Merge pull request #585 from teg/resolved-harden-2

resolved: harden

12 files changed, 229 insertions, 155 deletions

diff --git a/TODO b/TODO
index 2904e2b445..1f5023c3e5 100644
--- a/TODO
+++ b/TODO
@@ -353,8 +353,6 @@ Features:
   - edns0
   - dname
   - cname on PTR (?)
-  - maybe randomize DNS UDP source ports
-  - maybe compare query section of DNS replies
 
 * Allow multiple ExecStart= for all Type= settings, so that we can cover rescue.service nicely
 
diff --git a/src/resolve/resolved-dns-packet.c b/src/resolve/resolved-dns-packet.c
index fa0516f8a0..a9cc5ca6aa 100644
--- a/src/resolve/resolved-dns-packet.c
+++ b/src/resolve/resolved-dns-packet.c
@@ -32,10 +32,10 @@ int dns_packet_new(DnsPacket **ret, DnsProtocol protocol, size_t mtu) {
 
         assert(ret);
 
-        if (mtu <= 0)
+        if (mtu <= UDP_PACKET_HEADER_SIZE)
                 a = DNS_PACKET_SIZE_START;
         else
-                a = mtu;
+                a = mtu - UDP_PACKET_HEADER_SIZE;
 
         if (a < DNS_PACKET_HEADER_SIZE)
                 a = DNS_PACKET_HEADER_SIZE;
diff --git a/src/resolve/resolved-dns-packet.h b/src/resolve/resolved-dns-packet.h
index bf998aa84e..6588ed9df5 100644
--- a/src/resolve/resolved-dns-packet.h
+++ b/src/resolve/resolved-dns-packet.h
@@ -21,6 +21,8 @@
   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  ***/
 
+#include <netinet/udp.h>
+#include <netinet/ip.h>
 
 #include "macro.h"
 #include "sparse-endian.h"
@@ -53,6 +55,7 @@ struct DnsPacketHeader {
 };
 
 #define DNS_PACKET_HEADER_SIZE sizeof(DnsPacketHeader)
+#define UDP_PACKET_HEADER_SIZE (sizeof(struct iphdr) + sizeof(struct udphdr))
 
 /* The various DNS protocols deviate in how large a packet can grow,
    but the TCP transport has a 16bit size field, hence that appears to
diff --git a/src/resolve/resolved-dns-scope.c b/src/resolve/resolved-dns-scope.c
index 25392d21d7..7b72c090c2 100644
--- a/src/resolve/resolved-dns-scope.c
+++ b/src/resolve/resolved-dns-scope.c
@@ -125,7 +125,8 @@ void dns_scope_next_dns_server(DnsScope *s) {
                 manager_next_dns_server(s->manager);
 }
 
-int dns_scope_emit(DnsScope *s, DnsPacket *p) {
+int dns_scope_emit(DnsScope *s, DnsTransaction *t, DnsPacket *p, DnsServer **server) {
+        DnsServer *srv = NULL;
         union in_addr_union addr;
         int ifindex = 0, r;
         int family;
@@ -144,8 +145,6 @@ int dns_scope_emit(DnsScope *s, DnsPacket *p) {
                 mtu = manager_find_mtu(s->manager);
 
         if (s->protocol == DNS_PROTOCOL_DNS) {
-                DnsServer *srv;
-
                 if (DNS_PACKET_QDCOUNT(p) > 1)
                         return -EOPNOTSUPP;
 
@@ -160,13 +159,13 @@ int dns_scope_emit(DnsScope *s, DnsPacket *p) {
                 if (p->size > DNS_PACKET_UNICAST_SIZE_MAX)
                         return -EMSGSIZE;
 
-                if (p->size > mtu)
+                if (p->size + UDP_PACKET_HEADER_SIZE > mtu)
                         return -EMSGSIZE;
 
                 if (family == AF_INET)
-                        fd = manager_dns_ipv4_fd(s->manager);
+                        fd = transaction_dns_ipv4_fd(t);
                 else if (family == AF_INET6)
-                        fd = manager_dns_ipv6_fd(s->manager);
+                        fd = transaction_dns_ipv6_fd(t);
                 else
                         return -EAFNOSUPPORT;
                 if (fd < 0)
@@ -200,10 +199,14 @@ int dns_scope_emit(DnsScope *s, DnsPacket *p) {
         if (r < 0)
                 return r;
 
