static int on_llmnr_packet(sd_event_source *s, int fd, uint32_t revents, void *userdata) {
_cleanup_(dns_packet_unrefp) DnsPacket *p = NULL;
DnsTransaction *t = NULL;
Manager *m = userdata;
DnsScope *scope;
int r;
r = manager_recv(m, fd, DNS_PROTOCOL_LLMNR, &p);
if (r <= 0)
return r;
scope = manager_find_scope(m, p);
if (!scope) {
log_warning("Got LLMNR UDP packet on unknown scope. Ignoring.");
return 0;
}
if (dns_packet_validate_reply(p) > 0) {
log_debug("Got LLMNR reply packet for id %u", DNS_PACKET_ID(p));
dns_scope_check_conflicts(scope, p);
t = hashmap_get(m->dns_transactions, UINT_TO_PTR(DNS_PACKET_ID(p)));
if (t)
dns_transaction_process_reply(t, p);
} else if (dns_packet_validate_query(p) > 0) {
log_debug("Got LLMNR query packet for id %u", DNS_PACKET_ID(p));
dns_scope_process_query(scope, NULL, p);
} else
log_debug("Invalid LLMNR UDP packet.");
return 0;
}
static int on_dns_packet(sd_event_source *s, int fd, uint32_t revents, void *userdata) {
_cleanup_(dns_packet_unrefp) DnsPacket *p = NULL;
DnsTransaction *t = userdata;
int r;
assert(t);
assert(t->scope);
r = manager_recv(t->scope->manager, fd, DNS_PROTOCOL_DNS, &p);
if (r <= 0)
return r;
if (dns_packet_validate_reply(p) > 0 &&
DNS_PACKET_ID(p) == t->id)
dns_transaction_process_reply(t, p);
else
log_debug("Invalid DNS packet.");
return 0;
}
int manager_llmnr_ipv4_udp_fd(Manager *m) {
union sockaddr_union sa = {
.in.sin_family = AF_INET,
.in.sin_port = htobe16(LLMNR_PORT),
};
static const int one = 1, pmtu = IP_PMTUDISC_DONT, ttl = 255;
int r;
assert(m);
if (m->llmnr_ipv4_udp_fd >= 0)
return m->llmnr_ipv4_udp_fd;
m->llmnr_ipv4_udp_fd = socket(AF_INET, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
if (m->llmnr_ipv4_udp_fd < 0)
return -errno;
/* RFC 4795, section 2.5 recommends setting the TTL of UDP packets to 255. */
r = setsockopt(m->llmnr_ipv4_udp_fd, IPPROTO_IP, IP_TTL, &ttl, sizeof(ttl));
if (r < 0) {
r = -errno;
goto fail;
}
r = setsockopt(m->llmnr_ipv4_udp_fd, IPPROTO_IP, IP_MULTICAST_TTL, &ttl, sizeof(ttl));
if (r < 0) {
r = -errno;
goto fail;
}
r = setsockopt(m->llmnr_ipv4_udp_fd, IPPROTO_IP, IP_MULTICAST_LOOP, &one, sizeof(one));
if (r < 0) {
r = -errno;
goto fail;
}
r = setsockopt(m->llmnr_ipv4_udp_fd, SOL_SOCKET, SO_REUSEADDR, &one, sizeof(one));
if (r < 0) {
r = -errno;
goto fail;
}
r = setsockopt(m->llmnr_ipv4_udp_fd, IPPROTO_IP, IP_PKTINFO, &one, sizeof(one));
if (r < 0) {
r = -errno;
goto fail;
}
r = setsockopt(m->llmnr_ipv4_udp_fd, IPPROTO_IP, IP_RECVTTL, &one, sizeof(one));
if (r < 0) {
r = -errno;
goto fail;
}
/* Disable Don't-Fragment bit in the IP header */
r = setsockopt(m->llmnr_ipv4_udp_fd, IPPROTO_IP, IP_MTU_DISCOVER, &pmtu, sizeof(pmtu));
if (r < 0) {
r = -errno;
goto fail;
}
r = bind(m->llmnr_ipv4_udp_fd, &sa.sa, sizeof(sa.in));
if (r < 0) {
r = -errno;
goto fail;
}
r = sd_event_add_io(m->event, &m->llmnr_ipv4_udp_event_source, m->llmnr_ipv4_udp_fd, EPOLLIN, on_llmnr_packet, m);
if (r < 0)
goto fail;
return m->llmnr_ipv4_udp_fd;
