From bc7702b098b63031767174206f5df14a8ccb45cf Mon Sep 17 00:00:00 2001
From: Daniel Mack <daniel@zonque.org>
Date: Fri, 10 Jul 2015 15:48:13 -0400
Subject: resolved: add infrastructure for mDNS related sockets

Just hook up mDNS listeners with an empty packet dispather function,
introduce a config directive, man page updates etc.
---
 src/resolve/resolved-link.h    |   1 +
 src/resolve/resolved-manager.c |   7 ++
 src/resolve/resolved-manager.h |   8 ++
 src/resolve/resolved-mdns.c    | 231 +++++++++++++++++++++++++++++++++++++++++
 src/resolve/resolved-mdns.h    |  32 ++++++
 5 files changed, 279 insertions(+)
 create mode 100644 src/resolve/resolved-mdns.c
 create mode 100644 src/resolve/resolved-mdns.h

(limited to 'src')

diff --git a/src/resolve/resolved-link.h b/src/resolve/resolved-link.h
index eb00015bd5..3093050c98 100644
--- a/src/resolve/resolved-link.h
+++ b/src/resolve/resolved-link.h
@@ -67,6 +67,7 @@ struct Link {
         unsigned n_search_domains;
 
         Support llmnr_support;
+        Support mdns_support;
 
         DnsScope *unicast_scope;
         DnsScope *llmnr_ipv4_scope;
diff --git a/src/resolve/resolved-manager.c b/src/resolve/resolved-manager.c
index 5a3696ccb0..fc2fb4d47c 100644
--- a/src/resolve/resolved-manager.c
+++ b/src/resolve/resolved-manager.c
@@ -40,6 +40,7 @@
 #include "resolved-llmnr.h"
 #include "resolved-manager.h"
 #include "resolved-resolv-conf.h"
+#include "resolved-mdns.h"
 #include "socket-util.h"
 #include "string-table.h"
 #include "string-util.h"
@@ -472,6 +473,7 @@ int manager_new(Manager **ret) {
 
         m->llmnr_ipv4_udp_fd = m->llmnr_ipv6_udp_fd = -1;
         m->llmnr_ipv4_tcp_fd = m->llmnr_ipv6_tcp_fd = -1;
+        m->mdns_ipv4_fd = m->mdns_ipv6_fd = -1;
         m->hostname_fd = -1;
 
         m->llmnr_support = SUPPORT_YES;
@@ -528,6 +530,10 @@ int manager_start(Manager *m) {
         if (r < 0)
                 return r;
 
+        r = manager_mdns_start(m);
+        if (r < 0)
+                return r;
+
         return 0;
 }
 
@@ -559,6 +565,7 @@ Manager *manager_free(Manager *m) {
         sd_event_source_unref(m->rtnl_event_source);
 
         manager_llmnr_stop(m);
+        manager_mdns_stop(m);
 
         sd_bus_slot_unref(m->prepare_for_sleep_slot);
         sd_event_source_unref(m->bus_retry_event_source);
diff --git a/src/resolve/resolved-manager.h b/src/resolve/resolved-manager.h
index 1056f23ab7..b52273403a 100644
--- a/src/resolve/resolved-manager.h
+++ b/src/resolve/resolved-manager.h
@@ -54,6 +54,7 @@ struct Manager {
         sd_event *event;
 
         Support llmnr_support;
+        Support mdns_support;
 
         /* Network */
         Hashmap *links;
@@ -102,6 +103,13 @@ struct Manager {
         sd_event_source *llmnr_ipv4_tcp_event_source;
         sd_event_source *llmnr_ipv6_tcp_event_source;
 
+        /* mDNS */
+        int mdns_ipv4_fd;
+        int mdns_ipv6_fd;
+
+        sd_event_source *mdns_ipv4_event_source;
+        sd_event_source *mdns_ipv6_event_source;
+
         /* dbus */
         sd_bus *bus;
         sd_event_source *bus_retry_event_source;
diff --git a/src/resolve/resolved-mdns.c b/src/resolve/resolved-mdns.c
new file mode 100644
index 0000000000..6767706f6e
--- /dev/null
+++ b/src/resolve/resolved-mdns.c
@@ -0,0 +1,231 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+/***
+  This file is part of systemd.
+
+  Copyright 2015 Daniel Mack
+
+  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 <resolv.h>
+#include <netinet/in.h>
+#include <arpa/inet.h>
+
+#include "fd-util.h"
+#include "resolved-manager.h"
+#include "resolved-mdns.h"
+
+void manager_mdns_stop(Manager *m) {
+        assert(m);
+
+        m->mdns_ipv4_event_source = sd_event_source_unref(m->mdns_ipv4_event_source);
+        m->mdns_ipv4_fd = safe_close(m->mdns_ipv4_fd);
+
+        m->mdns_ipv6_event_source = sd_event_source_unref(m->mdns_ipv6_event_source);
+        m->mdns_ipv6_fd = safe_close(m->mdns_ipv6_fd);
+}
+
+int manager_mdns_start(Manager *m) {
+        int r;
+
+        assert(m);
+
+        if (m->mdns_support == SUPPORT_NO)
+                return 0;
+
+        r = manager_mdns_ipv4_fd(m);
+        if (r == -EADDRINUSE)
+                goto eaddrinuse;
+        if (r < 0)
+                return r;
+
+        if (socket_ipv6_is_supported()) {
+                r = manager_mdns_ipv6_fd(m);
+                if (r == -EADDRINUSE)
+                        goto eaddrinuse;
+                if (r < 0)
+                        return r;
+        }
+
+        return 0;
+
+eaddrinuse:
+        log_warning("There appears to be another mDNS responder running. Turning off mDNS support.");
+        m->mdns_support = SUPPORT_NO;
+        manager_mdns_stop(m);
+
+        return 0;
+}
+
+static int on_mdns_packet(sd_event_source *s, int fd, uint32_t revents, void *userdata) {
+        /* TODO */
+        return 0;
+}
+
+int manager_mdns_ipv4_fd(Manager *m) {
+        union sockaddr_union sa = {
+                .in.sin_family = AF_INET,
+                .in.sin_port = htobe16(MDNS_PORT),
+        };
+        static const int one = 1, pmtu = IP_PMTUDISC_DONT, ttl = 255;
+        int r;
+
+        assert(m);
+
+        if (m->mdns_ipv4_fd >= 0)
+                return m->mdns_ipv4_fd;
+
+        m->mdns_ipv4_fd = socket(AF_INET, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
+        if (m->mdns_ipv4_fd < 0)
+                return -errno;
+
+        r = setsockopt(m->mdns_ipv4_fd, IPPROTO_IP, IP_TTL, &ttl, sizeof(ttl));
+        if (r < 0) {
+                r = -errno;
+                goto fail;
+        }
+
+        r = setsockopt(m->mdns_ipv4_fd, IPPROTO_IP, IP_MULTICAST_TTL, &ttl, sizeof(ttl));
+        if (r < 0) {
+                r = -errno;
+                goto fail;
+        }
+
+        r = setsockopt(m->mdns_ipv4_fd, IPPROTO_IP, IP_MULTICAST_LOOP, &one, sizeof(one));
+        if (r < 0) {
+                r = -errno;
+                goto fail;
+        }
+
+        r = setsockopt(m->mdns_ipv4_fd, SOL_SOCKET, SO_REUSEADDR, &one, sizeof(one));
+        if (r < 0) {
+                r = -errno;
+                goto fail;
+        }
+
+        r = setsockopt(m->mdns_ipv4_fd, IPPROTO_IP, IP_PKTINFO, &one, sizeof(one));
+        if (r < 0) {
+                r = -errno;
+                goto fail;
+        }
+
+        r = setsockopt(m->mdns_ipv4_fd, IPPROTO_IP, IP_RECVTTL, &one, sizeof(one));
+        if (r < 0) {
+                r = -errno;
+                goto fail;
+        }
+
+        /* Disable Don't-Fragment bit in the IP header */
+        r = setsockopt(m->mdns_ipv4_fd, IPPROTO_IP, IP_MTU_DISCOVER, &pmtu, sizeof(pmtu));
+        if (r < 0) {
+                r = -errno;
+                goto fail;
+        }
+
+        r = bind(m->mdns_ipv4_fd, &sa.sa, sizeof(sa.in));
+        if (r < 0) {
+                r = -errno;
+                goto fail;
+        }
+
+        r = sd_event_add_io(m->event, &m->mdns_ipv4_event_source, m->mdns_ipv4_fd, EPOLLIN, on_mdns_packet, m);
+        if (r < 0)
+                goto fail;
+
+        return m->mdns_ipv4_fd;
+
+fail:
+        m->mdns_ipv4_fd = safe_close(m->mdns_ipv4_fd);
+        return r;
+}
+
+int manager_mdns_ipv6_fd(Manager *m) {
+        union sockaddr_union sa = {
+                .in6.sin6_family = AF_INET6,
+                .in6.sin6_port = htobe16(MDNS_PORT),
+        };
+        static const int one = 1, ttl = 255;
+        int r;
+
+        assert(m);
+
+        if (m->mdns_ipv6_fd >= 0)
+                return m->mdns_ipv6_fd;
+
+        m->mdns_ipv6_fd = socket(AF_INET6, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
+        if (m->mdns_ipv6_fd < 0)
+                return -errno;
+
+        r = setsockopt(m->mdns_ipv6_fd, IPPROTO_IPV6, IPV6_UNICAST_HOPS, &ttl, sizeof(ttl));
+        if (r < 0) {
+                r = -errno;
+                goto fail;
+        }
+
+        /* RFC 4795, section 2.5 recommends setting the TTL of UDP packets to 255. */
+        r = setsockopt(m->mdns_ipv6_fd, IPPROTO_IPV6, IPV6_MULTICAST_HOPS, &ttl, sizeof(ttl));
+        if (r < 0) {
+                r = -errno;
+                goto fail;
+        }
+
+        r = setsockopt(m->mdns_ipv6_fd, IPPROTO_IPV6, IPV6_MULTICAST_LOOP, &one, sizeof(one));
+        if (r < 0) {
+                r = -errno;
+                goto fail;
+        }
+
+        r = setsockopt(m->mdns_ipv6_fd, IPPROTO_IPV6, IPV6_V6ONLY, &one, sizeof(one));
+        if (r < 0) {
+                r = -errno;
+                goto fail;
+        }
+
+        r = setsockopt(m->mdns_ipv6_fd, SOL_SOCKET, SO_REUSEADDR, &one, sizeof(one));
+        if (r < 0) {
+                r = -errno;
+                goto fail;
+        }
+
+        r = setsockopt(m->mdns_ipv6_fd, IPPROTO_IPV6, IPV6_RECVPKTINFO, &one, sizeof(one));
+        if (r < 0) {
+                r = -errno;
+                goto fail;
+        }
+
+        r = setsockopt(m->mdns_ipv6_fd, IPPROTO_IPV6, IPV6_RECVHOPLIMIT, &one, sizeof(one));
+        if (r < 0) {
+                r = -errno;
+                goto fail;
+        }
+
+        r = bind(m->mdns_ipv6_fd, &sa.sa, sizeof(sa.in6));
+        if (r < 0) {
+                r = -errno;
+                goto fail;
+        }
+
+        r = sd_event_add_io(m->event, &m->mdns_ipv6_event_source, m->mdns_ipv6_fd, EPOLLIN, on_mdns_packet, m);
+        if (r < 0)  {
+                r = -errno;
+                goto fail;
+        }
+
+        return m->mdns_ipv6_fd;
+
+fail:
+        m->mdns_ipv6_fd = safe_close(m->mdns_ipv6_fd);
+        return r;
+}
diff --git a/src/resolve/resolved-mdns.h b/src/resolve/resolved-mdns.h
new file mode 100644
index 0000000000..8a84010615
--- /dev/null
+++ b/src/resolve/resolved-mdns.h
@@ -0,0 +1,32 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+#pragma once
+
+/***
+  This file is part of systemd.
+
+  Copyright 2015 Daniel Mack
+
+  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 "resolved-manager.h"
+
+#define MDNS_PORT 5353
+
+int manager_mdns_ipv4_fd(Manager *m);
+int manager_mdns_ipv6_fd(Manager *m);
+
+void manager_mdns_stop(Manager *m);
+int manager_mdns_start(Manager *m);
-- 
cgit v1.2.3-54-g00ecf


