Adding upstream version 255.4.upstream/255.4

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1683 insertions, 0 deletions

diff --git a/src/resolve/resolved-dns-scope.c b/src/resolve/resolved-dns-scope.c
new file mode 100644
index 0000000..2e8b3e5
--- /dev/null
+++ b/src/resolve/resolved-dns-scope.c
@@ -0,0 +1,1683 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <netinet/tcp.h>
+
+#include "af-list.h"
+#include "alloc-util.h"
+#include "dns-domain.h"
+#include "errno-util.h"
+#include "fd-util.h"
+#include "hostname-util.h"
+#include "missing_network.h"
+#include "random-util.h"
+#include "resolved-dnssd.h"
+#include "resolved-dns-scope.h"
+#include "resolved-dns-zone.h"
+#include "resolved-llmnr.h"
+#include "resolved-mdns.h"
+#include "socket-util.h"
+#include "strv.h"
+
+#define MULTICAST_RATELIMIT_INTERVAL_USEC (1*USEC_PER_SEC)
+#define MULTICAST_RATELIMIT_BURST 1000
+
+/* After how much time to repeat LLMNR requests, see RFC 4795 Section 7 */
+#define MULTICAST_RESEND_TIMEOUT_MIN_USEC (100 * USEC_PER_MSEC)
+#define MULTICAST_RESEND_TIMEOUT_MAX_USEC (1 * USEC_PER_SEC)
+
+int dns_scope_new(Manager *m, DnsScope **ret, Link *l, DnsProtocol protocol, int family) {
+        DnsScope *s;
+
+        assert(m);
+        assert(ret);
+
+        s = new(DnsScope, 1);
+        if (!s)
+                return -ENOMEM;
+
+        *s = (DnsScope) {
+                .manager = m,
+                .link = l,
+                .protocol = protocol,
+                .family = family,
+                .resend_timeout = MULTICAST_RESEND_TIMEOUT_MIN_USEC,
+        };
+
+        if (protocol == DNS_PROTOCOL_DNS) {
+                /* Copy DNSSEC mode from the link if it is set there,
+                 * otherwise take the manager's DNSSEC mode. Note that
+                 * we copy this only at scope creation time, and do
+                 * not update it from the on, even if the setting
+                 * changes. */
+
+                if (l) {
+                        s->dnssec_mode = link_get_dnssec_mode(l);
+                        s->dns_over_tls_mode = link_get_dns_over_tls_mode(l);
+                } else {
+                        s->dnssec_mode = manager_get_dnssec_mode(m);
+                        s->dns_over_tls_mode = manager_get_dns_over_tls_mode(m);
+                }
+
+        } else {
+                s->dnssec_mode = DNSSEC_NO;
+                s->dns_over_tls_mode = DNS_OVER_TLS_NO;
+        }
+
+        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->ifname : "*", dns_protocol_to_string(protocol), family == AF_UNSPEC ? "*" : af_to_name(family));
+
+        /* Enforce ratelimiting for the multicast protocols */
+        s->ratelimit = (const RateLimit) { MULTICAST_RATELIMIT_INTERVAL_USEC, MULTICAST_RATELIMIT_BURST };
+
+        *ret = s;
+        return 0;
+}
+
+static void dns_scope_abort_transactions(DnsScope *s) {
+        assert(s);
+
+        while (s->transactions) {
+                DnsTransaction *t = s->transactions;
+
+                /* Abort the transaction, but make sure it is not
+                 * freed while we still look at it */
+
+                t->block_gc++;
+                if (DNS_TRANSACTION_IS_LIVE(t->state))
+                        dns_transaction_complete(t, DNS_TRANSACTION_ABORTED);
+                t->block_gc--;
+
+                dns_transaction_free(t);
+        }
+}
+
+DnsScope* dns_scope_free(DnsScope *s) {
+        if (!s)
+                return NULL;
+
+        log_debug("Removing scope on link %s, protocol %s, family %s", s->link ? s->link->ifname : "*", 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)
+                dns_query_candidate_unref(s->query_candidates);
+
+        hashmap_free(s->transactions_by_key);
+
+        ordered_hashmap_free_with_destructor(s->conflict_queue, dns_resource_record_unref);
+        sd_event_source_disable_unref(s->conflict_event_source);
+
+        sd_event_source_disable_unref(s->announce_event_source);
+
+        dns_cache_flush(&s->cache);
+        dns_zone_flush(&s->zone);
+
+        LIST_REMOVE(scopes, s->manager->dns_scopes, s);
+        return mfree(s);
+}
+
+DnsServer *dns_scope_get_dns_server(DnsScope *s) {
+        assert(s);
+
+        if (s->protocol != DNS_PROTOCOL_DNS)
+                return NULL;
+
+        if (s->link)
+                return link_get_dns_server(s->link);
+        else
+                return manager_get_dns_server(s->manager);
+}
+
+unsigned dns_scope_get_n_dns_servers(DnsScope *s) {
+        unsigned n = 0;
+        DnsServer *i;
+
+        assert(s);
+
+        if (s->protocol != DNS_PROTOCOL_DNS)
+                return 0;
+
+        if (s->link)
+                i = s->link->dns_servers;
+        else
+                i = s->manager->dns_servers;
+
+        for (; i; i = i->servers_next)
+                n++;
+
+        return n;
+}
+
+void dns_scope_next_dns_server(DnsScope *s, DnsServer *if_current) {
+        assert(s);
+
+        if (s->protocol != DNS_PROTOCOL_DNS)
+                return;
+
+        /* Changes to the next DNS server in the list. If 'if_current' is passed will do so only if the
+         * current DNS server still matches it. */
+
+        if (s->link)
+                link_next_dns_server(s->link, if_current);
+        else
+                manager_next_dns_server(s->manager, if_current);
+}
+
+void dns_scope_packet_received(DnsScope *s, usec_t rtt) {
+        assert(s);
+
+        if (rtt <= s->max_rtt)
+                return;
+
+        s->max_rtt = rtt;
+        s->resend_timeout = MIN(MAX(MULTICAST_RESEND_TIMEOUT_MIN_USEC, s->max_rtt * 2), MULTICAST_RESEND_TIMEOUT_MAX_USEC);
+}
+
+void dns_scope_packet_lost(DnsScope *s, usec_t usec) {
+        assert(s);
+
+        if (s->resend_timeout <= usec)
+                s->resend_timeout = MIN(s->resend_timeout * 2, MULTICAST_RESEND_TIMEOUT_MAX_USEC);
+}
+
+static int dns_scope_emit_one(DnsScope *s, int fd, int family, DnsPacket *p) {
+        int r;
+
+        assert(s);
+        assert(p);
+        assert(p->protocol == s->protocol);
+
+        if (family == AF_UNSPEC) {
+                if (s->family == AF_UNSPEC)
+                        return -EAFNOSUPPORT;
+
+                family = s->family;
+        }
+
+        switch (s->protocol) {
+
+        case DNS_PROTOCOL_DNS: {
+                size_t mtu, udp_size, min_mtu, socket_mtu = 0;
+
+                assert(fd >= 0);
+
+                if (DNS_PACKET_QDCOUNT(p) > 1) /* Classic DNS only allows one question per packet */
+                        return -EOPNOTSUPP;
+
+                if (p->size > DNS_PACKET_UNICAST_SIZE_MAX)
+                        return -EMSGSIZE;
+
+                /* Determine the local most accurate MTU */
+                if (s->link)
+                        mtu = s->link->mtu;
+                else
+                        mtu = manager_find_mtu(s->manager);
+
+                /* Acquire the socket's PMDU MTU */
+                r = socket_get_mtu(fd, family, &socket_mtu);
+                if (r < 0 && !ERRNO_IS_DISCONNECT(r)) /* Will return ENOTCONN if no information is available yet */
+                        return log_debug_errno(r, "Failed to read socket MTU: %m");
+
+                /* Determine the appropriate UDP header size */
+                udp_size = udp_header_size(family);
+                min_mtu = udp_size + DNS_PACKET_HEADER_SIZE;
+
+                log_debug("Emitting UDP, link MTU is %zu, socket MTU is %zu, minimal MTU is %zu",
+                          mtu, socket_mtu, min_mtu);
+
+                /* Clamp by the kernel's idea of the (path) MTU */
+                if (socket_mtu != 0 && socket_mtu < mtu)
+                        mtu = socket_mtu;
+
+                /* Put a lower limit, in case all MTU data we acquired was rubbish */
+                if (mtu < min_mtu)
+                        mtu = min_mtu;
+
+                /* Now check our packet size against the MTU we determined */
+                if (udp_size + p->size > mtu)
+                        return -EMSGSIZE; /* This means: try TCP instead */
+
+                r = manager_write(s->manager, fd, p);
+                if (r < 0)
+                        return r;
