resolved: add CNAME lookup support

src/resolve/resolved-bus.c

@@ -82,15 +82,55 @@ static int reply_query_state(DnsQuery *q) {
         }
 
         case DNS_QUERY_NULL:
-        case DNS_QUERY_SENT:
+        case DNS_QUERY_PENDING:
         case DNS_QUERY_SUCCESS:
+        default:
                 assert_not_reached("Impossible state");
         }
 }
 
+static int append_address(sd_bus_message *reply, DnsResourceRecord *rr, int ifindex) {
+        int r;
+
+        assert(reply);
+        assert(rr);
+
+        r = sd_bus_message_open_container(reply, 'r', "yayi");
+        if (r < 0)
+                return r;
+
+        if (rr->key.type == DNS_TYPE_A) {
+                r = sd_bus_message_append(reply, "y", AF_INET);
+                if (r < 0)
+                        return r;
+
+                r = sd_bus_message_append_array(reply, 'y', &rr->a.in_addr, sizeof(struct in_addr));
+        } else {
+                r = sd_bus_message_append(reply, "y", AF_INET6);
+                if (r < 0)
+                        return r;
+
+                r = sd_bus_message_append_array(reply, 'y', &rr->aaaa.in6_addr, sizeof(struct in6_addr));
+        }
+        if (r < 0)
+                return r;
+
+        r = sd_bus_message_append(reply, "i", ifindex);
+        if (r < 0)
+                return r;
+
+        r = sd_bus_message_close_container(reply);
+        if (r < 0)
+                return r;
+
+        return 0;
+}
+
 static void bus_method_resolve_hostname_complete(DnsQuery *q) {
+        _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *cname = NULL;
         _cleanup_bus_message_unref_ sd_bus_message *reply = NULL;
         unsigned i, n, added = 0;
+        size_t answer_rindex;
         int r;
 
         assert(q);
@@ -106,6 +146,8 @@ static void bus_method_resolve_hostname_complete(DnsQuery *q) {
         if (r < 0)
                 goto parse_fail;
 
+        answer_rindex = q->received->rindex;
+
         r = sd_bus_message_new_method_return(q->request, &reply);
         if (r < 0)
                 goto finish;
@@ -117,6 +159,7 @@ static void bus_method_resolve_hostname_complete(DnsQuery *q) {
         n = DNS_PACKET_ANCOUNT(q->received) +
             DNS_PACKET_NSCOUNT(q->received) +
             DNS_PACKET_ARCOUNT(q->received);
+
         for (i = 0; i < n; i++) {
                 _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL;
 
@@ -124,41 +167,22 @@ static void bus_method_resolve_hostname_complete(DnsQuery *q) {
                 if (r < 0)
                         goto parse_fail;
 
-                if (rr->key.class != DNS_CLASS_IN)
-                        continue;
-
-                if (!(q->request_family != AF_INET6 && rr->key.type == DNS_TYPE_A) &&
-                    !(q->request_family != AF_INET && rr->key.type == DNS_TYPE_AAAA))
-                        continue;
-
-                if (!dns_name_equal(rr->key.name, q->request_hostname))
-                        continue;
-
-                r = sd_bus_message_open_container(reply, 'r', "yayi");
+                r = dns_query_matches_rr(q, rr);
                 if (r < 0)
-                        goto finish;
-
-                if (rr->key.type == DNS_TYPE_A) {
-                        r = sd_bus_message_append(reply, "y", AF_INET);
+                        goto parse_fail;
+                if (r == 0) {
+                        /* Hmm, if this is not an address record,
+                           maybe it's a cname? If so, remember this */
+                        r = dns_query_matches_cname(q, rr);
                         if (r < 0)
-                                goto finish;
+                                goto parse_fail;
+                        if (r > 0)
+                                cname = dns_resource_record_ref(rr);
 