From 4e5bf5e15899de3f9d11c2ddfe9721d9f8b07a37 Mon Sep 17 00:00:00 2001
From: Daniel Mack <daniel@zonque.org>
Date: Fri, 10 Jul 2015 20:44:46 -0400
Subject: resolved: add packet header details for mDNS

Validate mDNS queries and responses by looking at some header fields,
add mDNS flags.
---
 src/resolve/resolved-def.h             |  6 +++++-
 src/resolve/resolved-dns-packet.c      | 29 +++++++++++++++++++++++++++++
 src/resolve/resolved-dns-packet.h      |  3 +++
 src/resolve/resolved-dns-transaction.c | 12 ++++++++++++
 4 files changed, 49 insertions(+), 1 deletion(-)

(limited to 'src')

diff --git a/src/resolve/resolved-def.h b/src/resolve/resolved-def.h
index db5ee57b51..6014d345f3 100644
--- a/src/resolve/resolved-def.h
+++ b/src/resolve/resolved-def.h
@@ -24,6 +24,8 @@
 #define SD_RESOLVED_DNS           (UINT64_C(1) << 0)
 #define SD_RESOLVED_LLMNR_IPV4    (UINT64_C(1) << 1)
 #define SD_RESOLVED_LLMNR_IPV6    (UINT64_C(1) << 2)
+#define SD_RESOLVED_MDNS_IPV4     (UINT64_C(1) << 3)
+#define SD_RESOLVED_MDNS_IPV6     (UINT64_C(1) << 4)
 #define SD_RESOLVED_NO_CNAME      (UINT64_C(1) << 5)
 #define SD_RESOLVED_NO_TXT        (UINT64_C(1) << 6)
 #define SD_RESOLVED_NO_ADDRESS    (UINT64_C(1) << 7)
@@ -31,4 +33,6 @@
 #define SD_RESOLVED_AUTHENTICATED (UINT64_C(1) << 9)
 
 #define SD_RESOLVED_LLMNR         (SD_RESOLVED_LLMNR_IPV4|SD_RESOLVED_LLMNR_IPV6)
-#define SD_RESOLVED_PROTOCOLS_ALL (SD_RESOLVED_LLMNR|SD_RESOLVED_DNS)
+#define SD_RESOLVED_MDNS          (SD_RESOLVED_MDNS_IPV4|SD_RESOLVED_MDNS_IPV6)
+
+#define SD_RESOLVED_PROTOCOLS_ALL (SD_RESOLVED_MDNS|SD_RESOLVED_LLMNR|SD_RESOLVED_DNS)
diff --git a/src/resolve/resolved-dns-packet.c b/src/resolve/resolved-dns-packet.c
index ea776f7916..3a4482a1b7 100644
--- a/src/resolve/resolved-dns-packet.c
+++ b/src/resolve/resolved-dns-packet.c
@@ -88,6 +88,16 @@ int dns_packet_new_query(DnsPacket **ret, DnsProtocol protocol, size_t mtu, bool
                                                          0 /* ad */,
                                                          0 /* cd */,
                                                          0 /* rcode */));
+        else if (protocol == DNS_PROTOCOL_MDNS)
+                h->flags = htobe16(DNS_PACKET_MAKE_FLAGS(0 /* qr */,
+                                                         0 /* opcode */,
+                                                         0 /* aa */,
+                                                         0 /* tc */,
+                                                         0 /* rd (ask for recursion) */,
+                                                         0 /* ra */,
+                                                         0 /* ad */,
+                                                         0 /* cd */,
+                                                         0 /* rcode */));
         else
                 h->flags = htobe16(DNS_PACKET_MAKE_FLAGS(0 /* qr */,
                                                          0 /* opcode */,
@@ -182,6 +192,13 @@ int dns_packet_validate_reply(DnsPacket *p) {
 
                 break;
 
+        case DNS_PROTOCOL_MDNS:
+                /* RFC 6762, Section 18 */
+                if (DNS_PACKET_RCODE(p) != 0)
+                        return -EBADMSG;
+
+                break;
+
         default:
                 break;
         }
@@ -223,6 +240,18 @@ int dns_packet_validate_query(DnsPacket *p) {
 
                 break;
 
+        case DNS_PROTOCOL_MDNS:
+                /* RFC 6762, Section 18 */
+                if (DNS_PACKET_AA(p)    != 0 ||
+                    DNS_PACKET_RD(p)    != 0 ||
+                    DNS_PACKET_RA(p)    != 0 ||
+                    DNS_PACKET_AD(p)    != 0 ||
+                    DNS_PACKET_CD(p)    != 0 ||
+                    DNS_PACKET_RCODE(p) != 0)
+                        return -EBADMSG;
+
+                break;
+
         default:
                 break;
         }
diff --git a/src/resolve/resolved-dns-packet.h b/src/resolve/resolved-dns-packet.h
index aa2823cfb9..1d275f8110 100644
--- a/src/resolve/resolved-dns-packet.h
+++ b/src/resolve/resolved-dns-packet.h
@@ -239,6 +239,9 @@ static inline uint64_t SD_RESOLVED_FLAGS_MAKE(DnsProtocol protocol, int family,
         case DNS_PROTOCOL_LLMNR:
                 return f|(family == AF_INET6 ? SD_RESOLVED_LLMNR_IPV6 : SD_RESOLVED_LLMNR_IPV4);
 
+        case DNS_PROTOCOL_MDNS:
+                return family == AF_INET6 ? SD_RESOLVED_MDNS_IPV6 : SD_RESOLVED_MDNS_IPV4;
+
         default:
                 break;
         }
diff --git a/src/resolve/resolved-dns-transaction.c b/src/resolve/resolved-dns-transaction.c
index 1103a34c6f..f77931ed53 100644
--- a/src/resolve/resolved-dns-transaction.c
+++ b/src/resolve/resolved-dns-transaction.c
@@ -384,6 +384,18 @@ void dns_transaction_process_reply(DnsTransaction *t, DnsPacket *p) {
 
                 break;
 
+        case DNS_PROTOCOL_MDNS:
+                assert(t->scope->link);
+
+                /* For mDNS we will not accept any packets from other interfaces */
+                if (p->ifindex != t->scope->link->ifindex)
+                        return;
+
+                if (p->family != t->scope->family)
+                        return;
+
+                break;
+
         case DNS_PROTOCOL_DNS:
                 break;
 
-- 
cgit v1.2.3-54-g00ecf


From 0db4c90afd7d9c7c8884bf8b3ec459edc74a03da Mon Sep 17 00:00:00 2001
From: Daniel Mack <daniel@zonque.org>
Date: Sat, 11 Jul 2015 14:33:58 -0400
Subject: resolved: add code to join/leave mDNS multicast groups