+        if (server)
+                *server = srv;
+
         return 1;
 }
 
-int dns_scope_tcp_socket(DnsScope *s, int family, const union in_addr_union *address, uint16_t port) {
+int dns_scope_tcp_socket(DnsScope *s, 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 = {};
         socklen_t salen;
@@ -214,8 +217,6 @@ int dns_scope_tcp_socket(DnsScope *s, int family, const union in_addr_union *add
         assert((family == AF_UNSPEC) == !address);
 
         if (family == AF_UNSPEC) {
-                DnsServer *srv;
-
                 srv = dns_scope_get_dns_server(s);
                 if (!srv)
                         return -ESRCH;
@@ -288,6 +289,9 @@ int dns_scope_tcp_socket(DnsScope *s, int family, const union in_addr_union *add
         if (r < 0 && errno != EINPROGRESS)
                 return -errno;
 
+        if (server)
+                *server = srv;
+
         ret = fd;
         fd = -1;
 
@@ -696,7 +700,7 @@ static int on_conflict_dispatch(sd_event_source *es, usec_t usec, void *userdata
                         return 0;
                 }
 
-                r = dns_scope_emit(scope, p);
+                r = dns_scope_emit(scope, NULL, p, NULL);
                 if (r < 0)
                         log_debug_errno(r, "Failed to send conflict packet: %m");
         }
diff --git a/src/resolve/resolved-dns-scope.h b/src/resolve/resolved-dns-scope.h
index cfbde1343f..5c5ccc71c5 100644
--- a/src/resolve/resolved-dns-scope.h
+++ b/src/resolve/resolved-dns-scope.h
@@ -65,8 +65,8 @@ struct DnsScope {
 int dns_scope_new(Manager *m, DnsScope **ret, Link *l, DnsProtocol p, int family);
 DnsScope* dns_scope_free(DnsScope *s);
 
-int dns_scope_emit(DnsScope *s, DnsPacket *p);
-int dns_scope_tcp_socket(DnsScope *s, int family, const union in_addr_union *address, uint16_t port);
+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);
 
 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-server.c b/src/resolve/resolved-dns-server.c
index 9a62a63258..92e48ae442 100644
--- a/src/resolve/resolved-dns-server.c
+++ b/src/resolve/resolved-dns-server.c
@@ -41,6 +41,7 @@ int dns_server_new(
         if (!s)
                 return -ENOMEM;
 
+        s->n_ref = 1;
         s->type = type;
         s->family = family;
         s->address = *in_addr;
@@ -74,33 +75,46 @@ int dns_server_new(
         return 0;
 }
 
-DnsServer* dns_server_free(DnsServer *s)  {
+DnsServer* dns_server_ref(DnsServer *s)  {
         if (!s)
                 return NULL;
 
-        if (s->link) {
-                if (s->type == DNS_SERVER_LINK)
-                        LIST_REMOVE(servers, s->link->dns_servers, s);
+        assert(s->n_ref > 0);
 
-                if (s->link->current_dns_server == s)
-                        link_set_dns_server(s->link, NULL);
-        }
+        s->n_ref ++;
 
-        if (s->manager) {
-                if (s->type == DNS_SERVER_SYSTEM)
-                        LIST_REMOVE(servers, s->manager->dns_servers, s);
-                else if (s->type == DNS_SERVER_FALLBACK)
-                        LIST_REMOVE(servers, s->manager->fallback_dns_servers, s);
+        return s;
+}
+
+static DnsServer* dns_server_free(DnsServer *s)  {
+        if (!s)
+                return NULL;
 
