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Systemd/src/resolve/resolved-dns-scope.c

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/* 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 "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 = (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_free(s->query_candidates);
hashmap_free(s->transactions_by_key);
ordered_hashmap_free_with_destructor(s->conflict_queue, dns_resource_record_unref);
sd_event_source_unref(s->conflict_event_source);
sd_event_source_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) {
assert(s);
if (s->protocol != DNS_PROTOCOL_DNS)
return;
if (s->link)
link_next_dns_server(s->link);
else
manager_next_dns_server(s->manager);
}
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, DnsPacket *p) {
union in_addr_union addr;
int ifindex = 0, r;
int family;
uint32_t mtu;
assert(s);
assert(p);
assert(p->protocol == s->protocol);
if (s->link) {
mtu = s->link->mtu;
ifindex = s->link->ifindex;
} else
mtu = manager_find_mtu(s->manager);
switch (s->protocol) {
case DNS_PROTOCOL_DNS:
assert(fd >= 0);
if (DNS_PACKET_QDCOUNT(p) > 1)
return -EOPNOTSUPP;
if (p->size > DNS_PACKET_UNICAST_SIZE_MAX)
return -EMSGSIZE;
if (p->size + UDP_PACKET_HEADER_SIZE > mtu)
return -EMSGSIZE;
r = manager_write(s->manager, fd, p);
if (r < 0)
return r;
break;
case DNS_PROTOCOL_LLMNR:
assert(fd < 0);
if (DNS_PACKET_QDCOUNT(p) > 1)
return -EOPNOTSUPP;
if (!ratelimit_below(&s->ratelimit))
return -EBUSY;
family = s->family;
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, ifindex, family, &addr, LLMNR_PORT, NULL, p);
if (r < 0)
return r;
break;
case DNS_PROTOCOL_MDNS:
assert(fd < 0);
if (!ratelimit_below(&s->ratelimit))
return -EBUSY;
family = s->family;
if (family == AF_INET) {
addr.in = MDNS_MULTICAST_IPV4_ADDRESS;
fd = manager_mdns_ipv4_fd(s->manager);
} else if (family == AF_INET6) {
addr.in6 = MDNS_MULTICAST_IPV6_ADDRESS;
fd = manager_mdns_ipv6_fd(s->manager);
} else
return -EAFNOSUPPORT;
if (fd < 0)
return fd;
r = manager_send(s->manager, fd, ifindex, family, &addr, MDNS_PORT, NULL, p);
if (r < 0)
return r;
break;
default:
return -EAFNOSUPPORT;
}
return 1;
}
int dns_scope_emit_udp(DnsScope *s, int fd, 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, 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 = -1;
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 (s->link) {
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;
}
if (ret_socket_address)
*ret_socket_address = sa;
else {
r = connect(fd, &sa.sa, salen);
if (r < 0 && errno != EINPROGRESS)
return -errno;
}
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 accept_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;
}
DnsScopeMatch dns_scope_good_domain(
DnsScope *s,
int ifindex,
uint64_t flags,
const char *domain) {
DnsSearchDomain *d;
/* 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(domain);
/* 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, 0) & 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 */
if (dns_name_endswith(domain, "0.in-addr.arpa") > 0 ||
dns_name_equal(domain, "255.255.255.255.in-addr.arpa") > 0 ||
dns_name_equal(domain, "0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa") > 0)
return DNS_SCOPE_NO;
/* Never respond to some of the domains listed in RFC6761 */
if (dns_name_endswith(domain, "invalid") > 0)
return DNS_SCOPE_NO;
switch (s->protocol) {
case DNS_PROTOCOL_DNS: {
bool has_search_domains = false;
int n_best = -1;
/* 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, prefereably. 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;
/* 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;
}
/* See if this scope is suitable as default route. */
if (!dns_scope_is_default_route(s))
return DNS_SCOPE_NO;
/* Exclude link-local IP ranges */
if (dns_name_endswith(domain, "254.169.in-addr.arpa") == 0 &&
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 &&
/* 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_MAYBE;
return DNS_SCOPE_NO;
}
case DNS_PROTOCOL_MDNS: {
DnsScopeMatch m;
m = accept_link_local_reverse_lookups(domain);
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 = accept_link_local_reverse_lookups(domain);
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 */
!is_gateway_hostname(domain) && /* don't resolve "gateway" with LLMNR, let nss-myhostname handle this */
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("Unknown scope protocol");
}
}
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 as fully qualified
* name, i.e. the search suffixes already appended. */
if (key->class != DNS_CLASS_IN)
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);
}
/* 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;
int r;
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;
DNS_PACKET_HEADER(p)->id = id;
DNS_PACKET_HEADER(p)->flags = htobe16(DNS_PACKET_MAKE_FLAGS(
1 /* qr */,
0 /* opcode */,
0 /* c */,
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);
if (r < 0)
return r;
DNS_PACKET_HEADER(p)->ancount = htobe16(dns_answer_size(answer));
r = dns_packet_append_answer(p, soa);
if (r < 0)
return r;
DNS_PACKET_HEADER(p)->arcount = htobe16(dns_answer_size(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 && !in_addr_equal(AF_INET, &p->destination, (union in_addr_union*) &LLMNR_MULTICAST_IPV4_ADDRESS))
return;
if (p->family == AF_INET6 && !in_addr_equal(AF_INET6, &p->destination, (union in_addr_union*) &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;
}
assert(dns_question_size(p->question) == 1);
key = p->question->keys[0];
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, bool cache_ok) {
DnsTransaction *t;
assert(scope);
assert(key);
/* Try to find an ongoing transaction that is a equal to the
* specified question */
t = hashmap_get(scope->transactions_by_key, key);
if (!t)
return NULL;
/* Refuse reusing transactions that completed based on cached
* data instead of a real packet, if that's requested. */
if (!cache_ok &&
IN_SET(t->state, DNS_TRANSACTION_SUCCESS, DNS_TRANSACTION_RCODE_FAILURE) &&
t->answer_source != DNS_TRANSACTION_NETWORK)
return NULL;
return t;
}
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 = userdata;
int r;
assert(es);
assert(scope);
scope->conflict_event_source = sd_event_source_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, 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) {
usec_t jitter;
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;
random_bytes(&jitter, sizeof(jitter));
jitter %= LLMNR_JITTER_INTERVAL_USEC;
r = sd_event_add_time_relative(
scope->manager->event,
&scope->conflict_event_source,
clock_boottime_or_monotonic(),
jitter,
LLMNR_JITTER_INTERVAL_USEC,
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_our_packet(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;
return dns_name_is_single_label(name);
}
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_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;
DnsTransaction *t;
DnsZoneItem *z, *i;
unsigned size = 0;
char *service_type;
int r;
if (!scope)
return 0;
if (scope->protocol != DNS_PROTOCOL_MDNS)
return 0;
/* Check if we're done with probing. */
LIST_FOREACH(transactions_by_scope, t, scope->transactions)
if (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);
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;
rr = dns_resource_record_new_full(DNS_CLASS_IN, DNS_TYPE_PTR,
"_services._dns-sd._udp.local");
rr->ptr.name = strdup(service_type);
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: %m");
r = dns_answer_add(answer, rr, 0 , 0);
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, 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_or_monotonic(),
MDNS_ANNOUNCE_DELAY,
MDNS_JITTER_RANGE_USEC,
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;
DnssdTxtData *txt_data;
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;
DnssdTxtData *txt_data;
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 *domain, *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);
}
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