Per link, join the mDNS multicast groups when the scope is created, and
leave it again when the scope goes away.
---
 src/resolve/resolved-dns-packet.h |  3 +++
 src/resolve/resolved-dns-scope.c  | 28 +++++++++++++++++++++-------
 src/resolve/resolved-dns-scope.h  |  1 +
 3 files changed, 25 insertions(+), 7 deletions(-)

(limited to 'src')

diff --git a/src/resolve/resolved-dns-packet.h b/src/resolve/resolved-dns-packet.h
index 1d275f8110..48b3572cb4 100644
--- a/src/resolve/resolved-dns-packet.h
+++ b/src/resolve/resolved-dns-packet.h
@@ -225,6 +225,9 @@ DnsProtocol dns_protocol_from_string(const char *s) _pure_;
 #define LLMNR_MULTICAST_IPV4_ADDRESS ((struct in_addr) { .s_addr = htobe32(224U << 24 | 252U) })
 #define LLMNR_MULTICAST_IPV6_ADDRESS ((struct in6_addr) { .s6_addr = { 0xFF, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x03 } })
 
+#define MDNS_MULTICAST_IPV4_ADDRESS  ((struct in_addr) { .s_addr = htobe32(224U << 24 | 251U) })
+#define MDNS_MULTICAST_IPV6_ADDRESS  ((struct in6_addr) { .s6_addr = { 0xFF, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0xfb } })
+
 static inline uint64_t SD_RESOLVED_FLAGS_MAKE(DnsProtocol protocol, int family, bool authenticated) {
         uint64_t f;
 
diff --git a/src/resolve/resolved-dns-scope.c b/src/resolve/resolved-dns-scope.c
index a90692cdf4..10148cb08e 100644
--- a/src/resolve/resolved-dns-scope.c
+++ b/src/resolve/resolved-dns-scope.c
@@ -59,6 +59,7 @@ int dns_scope_new(Manager *m, DnsScope **ret, Link *l, DnsProtocol protocol, int
         LIST_PREPEND(scopes, m->dns_scopes, s);
 
         dns_scope_llmnr_membership(s, true);
+        dns_scope_mdns_membership(s, true);
 
         log_debug("New scope on link %s, protocol %s, family %s", l ? l->name : "*", dns_protocol_to_string(protocol), family == AF_UNSPEC ? "*" : af_to_name(family));
 
@@ -95,6 +96,7 @@ DnsScope* dns_scope_free(DnsScope *s) {
         log_debug("Removing scope on link %s, protocol %s, family %s", s->link ? s->link->name : "*", dns_protocol_to_string(s->protocol), s->family == AF_UNSPEC ? "*" : af_to_name(s->family));
 
         dns_scope_llmnr_membership(s, false);
+        dns_scope_mdns_membership(s, false);
         dns_scope_abort_transactions(s);
 
         while (s->query_candidates)
@@ -477,19 +479,15 @@ int dns_scope_good_key(DnsScope *s, DnsResourceKey *key) {
         return true;
 }
 
-int dns_scope_llmnr_membership(DnsScope *s, bool b) {
+static int dns_scope_multicast_membership(DnsScope *s, bool b, struct in_addr in, struct in6_addr in6) {
         int fd;
 
         assert(s);
-
-        if (s->protocol != DNS_PROTOCOL_LLMNR)
-                return 0;
-
         assert(s->link);
 
         if (s->family == AF_INET) {
                 struct ip_mreqn mreqn = {
-                        .imr_multiaddr = LLMNR_MULTICAST_IPV4_ADDRESS,
+                        .imr_multiaddr = in,
                         .imr_ifindex = s->link->ifindex,
                 };
 
@@ -508,7 +506,7 @@ int dns_scope_llmnr_membership(DnsScope *s, bool b) {
 
         } else if (s->family == AF_INET6) {
                 struct ipv6_mreq mreq = {
-                        .ipv6mr_multiaddr = LLMNR_MULTICAST_IPV6_ADDRESS,
+                        .ipv6mr_multiaddr = in6,
                         .ipv6mr_interface = s->link->ifindex,
                 };
 
@@ -527,6 +525,22 @@ int dns_scope_llmnr_membership(DnsScope *s, bool b) {
         return 0;
 }
 
+int dns_scope_llmnr_membership(DnsScope *s, bool b) {
+
+        if (s->protocol != DNS_PROTOCOL_LLMNR)
+                return 0;
+
+        return dns_scope_multicast_membership(s, b, LLMNR_MULTICAST_IPV4_ADDRESS, LLMNR_MULTICAST_IPV6_ADDRESS);
+}
+
+int dns_scope_mdns_membership(DnsScope *s, bool b) {
+
+        if (s->protocol != DNS_PROTOCOL_MDNS)
+                return 0;
+
+        return dns_scope_multicast_membership(s, b, MDNS_MULTICAST_IPV4_ADDRESS, MDNS_MULTICAST_IPV6_ADDRESS);
+}
+
 static int dns_scope_make_reply_packet(
                 DnsScope *s,
                 uint16_t id,
diff --git a/src/resolve/resolved-dns-scope.h b/src/resolve/resolved-dns-scope.h
index 15d9a1fd6f..2fc2e07deb 100644
--- a/src/resolve/resolved-dns-scope.h
+++ b/src/resolve/resolved-dns-scope.h
@@ -93,6 +93,7 @@ DnsServer *dns_scope_get_dns_server(DnsScope *s);
 void dns_scope_next_dns_server(DnsScope *s);
 
 int dns_scope_llmnr_membership(DnsScope *s, bool b);
+int dns_scope_mdns_membership(DnsScope *s, bool b);
 
 void dns_scope_process_query(DnsScope *s, DnsStream *stream, DnsPacket *p);
 
-- 
cgit v1.2.3-54-g00ecf


From b4f1862df2e45aba90386887d685b8bf3c840e10 Mon Sep 17 00:00:00 2001
From: Daniel Mack <daniel@zonque.org>
Date: Sat, 11 Jul 2015 13:17:51 -0400
Subject: resolved: create dns scopes for mDNS

Follow what LLMNR does, and create per-link DnsScope objects.
---
 src/resolve/resolved-dns-scope.c | 28 +++++++++++++++++++++++++---
 src/resolve/resolved-link.c      | 24 ++++++++++++++++++++++++
 src/resolve/resolved-link.h      |  2 ++
 src/resolve/resolved-manager.c   | 16 +++++++++++++++-
 4 files changed, 66 insertions(+), 4 deletions(-)

(limited to 'src')

diff --git a/src/resolve/resolved-dns-scope.c b/src/resolve/resolved-dns-scope.c
index 10148cb08e..eae903526b 100644
--- a/src/resolve/resolved-dns-scope.c
+++ b/src/resolve/resolved-dns-scope.c
@@ -30,6 +30,7 @@
 #include "random-util.h"
 #include "resolved-dns-scope.h"
 #include "resolved-llmnr.h"
+#include "resolved-mdns.h"
 #include "socket-util.h"
 #include "strv.h"
 
@@ -164,7 +165,6 @@ int dns_scope_emit(DnsScope *s, int fd, DnsServer *server, DnsPacket *p) {
         union in_addr_union addr;
         int ifindex = 0, r;
         int family;
-        uint16_t port;
         uint32_t mtu;
         size_t saved_size = 0;
 
@@ -230,7 +230,6 @@ int dns_scope_emit(DnsScope *s, int fd, DnsServer *server, DnsPacket *p) {
                         return -EBUSY;
 
                 family = s->family;
-                port = LLMNR_PORT;
 
                 if (family == AF_INET) {
                         addr.in = LLMNR_MULTICAST_IPV4_ADDRESS;
@@ -243,7 +242,30 @@ int dns_scope_emit(DnsScope *s, int fd, DnsServer *server, DnsPacket *p) {
                 if (fd < 0)
                         return fd;
 
-                r = manager_send(s->manager, fd, ifindex, family, &addr, port, p);
+                r = manager_send(s->manager, fd, ifindex, family, &addr, LLMNR_PORT, p);
+                if (r < 0)
+                        return r;
+
+                break;
+
+        case DNS_PROTOCOL_MDNS:
+                if (!ratelimit_test(&s->ratelimit))
+                        return -EBUSY;
+
+                family = s->family;
+
+                if (family == AF_INET) {
+                        addr.in = MDNS_MULTICAST_IPV4_ADDRESS;
+                        fd = manager_mdns_ipv4_fd(s->manager);
+                } else if (family == AF_INET6) {
+                        addr.in6 = MDNS_MULTICAST_IPV6_ADDRESS;
+                        fd = manager_mdns_ipv6_fd(s->manager);
+                } else
+                        return -EAFNOSUPPORT;
+                if (fd < 0)
+                        return fd;
+
+                r = manager_send(s->manager, fd, ifindex, family, &addr, MDNS_PORT, p);
                 if (r < 0)
                         return r;
 
diff --git a/src/resolve/resolved-link.c b/src/resolve/resolved-link.c
index ddd9427dab..84100bd988 100644
--- a/src/resolve/resolved-link.c
+++ b/src/resolve/resolved-link.c
@@ -77,6 +77,8 @@ Link *link_free(Link *l) {
         dns_scope_free(l->unicast_scope);
         dns_scope_free(l->llmnr_ipv4_scope);
         dns_scope_free(l->llmnr_ipv6_scope);
+        dns_scope_free(l->mdns_ipv4_scope);
+        dns_scope_free(l->mdns_ipv6_scope);
 