+
+                break;
+        }
+
+        case DNS_PROTOCOL_LLMNR: {
+                union in_addr_union addr;
+
+                assert(fd < 0);
+
+                if (DNS_PACKET_QDCOUNT(p) > 1)
+                        return -EOPNOTSUPP;
+
+                if (!ratelimit_below(&s->ratelimit))
+                        return -EBUSY;
+
+                if (family == AF_INET) {
+                        addr.in = LLMNR_MULTICAST_IPV4_ADDRESS;
+                        fd = manager_llmnr_ipv4_udp_fd(s->manager);
+                } else if (family == AF_INET6) {
+                        addr.in6 = LLMNR_MULTICAST_IPV6_ADDRESS;
+                        fd = manager_llmnr_ipv6_udp_fd(s->manager);
+                } else
+                        return -EAFNOSUPPORT;
+                if (fd < 0)
+                        return fd;
+
+                r = manager_send(s->manager, fd, s->link->ifindex, family, &addr, LLMNR_PORT, NULL, p);
+                if (r < 0)
+                        return r;
+
+                break;
+        }
+
+        case DNS_PROTOCOL_MDNS: {
+                union in_addr_union addr;
+                assert(fd < 0);
+
+                if (!ratelimit_below(&s->ratelimit))
+                        return -EBUSY;
+
+                if (family == AF_INET) {
+                        if (in4_addr_is_null(&p->destination.in))
+                                addr.in = MDNS_MULTICAST_IPV4_ADDRESS;
+                        else
+                                addr = p->destination;
+                        fd = manager_mdns_ipv4_fd(s->manager);
+                } else if (family == AF_INET6) {
+                        if (in6_addr_is_null(&p->destination.in6))
+                                addr.in6 = MDNS_MULTICAST_IPV6_ADDRESS;
+                        else
+                                addr = p->destination;
+                        fd = manager_mdns_ipv6_fd(s->manager);
+                } else
+                        return -EAFNOSUPPORT;
+                if (fd < 0)
+                        return fd;
+
+                r = manager_send(s->manager, fd, s->link->ifindex, family, &addr, p->destination_port ?: MDNS_PORT, NULL, p);
+                if (r < 0)
+                        return r;
+
+                break;
+        }
+
+        default:
+                return -EAFNOSUPPORT;
+        }
+
+        return 1;
+}
+
+int dns_scope_emit_udp(DnsScope *s, int fd, int af, DnsPacket *p) {
+        int r;
+
+        assert(s);
+        assert(p);
+        assert(p->protocol == s->protocol);
+        assert((s->protocol == DNS_PROTOCOL_DNS) == (fd >= 0));
+
+        do {
+                /* If there are multiple linked packets, set the TC bit in all but the last of them */
+                if (p->more) {
+                        assert(p->protocol == DNS_PROTOCOL_MDNS);
+                        dns_packet_set_flags(p, true, true);
+                }
+
+                r = dns_scope_emit_one(s, fd, af, p);
+                if (r < 0)
+                        return r;
+
+                p = p->more;
+        } while (p);
+
+        return 0;
+}
+
+static int dns_scope_socket(
+                DnsScope *s,
+                int type,
+                int family,
+                const union in_addr_union *address,
+                DnsServer *server,
+                uint16_t port,
+                union sockaddr_union *ret_socket_address) {
+
+        _cleanup_close_ int fd = -EBADF;
+        union sockaddr_union sa;
+        socklen_t salen;
+        int r, ifindex;
+
+        assert(s);
+
+        if (server) {
+                assert(family == AF_UNSPEC);
+                assert(!address);
+
+                ifindex = dns_server_ifindex(server);
+
+                switch (server->family) {
+                case AF_INET:
+                        sa = (union sockaddr_union) {
+                                .in.sin_family = server->family,
+                                .in.sin_port = htobe16(port),
+                                .in.sin_addr = server->address.in,
+                        };
+                        salen = sizeof(sa.in);
+                        break;
+                case AF_INET6:
+                        sa = (union sockaddr_union) {
+                                .in6.sin6_family = server->family,
+                                .in6.sin6_port = htobe16(port),
+                                .in6.sin6_addr = server->address.in6,
+                                .in6.sin6_scope_id = ifindex,
+                        };
+                        salen = sizeof(sa.in6);
+                        break;
+                default:
+                        return -EAFNOSUPPORT;
+                }
+        } else {
+                assert(family != AF_UNSPEC);
+                assert(address);
+
+                ifindex = s->link ? s->link->ifindex : 0;
+
+                switch (family) {
+                case AF_INET:
+                        sa = (union sockaddr_union) {
+                                .in.sin_family = family,
+                                .in.sin_port = htobe16(port),
+                                .in.sin_addr = address->in,
+                        };
+                        salen = sizeof(sa.in);
+                        break;
+                case AF_INET6:
+                        sa = (union sockaddr_union) {
+                                .in6.sin6_family = family,
+                                .in6.sin6_port = htobe16(port),
+                                .in6.sin6_addr = address->in6,
+                                .in6.sin6_scope_id = ifindex,
+                        };
+                        salen = sizeof(sa.in6);
+                        break;
+                default:
+                        return -EAFNOSUPPORT;
+                }
+        }
+
+        fd = socket(sa.sa.sa_family, type|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
+        if (fd < 0)
+                return -errno;
+
+        if (type == SOCK_STREAM) {
+                r = setsockopt_int(fd, IPPROTO_TCP, TCP_NODELAY, true);
+                if (r < 0)
+                        return r;
+        }
+
+        if (ifindex != 0) {
+                r = socket_set_unicast_if(fd, sa.sa.sa_family, ifindex);
+                if (r < 0)
+                        return r;
+        }
+
+        if (s->protocol == DNS_PROTOCOL_LLMNR) {
+                /* RFC 4795, section 2.5 requires the TTL to be set to 1 */
+                r = socket_set_ttl(fd, sa.sa.sa_family, 1);
+                if (r < 0)
+                        return r;
+        }
+
+        if (type == SOCK_DGRAM) {
+                /* Set IP_RECVERR or IPV6_RECVERR to get ICMP error feedback. See discussion in #10345. */
+                r = socket_set_recverr(fd, sa.sa.sa_family, true);
+                if (r < 0)
+                        return r;
+
+                r = socket_set_recvpktinfo(fd, sa.sa.sa_family, true);
+                if (r < 0)
+                        return r;
+
+                /* Turn of path MTU discovery for security reasons */
+                r = socket_disable_pmtud(fd, sa.sa.sa_family);
+                if (r < 0)
+                        log_debug_errno(r, "Failed to disable UDP PMTUD, ignoring: %m");
+
+                /* Learn about fragmentation taking place */
+                r = socket_set_recvfragsize(fd, sa.sa.sa_family, true);
+                if (r < 0)
+                        log_debug_errno(r, "Failed to enable fragment size reception, ignoring: %m");
+        }
+
+        if (ret_socket_address)
+                *ret_socket_address = sa;
+        else {
+                bool bound = false;
+
+                /* Let's temporarily bind the socket to the specified ifindex. The kernel currently takes
+                 * only the SO_BINDTODEVICE/SO_BINDTOINDEX ifindex into account when making routing decisions
+                 * in connect() — and not IP_UNICAST_IF. We don't really want any of the other semantics of
+                 * SO_BINDTODEVICE/SO_BINDTOINDEX, hence we immediately unbind the socket after the fact
+                 * again.