-                if (s->manager->current_dns_server == s)
-                        manager_set_dns_server(s->manager, NULL);
-        }
+        if (s->link && s->link->current_dns_server == s)
+                link_set_dns_server(s->link, NULL);
+
+        if (s->manager && s->manager->current_dns_server == s)
+                manager_set_dns_server(s->manager, NULL);
 
         free(s);
 
         return NULL;
 }
 
+DnsServer* dns_server_unref(DnsServer *s)  {
+        if (!s)
+                return NULL;
+
+        assert(s->n_ref > 0);
+
+        if (s->n_ref == 1)
+                dns_server_free(s);
+        else
+                s->n_ref --;
+
+        return NULL;
+}
+
 static unsigned long dns_server_hash_func(const void *p, const uint8_t hash_key[HASH_KEY_SIZE]) {
         const DnsServer *s = p;
         uint64_t u;
diff --git a/src/resolve/resolved-dns-server.h b/src/resolve/resolved-dns-server.h
index 70ff35b08f..06059e8829 100644
--- a/src/resolve/resolved-dns-server.h
+++ b/src/resolve/resolved-dns-server.h
@@ -37,6 +37,8 @@ typedef enum DnsServerType {
 struct DnsServer {
         Manager *manager;
 
+        unsigned n_ref;
+
         DnsServerType type;
 
         Link *link;
@@ -57,6 +59,9 @@ int dns_server_new(
                 int family,
                 const union in_addr_union *address);
 
-DnsServer* dns_server_free(DnsServer *s);
+DnsServer* dns_server_ref(DnsServer *s);
+DnsServer* dns_server_unref(DnsServer *s);
+
+DEFINE_TRIVIAL_CLEANUP_FUNC(DnsServer*, dns_server_unref);
 
 extern const struct hash_ops dns_server_hash_ops;
diff --git a/src/resolve/resolved-dns-transaction.c b/src/resolve/resolved-dns-transaction.c
index 3f4673df7a..e468f245f7 100644
--- a/src/resolve/resolved-dns-transaction.c
+++ b/src/resolve/resolved-dns-transaction.c
@@ -39,6 +39,12 @@ DnsTransaction* dns_transaction_free(DnsTransaction *t) {
         dns_packet_unref(t->received);
         dns_answer_unref(t->cached);
 
+        sd_event_source_unref(t->dns_ipv4_event_source);
+        sd_event_source_unref(t->dns_ipv6_event_source);
+        safe_close(t->dns_ipv4_fd);
+        safe_close(t->dns_ipv6_fd);
+
+        dns_server_unref(t->server);
         dns_stream_free(t->stream);
 
         if (t->scope) {
@@ -88,6 +94,8 @@ int dns_transaction_new(DnsTransaction **ret, DnsScope *s, DnsQuestion *q) {
         if (!t)
                 return -ENOMEM;
 
+        t->dns_ipv4_fd = t->dns_ipv6_fd = -1;
+
         t->question = dns_question_ref(q);
 
         do
@@ -237,6 +245,7 @@ static int on_stream_complete(DnsStream *s, int error) {
 }
 
 static int dns_transaction_open_tcp(DnsTransaction *t) {
+        _cleanup_(dns_server_unrefp) DnsServer *server = NULL;
         _cleanup_close_ int fd = -1;
         int r;
 
@@ -246,12 +255,12 @@ static int dns_transaction_open_tcp(DnsTransaction *t) {
                 return 0;
 
         if (t->scope->protocol == DNS_PROTOCOL_DNS)
-                fd = dns_scope_tcp_socket(t->scope, AF_UNSPEC, NULL, 53);
+                fd = dns_scope_tcp_socket(t->scope, AF_UNSPEC, NULL, 53, &server);
         else if (t->scope->protocol == DNS_PROTOCOL_LLMNR) {
 
                 /* When we already received a query to this (but it was truncated), send to its sender address */
                 if (t->received)
-                        fd = dns_scope_tcp_socket(t->scope, t->received->family, &t->received->sender, t->received->sender_port);
+                        fd = dns_scope_tcp_socket(t->scope, t->received->family, &t->received->sender, t->received->sender_port, NULL);
                 else {
                         union in_addr_union address;
                         int family = AF_UNSPEC;
@@ -265,7 +274,7 @@ static int dns_transaction_open_tcp(DnsTransaction *t) {
                         if (r == 0)
                                 return -EINVAL;
 
-                        fd = dns_scope_tcp_socket(t->scope, family, &address, LLMNR_PORT);
+                        fd = dns_scope_tcp_socket(t->scope, family, &address, LLMNR_PORT, NULL);
                 }
         } else
                 return -EAFNOSUPPORT;
@@ -285,6 +294,9 @@ static int dns_transaction_open_tcp(DnsTransaction *t) {
                 return r;
         }
 