         free(l);
         return NULL;
@@ -118,6 +120,28 @@ static void link_allocate_scopes(Link *l) {
                 }
         } else
                 l->llmnr_ipv6_scope = dns_scope_free(l->llmnr_ipv6_scope);
+
+        if (link_relevant(l, AF_INET) &&
+            l->mdns_support != SUPPORT_NO &&
+            l->manager->mdns_support != SUPPORT_NO) {
+                if (!l->mdns_ipv4_scope) {
+                        r = dns_scope_new(l->manager, &l->mdns_ipv4_scope, l, DNS_PROTOCOL_MDNS, AF_INET);
+                        if (r < 0)
+                                log_warning_errno(r, "Failed to allocate mDNS IPv4 scope: %m");
+                }
+        } else
+                l->mdns_ipv4_scope = dns_scope_free(l->mdns_ipv4_scope);
+
+        if (link_relevant(l, AF_INET6) &&
+            l->mdns_support != SUPPORT_NO &&
+            l->manager->mdns_support != SUPPORT_NO) {
+                if (!l->mdns_ipv6_scope) {
+                        r = dns_scope_new(l->manager, &l->mdns_ipv6_scope, l, DNS_PROTOCOL_MDNS, AF_INET6);
+                        if (r < 0)
+                                log_warning_errno(r, "Failed to allocate mDNS IPv6 scope: %m");
+                }
+        } else
+                l->mdns_ipv6_scope = dns_scope_free(l->mdns_ipv6_scope);
 }
 
 void link_add_rrs(Link *l, bool force_remove) {
diff --git a/src/resolve/resolved-link.h b/src/resolve/resolved-link.h
index 3093050c98..a3b406bbc2 100644
--- a/src/resolve/resolved-link.h
+++ b/src/resolve/resolved-link.h
@@ -72,6 +72,8 @@ struct Link {
         DnsScope *unicast_scope;
         DnsScope *llmnr_ipv4_scope;
         DnsScope *llmnr_ipv6_scope;
+        DnsScope *mdns_ipv4_scope;
+        DnsScope *mdns_ipv6_scope;
 
         char name[IF_NAMESIZE];
         uint32_t mtu;
diff --git a/src/resolve/resolved-manager.c b/src/resolve/resolved-manager.c
index fc2fb4d47c..a2677f442a 100644
--- a/src/resolve/resolved-manager.c
+++ b/src/resolve/resolved-manager.c
@@ -1031,11 +1031,25 @@ DnsScope* manager_find_scope(Manager *m, DnsPacket *p) {
         if (!l)
                 return NULL;
 
-        if (p->protocol == DNS_PROTOCOL_LLMNR) {
+        switch (p->protocol) {
+        case DNS_PROTOCOL_LLMNR:
                 if (p->family == AF_INET)
                         return l->llmnr_ipv4_scope;
                 else if (p->family == AF_INET6)
                         return l->llmnr_ipv6_scope;
+
+                break;
+
+        case DNS_PROTOCOL_MDNS:
+                if (p->family == AF_INET)
+                        return l->mdns_ipv4_scope;
+                else if (p->family == AF_INET6)
+                        return l->mdns_ipv6_scope;
+
+                break;
+
+        default:
+                break;
         }
 
         return NULL;
-- 
cgit v1.2.3-54-g00ecf


From ea12bcc78911fd3531955a799dbf6c5ac33bf567 Mon Sep 17 00:00:00 2001
From: Daniel Mack <daniel@zonque.org>
Date: Tue, 25 Aug 2015 14:08:29 +0200
Subject: resolved: add mDNS initial jitter

The logic is to kick off mDNS packets in a delayed way is mostly identical
to what LLMNR needs, except that the constants are different.
---
 src/resolve/resolved-dns-transaction.c | 26 ++++++++++++++++++++------
 src/resolve/resolved-dns-transaction.h |  4 ++++
 2 files changed, 24 insertions(+), 6 deletions(-)

(limited to 'src')

diff --git a/src/resolve/resolved-dns-transaction.c b/src/resolve/resolved-dns-transaction.c
index f77931ed53..2cf9417a4b 100644
--- a/src/resolve/resolved-dns-transaction.c
+++ b/src/resolve/resolved-dns-transaction.c
@@ -751,8 +751,10 @@ int dns_transaction_go(DnsTransaction *t) {
                 }
         }
 
-        if (t->scope->protocol == DNS_PROTOCOL_LLMNR && !t->initial_jitter) {
-                usec_t jitter;
+        if (!t->initial_jitter &&
+            (t->scope->protocol == DNS_PROTOCOL_LLMNR ||
+             t->scope->protocol == DNS_PROTOCOL_MDNS)) {
+                usec_t jitter, accuracy;
 
                 /* RFC 4795 Section 2.7 suggests all queries should be
                  * delayed by a random time from 0 to JITTER_INTERVAL. */
@@ -760,14 +762,26 @@ int dns_transaction_go(DnsTransaction *t) {
                 t->initial_jitter = true;
 
                 random_bytes(&jitter, sizeof(jitter));
-                jitter %= LLMNR_JITTER_INTERVAL_USEC;
+
+                switch (t->scope->protocol) {
+                case DNS_PROTOCOL_LLMNR:
+                        jitter %= LLMNR_JITTER_INTERVAL_USEC;
+                        accuracy = LLMNR_JITTER_INTERVAL_USEC;
+                        break;
+                case DNS_PROTOCOL_MDNS:
+                        jitter %= MDNS_JITTER_RANGE_USEC;
+                        jitter += MDNS_JITTER_MIN_USEC;
+                        accuracy = MDNS_JITTER_RANGE_USEC;
+                        break;
+                default:
+                        assert_not_reached("bad protocol");
+                }
 
                 r = sd_event_add_time(
                                 t->scope->manager->event,
                                 &t->timeout_event_source,
                                 clock_boottime_or_monotonic(),
-                                ts + jitter,
-                                LLMNR_JITTER_INTERVAL_USEC,
+                                ts + jitter, accuracy,
                                 on_transaction_timeout, t);
                 if (r < 0)
                         return r;
@@ -775,7 +789,7 @@ int dns_transaction_go(DnsTransaction *t) {
                 t->n_attempts = 0;
                 t->state = DNS_TRANSACTION_PENDING;
 
-                log_debug("Delaying LLMNR transaction for " USEC_FMT "us.", jitter);
+                log_debug("Delaying %s transaction for " USEC_FMT "us.", dns_protocol_to_string(t->scope->protocol), jitter);
                 return 0;
         }
 
diff --git a/src/resolve/resolved-dns-transaction.h b/src/resolve/resolved-dns-transaction.h
index a3058ce6e8..1d445ffee7 100644
--- a/src/resolve/resolved-dns-transaction.h
+++ b/src/resolve/resolved-dns-transaction.h
@@ -119,6 +119,10 @@ DnsTransactionSource dns_transaction_source_from_string(const char *s) _pure_;
 /* LLMNR Jitter interval, see RFC 4795 Section 7 */
 #define LLMNR_JITTER_INTERVAL_USEC (100 * USEC_PER_MSEC)
 
+/* mDNS Jitter interval, see RFC 6762 Section 5.2 */
+#define MDNS_JITTER_MIN_USEC   (20 * USEC_PER_MSEC)
+#define MDNS_JITTER_RANGE_USEC (100 * USEC_PER_MSEC)
+
 /* Maximum attempts to send DNS requests, across all DNS servers */
 #define DNS_TRANSACTION_ATTEMPTS_MAX 16
 
-- 
cgit v1.2.3-54-g00ecf


From 23502de3b0891455c8ce499a9eb61b69d060a829 Mon Sep 17 00:00:00 2001
From: Daniel Mack <daniel@zonque.org>
Date: Tue, 24 Nov 2015 15:45:15 +0100
Subject: resolved: add cache flush flag to DnsResourceKey

MDNS has a 'key cache flush' flag for records which must be masked out for
the parsers to do our right thing. We will also use that flag later (in a
different patch) in order to alter the cache behavior.
---
 src/resolve/resolved-dns-packet.c | 12 ++++++++++++
 src/resolve/resolved-dns-rr.h     |  4 ++++
 2 files changed, 16 insertions(+)

(limited to 'src')

diff --git a/src/resolve/resolved-dns-packet.c b/src/resolve/resolved-dns-packet.c
index 3a4482a1b7..35d1fb02be 100644
--- a/src/resolve/resolved-dns-packet.c
+++ b/src/resolve/resolved-dns-packet.c
@@ -1421,6 +1421,7 @@ fail:
 
 int dns_packet_read_key(DnsPacket *p, DnsResourceKey **ret, size_t *start) {
         _cleanup_free_ char *name = NULL;
+        bool cache_flush = false;
         uint16_t class, type;
         DnsResourceKey *key;
         size_t saved_rindex;
@@ -1443,12 +1444,23 @@ int dns_packet_read_key(DnsPacket *p, DnsResourceKey **ret, size_t *start) {
         if (r < 0)
                 goto fail;
 
+        if (p->protocol == DNS_PROTOCOL_MDNS) {
+                /* See RFC6762, Section 10.2 */
+
+                if (class & MDNS_RR_CACHE_FLUSH) {
+                        class &= ~MDNS_RR_CACHE_FLUSH;
+                        cache_flush = true;
+                }
+        }
+
         key = dns_resource_key_new_consume(class, type, name);
         if (!key) {
                 r = -ENOMEM;
                 goto fail;
         }
 
