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-rw-r--r--src/resolve/resolved-llmnr.c471
1 files changed, 471 insertions, 0 deletions
diff --git a/src/resolve/resolved-llmnr.c b/src/resolve/resolved-llmnr.c
new file mode 100644
index 0000000..9f5a0b5
--- /dev/null
+++ b/src/resolve/resolved-llmnr.c
@@ -0,0 +1,471 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <netinet/in.h>
+#include <netinet/tcp.h>
+#include <resolv.h>
+
+#include "errno-util.h"
+#include "fd-util.h"
+#include "resolved-llmnr.h"
+#include "resolved-manager.h"
+
+void manager_llmnr_stop(Manager *m) {
+ assert(m);
+
+ m->llmnr_ipv4_udp_event_source = sd_event_source_disable_unref(m->llmnr_ipv4_udp_event_source);
+ m->llmnr_ipv4_udp_fd = safe_close(m->llmnr_ipv4_udp_fd);
+
+ m->llmnr_ipv6_udp_event_source = sd_event_source_disable_unref(m->llmnr_ipv6_udp_event_source);
+ m->llmnr_ipv6_udp_fd = safe_close(m->llmnr_ipv6_udp_fd);
+
+ m->llmnr_ipv4_tcp_event_source = sd_event_source_disable_unref(m->llmnr_ipv4_tcp_event_source);
+ m->llmnr_ipv4_tcp_fd = safe_close(m->llmnr_ipv4_tcp_fd);
+
+ m->llmnr_ipv6_tcp_event_source = sd_event_source_disable_unref(m->llmnr_ipv6_tcp_event_source);
+ m->llmnr_ipv6_tcp_fd = safe_close(m->llmnr_ipv6_tcp_fd);
+}
+
+int manager_llmnr_start(Manager *m) {
+ int r;
+
+ assert(m);
+
+ if (m->llmnr_support == RESOLVE_SUPPORT_NO)
+ return 0;
+
+ r = manager_llmnr_ipv4_udp_fd(m);
+ if (r == -EADDRINUSE)
+ goto eaddrinuse;
+ if (r < 0)
+ return r;
+
+ r = manager_llmnr_ipv4_tcp_fd(m);
+ if (r == -EADDRINUSE)
+ goto eaddrinuse;
+ if (r < 0)
+ return r;
+
+ if (socket_ipv6_is_enabled()) {
+ r = manager_llmnr_ipv6_udp_fd(m);
+ if (r == -EADDRINUSE)
+ goto eaddrinuse;
+ if (r < 0)
+ return r;
+
+ r = manager_llmnr_ipv6_tcp_fd(m);
+ if (r == -EADDRINUSE)
+ goto eaddrinuse;
+ if (r < 0)
+ return r;
+ }
+
+ return 0;
+
+eaddrinuse:
+ log_warning("Another LLMNR responder prohibits binding the socket to the same port. Turning off LLMNR support.");
+ m->llmnr_support = RESOLVE_SUPPORT_NO;
+ manager_llmnr_stop(m);
+
+ return 0;
+}
+
+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 = ASSERT_PTR(userdata);
+ DnsScope *scope;
+ int r;
+
+ assert(s);
+ assert(fd >= 0);
+
+ r = manager_recv(m, fd, DNS_PROTOCOL_LLMNR, &p);
+ if (r <= 0)
+ return r;
+
+ if (manager_packet_from_local_address(m, p))
+ return 0;
+
+ scope = manager_find_scope(m, p);
+ if (!scope) {
+ log_debug("Got LLMNR UDP packet on unknown scope. Ignoring.");
+ return 0;
+ }
+
+ if (dns_packet_validate_reply(p) > 0) {
+ log_debug("Got LLMNR UDP 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, false);
+
+ } else if (dns_packet_validate_query(p) > 0) {
+ log_debug("Got LLMNR UDP query packet for id %u", DNS_PACKET_ID(p));
+
+ dns_scope_process_query(scope, NULL, p);
+ } else