fail:
m->llmnr_ipv4_udp_fd = safe_close(m->llmnr_ipv4_udp_fd);
return r;
}
int manager_llmnr_ipv6_udp_fd(Manager *m) {
union sockaddr_union sa = {
.in6.sin6_family = AF_INET6,
.in6.sin6_port = htobe16(LLMNR_PORT),
};
static const int one = 1, ttl = 255;
int r;
assert(m);
if (m->llmnr_ipv6_udp_fd >= 0)
return m->llmnr_ipv6_udp_fd;
m->llmnr_ipv6_udp_fd = socket(AF_INET6, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
if (m->llmnr_ipv6_udp_fd < 0)
return -errno;
r = setsockopt(m->llmnr_ipv6_udp_fd, IPPROTO_IPV6, IPV6_UNICAST_HOPS, &ttl, sizeof(ttl));
if (r < 0) {
r = -errno;
goto fail;
}
/* RFC 4795, section 2.5 recommends setting the TTL of UDP packets to 255. */
r = setsockopt(m->llmnr_ipv6_udp_fd, IPPROTO_IPV6, IPV6_MULTICAST_HOPS, &ttl, sizeof(ttl));
if (r < 0) {
r = -errno;
goto fail;
}
r = setsockopt(m->llmnr_ipv6_udp_fd, IPPROTO_IPV6, IPV6_MULTICAST_LOOP, &one, sizeof(one));
if (r < 0) {
r = -errno;
goto fail;
}
r = setsockopt(m->llmnr_ipv6_udp_fd, IPPROTO_IPV6, IPV6_V6ONLY, &one, sizeof(one));
if (r < 0) {
r = -errno;
goto fail;
}
r = setsockopt(m->llmnr_ipv6_udp_fd, SOL_SOCKET, SO_REUSEADDR, &one, sizeof(one));
if (r < 0) {
r = -errno;
goto fail;
}
r = setsockopt(m->llmnr_ipv6_udp_fd, IPPROTO_IPV6, IPV6_RECVPKTINFO, &one, sizeof(one));
if (r < 0) {
r = -errno;
goto fail;
}
r = setsockopt(m->llmnr_ipv6_udp_fd, IPPROTO_IPV6, IPV6_RECVHOPLIMIT, &one, sizeof(one));
if (r < 0) {
r = -errno;
goto fail;
}
r = bind(m->llmnr_ipv6_udp_fd, &sa.sa, sizeof(sa.in6));
if (r < 0) {
r = -errno;
goto fail;
}
r = sd_event_add_io(m->event, &m->llmnr_ipv6_udp_event_source, m->llmnr_ipv6_udp_fd, EPOLLIN, on_llmnr_packet, m);
if (r < 0) {
r = -errno;
goto fail;
}
return m->llmnr_ipv6_udp_fd;
fail:
m->llmnr_ipv6_udp_fd = safe_close(m->llmnr_ipv6_udp_fd);
return r;
}
static int on_llmnr_stream_packet(DnsStream *s) {
DnsScope *scope;
assert(s);
scope = manager_find_scope(s->manager, s->read_packet);
if (!scope) {
log_warning("Got LLMNR TCP packet on unknown scope. Ignroing.");
return 0;
}
if (dns_packet_validate_query(s->read_packet) > 0) {
log_debug("Got query packet for id %u", DNS_PACKET_ID(s->read_packet));
dns_scope_process_query(scope, s, s->read_packet);
/* If no reply packet was set, we free the stream */
if (s->write_packet)
return 0;
} else
log_debug("Invalid LLMNR TCP packet.");
dns_stream_free(s);
return 0;
}
static int on_llmnr_stream(sd_event_source *s, int fd, uint32_t revents, void *userdata) {
DnsStream *stream;
Manager *m = userdata;
int cfd, r;
cfd = accept4(fd, NULL, NULL, SOCK_NONBLOCK|SOCK_CLOEXEC);
if (cfd < 0) {
if (errno == EAGAIN || errno == EINTR)
return 0;
return -errno;
}
r = dns_stream_new(m, &stream, DNS_PROTOCOL_LLMNR, cfd);
if (r < 0) {
safe_close(cfd);
return r;
}
stream->on_packet = on_llmnr_stream_packet;
return 0;
}
void dns_transaction_process_reply(DnsTransaction *t, DnsPacket *p) {
usec_t ts;
int r;
assert(t);
assert(p);
assert(t->state == DNS_TRANSACTION_PENDING);
