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systemd/src/resolve/resolved-dns-scope.c
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Yu Watanabe 0b565facc4 Revert "resolve: query the parent zone for DS records" 
This reverts commit 49ff90c70d.
2025-07-10 15:18:07 +02:00

1873 lines
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/* SPDX-License-Identifier: LGPL-2.1-or-later */
#include <netinet/tcp.h>
#include "sd-event.h"
#include "sd-json.h"
#include "af-list.h"
#include "alloc-util.h"
#include "dns-domain.h"
#include "dns-type.h"
#include "errno-util.h"
#include "fd-util.h"
#include "hostname-util.h"
#include "log.h"
#include "random-util.h"
#include "resolved-dns-answer.h"
#include "resolved-dns-delegate.h"
#include "resolved-dns-packet.h"
#include "resolved-dns-query.h"
#include "resolved-dns-question.h"
#include "resolved-dns-rr.h"
#include "resolved-dns-scope.h"
#include "resolved-dns-search-domain.h"
#include "resolved-dns-server.h"
#include "resolved-dns-synthesize.h"
#include "resolved-dns-transaction.h"
#include "resolved-dns-zone.h"
#include "resolved-dnssd.h"
#include "resolved-link.h"
#include "resolved-llmnr.h"
#include "resolved-manager.h"
#include "resolved-mdns.h"
#include "resolved-timeouts.h"
#include "set.h"
#include "socket-util.h"
#include "string-table.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,
DnsScopeOrigin origin,
Link *link,
DnsDelegate *delegate,
DnsProtocol protocol,
int family) {
DnsScope *s;
assert(m);
assert(ret);
assert(origin >= 0);
assert(origin < _DNS_SCOPE_ORIGIN_MAX);
assert(!!link == (origin == DNS_SCOPE_LINK));
assert(!!delegate == (origin == DNS_SCOPE_DELEGATE));
s = new(DnsScope, 1);
if (!s)
return -ENOMEM;
*s = (DnsScope) {
.manager = m,
.link = link,
.delegate = delegate,
.origin = origin,
.protocol = protocol,
.family = family,
.resend_timeout = MULTICAST_RESEND_TIMEOUT_MIN_USEC,
/* Enforce ratelimiting for the multicast protocols */
.ratelimit = { MULTICAST_RATELIMIT_INTERVAL_USEC, MULTICAST_RATELIMIT_BURST },
};
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 (link) {
s->dnssec_mode = link_get_dnssec_mode(link);
s->dns_over_tls_mode = link_get_dns_over_tls_mode(link);
} 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, origin %s, delegate %s",
link ? link->ifname : "*",
dns_protocol_to_string(protocol),
family == AF_UNSPEC ? "*" : af_to_name(family),
dns_scope_origin_to_string(origin),
s->delegate ? s->delegate->id : "n/a");
*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, origin %s, delegate %s",
s->link ? s->link->ifname : "*",
dns_protocol_to_string(s->protocol),
s->family == AF_UNSPEC ? "*" : af_to_name(s->family),
dns_scope_origin_to_string(s->origin),
s->delegate ? s->delegate->id : "n/a");
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(s->conflict_queue);
sd_event_source_disable_unref(s->conflict_event_source);
sd_event_source_disable_unref(s->announce_event_source);
sd_event_source_disable_unref(s->mdns_goodbye_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) {
assert(!s->delegate);
return link_get_dns_server(s->link);
} else if (s->delegate)
return dns_delegate_get_dns_server(s->delegate);
else
return manager_get_dns_server(s->manager);
}
unsigned dns_scope_get_n_dns_servers(DnsScope *s) {
assert(s);
if (s->protocol != DNS_PROTOCOL_DNS)
return 0;
if (s->link) {
assert(!s->delegate);
return s->link->n_dns_servers;
} else if (s->delegate)
return s->delegate->n_dns_servers;
else
return s->manager->n_dns_servers;
}
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 if (s->delegate)
dns_delegate_next_dns_server(s->delegate, 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;
assert(s->link);
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;
assert(s->link);
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 = dns_scope_ifindex(s);
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;
}
bool addr_is_nonlocal = 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;
if (addr_is_nonlocal && ifindex != 0) {
/* As a special exception we don't use UNICAST_IF if we notice that the specified IP address
* is on the local host. Otherwise, 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. */
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. Older kernels only take
* 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.