+ log_debug("Invalid LLMNR UDP packet, ignoring.");
+
+ return 0;
+}
+
+static int set_llmnr_common_socket_options(int fd, int family) {
+ int r;
+
+ r = socket_set_recvpktinfo(fd, family, true);
+ if (r < 0)
+ return r;
+
+ r = socket_set_recvttl(fd, family, true);
+ if (r < 0)
+ return r;
+
+ return 0;
+}
+
+static int set_llmnr_common_udp_socket_options(int fd, int family) {
+ int r;
+
+ /* RFC 4795, section 2.5 recommends setting the TTL of UDP packets to 255. */
+ r = socket_set_ttl(fd, family, 255);
+ if (r < 0)
+ return r;
+
+ 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),
+ };
+ _cleanup_close_ int s = -1;
+ int r;
+
+ assert(m);
+
+ if (m->llmnr_ipv4_udp_fd >= 0)
+ return m->llmnr_ipv4_udp_fd;
+
+ s = socket(AF_INET, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
+ if (s < 0)
+ return log_error_errno(errno, "LLMNR-IPv4(UDP): Failed to create socket: %m");
+
+ r = set_llmnr_common_socket_options(s, AF_INET);
+ if (r < 0)
+ return log_error_errno(r, "LLMNR-IPv4(UDP): Failed to set common socket options: %m");
+
+ r = set_llmnr_common_udp_socket_options(s, AF_INET);
+ if (r < 0)
+ return log_error_errno(r, "LLMNR-IPv4(UDP): Failed to set common UDP socket options: %m");
+
+ r = setsockopt_int(s, IPPROTO_IP, IP_MULTICAST_TTL, 255);
+ if (r < 0)
+ return log_error_errno(r, "LLMNR-IPv4(UDP): Failed to set IP_MULTICAST_TTL: %m");
+
+ r = setsockopt_int(s, IPPROTO_IP, IP_MULTICAST_LOOP, true);
+ if (r < 0)
+ return log_error_errno(r, "LLMNR-IPv4(UDP): Failed to set IP_MULTICAST_LOOP: %m");
+
+ /* Disable Don't-Fragment bit in the IP header */
+ r = setsockopt_int(s, IPPROTO_IP, IP_MTU_DISCOVER, IP_PMTUDISC_DONT);
+ if (r < 0)
+ return log_error_errno(r, "LLMNR-IPv4(UDP): Failed to set IP_MTU_DISCOVER: %m");
+
+ /* first try to bind without SO_REUSEADDR to detect another LLMNR responder */
+ r = bind(s, &sa.sa, sizeof(sa.in));
+ if (r < 0) {
+ if (errno != EADDRINUSE)
+ return log_error_errno(errno, "LLMNR-IPv4(UDP): Failed to bind socket: %m");
+
+ log_warning("LLMNR-IPv4(UDP): There appears to be another LLMNR responder running, or previously systemd-resolved crashed with some outstanding transfers.");
+
+ /* try again with SO_REUSEADDR */
+ r = setsockopt_int(s, SOL_SOCKET, SO_REUSEADDR, true);
+ if (r < 0)
+ return log_error_errno(r, "LLMNR-IPv4(UDP): Failed to set SO_REUSEADDR: %m");
+
+ r = bind(s, &sa.sa, sizeof(sa.in));
+ if (r < 0)
+ return log_error_errno(errno, "LLMNR-IPv4(UDP): Failed to bind socket: %m");
+ } else {
+ /* enable SO_REUSEADDR for the case that the user really wants multiple LLMNR responders */
+ r = setsockopt_int(s, SOL_SOCKET, SO_REUSEADDR, true);
+ if (r < 0)
+ return log_error_errno(r, "LLMNR-IPv4(UDP): Failed to set SO_REUSEADDR: %m");
+ }
+
+ r = sd_event_add_io(m->event, &m->llmnr_ipv4_udp_event_source, s, EPOLLIN, on_llmnr_packet, m);
