resolved: transaction - move DNS UDP socket creation to the scope

With access to the server when creating the socket, we can connect()
to the server and hence simplify message sending and receiving in
follow-up patches.

4 files changed, 29 insertions, 18 deletions

diff --git a/src/resolve/resolved-dns-scope.c b/src/resolve/resolved-dns-scope.c
index ce419f1a04..5129412604 100644
--- a/src/resolve/resolved-dns-scope.c
+++ b/src/resolve/resolved-dns-scope.c
@@ -148,24 +148,20 @@ int dns_scope_emit(DnsScope *s, DnsTransaction *t, DnsPacket *p, DnsServer **ser
                 if (DNS_PACKET_QDCOUNT(p) > 1)
                         return -EOPNOTSUPP;
 
-                srv = dns_scope_get_dns_server(s);
-                if (!srv)
-                        return -ESRCH;
-
-                family = srv->family;
-                addr = srv->address;
-                port = 53;
-
                 if (p->size > DNS_PACKET_UNICAST_SIZE_MAX)
                         return -EMSGSIZE;
 
                 if (p->size + UDP_PACKET_HEADER_SIZE > mtu)
                         return -EMSGSIZE;
 
-                fd = transaction_dns_fd(t);
+                fd = transaction_dns_fd(t, &srv);
                 if (fd < 0)
                         return fd;
 
+                family = srv->family;
+                addr = srv->address;
+                port = 53;
+
         } else if (s->protocol == DNS_PROTOCOL_LLMNR) {
 
                 if (DNS_PACKET_QDCOUNT(p) > 1)
@@ -200,7 +196,7 @@ int dns_scope_emit(DnsScope *s, DnsTransaction *t, DnsPacket *p, DnsServer **ser
         return 1;
 }
 
-int dns_scope_tcp_socket(DnsScope *s, int family, const union in_addr_union *address, uint16_t port, DnsServer **server) {
+static int dns_scope_socket(DnsScope *s, int type, int family, const union in_addr_union *address, uint16_t port, DnsServer **server) {
         DnsServer *srv = NULL;
         _cleanup_close_ int fd = -1;
         union sockaddr_union sa = {};
@@ -244,13 +240,15 @@ int dns_scope_tcp_socket(DnsScope *s, int family, const union in_addr_union *add
                         return -EAFNOSUPPORT;
         }
 
-        fd = socket(sa.sa.sa_family, SOCK_STREAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
+        fd = socket(sa.sa.sa_family, type|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
         if (fd < 0)
                 return -errno;
 
-        r = setsockopt(fd, IPPROTO_TCP, TCP_NODELAY, &one, sizeof(one));
-        if (r < 0)
-                return -errno;
+        if (type == SOCK_STREAM) {
+                r = setsockopt(fd, IPPROTO_TCP, TCP_NODELAY, &one, sizeof(one));
+                if (r < 0)
+                        return -errno;
+        }
 
         if (s->link) {
                 uint32_t ifindex = htobe32(s->link->ifindex);
@@ -293,6 +291,14 @@ int dns_scope_tcp_socket(DnsScope *s, int family, const union in_addr_union *add
         return ret;
 }
 
+int dns_scope_udp_dns_socket(DnsScope *s, DnsServer **server) {
+        return dns_scope_socket(s, SOCK_DGRAM, AF_UNSPEC, NULL, 53, server);
+}
+
+int dns_scope_tcp_socket(DnsScope *s, int family, const union in_addr_union *address, uint16_t port, DnsServer **server) {
+        return dns_scope_socket(s, SOCK_STREAM, family, address, port, server);
+}
+
 DnsScopeMatch dns_scope_good_domain(DnsScope *s, int ifindex, uint64_t flags, const char *domain) {
         char **i;
 
diff --git a/src/resolve/resolved-dns-scope.h b/src/resolve/resolved-dns-scope.h
index 21a160ea39..9d08bc3259 100644
--- a/src/resolve/resolved-dns-scope.h
+++ b/src/resolve/resolved-dns-scope.h
@@ -67,6 +67,7 @@ DnsScope* dns_scope_free(DnsScope *s);
 
 int dns_scope_emit(DnsScope *s, DnsTransaction *t, DnsPacket *p, DnsServer **server);
 int dns_scope_tcp_socket(DnsScope *s, int family, const union in_addr_union *address, uint16_t port, DnsServer **server);
+int dns_scope_udp_dns_socket(DnsScope *s, DnsServer **server);
 
 DnsScopeMatch dns_scope_good_domain(DnsScope *s, int ifindex, uint64_t flags, const char *domain);
 int dns_scope_good_key(DnsScope *s, DnsResourceKey *key);
diff --git a/src/resolve/resolved-dns-transaction.c b/src/resolve/resolved-dns-transaction.c
index 5540cd386e..5580e376c0 100644
--- a/src/resolve/resolved-dns-transaction.c
+++ b/src/resolve/resolved-dns-transaction.c
@@ -663,7 +663,8 @@ static int on_dns_packet(sd_event_source *s, int fd, uint32_t revents, void *use
         return 0;
 }
 
-int transaction_dns_fd(DnsTransaction *t) {
+int transaction_dns_fd(DnsTransaction *t, DnsServer **_server) {
+        DnsServer *server;
         int r;
 
         assert(t);
@@ -673,14 +674,17 @@ int transaction_dns_fd(DnsTransaction *t) {
         if (t->dns_fd >= 0)
                 return t->dns_fd;
 
-        t->dns_fd = socket(t->scope->family, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
+        t->dns_fd = dns_scope_udp_dns_socket(t->scope, &server);
         if (t->dns_fd < 0)
-                return -errno;
+                return t->dns_fd;
 
         r = sd_event_add_io(t->scope->manager->event, &t->dns_event_source, t->dns_fd, EPOLLIN, on_dns_packet, t);
         if (r < 0)
                 goto fail;
 
+        if (_server)
+                *_server = server;
+
         return t->dns_fd;
 
 fail:
diff --git a/src/resolve/resolved-dns-transaction.h b/src/resolve/resolved-dns-transaction.h
index 1c8f82352a..ab4db0612f 100644
--- a/src/resolve/resolved-dns-transaction.h
+++ b/src/resolve/resolved-dns-transaction.h
@@ -92,7 +92,7 @@ int dns_transaction_go(DnsTransaction *t);
 void dns_transaction_process_reply(DnsTransaction *t, DnsPacket *p);
 void dns_transaction_complete(DnsTransaction *t, DnsTransactionState state);
 
-int transaction_dns_fd(DnsTransaction *t);
+int transaction_dns_fd(DnsTransaction *t, DnsServer **server);
 
 const char* dns_transaction_state_to_string(DnsTransactionState p) _const_;
 DnsTransactionState dns_transaction_state_from_string(const char *s) _pure_;