+                 *
+                 * As a special exception we don't do this if we notice that the specified IP address is on
+                 * the local host. SO_BINDTODEVICE in combination with destination addresses on the local
+                 * host result in EHOSTUNREACH, since Linux won't send the packets out of the specified
+                 * interface, but delivers them directly to the local socket. */
+                if (s->link &&
+                    !manager_find_link_address(s->manager, sa.sa.sa_family, sockaddr_in_addr(&sa.sa)) &&
+                    in_addr_is_localhost(sa.sa.sa_family, sockaddr_in_addr(&sa.sa)) == 0) {
+                        r = socket_bind_to_ifindex(fd, ifindex);
+                        if (r < 0)
+                                return r;
+
+                        bound = true;
+                }
+
+                r = connect(fd, &sa.sa, salen);
+                if (r < 0 && errno != EINPROGRESS)
+                        return -errno;
+
+                if (bound) {
+                        r = socket_bind_to_ifindex(fd, 0);
+                        if (r < 0)
+                                return r;
+                }
+        }
+
+        return TAKE_FD(fd);
+}
+
+int dns_scope_socket_udp(DnsScope *s, DnsServer *server) {
+        return dns_scope_socket(s, SOCK_DGRAM, AF_UNSPEC, NULL, server, dns_server_port(server), NULL);
+}
+
+int dns_scope_socket_tcp(DnsScope *s, int family, const union in_addr_union *address, DnsServer *server, uint16_t port, union sockaddr_union *ret_socket_address) {
+        /* If ret_socket_address is not NULL, the caller is responsible
+         * for calling connect() or sendmsg(). This is required by TCP
+         * Fast Open, to be able to send the initial SYN packet along
+         * with the first data packet. */
+        return dns_scope_socket(s, SOCK_STREAM, family, address, server, port, ret_socket_address);
+}
+
+static DnsScopeMatch match_link_local_reverse_lookups(const char *domain) {
+        assert(domain);
+
+        if (dns_name_endswith(domain, "254.169.in-addr.arpa") > 0)
+                return DNS_SCOPE_YES_BASE + 4; /* 4 labels match */
+
+        if (dns_name_endswith(domain, "8.e.f.ip6.arpa") > 0 ||
+            dns_name_endswith(domain, "9.e.f.ip6.arpa") > 0 ||
+            dns_name_endswith(domain, "a.e.f.ip6.arpa") > 0 ||
+            dns_name_endswith(domain, "b.e.f.ip6.arpa") > 0)
+                return DNS_SCOPE_YES_BASE + 5; /* 5 labels match */
+
+        return _DNS_SCOPE_MATCH_INVALID;
+}
+
+static DnsScopeMatch match_subnet_reverse_lookups(
+                DnsScope *s,
+                const char *domain,
+                bool exclude_own) {
+
+        union in_addr_union ia;
+        int f, r;
+
+        assert(s);
+        assert(domain);
+
+        /* Checks whether the specified domain is a reverse address domain (i.e. in the .in-addr.arpa or
+         * .ip6.arpa area), and if so, whether the address matches any of the local subnets of the link the
+         * scope is associated with. If so, our scope should consider itself relevant for any lookup in the
+         * domain, since it apparently refers to hosts on this link's subnet.
+         *
+         * If 'exclude_own' is true this will return DNS_SCOPE_NO for any IP addresses assigned locally. This
+         * is useful for LLMNR/mDNS as we never want to look up our own hostname on LLMNR/mDNS but always use
+         * the locally synthesized one. */
+
+        if (!s->link)
+                return _DNS_SCOPE_MATCH_INVALID; /* No link, hence no local addresses to check */
+
+        r = dns_name_address(domain, &f, &ia);
+        if (r < 0)
+                log_debug_errno(r, "Failed to determine whether '%s' is an address domain: %m", domain);
+        if (r <= 0)
+                return _DNS_SCOPE_MATCH_INVALID;
+
+        if (s->family != AF_UNSPEC && f != s->family)
+                return _DNS_SCOPE_MATCH_INVALID; /* Don't look for IPv4 addresses on LLMNR/mDNS over IPv6 and vice versa */
+
+        if (in_addr_is_null(f, &ia))
+                return DNS_SCOPE_NO;
+
+        LIST_FOREACH(addresses, a, s->link->addresses) {
+
+                if (a->family != f)
+                        continue;
+
+                /* Equals our own address? nah, let's not use this scope. The local synthesizer will pick it up for us. */
+                if (exclude_own &&
+                    in_addr_equal(f, &a->in_addr, &ia) > 0)
+                        return DNS_SCOPE_NO;
+
+                if (a->prefixlen == UCHAR_MAX) /* don't know subnet mask */
+                        continue;
+
+                /* Don't send mDNS queries for the IPv4 broadcast address */
+                if (f == AF_INET && in_addr_equal(f, &a->in_addr_broadcast, &ia) > 0)
+                        return DNS_SCOPE_NO;
+
+                /* Check if the address is in the local subnet */
+                r = in_addr_prefix_covers(f, &a->in_addr, a->prefixlen, &ia);
+                if (r < 0)
+                        log_debug_errno(r, "Failed to determine whether link address covers lookup address '%s': %m", domain);
+                if (r > 0)
+                        /* Note that we only claim zero labels match. This is so that this is at the same
+                         * priority a DNS scope with "." as routing domain is. */
+                        return DNS_SCOPE_YES_BASE + 0;
+        }
+
+        return _DNS_SCOPE_MATCH_INVALID;
+}
+
+DnsScopeMatch dns_scope_good_domain(
+                DnsScope *s,
+                DnsQuery *q) {
+
+        DnsQuestion *question;
+        const char *domain;
+        uint64_t flags;
+        int ifindex;
+
+        /* This returns the following return values:
+         *
+         *    DNS_SCOPE_NO         → This scope is not suitable for lookups of this domain, at all
+         *    DNS_SCOPE_MAYBE      → This scope is suitable, but only if nothing else wants it
+         *    DNS_SCOPE_YES_BASE+n → This scope is suitable, and 'n' suffix labels match
+         *
+         *  (The idea is that the caller will only use the scopes with the longest 'n' returned. If no scopes return
+         *  DNS_SCOPE_YES_BASE+n, then it should use those which returned DNS_SCOPE_MAYBE. It should never use those
+         *  which returned DNS_SCOPE_NO.)