-                        r = sd_bus_message_append_array(reply, 'y', &rr->a.in_addr, sizeof(struct in_addr));
-                } else {
-                        r = sd_bus_message_append(reply, "y", AF_INET6);
-                        if (r < 0)
-                                goto finish;
-
-                        r = sd_bus_message_append_array(reply, 'y', &rr->aaaa.in6_addr, sizeof(struct in6_addr));
+                        continue;
                 }
-                if (r < 0)
-                        goto finish;
 
-                r = sd_bus_message_append(reply, "i", q->received->ifindex);
-                if (r < 0)
-                        goto finish;
-
-                r = sd_bus_message_close_container(reply);
+                r = append_address(reply, rr, q->received->ifindex);
                 if (r < 0)
                         goto finish;
 
@@ -166,8 +190,56 @@ static void bus_method_resolve_hostname_complete(DnsQuery *q) {
         }
 
         if (added <= 0) {
-                r = sd_bus_reply_method_errorf(q->request, BUS_ERROR_NO_SUCH_RR, "'%s' does not have RR of this type", q->request_hostname);
-                goto finish;
+                if (!cname) {
+                        r = sd_bus_reply_method_errorf(q->request, BUS_ERROR_NO_SUCH_RR, "'%s' does not have RR of this type", q->request_hostname);
+                        goto finish;
+                }
+
+                /* This has a cname? Then update the query with the
+                 * new cname. */
+                r = dns_query_follow_cname(q, cname->cname.name);
+                if (r < 0) {
+                        if (r == -ELOOP)
+                                r = sd_bus_reply_method_errorf(q->request, BUS_ERROR_CNAME_LOOP, "CNAME loop on '%s'", q->request_hostname);
+                        else
+                                r = sd_bus_reply_method_errno(q->request, -r, NULL);
+
+                        goto finish;
+                }
+
+                /* Before we restart the query, let's see if any of
+                 * the RRs we already got already answers our query */
+                dns_packet_rewind(q->received, answer_rindex);
+                for (i = 0; i < n; i++) {
+                        _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL;
+
+                        r = dns_packet_read_rr(q->received, &rr, NULL);
+                        if (r < 0)
+                                goto parse_fail;
+
+                        r = dns_query_matches_rr(q, rr);
+                        if (r < 0)
+                                goto parse_fail;
+                        if (r == 0)
+                                continue;
+
+                        r = append_address(reply, rr, q->received->ifindex);
+                        if (r < 0)
+                                goto finish;
+
+                        added++;
+                }
+
+                /* If we didn't find anything, then let's restart the
+                 * query, this time with the cname */
+                if (added <= 0) {
+                        r = dns_query_start(q);
+                        if (r < 0) {
+                                r = sd_bus_reply_method_errno(q->request, -r, NULL);
+                                goto finish;
+                        }
+                        return;
+                }
         }
 
         r = sd_bus_message_close_container(reply);
@@ -245,7 +317,6 @@ static int bus_method_resolve_hostname(sd_bus *bus, sd_bus_message *message, voi
 static void bus_method_resolve_address_complete(DnsQuery *q) {
         _cleanup_bus_message_unref_ sd_bus_message *reply = NULL;
         unsigned i, n, added = 0;
-        _cleanup_free_ char *reverse = NULL;
         int r;
 
         assert(q);
@@ -257,10 +328,6 @@ static void bus_method_resolve_address_complete(DnsQuery *q) {
 
         assert(q->received);
 
-        r = dns_name_reverse(q->request_family, &q->request_address, &reverse);
-        if (r < 0)
-                goto finish;
-
         r = dns_packet_skip_question(q->received);
         if (r < 0)
                 goto parse_fail;
@@ -284,11 +351,10 @@ static void bus_method_resolve_address_complete(DnsQuery *q) {
                 if (r < 0)
                         goto parse_fail;
 
-                if (rr->key.class != DNS_CLASS_IN)
-                        continue;
-                if (rr->key.type != DNS_TYPE_PTR)
-                        continue;
-                if (!dns_name_equal(rr->key.name, reverse))
+                r = dns_query_matches_rr(q, rr);
+                if (r < 0)
+                        goto parse_fail;
+                if (r == 0)
                         continue;
 
                 r = sd_bus_message_append(reply, "s", rr->ptr.name);

src/resolve/resolved-dns-packet.c

@@ -395,7 +395,7 @@ int dns_packet_read(DnsPacket *p, size_t sz, const void **ret, size_t *start) {
         return 0;
 }
 
