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Diffstat (limited to 'src/resolve/resolved-dns-synthesize.c')
| -rw-r--r-- | src/resolve/resolved-dns-synthesize.c | 418 |
1 files changed, 418 insertions, 0 deletions
diff --git a/src/resolve/resolved-dns-synthesize.c b/src/resolve/resolved-dns-synthesize.c new file mode 100644 index 0000000000..e12bb6e828 --- /dev/null +++ b/src/resolve/resolved-dns-synthesize.c @@ -0,0 +1,418 @@ +/*** + 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; +} |