+         */
+
+        assert(s);
+        assert(q);
+
+        question = dns_query_question_for_protocol(q, s->protocol);
+        if (!question)
+                return DNS_SCOPE_NO;
+
+        domain = dns_question_first_name(question);
+        if (!domain)
+                return DNS_SCOPE_NO;
+
+        ifindex = q->ifindex;
+        flags = q->flags;
+
+        /* Checks if the specified domain is something to look up on this scope. Note that this accepts
+         * non-qualified hostnames, i.e. those without any search path suffixed. */
+
+        if (ifindex != 0 && (!s->link || s->link->ifindex != ifindex))
+                return DNS_SCOPE_NO;
+
+        if ((SD_RESOLVED_FLAGS_MAKE(s->protocol, s->family, false, false) & flags) == 0)
+                return DNS_SCOPE_NO;
+
+        /* Never resolve any loopback hostname or IP address via DNS, LLMNR or mDNS. Instead, always rely on
+         * synthesized RRs for these. */
+        if (is_localhost(domain) ||
+            dns_name_endswith(domain, "127.in-addr.arpa") > 0 ||
+            dns_name_equal(domain, "1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa") > 0)
+                return DNS_SCOPE_NO;
+
+        /* Never respond to some of the domains listed in RFC6303 + RFC6761 */
+        if (dns_name_dont_resolve(domain))
+                return DNS_SCOPE_NO;
+
+        /* Never go to network for the _gateway, _outbound, _localdnsstub, _localdnsproxy domain — they're something special, synthesized locally. */
+        if (is_gateway_hostname(domain) ||
+            is_outbound_hostname(domain) ||
+            is_dns_stub_hostname(domain) ||
+            is_dns_proxy_stub_hostname(domain))
+                return DNS_SCOPE_NO;
+
+        switch (s->protocol) {
+
+        case DNS_PROTOCOL_DNS: {
+                bool has_search_domains = false;
+                DnsScopeMatch m;
+                int n_best = -1;
+
+                if (dns_name_is_root(domain)) {
+                        DnsResourceKey *t;
+                        bool found = false;
+
+                        /* Refuse root name if only A and/or AAAA records are requested. */
+
+                        DNS_QUESTION_FOREACH(t, question)
+                                if (!IN_SET(t->type, DNS_TYPE_A, DNS_TYPE_AAAA)) {
+                                        found = true;
+                                        break;
+                                }
+
+                        if (!found)
+                                return DNS_SCOPE_NO;
+                }
+
+                /* Never route things to scopes that lack DNS servers */
+                if (!dns_scope_get_dns_server(s))
+                        return DNS_SCOPE_NO;
+
+                /* Always honour search domains for routing queries, except if this scope lacks DNS servers. Note that
+                 * we return DNS_SCOPE_YES here, rather than just DNS_SCOPE_MAYBE, which means other wildcard scopes
+                 * won't be considered anymore. */
+                LIST_FOREACH(domains, d, dns_scope_get_search_domains(s)) {
+
+                        if (!d->route_only && !dns_name_is_root(d->name))
+                                has_search_domains = true;
+
+                        if (dns_name_endswith(domain, d->name) > 0) {
+                                int c;
+
+                                c = dns_name_count_labels(d->name);
+                                if (c < 0)
+                                        continue;
+
+                                if (c > n_best)
+                                        n_best = c;
+                        }
+                }
+
+                /* If there's a true search domain defined for this scope, and the query is single-label,
+                 * then let's resolve things here, preferably. Note that LLMNR considers itself
+                 * authoritative for single-label names too, at the same preference, see below. */
+                if (has_search_domains && dns_name_is_single_label(domain))
+                        return DNS_SCOPE_YES_BASE + 1;
+
+                /* If ResolveUnicastSingleLabel=yes and the query is single-label, then bump match result
+                   to prevent LLMNR monopoly among candidates. */
+                if (s->manager->resolve_unicast_single_label && dns_name_is_single_label(domain))
+                        return DNS_SCOPE_YES_BASE + 1;
+
+                /* Let's return the number of labels in the best matching result */
+                if (n_best >= 0) {
+                        assert(n_best <= DNS_SCOPE_YES_END - DNS_SCOPE_YES_BASE);
+                        return DNS_SCOPE_YES_BASE + n_best;
+                }
+
+                /* Exclude link-local IP ranges */
+                if (match_link_local_reverse_lookups(domain) >= DNS_SCOPE_YES_BASE ||
+                    /* If networks use .local in their private setups, they are supposed to also add .local
+                     * to their search domains, which we already checked above. Otherwise, we consider .local
+                     * specific to mDNS and won't send such queries ordinary DNS servers. */
+                    dns_name_endswith(domain, "local") > 0)
+                        return DNS_SCOPE_NO;
+
+                /* If the IP address to look up matches the local subnet, then implicitly synthesizes
+                 * DNS_SCOPE_YES_BASE + 0 on this interface, i.e. preferably resolve IP addresses via the DNS
+                 * server belonging to this interface. */
+                m = match_subnet_reverse_lookups(s, domain, false);
+                if (m >= 0)
+                        return m;
+
+                /* If there was no match at all, then see if this scope is suitable as default route. */
+                if (!dns_scope_is_default_route(s))
+                        return DNS_SCOPE_NO;
+
+                return DNS_SCOPE_MAYBE;
+        }
+
+        case DNS_PROTOCOL_MDNS: {
+                DnsScopeMatch m;
+
+                m = match_link_local_reverse_lookups(domain);
+                if (m >= 0)
+                        return m;
+
+                m = match_subnet_reverse_lookups(s, domain, true);
+                if (m >= 0)
+                        return m;
+
+                if ((s->family == AF_INET && dns_name_endswith(domain, "in-addr.arpa") > 0) ||
+                    (s->family == AF_INET6 && dns_name_endswith(domain, "ip6.arpa") > 0))
+                        return DNS_SCOPE_MAYBE;
+
+                if ((dns_name_endswith(domain, "local") > 0 && /* only resolve names ending in .local via mDNS */
+                     dns_name_equal(domain, "local") == 0 &&   /* but not the single-label "local" name itself */
+                     manager_is_own_hostname(s->manager, domain) <= 0)) /* never resolve the local hostname via mDNS */
+                        return DNS_SCOPE_YES_BASE + 1; /* Return +1, as the top-level .local domain matches, i.e. one label */
+
+                return DNS_SCOPE_NO;
+        }
+
+        case DNS_PROTOCOL_LLMNR: {
+                DnsScopeMatch m;
+
+                m = match_link_local_reverse_lookups(domain);
+                if (m >= 0)
+                        return m;
+
+                m = match_subnet_reverse_lookups(s, domain, true);
+                if (m >= 0)
+                        return m;
+
+                if ((s->family == AF_INET && dns_name_endswith(domain, "in-addr.arpa") > 0) ||
+                    (s->family == AF_INET6 && dns_name_endswith(domain, "ip6.arpa") > 0))
+                        return DNS_SCOPE_MAYBE;
+
+                if ((dns_name_is_single_label(domain) && /* only resolve single label names via LLMNR */
+                     dns_name_equal(domain, "local") == 0 && /* don't resolve "local" with LLMNR, it's the top-level domain of mDNS after all, see above */
+                     manager_is_own_hostname(s->manager, domain) <= 0))  /* never resolve the local hostname via LLMNR */
+                        return DNS_SCOPE_YES_BASE + 1; /* Return +1, as we consider ourselves authoritative
+                                                        * for single-label names, i.e. one label. This is
+                                                        * particularly relevant as it means a "." route on some
+                                                        * other scope won't pull all traffic away from