+        key->cache_flush = cache_flush;
+
         name = NULL;
         *ret = key;
 
diff --git a/src/resolve/resolved-dns-rr.h b/src/resolve/resolved-dns-rr.h
index b82fa77562..5cbb927681 100644
--- a/src/resolve/resolved-dns-rr.h
+++ b/src/resolve/resolved-dns-rr.h
@@ -45,6 +45,9 @@ enum {
 #define DNSKEY_FLAG_ZONE_KEY (UINT16_C(1) << 8)
 #define DNSKEY_FLAG_SEP      (UINT16_C(1) << 0)
 
+/* mDNS RR flags */
+#define MDNS_RR_CACHE_FLUSH  (UINT16_C(1) << 15)
+
 /* DNSSEC algorithm identifiers, see
  * http://tools.ietf.org/html/rfc4034#appendix-A.1 and
  * https://www.iana.org/assignments/dns-sec-alg-numbers/dns-sec-alg-numbers.xhtml */
@@ -76,6 +79,7 @@ struct DnsResourceKey {
         unsigned n_ref;
         uint16_t class, type;
         char *_name; /* don't access directy, use DNS_RESOURCE_KEY_NAME()! */
+        bool cache_flush:1;
 };
 
 /* Creates a temporary resource key. This is only useful to quickly
-- 
cgit v1.2.3-54-g00ecf


From 90325e8c2e559a21ef0bc2f26b844c140faf8020 Mon Sep 17 00:00:00 2001
From: Daniel Mack <daniel@zonque.org>
Date: Tue, 4 Aug 2015 14:12:46 +0200
Subject: resolved: flush keys when DNS_RESOURCE_KEY_CACHE_FLUSH is set

In mDNS, DNS_RESOURCE_KEY_CACHE_FLUSH denotes whether other records with the
same key should be flushed from the cache.
---
 src/resolve/resolved-dns-cache.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

(limited to 'src')

diff --git a/src/resolve/resolved-dns-cache.c b/src/resolve/resolved-dns-cache.c
index bcb9994a8c..2179a61890 100644
--- a/src/resolve/resolved-dns-cache.c
+++ b/src/resolve/resolved-dns-cache.c
@@ -459,7 +459,12 @@ int dns_cache_put(
 
         /* Second, add in positive entries for all contained RRs */
         for (i = 0; i < MIN(max_rrs, answer->n_rrs); i++) {
-                r = dns_cache_put_positive(c, answer->items[i].rr, authenticated, timestamp, owner_family, owner_address);
+                DnsResourceRecord *rr = answer->items[i].rr;
+
+                if (rr->key->cache_flush)
+                        dns_cache_remove(c, rr->key);
+
+                r = dns_cache_put_positive(c, rr, authenticated, timestamp, owner_family, owner_address);
                 if (r < 0)
                         goto fail;
         }
-- 
cgit v1.2.3-54-g00ecf


From ef7ce6df4d5084bb0cba78e71a2bb932b59045e8 Mon Sep 17 00:00:00 2001
From: Daniel Mack <daniel@zonque.org>
Date: Tue, 25 Aug 2015 17:57:58 +0200
Subject: resolved: short-cut jitter callbacks for LLMNR and mDNS

When a jitter callback is issued instead of sending a DNS packet directly,
on_transaction_timeout() is invoked to 'retry' the transaction. However,
this function has side effects. For once, it increases the packet loss
counter on the scope, and it also unrefs/refs the server instances.

Fix this by tracking the jitter with two bool variables. One saying that
the initial jitter has been scheduled in the first place, and one that
tells us the delay packet has been sent.
---
 src/resolve/resolved-dns-transaction.c | 33 +++++++++++++++++++--------------
 src/resolve/resolved-dns-transaction.h |  3 ++-
 2 files changed, 21 insertions(+), 15 deletions(-)

(limited to 'src')

diff --git a/src/resolve/resolved-dns-transaction.c b/src/resolve/resolved-dns-transaction.c
index 2cf9417a4b..f8063b93f1 100644
--- a/src/resolve/resolved-dns-transaction.c
+++ b/src/resolve/resolved-dns-transaction.c
@@ -583,21 +583,26 @@ static int on_transaction_timeout(sd_event_source *s, usec_t usec, void *userdat
         assert(s);
         assert(t);
 
-        /* Timeout reached? Increase the timeout for the server used */
-        switch (t->scope->protocol) {
-        case DNS_PROTOCOL_DNS:
-                assert(t->server);
+        if (!t->initial_jitter_scheduled || t->initial_jitter_elapsed) {
+                /* Timeout reached? Increase the timeout for the server used */
+                switch (t->scope->protocol) {
+                case DNS_PROTOCOL_DNS:
+                        assert(t->server);
 
-                dns_server_packet_lost(t->server, t->current_features, usec - t->start_usec);
+                        dns_server_packet_lost(t->server, t->current_features, usec - t->start_usec);
 
-                break;
-        case DNS_PROTOCOL_LLMNR:
-        case DNS_PROTOCOL_MDNS:
-                dns_scope_packet_lost(t->scope, usec - t->start_usec);
+                        break;
+                case DNS_PROTOCOL_LLMNR:
+                case DNS_PROTOCOL_MDNS:
+                        dns_scope_packet_lost(t->scope, usec - t->start_usec);
 
-                break;
-        default:
-                assert_not_reached("Invalid DNS protocol.");
+                        break;
+                default:
+                        assert_not_reached("Invalid DNS protocol.");
+                }
+
+                if (t->initial_jitter_scheduled)
+                        t->initial_jitter_elapsed = true;
         }
 
         /* ...and try again with a new server */
@@ -751,7 +756,7 @@ int dns_transaction_go(DnsTransaction *t) {
                 }
         }
 
-        if (!t->initial_jitter &&
+        if (!t->initial_jitter_scheduled &&
             (t->scope->protocol == DNS_PROTOCOL_LLMNR ||
              t->scope->protocol == DNS_PROTOCOL_MDNS)) {
                 usec_t jitter, accuracy;
@@ -759,7 +764,7 @@ int dns_transaction_go(DnsTransaction *t) {
                 /* RFC 4795 Section 2.7 suggests all queries should be
                  * delayed by a random time from 0 to JITTER_INTERVAL. */
 
-                t->initial_jitter = true;
+                t->initial_jitter_scheduled = true;
 
                 random_bytes(&jitter, sizeof(jitter));
 
diff --git a/src/resolve/resolved-dns-transaction.h b/src/resolve/resolved-dns-transaction.h
index 1d445ffee7..e3d4b861be 100644
--- a/src/resolve/resolved-dns-transaction.h
+++ b/src/resolve/resolved-dns-transaction.h
@@ -62,7 +62,8 @@ struct DnsTransaction {
         DnsTransactionState state;
         uint16_t id;
 
-        bool initial_jitter;
+        bool initial_jitter_scheduled;
+        bool initial_jitter_elapsed;
 
         DnsPacket *sent, *received;
 
-- 
cgit v1.2.3-54-g00ecf


From 11a27c2ec1f3bdb1df828883365903ce47576c51 Mon Sep 17 00:00:00 2001
From: Daniel Mack <daniel@zonque.org>
Date: Fri, 28 Aug 2015 16:48:37 +0200
Subject: resolved: handle mDNS timeouts per transaction

mDNS packet timeouts need to be handled per transaction, not per link.
Re-use the n_attempts field for this purpose, as packets timeouts should be
determined by starting at 1 second, and doubling the value on each try.
---
 src/resolve/resolved-dns-transaction.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

(limited to 'src')

diff --git a/src/resolve/resolved-dns-transaction.c b/src/resolve/resolved-dns-transaction.c
index f8063b93f1..7c81c907f2 100644
--- a/src/resolve/resolved-dns-transaction.c
+++ b/src/resolve/resolved-dns-transaction.c
@@ -656,8 +656,10 @@ static usec_t transaction_get_resend_timeout(DnsTransaction *t) {
                 assert(t->server);
 
                 return t->server->resend_timeout;
-        case DNS_PROTOCOL_LLMNR:
         case DNS_PROTOCOL_MDNS:
+                assert(t->n_attempts > 0);
+                return (1 << (t->n_attempts - 1)) * USEC_PER_SEC;
+        case DNS_PROTOCOL_LLMNR:
                 return t->scope->resend_timeout;
         default:
                 assert_not_reached("Invalid DNS protocol.");
-- 
cgit v1.2.3-54-g00ecf


From d84e543d927926fbcc6a5eec730b4db97d9272c7 Mon Sep 17 00:00:00 2001
From: Daniel Mack <daniel@zonque.org>
Date: Tue, 1 Sep 2015 17:17:27 +0200
Subject: resolved: allow name compression in NSEC records

---
 src/resolve/resolved-dns-packet.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

(limited to 'src')

diff --git a/src/resolve/resolved-dns-packet.c b/src/resolve/resolved-dns-packet.c
index 35d1fb02be..9bd08eeec2 100644
--- a/src/resolve/resolved-dns-packet.c
+++ b/src/resolve/resolved-dns-packet.c
@@ -1819,8 +1819,16 @@ int dns_packet_read_rr(DnsPacket *p, DnsResourceRecord **ret, size_t *start) {
 
                 break;
 
-        case DNS_TYPE_NSEC:
-                r = dns_packet_read_name(p, &rr->nsec.next_domain_name, false, NULL);
+        case DNS_TYPE_NSEC: {
+
+                /*
+                 * RFC6762, section 18.14 explicly states mDNS should use name compression.
+                 * This contradicts RFC3845, section 2.1.1
+                 */
+
+                bool allow_compressed = p->protocol == DNS_PROTOCOL_MDNS;
+
+                r = dns_packet_read_name(p, &rr->nsec.next_domain_name, allow_compressed, NULL);
                 if (r < 0)
                         goto fail;
 
@@ -1833,7 +1841,7 @@ int dns_packet_read_rr(DnsPacket *p, DnsResourceRecord **ret, size_t *start) {
                  * without the NSEC bit set. */
 
                 break;
-
+        }
         case DNS_TYPE_NSEC3: {
                 uint8_t size;
 
-- 
cgit v1.2.3-54-g00ecf


From 124602aea81a27dda02e898798a18f95bf03734e Mon Sep 17 00:00:00 2001
From: Daniel Mack <daniel@zonque.org>
Date: Fri, 10 Jul 2015 20:44:59 -0400
Subject: resolved: add mDNS packet dispatcher

Add the packet dispatching routine for mDNS.