-static void dns_packet_rewind(DnsPacket *p, size_t idx) {
+void dns_packet_rewind(DnsPacket *p, size_t idx) {
         assert(p);
         assert(idx <= p->size);
         assert(idx >= DNS_PACKET_HEADER_SIZE);

src/resolve/resolved-dns-packet.h

@@ -116,6 +116,8 @@ int dns_packet_read_name(DnsPacket *p, char **ret, size_t *start);
 int dns_packet_read_key(DnsPacket *p, DnsResourceKey *ret, size_t *start);
 int dns_packet_read_rr(DnsPacket *p, DnsResourceRecord **ret, size_t *start);
 
+void dns_packet_rewind(DnsPacket *p, size_t idx);
+
 int dns_packet_skip_question(DnsPacket *p);
 
 enum {

src/resolve/resolved-dns-query.c

@@ -25,6 +25,9 @@
 #define TRANSACTION_TIMEOUT_USEC (5 * USEC_PER_SEC)
 #define QUERY_TIMEOUT_USEC (30 * USEC_PER_SEC)
 #define ATTEMPTS_MAX 8
+#define CNAME_MAX 8
+
+static int dns_query_transaction_start(DnsQueryTransaction *t);
 
 DnsQueryTransaction* dns_query_transaction_free(DnsQueryTransaction *t) {
         if (!t)
@@ -110,7 +113,7 @@ static void dns_query_transaction_set_state(DnsQueryTransaction *t, DnsQueryStat
 
         t->state = state;
 
-        if (state != DNS_QUERY_SENT) {
+        if (state != DNS_QUERY_PENDING) {
                 dns_query_transaction_stop(t);
                 dns_query_finish(t->query);
         }
@@ -248,7 +251,7 @@ void dns_query_transaction_reply(DnsQueryTransaction *t, DnsPacket *p) {
         assert(t);
         assert(p);
 
-        if (t->state != DNS_QUERY_SENT)
+        if (t->state != DNS_QUERY_PENDING)
                 return;
 
         if (t->received != p) {
@@ -273,8 +276,21 @@ void dns_query_transaction_reply(DnsQueryTransaction *t, DnsPacket *p) {
         if (DNS_PACKET_TC(p)) {
                 /* Response was truncated, let's try again with good old TCP */
                 r = dns_query_transaction_start_tcp(t);
+                if (r == -ESRCH) {
+                        /* No servers found? Damn! */
+                        dns_query_transaction_set_state(t, DNS_QUERY_NO_SERVERS);
+                        return;
+                }
                 if (r < 0) {
-                        dns_query_transaction_set_state(t, DNS_QUERY_RESOURCES);
+                        /* Couldn't send? Try immediately again, with a new server */
+                        dns_scope_next_dns_server(t->scope);
+
+                        r = dns_query_transaction_start(t);
+                        if (r < 0) {
+                                dns_query_transaction_set_state(t, DNS_QUERY_RESOURCES);
+                                return;
+                        }
+
                         return;
                 }
         }
@@ -331,7 +347,7 @@ static int dns_query_make_packet(DnsQueryTransaction *t) {
         return 0;
 }
 
-int dns_query_transaction_start(DnsQueryTransaction *t) {
+static int dns_query_transaction_start(DnsQueryTransaction *t) {
         int r;
 
         assert(t);
@@ -342,12 +358,14 @@ int dns_query_transaction_start(DnsQueryTransaction *t) {
                 dns_query_transaction_set_state(t, DNS_QUERY_ATTEMPTS_MAX);
                 return 0;
         }
-        t->n_attempts++;
 
         r = dns_query_make_packet(t);
         if (r < 0)
                 return r;
 