+
+        dns_server_unref(t->server);
+        t->server = dns_server_ref(server);
         t->received = dns_packet_unref(t->received);
         t->stream->complete = on_stream_complete;
         t->stream->transaction = t;
@@ -333,10 +345,15 @@ void dns_transaction_process_reply(DnsTransaction *t, DnsPacket *p) {
         if (t->scope->protocol == DNS_PROTOCOL_DNS) {
 
                 /* For DNS we are fine with accepting packets on any
-                 * interface, but the source IP address must be one of
-                 * a valid DNS server */
+                 * interface, but the source IP address must be the
+                 * one of the DNS server we queried */
+
+                assert(t->server);
 
-                if (!dns_scope_good_dns_server(t->scope, p->family, &p->sender))
+                if (t->server->family != p->family)
+                        return;
+
+                if (!in_addr_equal(p->family, &p->sender, &t->server->address))
                         return;
 
                 if (p->sender_port != 53)
@@ -398,6 +415,11 @@ void dns_transaction_process_reply(DnsTransaction *t, DnsPacket *p) {
                 return;
         }
 
+        /* Only consider responses with equivalent query section to the request */
+        if (!dns_question_is_superset(p->question, t->question) ||
+            !dns_question_is_superset(t->question, p->question))
+                dns_transaction_complete(t, DNS_TRANSACTION_INVALID_REPLY);
+
         /* According to RFC 4795, section 2.9. only the RRs from the answer section shall be cached */
         dns_cache_put(&t->scope->cache, p->question, DNS_PACKET_RCODE(p), p->answer, DNS_PACKET_ANCOUNT(p), 0, p->family, &p->sender);
 
@@ -492,6 +514,7 @@ int dns_transaction_go(DnsTransaction *t) {
         }
 
         t->n_attempts++;
+        t->server = dns_server_unref(t->server);
         t->received = dns_packet_unref(t->received);
         t->cached = dns_answer_unref(t->cached);
         t->cached_rcode = 0;
@@ -571,17 +594,20 @@ int dns_transaction_go(DnsTransaction *t) {
                  * always be made via TCP on LLMNR */
                 r = dns_transaction_open_tcp(t);
         } else {
+                DnsServer *server;
+
                 /* Try via UDP, and if that fails due to large size try via TCP */
-                r = dns_scope_emit(t->scope, t->sent);
-                if (r == -EMSGSIZE)
+                r = dns_scope_emit(t->scope, t, t->sent, &server);
+                if (r >= 0)
+                        t->server = dns_server_ref(server);
+                else if (r == -EMSGSIZE)
                         r = dns_transaction_open_tcp(t);
         }
         if (r == -ESRCH) {
                 /* No servers to send this to? */
                 dns_transaction_complete(t, DNS_TRANSACTION_NO_SERVERS);
                 return 0;
-        }
-        if (r < 0) {
+        } else if (r < 0) {
                 if (t->scope->protocol != DNS_PROTOCOL_DNS) {
                         dns_transaction_complete(t, DNS_TRANSACTION_RESOURCES);
                         return 0;
@@ -606,6 +632,91 @@ int dns_transaction_go(DnsTransaction *t) {
         return 1;
 }
 