It differs to what LLMNR and DNS dispatchers do in the way it matches
incoming packets. In mDNS, we actually handle all incoming packets,
regardless whether we asked for them earlier or not.
---
 src/resolve/resolved-mdns.c | 59 ++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 58 insertions(+), 1 deletion(-)

(limited to 'src')

diff --git a/src/resolve/resolved-mdns.c b/src/resolve/resolved-mdns.c
index 6767706f6e..096a4b1fe5 100644
--- a/src/resolve/resolved-mdns.c
+++ b/src/resolve/resolved-mdns.c
@@ -70,7 +70,64 @@ eaddrinuse:
 }
 
 static int on_mdns_packet(sd_event_source *s, int fd, uint32_t revents, void *userdata) {
-        /* TODO */
+        _cleanup_(dns_packet_unrefp) DnsPacket *p = NULL;
+        Manager *m = userdata;
+        DnsScope *scope;
+        int r;
+
+        r = manager_recv(m, fd, DNS_PROTOCOL_MDNS, &p);
+        if (r <= 0)
+                return r;
+
+        scope = manager_find_scope(m, p);
+        if (!scope) {
+                log_warning("Got mDNS UDP packet on unknown scope. Ignoring.");
+                return 0;
+        }
+
+        if (dns_packet_validate_reply(p) > 0) {
+                unsigned i;
+
+                log_debug("Got mDNS reply packet");
+
+                /*
+                 * mDNS is different from regular DNS and LLMNR with regard to handling responses.
+                 * While on other protocols, we can ignore every answer that doesn't match a question
+                 * we broadcast earlier, RFC6762, section 18.1 recommends looking at and caching all
+                 * incoming information, regardless of the DNS packet ID.
+                 *
+                 * Hence, extract the packet here, and try to find a transaction for answer the we got
+                 * and complete it. Also store the new information in scope's cache.
+                 */
+                r = dns_packet_extract(p);
+                if (r < 0) {
+                        log_debug("mDNS packet extraction failed.");
+                        return 0;
+                }
+
+                dns_scope_check_conflicts(scope, p);
+
+                for (i = 0; i < p->answer->n_rrs; i++) {
+                        DnsResourceRecord *rr;
+                        DnsTransaction *t;
+
+                        rr = p->answer->items[i].rr;
+
+                        t = dns_scope_find_transaction(scope, rr->key, false);
+                        if (t)
+                                dns_transaction_process_reply(t, p);
+                }
+
+                dns_cache_put(&scope->cache, NULL, DNS_PACKET_RCODE(p), p->answer,
+                              p->answer->n_rrs, false, 0, p->family, &p->sender);
+
+        } else if (dns_packet_validate_query(p) > 0)  {
+                log_debug("Got mDNS query packet for id %u", DNS_PACKET_ID(p));
+
+                dns_scope_process_query(scope, NULL, p);
+        } else
+                log_debug("Invalid mDNS UDP packet.");
+
         return 0;
 }
 
-- 
cgit v1.2.3-54-g00ecf


From a20b9592178ff728ddeefa13c77e00be91af14c4 Mon Sep 17 00:00:00 2001
From: Daniel Mack <daniel@zonque.org>
Date: Thu, 3 Sep 2015 12:04:31 +0200
Subject: resolved: fix debug message

---
 src/resolve/resolved-dns-transaction.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

(limited to 'src')

diff --git a/src/resolve/resolved-dns-transaction.c b/src/resolve/resolved-dns-transaction.c
index 7c81c907f2..22ea88ab0b 100644
--- a/src/resolve/resolved-dns-transaction.c
+++ b/src/resolve/resolved-dns-transaction.c
@@ -243,7 +243,7 @@ static int on_stream_complete(DnsStream *s, int error) {
         }
 
         if (dns_packet_validate_reply(p) <= 0) {
-                log_debug("Invalid LLMNR TCP packet.");
+                log_debug("Invalid TCP reply packet.");
                 dns_transaction_complete(t, DNS_TRANSACTION_INVALID_REPLY);
                 return 0;
         }
-- 
cgit v1.2.3-54-g00ecf


From 547493c5ad5c82032e247609970f96be76c2d661 Mon Sep 17 00:00:00 2001
From: Daniel Mack <daniel@zonque.org>
Date: Thu, 3 Sep 2015 12:09:11 +0200
Subject: resolved: handle more mDNS protocol details

---
 src/resolve/resolved-dns-transaction.c | 55 ++++++++++++++++++++--------------
 1 file changed, 32 insertions(+), 23 deletions(-)

(limited to 'src')

diff --git a/src/resolve/resolved-dns-transaction.c b/src/resolve/resolved-dns-transaction.c
index 22ea88ab0b..22a7a5340c 100644
--- a/src/resolve/resolved-dns-transaction.c
+++ b/src/resolve/resolved-dns-transaction.c
@@ -458,6 +458,13 @@ void dns_transaction_process_reply(DnsTransaction *t, DnsPacket *p) {
         }
 
         if (DNS_PACKET_TC(p)) {
+
+                /* Truncated packets for mDNS are not allowed. Give up immediately. */
+                if (t->scope->protocol == DNS_PROTOCOL_MDNS) {
+                        dns_transaction_complete(t, DNS_TRANSACTION_INVALID_REPLY);
+                        return;
+                }
+
                 /* Response was truncated, let's try again with good old TCP */
                 r = dns_transaction_open_tcp(t);
                 if (r == -ESRCH) {
@@ -466,7 +473,7 @@ void dns_transaction_process_reply(DnsTransaction *t, DnsPacket *p) {
                         return;
                 }
                 if (r < 0) {
-                        /* On LLMNR, if we cannot connect to the host,
+                        /* On LLMNR and mDNS, if we cannot connect to the host,
                          * we immediately give up */
                         if (t->scope->protocol == DNS_PROTOCOL_LLMNR) {
                                 dns_transaction_complete(t, DNS_TRANSACTION_RESOURCES);
@@ -493,29 +500,31 @@ void dns_transaction_process_reply(DnsTransaction *t, DnsPacket *p) {
                 return;
         }
 
-        /* Only consider responses with equivalent query section to the request */
-        if (p->question->n_keys != 1 || dns_resource_key_equal(p->question->keys[0], t->key) <= 0) {
-                dns_transaction_complete(t, DNS_TRANSACTION_INVALID_REPLY);
-                return;
-        }
+        if (t->scope->protocol == DNS_PROTOCOL_DNS) {
+                /* Only consider responses with equivalent query section to the request */
+                if (p->question->n_keys != 1 || dns_resource_key_equal(p->question->keys[0], t->key) <= 0) {
+                        dns_transaction_complete(t, DNS_TRANSACTION_INVALID_REPLY);
+                        return;
+                }
 
-        /* Install the answer as answer to the transaction */
-        dns_answer_unref(t->answer);
-        t->answer = dns_answer_ref(p->answer);
-        t->answer_rcode = DNS_PACKET_RCODE(p);
-        t->answer_authenticated = t->scope->dnssec_mode == DNSSEC_TRUST && DNS_PACKET_AD(p);
-
-        /* According to RFC 4795, section 2.9. only the RRs from the answer section shall be cached */
-        if (DNS_PACKET_SHALL_CACHE(p))
-                dns_cache_put(&t->scope->cache,
-                              t->key,
-                              DNS_PACKET_RCODE(p),
-                              p->answer,
-                              DNS_PACKET_ANCOUNT(p),
-                              t->answer_authenticated,
-                              0,
-                              p->family,
-                              &p->sender);
+                /* Install the answer as answer to the transaction */
+                dns_answer_unref(t->answer);
+                t->answer = dns_answer_ref(p->answer);
+                t->answer_rcode = DNS_PACKET_RCODE(p);
+                t->answer_authenticated = t->scope->dnssec_mode == DNSSEC_TRUST && DNS_PACKET_AD(p);
+
+                /* According to RFC 4795, section 2.9. only the RRs from the answer section shall be cached */
+                if (DNS_PACKET_SHALL_CACHE(p))
+                        dns_cache_put(&t->scope->cache,
+                                      t->key,
+                                      DNS_PACKET_RCODE(p),
+                                      p->answer,
+                                      DNS_PACKET_ANCOUNT(p),
+                                      t->answer_authenticated,
+                                      0,
+                                      p->family,
+                                      &p->sender);
+        }
 
         if (DNS_PACKET_RCODE(p) == DNS_RCODE_SUCCESS)
                 dns_transaction_complete(t, DNS_TRANSACTION_SUCCESS);
-- 
cgit v1.2.3-54-g00ecf


From 1effe9656899c4e4976d4d44f9bde634715daca2 Mon Sep 17 00:00:00 2001
From: Daniel Mack <daniel@zonque.org>
Date: Mon, 30 Nov 2015 19:06:36 +0100
Subject: resolved: split dns_transaction_go()

Split some code out of dns_transaction_go() so we can re-use it later from
different context. The new function dns_transaction_prepare_next_attempt()
takes care of preparing everything so that a new packet can conditionally
be formulated for a transaction.