+        t->n_attempts++;
+        t->received = dns_packet_unref(t->received);
+
         /* Try via UDP, and if that fails due to large size try via TCP */
         r = dns_scope_send(t->scope, t->sent);
         if (r == -EMSGSIZE)
@@ -368,7 +386,7 @@ int dns_query_transaction_start(DnsQueryTransaction *t) {
         if (r < 0)
                 return r;
 
-        dns_query_transaction_set_state(t, DNS_QUERY_SENT);
+        dns_query_transaction_set_state(t, DNS_QUERY_PENDING);
         return 1;
 }
 
@@ -398,10 +416,7 @@ DnsQuery *dns_query_free(DnsQuery *q) {
 
 int dns_query_new(Manager *m, DnsQuery **ret, DnsResourceKey *keys, unsigned n_keys) {
         _cleanup_(dns_query_freep) DnsQuery *q = NULL;
-        DnsScope *s, *first = NULL;
-        DnsScopeMatch found = DNS_SCOPE_NO;
         const char *name = NULL;
-        int n, r;
 
         assert(m);
 
@@ -434,10 +449,67 @@ int dns_query_new(Manager *m, DnsQuery **ret, DnsResourceKey *keys, unsigned n_k
         LIST_PREPEND(queries, m->dns_queries, q);
         q->manager = m;
 
-        LIST_FOREACH(scopes, s, m->dns_scopes) {
+        if (ret)
+                *ret = q;
+        q = NULL;
+
+        return 0;
+}
+
+static void dns_query_stop(DnsQuery *q) {
+        assert(q);
+
+        q->timeout_event_source = sd_event_source_unref(q->timeout_event_source);
+
+        while (q->transactions)
+                dns_query_transaction_free(q->transactions);
+}
+
+static void dns_query_set_state(DnsQuery *q, DnsQueryState state) {
+        DnsQueryState old_state;
+        assert(q);
+
+        if (q->state == state)
+                return;
+
+        old_state = q->state;
+        q->state = state;
+
+        if (!IN_SET(state, DNS_QUERY_NULL, DNS_QUERY_PENDING)) {
+                dns_query_stop(q);
+
+                if (old_state == DNS_QUERY_PENDING && q->complete)
+                        q->complete(q);
+        }
+}
+
+static int on_query_timeout(sd_event_source *s, usec_t usec, void *userdata) {
+        DnsQuery *q = userdata;
+
+        assert(s);
+        assert(q);
+
+        dns_query_set_state(q, DNS_QUERY_TIMEOUT);
+        return 0;
+}
+
+int dns_query_start(DnsQuery *q) {
+        DnsScopeMatch found = DNS_SCOPE_NO;
+        DnsScope *s, *first = NULL;
+        DnsQueryTransaction *t;
+        int r;
+
+        assert(q);
+
+        if (q->state != DNS_QUERY_NULL)
+                return 0;
+
+        assert(q->n_keys > 0);
+
+        LIST_FOREACH(scopes, s, q->manager->dns_scopes) {
                 DnsScopeMatch match;
 
-                match = dns_scope_test(s, name);
+                match = dns_scope_test(s, q->keys[0].name);
                 if (match < 0)
                         return match;
 
@@ -458,17 +530,16 @@ int dns_query_new(Manager *m, DnsQuery **ret, DnsResourceKey *keys, unsigned n_k
         }
 
         if (found == DNS_SCOPE_NO)
-                return -ENETDOWN;
+                return -ESRCH;
 
         r = dns_query_transaction_new(q, NULL, first);
         if (r < 0)
                 return r;
 
-        n = 1;
         LIST_FOREACH(scopes, s, first->scopes_next) {
                 DnsScopeMatch match;
 
-                match = dns_scope_test(s, name);
+                match = dns_scope_test(s, q->keys[0].name);
                 if (match < 0)
                         return match;
 
@@ -478,62 +549,15 @@ int dns_query_new(Manager *m, DnsQuery **ret, DnsResourceKey *keys, unsigned n_k
                 r = dns_query_transaction_new(q, NULL, s);
                 if (r < 0)
                         return r;
-
-                n++;
         }
 