+static int on_dns_packet(sd_event_source *s, int fd, uint32_t revents, void *userdata) {
+        _cleanup_(dns_packet_unrefp) DnsPacket *p = NULL;
+        DnsTransaction *t = userdata;
+        int r;
+
+        assert(t);
+        assert(t->scope);
+
+        r = manager_recv(t->scope->manager, fd, DNS_PROTOCOL_DNS, &p);
+        if (r <= 0)
+                return r;
+
+        if (dns_packet_validate_reply(p) > 0 &&
+            DNS_PACKET_ID(p) == t->id) {
+                dns_transaction_process_reply(t, p);
+        } else
+                log_debug("Invalid DNS packet.");
+
+        return 0;
+}
+
+int transaction_dns_ipv4_fd(DnsTransaction *t) {
+        const int one = 1;
+        int r;
+
+        assert(t);
+        assert(t->scope);
+        assert(t->scope->manager);
+
+        if (t->dns_ipv4_fd >= 0)
+                return t->dns_ipv4_fd;
+
+        t->dns_ipv4_fd = socket(AF_INET, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
+        if (t->dns_ipv4_fd < 0)
+                return -errno;
+
+        r = setsockopt(t->dns_ipv4_fd, IPPROTO_IP, IP_PKTINFO, &one, sizeof(one));
+        if (r < 0) {
+                r = -errno;
+                goto fail;
+        }
+
+        r = sd_event_add_io(t->scope->manager->event, &t->dns_ipv4_event_source, t->dns_ipv4_fd, EPOLLIN, on_dns_packet, t);
+        if (r < 0)
+                goto fail;
+
+        return t->dns_ipv4_fd;
+
+fail:
+        t->dns_ipv4_fd = safe_close(t->dns_ipv4_fd);
+        return r;
+}
+
+int transaction_dns_ipv6_fd(DnsTransaction *t) {
+        const int one = 1;
+        int r;
+
+        assert(t);
+        assert(t->scope);
+        assert(t->scope->manager);
+
+        if (t->dns_ipv6_fd >= 0)
+                return t->dns_ipv6_fd;
+
+        t->dns_ipv6_fd = socket(AF_INET6, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
+        if (t->dns_ipv6_fd < 0)
+                return -errno;
+
+        r = setsockopt(t->dns_ipv6_fd, IPPROTO_IPV6, IPV6_RECVPKTINFO, &one, sizeof(one));
+        if (r < 0) {
+                r = -errno;
+                goto fail;
+        }
+
+        r = sd_event_add_io(t->scope->manager->event, &t->dns_ipv6_event_source, t->dns_ipv6_fd, EPOLLIN, on_dns_packet, t);
+        if (r < 0)
+                goto fail;
+
+        return t->dns_ipv6_fd;
+
+fail:
+        t->dns_ipv6_fd = safe_close(t->dns_ipv6_fd);
+        return r;
+}
+
 static const char* const dns_transaction_state_table[_DNS_TRANSACTION_STATE_MAX] = {
         [DNS_TRANSACTION_NULL] = "null",
         [DNS_TRANSACTION_PENDING] = "pending",
diff --git a/src/resolve/resolved-dns-transaction.h b/src/resolve/resolved-dns-transaction.h
index f6d539d315..87f342ca11 100644
--- a/src/resolve/resolved-dns-transaction.h
+++ b/src/resolve/resolved-dns-transaction.h
@@ -61,6 +61,15 @@ struct DnsTransaction {
         sd_event_source *timeout_event_source;
         unsigned n_attempts;
 
+        int dns_ipv4_fd;
+        int dns_ipv6_fd;
+
+        sd_event_source *dns_ipv4_event_source;
+        sd_event_source *dns_ipv6_event_source;
+
+        /* the active server */
+        DnsServer *server;
+
         /* TCP connection logic, if we need it */
         DnsStream *stream;
 
@@ -86,6 +95,9 @@ 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_ipv4_fd(DnsTransaction *t);
+int transaction_dns_ipv6_fd(DnsTransaction *t);
+
 const char* dns_transaction_state_to_string(DnsTransactionState p) _const_;
 DnsTransactionState dns_transaction_state_from_string(const char *s) _pure_;
 
diff --git a/src/resolve/resolved-link.c b/src/resolve/resolved-link.c
index ff8dc3a5bc..d66b3a88fc 100644
--- a/src/resolve/resolved-link.c
+++ b/src/resolve/resolved-link.c
@@ -58,7 +58,6 @@ int link_new(Manager *m, Link **ret, int ifindex) {
 }
 
 Link *link_free(Link *l) {
-
         if (!l)
                 return NULL;
 
@@ -68,8 +67,12 @@ Link *link_free(Link *l) {
         if (l->manager)
                 hashmap_remove(l->manager->links, INT_TO_PTR(l->ifindex));
 
-        while (l->dns_servers)
-                dns_server_free(l->dns_servers);
+        while (l->dns_servers) {
+                DnsServer *s = l->dns_servers;
+
+                LIST_REMOVE(servers, l->dns_servers, s);
+                dns_server_unref(s);
+        }
 
         dns_scope_free(l->unicast_scope);
         dns_scope_free(l->llmnr_ipv4_scope);
@@ -182,14 +185,20 @@ static int link_update_dns_servers(Link *l) {
         }
 