+                                                        * us. (If people actually want to pull traffic away
+                                                        * from us they should turn off LLMNR on the
+                                                        * link). Note that unicast DNS scopes with search
+                                                        * domains also consider themselves authoritative for
+                                                        * single-label domains, at the same preference (see
+                                                        * above). */
+
+                return DNS_SCOPE_NO;
+        }
+
+        default:
+                assert_not_reached();
+        }
+}
+
+bool dns_scope_good_key(DnsScope *s, const DnsResourceKey *key) {
+        int key_family;
+
+        assert(s);
+        assert(key);
+
+        /* Check if it makes sense to resolve the specified key on this scope. Note that this call assumes a
+         * fully qualified name, i.e. the search suffixes already appended. */
+
+        if (!IN_SET(key->class, DNS_CLASS_IN, DNS_CLASS_ANY))
+                return false;
+
+        if (s->protocol == DNS_PROTOCOL_DNS) {
+
+                /* On classic DNS, looking up non-address RRs is always fine. (Specifically, we want to
+                 * permit looking up DNSKEY and DS records on the root and top-level domains.) */
+                if (!dns_resource_key_is_address(key))
+                        return true;
+
+                /* Unless explicitly overridden, we refuse to look up A and AAAA RRs on the root and
+                 * single-label domains, under the assumption that those should be resolved via LLMNR or
+                 * search path only, and should not be leaked onto the internet. */
+                const char* name = dns_resource_key_name(key);
+
+                if (!s->manager->resolve_unicast_single_label &&
+                    dns_name_is_single_label(name))
+                        return false;
+
+                return !dns_name_is_root(name);
+        }
+
+        /* Never route DNSSEC RR queries to LLMNR/mDNS scopes */
+        if (dns_type_is_dnssec(key->type))
+                return false;
+
+        /* On mDNS and LLMNR, send A and AAAA queries only on the respective scopes */
+
+        key_family = dns_type_to_af(key->type);
+        if (key_family < 0)
+                return true;
+
+        return key_family == s->family;
+}
+
+static int dns_scope_multicast_membership(DnsScope *s, bool b, struct in_addr in, struct in6_addr in6) {
+        int fd;
+
+        assert(s);
+        assert(s->link);
+
+        if (s->family == AF_INET) {
+                struct ip_mreqn mreqn = {
+                        .imr_multiaddr = in,
+                        .imr_ifindex = s->link->ifindex,
+                };
+
+                if (s->protocol == DNS_PROTOCOL_LLMNR)
+                        fd = manager_llmnr_ipv4_udp_fd(s->manager);
+                else
+                        fd = manager_mdns_ipv4_fd(s->manager);
+
+                if (fd < 0)
+                        return fd;
+
+                /* Always first try to drop membership before we add
+                 * one. This is necessary on some devices, such as
+                 * veth. */
+                if (b)
+                        (void) setsockopt(fd, IPPROTO_IP, IP_DROP_MEMBERSHIP, &mreqn, sizeof(mreqn));
+
+                if (setsockopt(fd, IPPROTO_IP, b ? IP_ADD_MEMBERSHIP : IP_DROP_MEMBERSHIP, &mreqn, sizeof(mreqn)) < 0)
+                        return -errno;
+
+        } else if (s->family == AF_INET6) {
+                struct ipv6_mreq mreq = {
+                        .ipv6mr_multiaddr = in6,
+                        .ipv6mr_interface = s->link->ifindex,
+                };
+
+                if (s->protocol == DNS_PROTOCOL_LLMNR)
+                        fd = manager_llmnr_ipv6_udp_fd(s->manager);
+                else
+                        fd = manager_mdns_ipv6_fd(s->manager);
+
+                if (fd < 0)
+                        return fd;
+
+                if (b)
+                        (void) setsockopt(fd, IPPROTO_IPV6, IPV6_DROP_MEMBERSHIP, &mreq, sizeof(mreq));
+
+                if (setsockopt(fd, IPPROTO_IPV6, b ? IPV6_ADD_MEMBERSHIP : IPV6_DROP_MEMBERSHIP, &mreq, sizeof(mreq)) < 0)
+                        return -errno;
+        } else
+                return -EAFNOSUPPORT;
+
+        return 0;
+}
+
+int dns_scope_llmnr_membership(DnsScope *s, bool b) {
+        assert(s);
+
+        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) {
+        assert(s);
+
+        if (s->protocol != DNS_PROTOCOL_MDNS)
+                return 0;
+
+        return dns_scope_multicast_membership(s, b, MDNS_MULTICAST_IPV4_ADDRESS, MDNS_MULTICAST_IPV6_ADDRESS);
+}
+
+int dns_scope_make_reply_packet(
+                DnsScope *s,
+                uint16_t id,
+                int rcode,
+                DnsQuestion *q,
+                DnsAnswer *answer,
+                DnsAnswer *soa,
+                bool tentative,
+                DnsPacket **ret) {
+
+        _cleanup_(dns_packet_unrefp) DnsPacket *p = NULL;
+        unsigned n_answer = 0, n_soa = 0;
+        int r;
+        bool c_or_aa;
+
+        assert(s);
+        assert(ret);
+
+        if (dns_question_isempty(q) &&
+            dns_answer_isempty(answer) &&
+            dns_answer_isempty(soa))
+                return -EINVAL;
+
+        r = dns_packet_new(&p, s->protocol, 0, DNS_PACKET_SIZE_MAX);
+        if (r < 0)
+                return r;
+
+        /* mDNS answers must have the Authoritative Answer bit set, see RFC 6762, section 18.4. */
+        c_or_aa = s->protocol == DNS_PROTOCOL_MDNS;
+
+        DNS_PACKET_HEADER(p)->id = id;
+        DNS_PACKET_HEADER(p)->flags = htobe16(DNS_PACKET_MAKE_FLAGS(
+                                                              1 /* qr */,
+                                                              0 /* opcode */,
+                                                              c_or_aa,
+                                                              0 /* tc */,
+                                                              tentative,
+                                                              0 /* (ra) */,
+                                                              0 /* (ad) */,
+                                                              0 /* (cd) */,
+                                                              rcode));
+
+        r = dns_packet_append_question(p, q);
+        if (r < 0)
+                return r;
+        DNS_PACKET_HEADER(p)->qdcount = htobe16(dns_question_size(q));
+
+        r = dns_packet_append_answer(p, answer, &n_answer);
+        if (r < 0)
+                return r;
+        DNS_PACKET_HEADER(p)->ancount = htobe16(n_answer);
+
+        r = dns_packet_append_answer(p, soa, &n_soa);
+        if (r < 0)
+                return r;
+        DNS_PACKET_HEADER(p)->arcount = htobe16(n_soa);
+
+        *ret = TAKE_PTR(p);
+
+        return 0;
+}
+
+static void dns_scope_verify_conflicts(DnsScope *s, DnsPacket *p) {
+        DnsResourceRecord *rr;
+        DnsResourceKey *key;
+
+        assert(s);
+        assert(p);
+
+        DNS_QUESTION_FOREACH(key, p->question)
+                dns_zone_verify_conflicts(&s->zone, key);
+
+        DNS_ANSWER_FOREACH(rr, p->answer)
+                dns_zone_verify_conflicts(&s->zone, rr->key);
+}
+
+void dns_scope_process_query(DnsScope *s, DnsStream *stream, DnsPacket *p) {
+        _cleanup_(dns_answer_unrefp) DnsAnswer *answer = NULL, *soa = NULL;
+        _cleanup_(dns_packet_unrefp) DnsPacket *reply = NULL;
+        DnsResourceKey *key = NULL;
+        bool tentative = false;
+        int r;
+
+        assert(s);
+        assert(p);
+
+        if (p->protocol != DNS_PROTOCOL_LLMNR)
+                return;
+
+        if (p->ipproto == IPPROTO_UDP) {
+                /* Don't accept UDP queries directed to anything but
+                 * the LLMNR multicast addresses. See RFC 4795,
+                 * section 2.5. */
+
+                if (p->family == AF_INET && !in4_addr_equal(&p->destination.in, &LLMNR_MULTICAST_IPV4_ADDRESS))
+                        return;
+
+                if (p->family == AF_INET6 && !in6_addr_equal(&p->destination.in6, &LLMNR_MULTICAST_IPV6_ADDRESS))
+                        return;
+        }
+
+        r = dns_packet_extract(p);
+        if (r < 0) {