-        if (ret)
-                *ret = q;
-        q = NULL;
-
-        return n;
-}
-
-static void dns_query_set_state(DnsQuery *q, DnsQueryState state) {
-        assert(q);
-
-        if (q->state == state)
-                return;
-
-        q->state = state;
-
-        if (state == DNS_QUERY_SENT)
-                return;
-
-        q->timeout_event_source = sd_event_source_unref(q->timeout_event_source);
-
-        while (q->transactions)
-                dns_query_transaction_free(q->transactions);
-
-        if (q->complete)
-                q->complete(q);
-}
-
-static int on_query_timeout(sd_event_source *s, usec_t usec, void *userdata) {
-        DnsQuery *q = userdata;
-
-        assert(s);
-        assert(q);
-
-        dns_query_set_state(q, DNS_QUERY_TIMEOUT);
-        return 0;
-}
-
-int dns_query_start(DnsQuery *q) {
-        DnsQueryTransaction *t;
-        int r;
-
-        assert(q);
-        assert(q->state == DNS_QUERY_NULL);
-
-        if (!q->transactions)
-                return -ENETDOWN;
+        q->received = dns_packet_unref(q->received);
 
         r = sd_event_add_time(q->manager->event, &q->timeout_event_source, CLOCK_MONOTONIC, now(CLOCK_MONOTONIC) + QUERY_TIMEOUT_USEC, 0, on_query_timeout, q);
         if (r < 0)
                 goto fail;
 
-        dns_query_set_state(q, DNS_QUERY_SENT);
+        dns_query_set_state(q, DNS_QUERY_PENDING);
 
         LIST_FOREACH(transactions_by_query, t, q->transactions) {
 
@@ -541,16 +565,14 @@ int dns_query_start(DnsQuery *q) {
                 if (r < 0)
                         goto fail;
 
-                if (q->state != DNS_QUERY_SENT)
+                if (q->state != DNS_QUERY_PENDING)
                         break;
         }
 
-        return 0;
+        return 1;
 
 fail:
-        while (q->transactions)
-                dns_query_transaction_free(q->transactions);
-
+        dns_query_stop(q);
         return r;
 }
 
@@ -561,13 +583,13 @@ void dns_query_finish(DnsQuery *q) {
 
         assert(q);
 
-        if (q->state != DNS_QUERY_SENT)
+        if (q->state != DNS_QUERY_PENDING)
                 return;
 
         LIST_FOREACH(transactions_by_query, t, q->transactions) {
 
                 /* One of the transactions is still going on, let's wait for it */
-                if (t->state == DNS_QUERY_SENT || t->state == DNS_QUERY_NULL)
+                if (t->state == DNS_QUERY_PENDING || t->state == DNS_QUERY_NULL)
                         return;
 
                 /* One of the transactions is successful, let's use it */
@@ -595,3 +617,88 @@ void dns_query_finish(DnsQuery *q) {
 
