diff options
| -rw-r--r-- | src/resolve/resolved-dns-query.c | 166 |
1 files changed, 165 insertions, 1 deletions
diff --git a/src/resolve/resolved-dns-query.c b/src/resolve/resolved-dns-query.c index 418d9721ef..3ada442006 100644 --- a/src/resolve/resolved-dns-query.c +++ b/src/resolve/resolved-dns-query.c @@ -19,6 +19,8 @@ along with systemd; If not, see <http://www.gnu.org/licenses/>. ***/ +#include "hostname-util.h" +#include "dns-domain.h" #include "resolved-dns-query.h" @@ -212,6 +214,156 @@ static int dns_query_add_transaction_split(DnsQuery *q, DnsScope *s) { return 0; } +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, 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) + return AF_INET; + if (flags & SD_RESOLVED_LLMNR_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; + + return DNS_PROTOCOL_DNS; +} + +static void dns_query_synthesize_reply(DnsQuery *q, DnsTransactionState *state) { + _cleanup_(dns_answer_unrefp) DnsAnswer *answer = NULL; + unsigned i; + int r; + + assert(q); + assert(state); + + /* Tries to synthesize localhost RR replies where appropriate */ + + if (!IN_SET(*state, + DNS_TRANSACTION_FAILURE, + DNS_TRANSACTION_NO_SERVERS, + DNS_TRANSACTION_TIMEOUT, + DNS_TRANSACTION_ATTEMPTS_MAX_REACHED)) + return; + + for (i = 0; i < q->question->n_keys; i++) { + _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL; + const char *name; + + if (q->question->keys[i]->class != DNS_CLASS_IN && + q->question->keys[i]->class != DNS_CLASS_ANY) + continue; + + name = DNS_RESOURCE_KEY_NAME(q->question->keys[i]); + + if (is_localhost(name)) { + + switch (q->question->keys[i]->type) { + + case DNS_TYPE_A: + case DNS_TYPE_ANY: + rr = dns_resource_record_new_full(DNS_CLASS_IN, DNS_TYPE_A, name); + if (!rr) { + log_oom(); + return; + } + + rr->a.in_addr.s_addr = htobe32(INADDR_LOOPBACK); + break; + + case DNS_TYPE_AAAA: + rr = dns_resource_record_new_full(DNS_CLASS_IN, DNS_TYPE_AAAA, name); + if (!rr) { + log_oom(); + return; + } + + rr->aaaa.in6_addr = in6addr_loopback; + break; + } + + } else if (IN_SET(q->question->keys[i]->type, DNS_TYPE_PTR, DNS_TYPE_ANY) && + (dns_name_endswith(name, "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)) { + + rr = dns_resource_record_new_full(DNS_CLASS_IN, DNS_TYPE_PTR, name); + if (!rr) { + log_oom(); + return; + } + + rr->ptr.name = strdup("localhost"); + if (!rr->ptr.name) { + log_oom(); + return; + } + } + + if (!rr) + continue; + + if (!answer) { + answer = dns_answer_new(q->question->n_keys); + if (!answer) { + log_oom(); + return; + } + } + + r = dns_answer_add(answer, rr); + if (r < 0) { + log_error_errno(r, "Failed to add synthetic RR to answer: %m"); + return; + } + } + + if (!answer) + return; + + dns_answer_unref(q->answer); + q->answer = answer; + answer = NULL; + + q->answer_ifindex = SYNTHESIZE_IFINDEX(q->ifindex); + q->answer_family = SYNTHESIZE_FAMILY(q->flags); + q->answer_protocol = SYNTHESIZE_PROTOCOL(q->flags); + q->answer_rcode = DNS_RCODE_SUCCESS; + + *state = DNS_TRANSACTION_SUCCESS; +} + int dns_query_go(DnsQuery *q) { DnsScopeMatch found = DNS_SCOPE_NO; DnsScope *s, *first = NULL; @@ -253,8 +405,17 @@ int dns_query_go(DnsQuery *q) { } } - if (found == DNS_SCOPE_NO) + if (found == DNS_SCOPE_NO) { + DnsTransactionState state = DNS_TRANSACTION_NO_SERVERS; + + dns_query_synthesize_reply(q, &state); + if (state != DNS_TRANSACTION_NO_SERVERS) { + dns_query_complete(q, state); + return 1; + } + return -ESRCH; + } r = dns_query_add_transaction_split(q, first); if (r < 0) @@ -428,6 +589,9 @@ void dns_query_ready(DnsQuery *q) { q->answer_family = scope ? scope->family : AF_UNSPEC; } + /* Try to synthesize a reply if we couldn't resolve something. */ + dns_query_synthesize_reply(q, &state); + dns_query_complete(q, state); } |