+                log_debug_errno(r, "Failed to extract resource records from incoming packet: %m");
+                return;
+        }
+
+        if (DNS_PACKET_LLMNR_C(p)) {
+                /* Somebody notified us about a possible conflict */
+                dns_scope_verify_conflicts(s, p);
+                return;
+        }
+
+        if (dns_question_size(p->question) != 1)
+                return (void) log_debug("Received LLMNR query without question or multiple questions, ignoring.");
+
+        key = dns_question_first_key(p->question);
+
+        r = dns_zone_lookup(&s->zone, key, 0, &answer, &soa, &tentative);
+        if (r < 0) {
+                log_debug_errno(r, "Failed to look up key: %m");
+                return;
+        }
+        if (r == 0)
+                return;
+
+        if (answer)
+                dns_answer_order_by_scope(answer, in_addr_is_link_local(p->family, &p->sender) > 0);
+
+        r = dns_scope_make_reply_packet(s, DNS_PACKET_ID(p), DNS_RCODE_SUCCESS, p->question, answer, soa, tentative, &reply);
+        if (r < 0) {
+                log_debug_errno(r, "Failed to build reply packet: %m");
+                return;
+        }
+
+        if (stream) {
+                r = dns_stream_write_packet(stream, reply);
+                if (r < 0) {
+                        log_debug_errno(r, "Failed to enqueue reply packet: %m");
+                        return;
+                }
+
+                /* Let's take an extra reference on this stream, so that it stays around after returning. The reference
+                 * will be dangling until the stream is disconnected, and the default completion handler of the stream
+                 * will then unref the stream and destroy it */
+                if (DNS_STREAM_QUEUED(stream))
+                        dns_stream_ref(stream);
+        } else {
+                int fd;
+
+                if (!ratelimit_below(&s->ratelimit))
+                        return;
+
+                if (p->family == AF_INET)
+                        fd = manager_llmnr_ipv4_udp_fd(s->manager);
+                else if (p->family == AF_INET6)
+                        fd = manager_llmnr_ipv6_udp_fd(s->manager);
+                else {
+                        log_debug("Unknown protocol");
+                        return;
+                }
+                if (fd < 0) {
+                        log_debug_errno(fd, "Failed to get reply socket: %m");
+                        return;
+                }
+
+                /* Note that we always immediately reply to all LLMNR
+                 * requests, and do not wait any time, since we
+                 * verified uniqueness for all records. Also see RFC
+                 * 4795, Section 2.7 */
+
+                r = manager_send(s->manager, fd, p->ifindex, p->family, &p->sender, p->sender_port, NULL, reply);
+                if (r < 0) {
+                        log_debug_errno(r, "Failed to send reply packet: %m");
+                        return;
+                }
+        }
+}
+
+DnsTransaction *dns_scope_find_transaction(
+                DnsScope *scope,
+                DnsResourceKey *key,
+                uint64_t query_flags) {
+
+        DnsTransaction *first;
+
+        assert(scope);
+        assert(key);
+
+        /* Iterate through the list of transactions with a matching key */
+        first = hashmap_get(scope->transactions_by_key, key);
+        LIST_FOREACH(transactions_by_key, t, first) {
+
+                /* These four flags must match exactly: we cannot use a validated response for a
+                 * non-validating client, and we cannot use a non-validated response for a validating
+                 * client. Similar, if the sources don't match things aren't usable either. */
+                if (((query_flags ^ t->query_flags) &
+                     (SD_RESOLVED_NO_VALIDATE|
+                     SD_RESOLVED_NO_ZONE|
+                      SD_RESOLVED_NO_TRUST_ANCHOR|
+                      SD_RESOLVED_NO_NETWORK)) != 0)
+                        continue;
+
+                /* We can reuse a primary query if a regular one is requested, but not vice versa */
+                if ((query_flags & SD_RESOLVED_REQUIRE_PRIMARY) &&
+                    !(t->query_flags & SD_RESOLVED_REQUIRE_PRIMARY))
+                        continue;
+
+                /* Don't reuse a transaction that allowed caching when we got told not to use it */
+                if ((query_flags & SD_RESOLVED_NO_CACHE) &&
+                    !(t->query_flags & SD_RESOLVED_NO_CACHE))
+                        continue;
+
+                /* If we are asked to clamp ttls and the existing transaction doesn't do it, we can't
+                 * reuse */
+                if ((query_flags & SD_RESOLVED_CLAMP_TTL) &&
+                    !(t->query_flags & SD_RESOLVED_CLAMP_TTL))
+                        continue;
+
+                return t;
+        }
+
+        return NULL;
+}
+
+static int dns_scope_make_conflict_packet(
+                DnsScope *s,
+                DnsResourceRecord *rr,
+                DnsPacket **ret) {
+
+        _cleanup_(dns_packet_unrefp) DnsPacket *p = NULL;
+        int r;
+
+        assert(s);
+        assert(rr);
+        assert(ret);
+
+        r = dns_packet_new(&p, s->protocol, 0, DNS_PACKET_SIZE_MAX);
+        if (r < 0)
+                return r;
+
+        DNS_PACKET_HEADER(p)->flags = htobe16(DNS_PACKET_MAKE_FLAGS(
+                                                              0 /* qr */,
+                                                              0 /* opcode */,
+                                                              1 /* conflict */,
+                                                              0 /* tc */,
+                                                              0 /* t */,
+                                                              0 /* (ra) */,
+                                                              0 /* (ad) */,
+                                                              0 /* (cd) */,
+                                                              0));
+
+        /* For mDNS, the transaction ID should always be 0 */
+        if (s->protocol != DNS_PROTOCOL_MDNS)
+                random_bytes(&DNS_PACKET_HEADER(p)->id, sizeof(uint16_t));
+
+        DNS_PACKET_HEADER(p)->qdcount = htobe16(1);
+        DNS_PACKET_HEADER(p)->arcount = htobe16(1);
+
+        r = dns_packet_append_key(p, rr->key, 0, NULL);
+        if (r < 0)
+                return r;
+
+        r = dns_packet_append_rr(p, rr, 0, NULL, NULL);
+        if (r < 0)
+                return r;
+
+        *ret = TAKE_PTR(p);
+
+        return 0;
+}
+
+static int on_conflict_dispatch(sd_event_source *es, usec_t usec, void *userdata) {
+        DnsScope *scope = ASSERT_PTR(userdata);
+        int r;
+
+        assert(es);
+
+        scope->conflict_event_source = sd_event_source_disable_unref(scope->conflict_event_source);
+
+        for (;;) {
+                _cleanup_(dns_resource_key_unrefp) DnsResourceKey *key = NULL;
+                _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL;
+                _cleanup_(dns_packet_unrefp) DnsPacket *p = NULL;
+
+                key = ordered_hashmap_first_key(scope->conflict_queue);
+                if (!key)
+                        break;
+
+                rr = ordered_hashmap_remove(scope->conflict_queue, key);
+                assert(rr);
+
+                r = dns_scope_make_conflict_packet(scope, rr, &p);
+                if (r < 0) {
+                        log_error_errno(r, "Failed to make conflict packet: %m");
+                        return 0;
+                }
+
+                r = dns_scope_emit_udp(scope, -1, AF_UNSPEC, p);
+                if (r < 0)
+                        log_debug_errno(r, "Failed to send conflict packet: %m");
+        }
+
+        return 0;
+}
+
+int dns_scope_notify_conflict(DnsScope *scope, DnsResourceRecord *rr) {
+        int r;
+
+        assert(scope);
+        assert(rr);
+
+        /* We don't send these queries immediately. Instead, we queue
+         * them, and send them after some jitter delay. */
+        r = ordered_hashmap_ensure_allocated(&scope->conflict_queue, &dns_resource_key_hash_ops);
+        if (r < 0) {
+                log_oom();
+                return r;
+        }
+
+        /* We only place one RR per key in the conflict
+         * messages, not all of them. That should be enough to