         LIST_FOREACH_SAFE(servers, s, nx, l->dns_servers)
-                if (s->marked)
-                        dns_server_free(s);
+                if (s->marked) {
+                        LIST_REMOVE(servers, l->dns_servers, s);
+                        dns_server_unref(s);
+                }
 
         return 0;
 
 clear:
-        while (l->dns_servers)
-                dns_server_free(l->dns_servers);
+        while (l->dns_servers) {
+                s = l->dns_servers;
+
+                LIST_REMOVE(servers, l->dns_servers, s);
+                dns_server_unref(s);
+        }
 
         return r;
 }
diff --git a/src/resolve/resolved-manager.c b/src/resolve/resolved-manager.c
index 6785a2e3c7..17de14bae1 100644
--- a/src/resolve/resolved-manager.c
+++ b/src/resolve/resolved-manager.c
@@ -404,7 +404,6 @@ int manager_new(Manager **ret) {
         if (!m)
                 return -ENOMEM;
 
-        m->dns_ipv4_fd = m->dns_ipv6_fd = -1;
         m->llmnr_ipv4_udp_fd = m->llmnr_ipv6_udp_fd = -1;
         m->llmnr_ipv4_tcp_fd = m->llmnr_ipv6_tcp_fd = -1;
         m->hostname_fd = -1;
@@ -486,11 +485,6 @@ Manager *manager_free(Manager *m) {
         sd_event_source_unref(m->network_event_source);
         sd_network_monitor_unref(m->network_monitor);
 
-        sd_event_source_unref(m->dns_ipv4_event_source);
-        sd_event_source_unref(m->dns_ipv6_event_source);
-        safe_close(m->dns_ipv4_fd);
-        safe_close(m->dns_ipv6_fd);
-
         manager_llmnr_stop(m);
 
         sd_bus_slot_unref(m->prepare_for_sleep_slot);
@@ -603,8 +597,10 @@ int manager_read_resolv_conf(Manager *m) {
         }
 
         LIST_FOREACH_SAFE(servers, s, nx, m->dns_servers)
-                if (s->marked)
-                        dns_server_free(s);
+                if (s->marked) {
+                        LIST_REMOVE(servers, m->dns_servers, s);
+                        dns_server_unref(s);
+                }
 
         /* Whenever /etc/resolv.conf changes, start using the first
          * DNS server of it. This is useful to deal with broken
@@ -619,8 +615,12 @@ int manager_read_resolv_conf(Manager *m) {
         return 0;
 
 clear:
-        while (m->dns_servers)
-                dns_server_free(m->dns_servers);
+        while (m->dns_servers) {
+                s = m->dns_servers;
+
+                LIST_REMOVE(servers, m->dns_servers, s);
+                dns_server_unref(s);
+        }
 
         return r;
 }
@@ -923,89 +923,6 @@ int manager_recv(Manager *m, int fd, DnsProtocol protocol, DnsPacket **ret) {
         return 1;
 }
 
