ return r;
+
+ r = dns_answer_add(*answer, rr, addresses[j].ifindex, DNS_ANSWER_AUTHENTICATED);
+ if (r < 0)
+ return r;
+ }
+
+ return 0;
+}
+
+static int synthesize_system_hostname_rr(Manager *m, const DnsResourceKey *key, int ifindex, DnsAnswer **answer) {
+ _cleanup_free_ struct local_address *addresses = NULL;
+ int n = 0, af;
+
+ assert(m);
+ assert(key);
+ assert(answer);
+
+ af = dns_type_to_af(key->type);
+ if (af >= 0) {
+ n = local_addresses(m->rtnl, ifindex, af, &addresses);
+ if (n < 0)
+ return n;
+
+ if (n == 0) {
+ struct local_address buffer[2];
+
+ /* If we have no local addresses then use ::1
+ * and 127.0.0.2 as local ones. */
+
+ if (af == AF_INET || af == AF_UNSPEC)
+ buffer[n++] = (struct local_address) {
+ .family = AF_INET,
+ .ifindex = SYNTHESIZE_IFINDEX(ifindex),
+ .address.in.s_addr = htobe32(0x7F000002),
+ };
+
+ if (af == AF_INET6 || af == AF_UNSPEC)
+ buffer[n++] = (struct local_address) {
+ .family = AF_INET6,
+ .ifindex = SYNTHESIZE_IFINDEX(ifindex),
+ .address.in6 = in6addr_loopback,
+ };
+
+ return answer_add_addresses_rr(answer, DNS_RESOURCE_KEY_NAME(key), buffer, n);
+ }
+ }
+
+ return answer_add_addresses_rr(answer, DNS_RESOURCE_KEY_NAME(key), addresses, n);
+}
+
+static int synthesize_system_hostname_ptr(Manager *m, int af, const union in_addr_union *address, int ifindex, DnsAnswer **answer) {
+ _cleanup_free_ struct local_address *addresses = NULL;
+ int n, r;
+
+ assert(m);
+ assert(address);
+ assert(answer);
+
+ if (af == AF_INET && address->in.s_addr == htobe32(0x7F000002)) {
+
+ /* Always map the IPv4 address 127.0.0.2 to the local
+ * hostname, in addition to "localhost": */
+
+ r = dns_answer_reserve(answer, 3);
+ if (r < 0)
+ return r;
+
+ r = answer_add_ptr(answer, "2.0.0.127.in-addr.arpa", m->llmnr_hostname, SYNTHESIZE_IFINDEX(ifindex), DNS_ANSWER_AUTHENTICATED);
+ if (r < 0)
+ return r;
+
+ r = answer_add_ptr(answer, "2.0.0.127.in-addr.arpa", m->mdns_hostname, SYNTHESIZE_IFINDEX(ifindex), DNS_ANSWER_AUTHENTICATED);
+ if (r < 0)
+ return r;
+
+ r = answer_add_ptr(answer, "2.0.0.127.in-addr.arpa", "localhost", SYNTHESIZE_IFINDEX(ifindex), DNS_ANSWER_AUTHENTICATED);
+ if (r < 0)
+ return r;
+
+ return 0;
+ }
+
+ n = local_addresses(m->rtnl, ifindex, af, &addresses);
+ if (n < 0)
+ return n;
+
+ r = answer_add_addresses_ptr(answer, m->llmnr_hostname, addresses, n, af, address);
+ if (r < 0)
+ return r;
+
+ return answer_add_addresses_ptr(answer, m->mdns_hostname, addresses, n, af, address);
+}
+
+static int synthesize_gateway_rr(Manager *m, const DnsResourceKey *key, int ifindex, DnsAnswer **answer) {
+ _cleanup_free_ struct local_address *addresses = NULL;
+ int n = 0, af;
+
+ assert(m);
+ assert(key);
+ assert(answer);
+
+ af = dns_type_to_af(key->type);
+ if (af >= 0) {
+ n = local_gateways(m->rtnl, ifindex, af, &addresses);
+ if (n < 0)
+ return n;
+ }
+
+ return answer_add_addresses_rr(answer, DNS_RESOURCE_KEY_NAME(key), addresses, n);
+}
+
+static int synthesize_gateway_ptr(Manager *m, int af, const union in_addr_union *address, int ifindex, DnsAnswer **answer) {
+ _cleanup_free_ struct local_address *addresses = NULL;
+ int n;
+
+ assert(m);
+ assert(address);
+ assert(answer);
+
+ n = local_gateways(m->rtnl, ifindex, af, &addresses);
+ if (n < 0)
+ return n;
+
+ return answer_add_addresses_ptr(answer, "gateway", addresses, n, af, address);
+}
+
+int dns_synthesize_answer(
+ Manager *m,
+ DnsQuestion *q,
+ int ifindex,
+ uint64_t flags,
+ DnsAnswer **ret,
+ DnsProtocol *ret_protocol,
+ int *ret_family) {
+
+ _cleanup_(dns_answer_unrefp) DnsAnswer *answer = NULL;
+ DnsResourceKey *key;
+ int r;
+
+ assert(m);
+ assert(q);
+
+ DNS_QUESTION_FOREACH(key, q) {
+ union in_addr_union address;
+ const char *name;
+ int af;
+
+ if (key->class != DNS_CLASS_IN &&
+ key->class != DNS_CLASS_ANY)
+ continue;
+
+ name = DNS_RESOURCE_KEY_NAME(key);
+
+ if (is_localhost(name)) {
+
+ r = synthesize_localhost_rr(m, key, ifindex, &answer);
+ if (r < 0)
+ return log_error_errno(r, "Failed to synthesize localhost RRs: %m");
+
+ } else if (manager_is_own_hostname(m, name)) {
+
+ r = synthesize_system_hostname_rr(m, key, ifindex, &answer);
+ if (r < 0)
+ return log_error_errno(r, "Failed to synthesize system hostname RRs: %m");
+
+ } else if (is_gateway_hostname(name)) {
+
+ r = synthesize_gateway_rr(m, key, ifindex, &answer);
+ if (r < 0)
+ return log_error_errno(r, "Failed to synthesize gateway RRs: %m");
+
+ } else if ((dns_name_endswith(name, "127.in-addr.arpa") > 0 && dns_name_equal(name, "2.0.0.127.in-addr.arpa") == 0) ||
+ 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) {
+
+ r = synthesize_localhost_ptr(m, key, ifindex, &answer);
+ if (r < 0)
+ return log_error_errno(r, "Failed to synthesize localhost PTR RRs: %m");
+
+ } else if (dns_name_address(name, &af, &address) > 0) {
+
+ r = synthesize_system_hostname_ptr(m, af, &address, ifindex, &answer);
+ if (r < 0)
+ return log_error_errno(r, "Failed to synthesize system hostname PTR RR: %m");
+
+ r = synthesize_gateway_ptr(m, af, &address, ifindex, &answer);
+ if (r < 0)
+ return log_error_errno(r, "Failed to synthesize gateway hostname PTR RR: %m");
+ }
+ }
+
+ r = dns_answer_size(answer) > 0;
+
+ if (ret) {
+ *ret = answer;
+ answer = NULL;
+ }
+
+ if (ret_protocol)
+ *ret_protocol = SYNTHESIZE_PROTOCOL(flags);
+
+ if (ret_family)
+ *ret_family = SYNTHESIZE_FAMILY(flags);
+
+ return r;
+}