         dns_query_set_state(q, state);
 }
+
+int dns_query_follow_cname(DnsQuery *q, const char *name) {
+        DnsResourceKey *keys;
+        unsigned i;
+
+        assert(q);
+
+        if (q->n_cname > CNAME_MAX)
+                return -ELOOP;
+
+        keys = new(DnsResourceKey, q->n_keys);
+        if (!keys)
+                return -ENOMEM;
+
+        for (i = 0; i < q->n_keys; i++) {
+                keys[i].class = q->keys[i].class;
+                keys[i].type = q->keys[i].type;
+                keys[i].name = strdup(name);
+                if (!keys[i].name) {
+
+                        for (; i > 0; i--)
+                                free(keys[i-1].name);
+                        free(keys);
+                        return -ENOMEM;
+                }
+        }
+
+        for (i = 0; i < q->n_keys; i++)
+                free(q->keys[i].name);
+        free(q->keys);
+
+        q->keys = keys;
+
+        q->n_cname++;
+
+        dns_query_set_state(q, DNS_QUERY_NULL);
+        return 0;
+}
+
+int dns_query_matches_rr(DnsQuery *q, DnsResourceRecord *rr) {
+        unsigned i;
+        int r;
+
+        assert(q);
+        assert(rr);
+
+        for (i = 0; i < q->n_keys; i++) {
+
+                if (rr->key.class != q->keys[i].class)
+                        continue;
+
+                if (rr->key.type != q->keys[i].type &&
+                    q->keys[i].type != DNS_TYPE_ANY)
+                        continue;
+
+                r = dns_name_equal(rr->key.name, q->keys[i].name);
+                if (r != 0)
+                        return r;
+        }
+
+        return 0;
+}
+
+int dns_query_matches_cname(DnsQuery *q, DnsResourceRecord *rr) {
+        unsigned i;
+        int r;
+
+        assert(q);
+        assert(rr);
+
+        for (i = 0; i < q->n_keys; i++) {
+
+                if (rr->key.class != q->keys[i].class)
+                        continue;
+
+                if (rr->key.type != DNS_TYPE_CNAME)
+                        continue;
+
+                r = dns_name_equal(rr->key.name, q->keys[i].name);
+                if (r != 0)
+                        return r;
+        }
+
+        return 0;
+}

src/resolve/resolved-dns-query.h

@@ -36,14 +36,14 @@ typedef struct DnsQueryTransaction DnsQueryTransaction;
 
 typedef enum DnsQueryState {
         DNS_QUERY_NULL,
-        DNS_QUERY_SENT,
+        DNS_QUERY_PENDING,
         DNS_QUERY_FAILURE,
         DNS_QUERY_SUCCESS,
         DNS_QUERY_NO_SERVERS,
         DNS_QUERY_TIMEOUT,
         DNS_QUERY_ATTEMPTS_MAX,
         DNS_QUERY_INVALID_REPLY,
-        DNS_QUERY_RESOURCES,
+        DNS_QUERY_RESOURCES
 } DnsQueryState;
 
 struct DnsQueryTransaction {
@@ -75,11 +75,13 @@ struct DnsQuery {
         unsigned n_keys;
 
         DnsQueryState state;
+        unsigned n_cname;
 
         sd_event_source *timeout_event_source;
 
         DnsPacket *received;
 
+        /* Bus client information */
         sd_bus_message *request;
         unsigned char request_family;
         const char *request_hostname;
@@ -94,10 +96,12 @@ struct DnsQuery {
 int dns_query_new(Manager *m, DnsQuery **q, DnsResourceKey *keys, unsigned n_keys);
 DnsQuery *dns_query_free(DnsQuery *q);
 int dns_query_start(DnsQuery *q);
-void dns_query_finish(DnsQuery *q);
+int dns_query_follow_cname(DnsQuery *q, const char *name);
+int dns_query_matches_rr(DnsQuery *q, DnsResourceRecord *rr);
+int dns_query_matches_cname(DnsQuery *q, DnsResourceRecord *rr);
 
 DnsQueryTransaction* dns_query_transaction_free(DnsQueryTransaction *t);
-int dns_query_transaction_start(DnsQueryTransaction *t);
 void dns_query_transaction_reply(DnsQueryTransaction *t, DnsPacket *p);
+void dns_query_finish(DnsQuery *q);
 
 DEFINE_TRIVIAL_CLEANUP_FUNC(DnsQuery*, dns_query_free);

src/shared/bus-errors.h

@@ -64,4 +64,5 @@
 #define BUS_ERROR_INVALID_REPLY "org.freedesktop.resolve1.InvalidReply"
 #define BUS_ERROR_NO_SUCH_RR "org.freedesktop.resolve1.NoSuchRR"
 #define BUS_ERROR_NO_RESOURCES "org.freedesktop.resolve1.NoResources"
+#define BUS_ERROR_CNAME_LOOP "org.freedesktop.resolve1.CNameLoop"
 #define _BUS_ERROR_DNS "org.freedesktop.resolve1.DnsError."