+ if (r < 0)
+ return log_error_errno(r, "LLMNR-IPv4(UDP): Failed to create event source: %m");
+
+ (void) sd_event_source_set_description(m->llmnr_ipv4_udp_event_source, "llmnr-ipv4-udp");
+
+ return m->llmnr_ipv4_udp_fd = TAKE_FD(s);
+}
+
+int manager_llmnr_ipv6_udp_fd(Manager *m) {
+ union sockaddr_union sa = {
+ .in6.sin6_family = AF_INET6,
+ .in6.sin6_port = htobe16(LLMNR_PORT),
+ };
+ _cleanup_close_ int s = -1;
+ int r;
+
+ assert(m);
+
+ if (m->llmnr_ipv6_udp_fd >= 0)
+ return m->llmnr_ipv6_udp_fd;
+
+ s = socket(AF_INET6, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
+ if (s < 0)
+ return log_error_errno(errno, "LLMNR-IPv6(UDP): Failed to create socket: %m");
+
+ r = set_llmnr_common_socket_options(s, AF_INET6);
+ if (r < 0)
+ return log_error_errno(r, "LLMNR-IPv6(UDP): Failed to set common socket options: %m");
+
+ r = set_llmnr_common_udp_socket_options(s, AF_INET6);
+ if (r < 0)
+ return log_error_errno(r, "LLMNR-IPv6(UDP): Failed to set common UDP socket options: %m");
+
+ /* RFC 4795, section 2.5 recommends setting the TTL of UDP packets to 255. */
+ r = setsockopt_int(s, IPPROTO_IPV6, IPV6_MULTICAST_HOPS, 255);
+ if (r < 0)
+ return log_error_errno(r, "LLMNR-IPv6(UDP): Failed to set IPV6_MULTICAST_HOPS: %m");
+
+ r = setsockopt_int(s, IPPROTO_IPV6, IPV6_MULTICAST_LOOP, true);
+ if (r < 0)
+ return log_error_errno(r, "LLMNR-IPv6(UDP): Failed to set IPV6_MULTICAST_LOOP: %m");
+
+ r = setsockopt_int(s, IPPROTO_IPV6, IPV6_V6ONLY, true);
+ if (r < 0)
+ return log_error_errno(r, "LLMNR-IPv6(UDP): Failed to set IPV6_V6ONLY: %m");
+
+ /* first try to bind without SO_REUSEADDR to detect another LLMNR responder */
+ r = bind(s, &sa.sa, sizeof(sa.in6));
+ if (r < 0) {
+ if (errno != EADDRINUSE)
+ return log_error_errno(errno, "LLMNR-IPv6(UDP): Failed to bind socket: %m");
+
+ log_warning("LLMNR-IPv6(UDP): There appears to be another LLMNR responder running, or previously systemd-resolved crashed with some outstanding transfers.");
+
+ /* try again with SO_REUSEADDR */
+ r = setsockopt_int(s, SOL_SOCKET, SO_REUSEADDR, true);
+ if (r < 0)
+ return log_error_errno(r, "LLMNR-IPv6(UDP): Failed to set SO_REUSEADDR: %m");
+
+ r = bind(s, &sa.sa, sizeof(sa.in6));
+ if (r < 0)
+ return log_error_errno(errno, "LLMNR-IPv6(UDP): Failed to bind socket: %m");
+ } else {
+ /* enable SO_REUSEADDR for the case that the user really wants multiple LLMNR responders */
+ r = setsockopt_int(s, SOL_SOCKET, SO_REUSEADDR, true);
+ if (r < 0)
+ return log_error_errno(r, "LLMNR-IPv6(UDP): Failed to set SO_REUSEADDR: %m");
+ }
+
+ r = sd_event_add_io(m->event, &m->llmnr_ipv6_udp_event_source, s, EPOLLIN, on_llmnr_packet, m);
+ if (r < 0)
+ return log_error_errno(r, "LLMNR-IPv6(UDP): Failed to create event source: %m");