This patch shouldn't cause any functional change.
---
 src/resolve/resolved-dns-transaction.c | 29 ++++++++++++++++++++---------
 1 file changed, 20 insertions(+), 9 deletions(-)

(limited to 'src')

diff --git a/src/resolve/resolved-dns-transaction.c b/src/resolve/resolved-dns-transaction.c
index 22a7a5340c..6eec1446d7 100644
--- a/src/resolve/resolved-dns-transaction.c
+++ b/src/resolve/resolved-dns-transaction.c
@@ -675,9 +675,8 @@ static usec_t transaction_get_resend_timeout(DnsTransaction *t) {
         }
 }
 
-int dns_transaction_go(DnsTransaction *t) {
+static int dns_transaction_prepare_next_attempt(DnsTransaction *t, usec_t ts) {
         bool had_stream;
-        usec_t ts;
         int r;
 
         assert(t);
@@ -686,11 +685,6 @@ int dns_transaction_go(DnsTransaction *t) {
 
         dns_transaction_stop(t);
 
-        log_debug("Excercising transaction on scope %s on %s/%s",
-                  dns_protocol_to_string(t->scope->protocol),
-                  t->scope->link ? t->scope->link->name : "*",
-                  t->scope->family == AF_UNSPEC ? "*" : af_to_name(t->scope->family));
-
         if (t->n_attempts >= TRANSACTION_ATTEMPTS_MAX(t->scope->protocol)) {
                 dns_transaction_complete(t, DNS_TRANSACTION_ATTEMPTS_MAX_REACHED);
                 return 0;
@@ -703,8 +697,6 @@ int dns_transaction_go(DnsTransaction *t) {
                 return 0;
         }
 
-        assert_se(sd_event_now(t->scope->manager->event, clock_boottime_or_monotonic(), &ts) >= 0);
-
         t->n_attempts++;
         t->start_usec = ts;
         t->received = dns_packet_unref(t->received);
@@ -767,6 +759,25 @@ int dns_transaction_go(DnsTransaction *t) {
                 }
         }
 
+        return 1;
+}
+
+int dns_transaction_go(DnsTransaction *t) {
+        usec_t ts;
+        int r;
+
+        assert(t);
+
+        assert_se(sd_event_now(t->scope->manager->event, clock_boottime_or_monotonic(), &ts) >= 0);
+        r = dns_transaction_prepare_next_attempt(t, ts);
+        if (r <= 0)
+                return r;
+
+        log_debug("Excercising transaction on scope %s on %s/%s",
+                  dns_protocol_to_string(t->scope->protocol),
+                  t->scope->link ? t->scope->link->name : "*",
+                  t->scope->family == AF_UNSPEC ? "*" : af_to_name(t->scope->family));
+
         if (!t->initial_jitter_scheduled &&
             (t->scope->protocol == DNS_PROTOCOL_LLMNR ||
              t->scope->protocol == DNS_PROTOCOL_MDNS)) {
-- 
cgit v1.2.3-54-g00ecf


From a9da14e1e97ff774761966c2e1d83b0c6750b367 Mon Sep 17 00:00:00 2001
From: Daniel Mack <daniel@zonque.org>
Date: Mon, 30 Nov 2015 22:35:51 +0100
Subject: resolved: add 'next_attempt_after' field to DnsTransaction

For each transaction, record when the earliest point in time when the
query packet may hit the wire. This is the same time stamp for which
the timer is scheduled in retries, except for the initial query packets
which are delayed by a random jitter. In this case, we denote that the
packet may actually be sent at the nominal time, without the jitter.

Transactions that share the same timestamp will also have identical
values in this field. It is used to coalesce pending queries in a later
patch.
---
 src/resolve/resolved-dns-transaction.c | 7 ++++++-
 src/resolve/resolved-dns-transaction.h | 1 +
 2 files changed, 7 insertions(+), 1 deletion(-)

(limited to 'src')

diff --git a/src/resolve/resolved-dns-transaction.c b/src/resolve/resolved-dns-transaction.c
index 6eec1446d7..7924b24354 100644
--- a/src/resolve/resolved-dns-transaction.c
+++ b/src/resolve/resolved-dns-transaction.c
@@ -814,6 +814,7 @@ int dns_transaction_go(DnsTransaction *t) {
                         return r;
 
                 t->n_attempts = 0;
+                t->next_attempt_after = ts;
                 t->state = DNS_TRANSACTION_PENDING;
 
                 log_debug("Delaying %s transaction for " USEC_FMT "us.", dns_protocol_to_string(t->scope->protocol), jitter);
@@ -863,16 +864,20 @@ int dns_transaction_go(DnsTransaction *t) {
                 return dns_transaction_go(t);
         }
 
+        ts += transaction_get_resend_timeout(t);
+
         r = sd_event_add_time(
                         t->scope->manager->event,
                         &t->timeout_event_source,
                         clock_boottime_or_monotonic(),
-                        ts + transaction_get_resend_timeout(t), 0,
+                        ts, 0,
                         on_transaction_timeout, t);
         if (r < 0)
                 return r;
 
         t->state = DNS_TRANSACTION_PENDING;
+        t->next_attempt_after = ts;
+
         return 1;
 }
 
diff --git a/src/resolve/resolved-dns-transaction.h b/src/resolve/resolved-dns-transaction.h
index e3d4b861be..af08b20e44 100644
--- a/src/resolve/resolved-dns-transaction.h
+++ b/src/resolve/resolved-dns-transaction.h
@@ -73,6 +73,7 @@ struct DnsTransaction {
         bool answer_authenticated;
 
         usec_t start_usec;
+        usec_t next_attempt_after;
         sd_event_source *timeout_event_source;
         unsigned n_attempts;
 
-- 
cgit v1.2.3-54-g00ecf


From 0afa57e2e7645f3a550729e4daadda419de179c5 Mon Sep 17 00:00:00 2001
From: Daniel Mack <daniel@zonque.org>
Date: Mon, 30 Nov 2015 12:47:11 +0100
Subject: resolved: implement query coalescing

Implement dns_transaction_make_packet_mdns(), a special version of
dns_transaction_make_packet() for mDNS which differs in many ways:

a) We coalesce queries of currently active transaction on the scope.
   This is possible because mDNS actually allows many questions in a
   to be sent in a single packet and it takes some burden from the
   network.

b) Both A and AAAA query keys are broadcast on both IPv4 and IPv6
   scopes, because other hosts might only respond on one of their
   addresses but resolve both types.

c) We discard previously sent packages (t->sent) so we can start over
   and coalesce pending transactions again.
---
 src/resolve/resolved-dns-transaction.c | 156 ++++++++++++++++++++++++++-------
 1 file changed, 124 insertions(+), 32 deletions(-)

(limited to 'src')

diff --git a/src/resolve/resolved-dns-transaction.c b/src/resolve/resolved-dns-transaction.c
index 7924b24354..dccb8000a2 100644
--- a/src/resolve/resolved-dns-transaction.c
+++ b/src/resolve/resolved-dns-transaction.c
@@ -624,38 +624,6 @@ static int on_transaction_timeout(sd_event_source *s, usec_t usec, void *userdat
         return 0;
 }
 
-static int dns_transaction_make_packet(DnsTransaction *t) {
-        _cleanup_(dns_packet_unrefp) DnsPacket *p = NULL;
-        int r;
-
-        assert(t);
-
-        if (t->sent)
-                return 0;
-
-        r = dns_packet_new_query(&p, t->scope->protocol, 0, t->scope->dnssec_mode == DNSSEC_YES);
-        if (r < 0)
-                return r;
-
-        r = dns_scope_good_key(t->scope, t->key);
-        if (r < 0)
-                return r;
-        if (r == 0)
-                return -EDOM;
-
-        r = dns_packet_append_key(p, t->key, NULL);
-        if (r < 0)
-                return r;
-
-        DNS_PACKET_HEADER(p)->qdcount = htobe16(1);
-        DNS_PACKET_HEADER(p)->id = t->id;
-
-        t->sent = p;
-        p = NULL;
-
-        return 0;
-}
-
 static usec_t transaction_get_resend_timeout(DnsTransaction *t) {
         assert(t);
         assert(t->scope);
@@ -762,6 +730,130 @@ static int dns_transaction_prepare_next_attempt(DnsTransaction *t, usec_t ts) {
         return 1;
 }
 