-static int on_dns_packet(sd_event_source *s, int fd, uint32_t revents, void *userdata) {
-        _cleanup_(dns_packet_unrefp) DnsPacket *p = NULL;
-        DnsTransaction *t = NULL;
-        Manager *m = userdata;
-        int r;
-
-        r = manager_recv(m, fd, DNS_PROTOCOL_DNS, &p);
-        if (r <= 0)
-                return r;
-
-        if (dns_packet_validate_reply(p) > 0) {
-                t = hashmap_get(m->dns_transactions, UINT_TO_PTR(DNS_PACKET_ID(p)));
-                if (!t)
-                        return 0;
-
-                dns_transaction_process_reply(t, p);
-
-        } else
-                log_debug("Invalid DNS packet.");
-
-        return 0;
-}
-
-int manager_dns_ipv4_fd(Manager *m) {
-        const int one = 1;
-        int r;
-
-        assert(m);
-
-        if (m->dns_ipv4_fd >= 0)
-                return m->dns_ipv4_fd;
-
-        m->dns_ipv4_fd = socket(AF_INET, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
-        if (m->dns_ipv4_fd < 0)
-                return -errno;
-
-        r = setsockopt(m->dns_ipv4_fd, IPPROTO_IP, IP_PKTINFO, &one, sizeof(one));
-        if (r < 0) {
-                r = -errno;
-                goto fail;
-        }
-
-        r = sd_event_add_io(m->event, &m->dns_ipv4_event_source, m->dns_ipv4_fd, EPOLLIN, on_dns_packet, m);
-        if (r < 0)
-                goto fail;
-
-        return m->dns_ipv4_fd;
-
-fail:
-        m->dns_ipv4_fd = safe_close(m->dns_ipv4_fd);
-        return r;
-}
-
-int manager_dns_ipv6_fd(Manager *m) {
-        const int one = 1;
-        int r;
-
-        assert(m);
-
-        if (m->dns_ipv6_fd >= 0)
-                return m->dns_ipv6_fd;
-
-        m->dns_ipv6_fd = socket(AF_INET6, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
-        if (m->dns_ipv6_fd < 0)
-                return -errno;
-
-        r = setsockopt(m->dns_ipv6_fd, IPPROTO_IPV6, IPV6_RECVPKTINFO, &one, sizeof(one));
-        if (r < 0) {
-                r = -errno;
-                goto fail;
-        }
-
-        r = sd_event_add_io(m->event, &m->dns_ipv6_event_source, m->dns_ipv6_fd, EPOLLIN, on_dns_packet, m);
-        if (r < 0)
-                goto fail;
-
-        return m->dns_ipv6_fd;
-
-fail:
-        m->dns_ipv6_fd = safe_close(m->dns_ipv6_fd);
-        return r;
-}
-
 static int sendmsg_loop(int fd, struct msghdr *mh, int flags) {
         int r;
 
@@ -1381,15 +1298,25 @@ void manager_verify_all(Manager *m) {
 }
 
 void manager_flush_dns_servers(Manager *m, DnsServerType t) {
+        DnsServer *s;
+
         assert(m);
 
         if (t == DNS_SERVER_SYSTEM)
-                while (m->dns_servers)
-                        dns_server_free(m->dns_servers);
+                while (m->dns_servers) {
+                        s = m->dns_servers;
+
+                        LIST_REMOVE(servers, m->dns_servers, s);
+                        dns_server_unref(s);
+                }
 
         if (t == DNS_SERVER_FALLBACK)
-                while (m->fallback_dns_servers)
-                        dns_server_free(m->fallback_dns_servers);
+                while (m->fallback_dns_servers) {
+                        s = m->fallback_dns_servers;
+
+                        LIST_REMOVE(servers, m->fallback_dns_servers, s);
+                        dns_server_unref(s);
+                }
 }
 
 static const char* const support_table[_SUPPORT_MAX] = {
diff --git a/src/resolve/resolved-manager.h b/src/resolve/resolved-manager.h
index 4e70a5b500..005f844df2 100644
--- a/src/resolve/resolved-manager.h
+++ b/src/resolve/resolved-manager.h
@@ -65,12 +65,6 @@ struct Manager {
         unsigned n_dns_streams;
 
         /* Unicast dns */
-        int dns_ipv4_fd;
-        int dns_ipv6_fd;
-
-        sd_event_source *dns_ipv4_event_source;
-        sd_event_source *dns_ipv6_event_source;
-
         LIST_HEAD(DnsServer, dns_servers);
         LIST_HEAD(DnsServer, fallback_dns_servers);
         DnsServer *current_dns_server;
@@ -128,9 +122,6 @@ uint32_t manager_find_mtu(Manager *m);
 int manager_send(Manager *m, int fd, int ifindex, int family, const union in_addr_union *addr, uint16_t port, DnsPacket *p);
 int manager_recv(Manager *m, int fd, DnsProtocol protocol, DnsPacket **ret);
 
-int manager_dns_ipv4_fd(Manager *m);
-int manager_dns_ipv6_fd(Manager *m);
-
 int manager_find_ifindex(Manager *m, int family, const union in_addr_union *in_addr);
 LinkAddress* manager_find_link_address(Manager *m, int family, const union in_addr_union *in_addr);