+         * indicate where there might be a conflict */
+        r = ordered_hashmap_put(scope->conflict_queue, rr->key, rr);
+        if (IN_SET(r, 0, -EEXIST))
+                return 0;
+        if (r < 0)
+                return log_debug_errno(r, "Failed to queue conflicting RR: %m");
+
+        dns_resource_key_ref(rr->key);
+        dns_resource_record_ref(rr);
+
+        if (scope->conflict_event_source)
+                return 0;
+
+        r = sd_event_add_time_relative(
+                        scope->manager->event,
+                        &scope->conflict_event_source,
+                        CLOCK_BOOTTIME,
+                        random_u64_range(LLMNR_JITTER_INTERVAL_USEC),
+                        0,
+                        on_conflict_dispatch, scope);
+        if (r < 0)
+                return log_debug_errno(r, "Failed to add conflict dispatch event: %m");
+
+        (void) sd_event_source_set_description(scope->conflict_event_source, "scope-conflict");
+
+        return 0;
+}
+
+void dns_scope_check_conflicts(DnsScope *scope, DnsPacket *p) {
+        DnsResourceRecord *rr;
+        int r;
+
+        assert(scope);
+        assert(p);
+
+        if (!IN_SET(p->protocol, DNS_PROTOCOL_LLMNR, DNS_PROTOCOL_MDNS))
+                return;
+
+        if (DNS_PACKET_RRCOUNT(p) <= 0)
+                return;
+
+        if (p->protocol == DNS_PROTOCOL_LLMNR) {
+                if (DNS_PACKET_LLMNR_C(p) != 0)
+                        return;
+
+                if (DNS_PACKET_LLMNR_T(p) != 0)
+                        return;
+        }
+
+        if (manager_packet_from_local_address(scope->manager, p))
+                return;
+
+        r = dns_packet_extract(p);
+        if (r < 0) {
+                log_debug_errno(r, "Failed to extract packet: %m");
+                return;
+        }
+
+        log_debug("Checking for conflicts...");
+
+        DNS_ANSWER_FOREACH(rr, p->answer) {
+                /* No conflict if it is DNS-SD RR used for service enumeration. */
+                if (dns_resource_key_is_dnssd_ptr(rr->key))
+                        continue;
+
+                /* Check for conflicts against the local zone. If we
+                 * found one, we won't check any further */
+                r = dns_zone_check_conflicts(&scope->zone, rr);
+                if (r != 0)
+                        continue;
+
+                /* Check for conflicts against the local cache. If so,
+                 * send out an advisory query, to inform everybody */
+                r = dns_cache_check_conflicts(&scope->cache, rr, p->family, &p->sender);
+                if (r <= 0)
+                        continue;
+
+                dns_scope_notify_conflict(scope, rr);
+        }
+}
+
+void dns_scope_dump(DnsScope *s, FILE *f) {
+        assert(s);
+
+        if (!f)
+                f = stdout;
+
+        fputs("[Scope protocol=", f);
+        fputs(dns_protocol_to_string(s->protocol), f);
+
+        if (s->link) {
+                fputs(" interface=", f);
+                fputs(s->link->ifname, f);
+        }
+
+        if (s->family != AF_UNSPEC) {
+                fputs(" family=", f);
+                fputs(af_to_name(s->family), f);
+        }
+
+        fputs("]\n", f);
+
+        if (!dns_zone_is_empty(&s->zone)) {
+                fputs("ZONE:\n", f);
+                dns_zone_dump(&s->zone, f);
+        }
+
+        if (!dns_cache_is_empty(&s->cache)) {
+                fputs("CACHE:\n", f);
+                dns_cache_dump(&s->cache, f);
+        }
+}
+
+DnsSearchDomain *dns_scope_get_search_domains(DnsScope *s) {
+        assert(s);
+
+        if (s->protocol != DNS_PROTOCOL_DNS)
+                return NULL;
+
+        if (s->link)
+                return s->link->search_domains;
+
+        return s->manager->search_domains;
+}
+
+bool dns_scope_name_wants_search_domain(DnsScope *s, const char *name) {
+        assert(s);
+
+        if (s->protocol != DNS_PROTOCOL_DNS)
+                return false;
+
+        if (!dns_name_is_single_label(name))
+                return false;
+
+        /* If we allow single-label domain lookups on unicast DNS, and this scope has a search domain that matches
+         * _exactly_ this name, then do not use search domains. */
+        if (s->manager->resolve_unicast_single_label)
+                LIST_FOREACH(domains, d, dns_scope_get_search_domains(s))
+                        if (dns_name_equal(name, d->name) > 0)
+                                return false;
+
+        return true;
+}
+
+bool dns_scope_network_good(DnsScope *s) {
+        /* Checks whether the network is in good state for lookups on this scope. For mDNS/LLMNR/Classic DNS scopes
+         * bound to links this is easy, as they don't even exist if the link isn't in a suitable state. For the global
+         * DNS scope we check whether there are any links that are up and have an address.
+         *
+         * Note that Linux routing is complex and even systems that superficially have no IPv4 address might
+         * be able to route IPv4 (and similar for IPv6), hence let's make a check here independent of address
+         * family. */
+
+        if (s->link)
+                return true;
+
+        return manager_routable(s->manager);
+}
+
+int dns_scope_ifindex(DnsScope *s) {
+        assert(s);
+
+        if (s->link)
+                return s->link->ifindex;
+
+        return 0;
+}
+
+static int on_announcement_timeout(sd_event_source *s, usec_t usec, void *userdata) {
+        DnsScope *scope = userdata;
+
+        assert(s);
+
+        scope->announce_event_source = sd_event_source_disable_unref(scope->announce_event_source);
+
+        (void) dns_scope_announce(scope, false);
+        return 0;
+}
+
+int dns_scope_announce(DnsScope *scope, bool goodbye) {
+        _cleanup_(dns_answer_unrefp) DnsAnswer *answer = NULL;
+        _cleanup_(dns_packet_unrefp) DnsPacket *p = NULL;
+        _cleanup_set_free_ Set *types = NULL;
+        DnsZoneItem *z;
+        unsigned size = 0;
+        char *service_type;
+        int r;
+
+        if (!scope)
+                return 0;
+
+        if (scope->protocol != DNS_PROTOCOL_MDNS)
+                return 0;
+
+        r = sd_event_get_state(scope->manager->event);
+        if (r < 0)
+                return log_debug_errno(r, "Failed to get event loop state: %m");
+
+        /* If this is called on exit, through manager_free() -> link_free(), then we cannot announce. */
+        if (r == SD_EVENT_FINISHED)
+                return 0;
+
+        /* Check if we're done with probing. */
+        LIST_FOREACH(transactions_by_scope, t, scope->transactions)
+                if (t->probing && DNS_TRANSACTION_IS_LIVE(t->state))
+                        return 0;
+
+        /* Check if there're services pending conflict resolution. */
+        if (manager_next_dnssd_names(scope->manager))
+                return 0; /* we reach this point only if changing hostname didn't help */
+
+        /* Calculate answer's size. */
+        HASHMAP_FOREACH(z, scope->zone.by_key) {
+                if (z->state != DNS_ZONE_ITEM_ESTABLISHED)
+                        continue;
+
+                if (z->rr->key->type == DNS_TYPE_PTR &&
+                    !dns_zone_contains_name(&scope->zone, z->rr->ptr.name)) {
+                        char key_str[DNS_RESOURCE_KEY_STRING_MAX];
+
+                        log_debug("Skip PTR RR <%s> since its counterparts seem to be withdrawn", dns_resource_key_to_string(z->rr->key, key_str, sizeof key_str));
+                        z->state = DNS_ZONE_ITEM_WITHDRAWN;
+                        continue;
+                }
+
+                /* Collect service types for _services._dns-sd._udp.local RRs in a set */
+                if (!scope->announced &&
+                    dns_resource_key_is_dnssd_ptr(z->rr->key)) {
+                        if (!set_contains(types, dns_resource_key_name(z->rr->key))) {
+                                r = set_ensure_put(&types, &dns_name_hash_ops, dns_resource_key_name(z->rr->key));
+                                if (r < 0)
+                                        return log_debug_errno(r, "Failed to add item to set: %m");
+                        }
+                }
+
+                LIST_FOREACH(by_key, i, z)
+                        size++;
+        }
+
+        answer = dns_answer_new(size + set_size(types));
+        if (!answer)
+                return log_oom();
+
