diff options
Diffstat (limited to 'src/resolve/resolved-dns-scope.c')
| -rw-r--r-- | src/resolve/resolved-dns-scope.c | 1683 |
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))); +} |