*/
if (addr_is_nonlocal) {
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;
}
/* https://www.iana.org/assignments/special-use-domain-names/special-use-domain-names.xhtml */
/* https://www.iana.org/assignments/locally-served-dns-zones/locally-served-dns-zones.xhtml */
static bool dns_refuse_special_use_domain(const char *domain, DnsQuestion *question) {
/* RFC9462 § 6.4: resolvers SHOULD respond to queries of any type other than SVCB for
* _dns.resolver.arpa. with NODATA and queries of any type for any domain name under
* resolver.arpa with NODATA. */
if (dns_name_equal(domain, "_dns.resolver.arpa") > 0) {
DnsResourceKey *t;
/* Only SVCB is permitted to _dns.resolver.arpa */
DNS_QUESTION_FOREACH(t, question)
if (t->type == DNS_TYPE_SVCB)
return false;
return true;
}
if (dns_name_endswith(domain, "resolver.arpa") > 0)
return true;
return false;
}
DnsScopeMatch dns_scope_good_domain(
DnsScope *s,
DnsQuery *q,
uint64_t query_flags) {
DnsQuestion *question;
const char *domain;
uint64_t flags;
int ifindex, r;
/* This returns the following return values:
*
* DNS_SCOPE_NO → This scope is not suitable for lookups of this domain, at all
* DNS_SCOPE_LAST_RESORT→ This scope is not suitable, unless we have no alternative
* 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;
/* Avoid asking invalid questions of some special use domains */
if (dns_refuse_special_use_domain(domain, question))
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;
/* Don't look up the local host name via the network, unless user turned of local synthesis of it */
if (manager_is_own_hostname(s->manager, domain) && shall_synthesize_own_hostname_rrs())
return DNS_SCOPE_NO;
/* Never send SOA or NS or DNSSEC request to LLMNR, where they make little sense. */
r = dns_question_types_suitable_for_protocol(question, s->protocol);
if (r <= 0)
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 || (query_flags & SD_RESOLVED_RELAX_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;
/* Prefer suitable per-link scopes where possible */
if (dns_server_is_fallback(dns_scope_get_dns_server(s)))
return DNS_SCOPE_LAST_RESORT;
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_LAST_RESORT;
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_LAST_RESORT;
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_ifindex = 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;
rr = ordered_hashmap_steal_first_key_and_value(scope->conflict_queue, (void**) &key);
if (!rr)
break;
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. 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_ensure_put(&scope->conflict_queue, &dns_resource_record_hash_ops_by_key, 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(" origin=", f);
fputs(dns_scope_origin_to_string(s->origin), f);
if (s->delegate) {
fputs(" id=", f);
fputs(s->delegate->id, 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;
if (s->delegate)
return s->delegate->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;
}
const char* dns_scope_ifname(DnsScope *s) {
assert(s);
if (s->link)
return s->link->ifname;
return NULL;
}
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. Only two-label names
* (not selective names) are considered according to RFC6763 § 9. */
if (!scope->announced &&
dns_resource_key_is_dnssd_two_label_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_isempty(scope->manager->dnssd_services))
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");
if (service->sub_ptr_rr) {
r = dns_zone_put(&scope->zone, scope, service->sub_ptr_rr, false);
if (r < 0)
log_warning_errno(r, "Failed to add selective 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->sub_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 if (scope->delegate)
first = scope->delegate->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;
if (scope->link) {
/* 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);
} else if (scope->delegate) {
if (scope->delegate->default_route >= 0)
return scope->delegate->default_route;
/* Delegates are by default not used as default route */
return false;
} else
/* The global DNS scope is always suitable as default route */
return true;
}
int dns_scope_dump_cache_to_json(DnsScope *scope, sd_json_variant **ret) {
_cleanup_(sd_json_variant_unrefp) sd_json_variant *cache = NULL;
int r;
assert(scope);
assert(ret);
r = dns_cache_dump_to_json(&scope->cache, &cache);
if (r < 0)
return r;
return sd_json_buildo(
ret,
SD_JSON_BUILD_PAIR_STRING("protocol", dns_protocol_to_string(scope->protocol)),
SD_JSON_BUILD_PAIR_CONDITION(scope->family != AF_UNSPEC, "family", SD_JSON_BUILD_INTEGER(scope->family)),
SD_JSON_BUILD_PAIR_CONDITION(!!scope->link, "ifindex", SD_JSON_BUILD_INTEGER(dns_scope_ifindex(scope))),
SD_JSON_BUILD_PAIR_CONDITION(!!scope->link, "ifname", SD_JSON_BUILD_STRING(dns_scope_ifname(scope))),
SD_JSON_BUILD_PAIR_VARIANT("cache", cache));
}
int dns_type_suitable_for_protocol(uint16_t type, DnsProtocol protocol) {
/* Tests whether it makes sense to route queries for the specified DNS RR types to the specified
* protocol. For classic DNS pretty much all RR types are suitable, but for LLMNR/mDNS let's
* allowlist only a few that make sense. We use this when routing queries so that we can more quickly
* return errors for queries that will almost certainly fail/time out otherwise. For example, this
* ensures that SOA, NS, or DS/DNSKEY queries are never routed to mDNS/LLMNR where they simply make
* no sense. */
if (dns_type_is_obsolete(type))
return false;
if (!dns_type_is_valid_query(type))
return false;
switch (protocol) {
case DNS_PROTOCOL_DNS:
return true;
case DNS_PROTOCOL_LLMNR:
return IN_SET(type,
DNS_TYPE_ANY,
DNS_TYPE_A,
DNS_TYPE_AAAA,
DNS_TYPE_CNAME,
DNS_TYPE_PTR,
DNS_TYPE_TXT);
case DNS_PROTOCOL_MDNS:
return IN_SET(type,
DNS_TYPE_ANY,
DNS_TYPE_A,
DNS_TYPE_AAAA,
DNS_TYPE_CNAME,
DNS_TYPE_PTR,
DNS_TYPE_TXT,
DNS_TYPE_SRV,
DNS_TYPE_NSEC,
DNS_TYPE_HINFO);
default:
return -EPROTONOSUPPORT;
}
}
int dns_question_types_suitable_for_protocol(DnsQuestion *q, DnsProtocol protocol) {
DnsResourceKey *key;
int r;
/* Tests whether the types in the specified question make any sense to be routed to the specified
* protocol, i.e. if dns_type_suitable_for_protocol() is true for any of the contained RR types */
DNS_QUESTION_FOREACH(key, q) {
r = dns_type_suitable_for_protocol(key->type, protocol);
if (r != 0)
return r;
}
return false;
}
static const char* const dns_scope_origin_table[_DNS_SCOPE_ORIGIN_MAX] = {
[DNS_SCOPE_GLOBAL] = "global",
[DNS_SCOPE_LINK] = "link",
[DNS_SCOPE_DELEGATE] = "delegate",
};
DEFINE_STRING_TABLE_LOOKUP(dns_scope_origin, DnsScopeOrigin);
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