+        /* Second iteration, actually add RRs to the answer. */
+        HASHMAP_FOREACH(z, scope->zone.by_key)
+                LIST_FOREACH (by_key, i, z) {
+                        DnsAnswerFlags flags;
+
+                        if (i->state != DNS_ZONE_ITEM_ESTABLISHED)
+                                continue;
+
+                        if (dns_resource_key_is_dnssd_ptr(i->rr->key))
+                                flags = goodbye ? DNS_ANSWER_GOODBYE : 0;
+                        else
+                                flags = goodbye ? (DNS_ANSWER_GOODBYE|DNS_ANSWER_CACHE_FLUSH) : DNS_ANSWER_CACHE_FLUSH;
+
+                        r = dns_answer_add(answer, i->rr, 0, flags, NULL);
+                        if (r < 0)
+                                return log_debug_errno(r, "Failed to add RR to announce: %m");
+                }
+
+        /* Since all the active services are in the zone make them discoverable now. */
+        SET_FOREACH(service_type, types) {
+                _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL;
+
+                rr = dns_resource_record_new_full(DNS_CLASS_IN, DNS_TYPE_PTR,
+                                                  "_services._dns-sd._udp.local");
+                if (!rr)
+                        return log_oom();
+
+                rr->ptr.name = strdup(service_type);
+                if (!rr->ptr.name)
+                        return log_oom();
+
+                rr->ttl = MDNS_DEFAULT_TTL;
+
+                r = dns_zone_put(&scope->zone, scope, rr, false);
+                if (r < 0)
+                        log_warning_errno(r, "Failed to add DNS-SD PTR record to MDNS zone, ignoring: %m");
+
+                r = dns_answer_add(answer, rr, 0, 0, NULL);
+                if (r < 0)
+                        return log_debug_errno(r, "Failed to add RR to announce: %m");
+        }
+
+        if (dns_answer_isempty(answer))
+                return 0;
+
+        r = dns_scope_make_reply_packet(scope, 0, DNS_RCODE_SUCCESS, NULL, answer, NULL, false, &p);
+        if (r < 0)
+                return log_debug_errno(r, "Failed to build reply packet: %m");
+
+        r = dns_scope_emit_udp(scope, -1, AF_UNSPEC, p);
+        if (r < 0)
+                return log_debug_errno(r, "Failed to send reply packet: %m");
+
+        /* In section 8.3 of RFC6762: "The Multicast DNS responder MUST send at least two unsolicited
+         * responses, one second apart." */
+        if (!scope->announced) {
+                scope->announced = true;
+
+                r = sd_event_add_time_relative(
+                                scope->manager->event,
+                                &scope->announce_event_source,
+                                CLOCK_BOOTTIME,
+                                MDNS_ANNOUNCE_DELAY,
+                                0,
+                                on_announcement_timeout, scope);
+                if (r < 0)
+                        return log_debug_errno(r, "Failed to schedule second announcement: %m");
+
+                (void) sd_event_source_set_description(scope->announce_event_source, "mdns-announce");
+        }
+
+        return 0;
+}
+
+int dns_scope_add_dnssd_services(DnsScope *scope) {
+        DnssdService *service;
+        int r;
+
+        assert(scope);
+
+        if (hashmap_size(scope->manager->dnssd_services) == 0)
+                return 0;
+
+        scope->announced = false;
+
+        HASHMAP_FOREACH(service, scope->manager->dnssd_services) {
+                service->withdrawn = false;
+
+                r = dns_zone_put(&scope->zone, scope, service->ptr_rr, false);
+                if (r < 0)
+                        log_warning_errno(r, "Failed to add PTR record to MDNS zone: %m");
+
+                r = dns_zone_put(&scope->zone, scope, service->srv_rr, true);
+                if (r < 0)
+                        log_warning_errno(r, "Failed to add SRV record to MDNS zone: %m");
+
+                LIST_FOREACH(items, txt_data, service->txt_data_items) {
+                        r = dns_zone_put(&scope->zone, scope, txt_data->rr, true);
+                        if (r < 0)
+                                log_warning_errno(r, "Failed to add TXT record to MDNS zone: %m");
+                }
+        }
+
+        return 0;
+}
+
+int dns_scope_remove_dnssd_services(DnsScope *scope) {
+        _cleanup_(dns_resource_key_unrefp) DnsResourceKey *key = NULL;
+        DnssdService *service;
+        int r;
+
+        assert(scope);
+
+        key = dns_resource_key_new(DNS_CLASS_IN, DNS_TYPE_PTR,
+                                   "_services._dns-sd._udp.local");
+        if (!key)
+                return log_oom();
+
+        r = dns_zone_remove_rrs_by_key(&scope->zone, key);
+        if (r < 0)
+                return r;
+
+        HASHMAP_FOREACH(service, scope->manager->dnssd_services) {
+                dns_zone_remove_rr(&scope->zone, service->ptr_rr);
+                dns_zone_remove_rr(&scope->zone, service->srv_rr);
+                LIST_FOREACH(items, txt_data, service->txt_data_items)
+                        dns_zone_remove_rr(&scope->zone, txt_data->rr);
+        }
+
+        return 0;
+}
+
+static bool dns_scope_has_route_only_domains(DnsScope *scope) {
+        DnsSearchDomain *first;
+        bool route_only = false;
+
+        assert(scope);
+        assert(scope->protocol == DNS_PROTOCOL_DNS);
+
+        /* Returns 'true' if this scope is suitable for queries to specific domains only. For that we check
+         * if there are any route-only domains on this interface, as a heuristic to discern VPN-style links
+         * from non-VPN-style links. Returns 'false' for all other cases, i.e. if the scope is intended to
+         * take queries to arbitrary domains, i.e. has no routing domains set. */
+
+        if (scope->link)
+                first = scope->link->search_domains;
+        else
+                first = scope->manager->search_domains;
+
+        LIST_FOREACH(domains, domain, first) {
+                /* "." means "any domain", thus the interface takes any kind of traffic. Thus, we exit early
+                 * here, as it doesn't really matter whether this link has any route-only domains or not,
+                 * "~."  really trumps everything and clearly indicates that this interface shall receive all
+                 * traffic it can get. */
+                if (dns_name_is_root(DNS_SEARCH_DOMAIN_NAME(domain)))
+                        return false;
+
+                if (domain->route_only)
+                        route_only = true;
+        }
+
+        return route_only;
+}
+
+bool dns_scope_is_default_route(DnsScope *scope) {
+        assert(scope);
+
+        /* Only use DNS scopes as default routes */
+        if (scope->protocol != DNS_PROTOCOL_DNS)
+                return false;
+
+        /* The global DNS scope is always suitable as default route */
+        if (!scope->link)
+                return true;
+
+        /* Honour whatever is explicitly configured. This is really the best approach, and trumps any
+         * automatic logic. */
+        if (scope->link->default_route >= 0)
+                return scope->link->default_route;
+
+        /* Otherwise check if we have any route-only domains, as a sensible heuristic: if so, let's not
+         * volunteer as default route. */
+        return !dns_scope_has_route_only_domains(scope);
+}
+
+int dns_scope_dump_cache_to_json(DnsScope *scope, JsonVariant **ret) {
+        _cleanup_(json_variant_unrefp) JsonVariant *cache = NULL;
+        int r;
+
+        assert(scope);
+        assert(ret);
+
+        r = dns_cache_dump_to_json(&scope->cache, &cache);
+        if (r < 0)
+                return r;
+
+        return json_build(ret,
+                          JSON_BUILD_OBJECT(
+                                          JSON_BUILD_PAIR_STRING("protocol", dns_protocol_to_string(scope->protocol)),
+                                          JSON_BUILD_PAIR_CONDITION(scope->family != AF_UNSPEC, "family", JSON_BUILD_INTEGER(scope->family)),
+                                          JSON_BUILD_PAIR_CONDITION(scope->link, "ifindex", JSON_BUILD_INTEGER(scope->link ? scope->link->ifindex : 0)),
+                                          JSON_BUILD_PAIR_CONDITION(scope->link, "ifname", JSON_BUILD_STRING(scope->link ? scope->link->ifname : NULL)),
+                                          JSON_BUILD_PAIR_VARIANT("cache", cache)));
+}