+static int dns_transaction_make_packet_mdns(DnsTransaction *t) {
+
+        _cleanup_(dns_packet_unrefp) DnsPacket *p = NULL;
+        DnsTransaction *other;
+        unsigned qdcount;
+        usec_t ts;
+        int r;
+
+        assert(t);
+        assert(t->scope->protocol == DNS_PROTOCOL_MDNS);
+
+        /* Discard any previously prepared packet, so we can start over and coaleasce again */
+        t->sent = dns_packet_unref(t->sent);
+
+        r = dns_packet_new_query(&p, t->scope->protocol, 0, false);
+        if (r < 0)
+                return r;
+
+        r = dns_packet_append_key(p, t->key, NULL);
+        if (r < 0)
+                return r;
+
+        qdcount = 1;
+
+        /*
+         * For mDNS, we want to coalesce as many open queries in pending transactions into one single
+         * query packet on the wire as possible. To achieve that, we iterate through all pending transactions
+         * in our current scope, and see whether their timing contraints allow them to be sent.
+         */
+
+        assert_se(sd_event_now(t->scope->manager->event, clock_boottime_or_monotonic(), &ts) >= 0);
+
+        LIST_FOREACH(transactions_by_scope, other, t->scope->transactions) {
+
+                /* Skip ourselves */
+                if (other == t)
+                        continue;
+
+                if (other->state != DNS_TRANSACTION_PENDING)
+                        continue;
+
+                if (other->next_attempt_after > ts)
+                        continue;
+
+                if (qdcount >= UINT16_MAX)
+                        break;
+
+                r = dns_packet_append_key(p, other->key, NULL);
+
+                /*
+                 * If we can't stuff more questions into the packet, just give up.
+                 * One of the 'other' transactions will fire later and take care of the rest.
+                 */
+                if (r == -EMSGSIZE)
+                        break;
+
+                if (r < 0)
+                        return r;
+
+                r = dns_transaction_prepare_next_attempt(other, ts);
+                if (r <= 0)
+                        continue;
+
+                ts += transaction_get_resend_timeout(other);
+
+                r = sd_event_add_time(
+                                other->scope->manager->event,
+                                &other->timeout_event_source,
+                                clock_boottime_or_monotonic(),
+                                ts, 0,
+                                on_transaction_timeout, other);
+                if (r < 0)
+                        return r;
+
+                other->state = DNS_TRANSACTION_PENDING;
+                other->next_attempt_after = ts;
+
+                qdcount ++;
+        }
+
+        DNS_PACKET_HEADER(p)->qdcount = htobe16(qdcount);
+        DNS_PACKET_HEADER(p)->id = t->id;
+
+        t->sent = p;
+        p = NULL;
+
+        return 0;
+}
+
+static int dns_transaction_make_packet(DnsTransaction *t) {
+        _cleanup_(dns_packet_unrefp) DnsPacket *p = NULL;
+        int r;
+
+        assert(t);
+
+        if (t->scope->protocol == DNS_PROTOCOL_MDNS)
+                return dns_transaction_make_packet_mdns(t);
+
+        if (t->sent)
+                return 0;
+
+        r = dns_packet_new_query(&p, t->scope->protocol, 0, t->scope->dnssec_mode == DNSSEC_YES);
+        if (r < 0)
+                return r;
+
+        r = dns_scope_good_key(t->scope, t->key);
+        if (r < 0)
+                return r;
+        if (r == 0)
+                return -EDOM;
+
+        r = dns_packet_append_key(p, t->key, NULL);
+        if (r < 0)
+                return r;
+
+        DNS_PACKET_HEADER(p)->qdcount = htobe16(1);
+        DNS_PACKET_HEADER(p)->id = t->id;
+
+        t->sent = p;
+        p = NULL;
+
+        return 0;
+}
+
 int dns_transaction_go(DnsTransaction *t) {
         usec_t ts;
         int r;
-- 
cgit v1.2.3-54-g00ecf


From 7778dffff3d8bd7438fe19a248c16203668324c9 Mon Sep 17 00:00:00 2001
From: Daniel Mack <daniel@zonque.org>
Date: Tue, 1 Dec 2015 00:53:42 +0100
Subject: resolved: add dns_cache_export_to_packet()

This new functions exports cached records of type PTR, SRV and TXT into
an existing DnsPacket. This is used in order to fill in known records
to mDNS queries, for known answer supression.
---
 src/resolve/resolved-dns-cache.c       | 33 +++++++++++++++++++++++++++++++++
 src/resolve/resolved-dns-cache.h       |  3 +++
 src/resolve/resolved-dns-rr.h          |  4 ++++
 src/resolve/resolved-dns-transaction.c | 15 +++++++++++++++
 4 files changed, 55 insertions(+)

(limited to 'src')

diff --git a/src/resolve/resolved-dns-cache.c b/src/resolve/resolved-dns-cache.c
index 2179a61890..6124ff659c 100644
--- a/src/resolve/resolved-dns-cache.c
+++ b/src/resolve/resolved-dns-cache.c
@@ -731,6 +731,39 @@ int dns_cache_check_conflicts(DnsCache *cache, DnsResourceRecord *rr, int owner_
         return 1;
 }
 
+int dns_cache_export_shared_to_packet(DnsCache *cache, DnsPacket *p) {
+        unsigned ancount = 0;
+        Iterator iterator;
+        DnsCacheItem *i;
+        int r;
+
+        assert(cache);
+
+        HASHMAP_FOREACH(i, cache->by_key, iterator) {
+                DnsCacheItem *j;
+
+                LIST_FOREACH(by_key, j, i) {
+                        _cleanup_free_ char *t = NULL;
+
+                        if (!j->rr)
+                                continue;
+
+                        if (!dns_key_is_shared(j->rr->key))
+                                continue;
+
+                        r = dns_packet_append_rr(p, j->rr, NULL, NULL);
+                        if (r < 0)
+                                return r;
+
+                        ancount ++;
+                }
+        }
+
+        DNS_PACKET_HEADER(p)->ancount = htobe16(ancount);
+
+        return 0;
+}
+
 void dns_cache_dump(DnsCache *cache, FILE *f) {
         Iterator iterator;
         DnsCacheItem *i;
diff --git a/src/resolve/resolved-dns-cache.h b/src/resolve/resolved-dns-cache.h
index 5f91164785..0f28bbe543 100644
--- a/src/resolve/resolved-dns-cache.h
+++ b/src/resolve/resolved-dns-cache.h
@@ -32,6 +32,7 @@ typedef struct DnsCache {
 } DnsCache;
 
 #include "resolved-dns-answer.h"
+#include "resolved-dns-packet.h"
 #include "resolved-dns-question.h"
 #include "resolved-dns-rr.h"
 
@@ -45,3 +46,5 @@ int dns_cache_check_conflicts(DnsCache *cache, DnsResourceRecord *rr, int owner_
 
 void dns_cache_dump(DnsCache *cache, FILE *f);
 bool dns_cache_is_empty(DnsCache *cache);
+
+int dns_cache_export_shared_to_packet(DnsCache *cache, DnsPacket *p);
diff --git a/src/resolve/resolved-dns-rr.h b/src/resolve/resolved-dns-rr.h
index 5cbb927681..5c2306ba96 100644
--- a/src/resolve/resolved-dns-rr.h
+++ b/src/resolve/resolved-dns-rr.h
@@ -250,6 +250,10 @@ int dns_resource_key_match_cname(const DnsResourceKey *key, const DnsResourceRec
 int dns_resource_key_to_string(const DnsResourceKey *key, char **ret);
 DEFINE_TRIVIAL_CLEANUP_FUNC(DnsResourceKey*, dns_resource_key_unref);
 
+static inline bool dns_key_is_shared(const DnsResourceKey *key) {
+        return IN_SET(key->type, DNS_TYPE_PTR);
+}
+
 DnsResourceRecord* dns_resource_record_new(DnsResourceKey *key);
 DnsResourceRecord* dns_resource_record_new_full(uint16_t class, uint16_t type, const char *name);
 DnsResourceRecord* dns_resource_record_ref(DnsResourceRecord *rr);
diff --git a/src/resolve/resolved-dns-transaction.c b/src/resolve/resolved-dns-transaction.c
index dccb8000a2..90f07e6c4b 100644
--- a/src/resolve/resolved-dns-transaction.c
+++ b/src/resolve/resolved-dns-transaction.c
@@ -24,6 +24,7 @@
 #include "dns-domain.h"
 #include "fd-util.h"
 #include "random-util.h"
+#include "resolved-dns-cache.h"
 #include "resolved-dns-transaction.h"
 #include "resolved-llmnr.h"
 #include "string-table.h"
@@ -733,6 +734,7 @@ static int dns_transaction_prepare_next_attempt(DnsTransaction *t, usec_t ts) {
 static int dns_transaction_make_packet_mdns(DnsTransaction *t) {
 
         _cleanup_(dns_packet_unrefp) DnsPacket *p = NULL;
+        bool add_known_answers = false;
         DnsTransaction *other;
         unsigned qdcount;
         usec_t ts;
@@ -754,6 +756,9 @@ static int dns_transaction_make_packet_mdns(DnsTransaction *t) {
 
         qdcount = 1;
 
+        if (dns_key_is_shared(t->key))
+                add_known_answers = true;
+
         /*
          * For mDNS, we want to coalesce as many open queries in pending transactions into one single
          * query packet on the wire as possible. To achieve that, we iterate through all pending transactions
@@ -808,11 +813,21 @@ static int dns_transaction_make_packet_mdns(DnsTransaction *t) {
                 other->next_attempt_after = ts;
 
                 qdcount ++;
+
+                if (dns_key_is_shared(other->key))
+                        add_known_answers = true;
         }
 
         DNS_PACKET_HEADER(p)->qdcount = htobe16(qdcount);
         DNS_PACKET_HEADER(p)->id = t->id;
 
+        /* Append known answer section if we're asking for any shared record */
+        if (add_known_answers) {
+                r = dns_cache_export_shared_to_packet(&t->scope->cache, p);
+                if (r < 0)
+                        return r;
+        }
+
         t->sent = p;
         p = NULL;
 
-- 
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