assert(t->scope);
assert(t->scope->manager);
/* Note that this call might invalidate the query. Callers
* should hence not attempt to access the query or transaction
* after calling this function. */
switch (t->scope->protocol) {
case DNS_PROTOCOL_LLMNR:
assert(t->scope->link);
/* For LLMNR we will not accept any packets from other
* interfaces */
if (p->ifindex != t->scope->link->ifindex)
return;
if (p->family != t->scope->family)
return;
/* Tentative packets are not full responses but still
* useful for identifying uniqueness conflicts during
* probing. */
if (DNS_PACKET_LLMNR_T(p)) {
dns_transaction_tentative(t, p);
return;
}
break;
case DNS_PROTOCOL_DNS:
break;
default:
assert_not_reached("Invalid DNS protocol.");
}
if (t->received != p) {
dns_packet_unref(t->received);
t->received = dns_packet_ref(p);
}
if (p->ipproto == IPPROTO_TCP) {
if (DNS_PACKET_TC(p)) {
/* Truncated via TCP? Somebody must be f*****g with us */
dns_transaction_complete(t, DNS_TRANSACTION_INVALID_REPLY);
return;
}
if (DNS_PACKET_ID(p) != t->id) {
/* Not the reply to our query? Somebody must be f*****g with us */
dns_transaction_complete(t, DNS_TRANSACTION_INVALID_REPLY);
return;
}
}
assert_se(sd_event_now(t->scope->manager->event, clock_boottime_or_monotonic(), &ts) >= 0);
switch (t->scope->protocol) {
case DNS_PROTOCOL_DNS:
assert(t->server);
dns_server_packet_received(t->server, ts - t->start_usec);
break;
case DNS_PROTOCOL_LLMNR:
case DNS_PROTOCOL_MDNS:
dns_scope_packet_received(t->scope, ts - t->start_usec);
break;
default:
break;
}
if (DNS_PACKET_TC(p)) {
/* Response was truncated, let's try again with good old TCP */
r = dns_transaction_open_tcp(t);
if (r == -ESRCH) {
/* No servers found? Damn! */
dns_transaction_complete(t, DNS_TRANSACTION_NO_SERVERS);
return;
}
if (r < 0) {
/* On LLMNR, if we cannot connect to the host,
* we immediately give up */
if (t->scope->protocol == DNS_PROTOCOL_LLMNR) {
dns_transaction_complete(t, DNS_TRANSACTION_RESOURCES);
return;
}
/* On DNS, couldn't send? Try immediately again, with a new server */
dns_transaction_next_dns_server(t);
r = dns_transaction_go(t);
if (r < 0) {
dns_transaction_complete(t, DNS_TRANSACTION_RESOURCES);
return;
}
return;
}
}
/* Parse and update the cache */
r = dns_packet_extract(p);
if (r < 0) {
dns_transaction_complete(t, DNS_TRANSACTION_INVALID_REPLY);
return;
}
/* Only consider responses with equivalent query section to the request */
if (p->question->n_keys != 1 || dns_resource_key_equal(p->question->keys[0], t->key) <= 0) {
dns_transaction_complete(t, DNS_TRANSACTION_INVALID_REPLY);
return;
}
/* According to RFC 4795, section 2.9. only the RRs from the answer section shall be cached */
dns_cache_put(&t->scope->cache, p->question, DNS_PACKET_RCODE(p), p->answer, DNS_PACKET_ANCOUNT(p), 0, p->family, &p->sender);
if (DNS_PACKET_RCODE(p) == DNS_RCODE_SUCCESS)
dns_transaction_complete(t, DNS_TRANSACTION_SUCCESS);
else
dns_transaction_complete(t, DNS_TRANSACTION_FAILURE);
}