+
+ (void) sd_event_source_set_description(m->llmnr_ipv6_udp_event_source, "llmnr-ipv6-udp");
+
+ return m->llmnr_ipv6_udp_fd = TAKE_FD(s);
+}
+
+static int on_llmnr_stream_packet(DnsStream *s, DnsPacket *p) {
+ DnsScope *scope;
+
+ assert(s);
+ assert(s->manager);
+ assert(p);
+
+ scope = manager_find_scope(s->manager, p);
+ if (!scope)
+ log_debug("Got LLMNR TCP packet on unknown scope. Ignoring.");
+ else if (dns_packet_validate_query(p) > 0) {
+ log_debug("Got LLMNR TCP query packet for id %u", DNS_PACKET_ID(p));
+
+ dns_scope_process_query(scope, s, p);
+ } else
+ log_debug("Invalid LLMNR TCP packet, ignoring.");
+
+ 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_IS_ACCEPT_AGAIN(errno))
+ return 0;
+
+ return -errno;
+ }
+
+ /* We don't configure a "complete" handler here, we rely on the default handler, thus freeing it */
+ r = dns_stream_new(m, &stream, DNS_STREAM_LLMNR_RECV, DNS_PROTOCOL_LLMNR, cfd, NULL,
+ on_llmnr_stream_packet, NULL, DNS_STREAM_DEFAULT_TIMEOUT_USEC);
+ if (r < 0) {
+ safe_close(cfd);
+ return r;
+ }
+
+ return 0;
+}
+
+static int set_llmnr_common_tcp_socket_options(int fd, int family) {
+ int r;
+
+ /* RFC 4795, section 2.5. requires setting the TTL of TCP streams to 1 */
+ r = socket_set_ttl(fd, family, 1);
+ if (r < 0)
+ return r;
+
+ r = setsockopt_int(fd, IPPROTO_TCP, TCP_FASTOPEN, 5); /* Everybody appears to pick qlen=5, let's do the same here. */
+ if (r < 0)
+ log_debug_errno(r, "Failed to enable TCP_FASTOPEN on TCP listening socket, ignoring: %m");
+
+ r = setsockopt_int(fd, IPPROTO_TCP, TCP_NODELAY, true);
+ if (r < 0)
+ log_debug_errno(r, "Failed to enable TCP_NODELAY mode, ignoring: %m");
+
+ return 0;
+}
+
+int manager_llmnr_ipv4_tcp_fd(Manager *m) {
+ union sockaddr_union sa = {
+ .in.sin_family = AF_INET,
+ .in.sin_port = htobe16(LLMNR_PORT),
+ };
+ _cleanup_close_ int s = -1;
+ int r;
+
+ assert(m);
+
+ if (m->llmnr_ipv4_tcp_fd >= 0)
+ return m->llmnr_ipv4_tcp_fd;
+
+ s = socket(AF_INET, SOCK_STREAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
+ if (s < 0)
+ return log_error_errno(errno, "LLMNR-IPv4(TCP): Failed to create socket: %m");
+
+ r = set_llmnr_common_socket_options(s, AF_INET);
+ if (r < 0)
+ return log_error_errno(r, "LLMNR-IPv4(TCP): Failed to set common socket options: %m");
+
+ r = set_llmnr_common_tcp_socket_options(s, AF_INET);
+ if (r < 0)
+ return log_error_errno(r, "LLMNR-IPv4(TCP): Failed to set common TCP socket options: %m");
+
+ /* Disable Don't-Fragment bit in the IP header */
+ r = setsockopt_int(s, IPPROTO_IP, IP_MTU_DISCOVER, IP_PMTUDISC_DONT);
+ if (r < 0)
+ return log_error_errno(r, "LLMNR-IPv4(TCP): Failed to set IP_MTU_DISCOVER: %m");
+
+ /* first try to bind without SO_REUSEADDR to detect another LLMNR responder */
+ r = bind(s, &sa.sa, sizeof(sa.in));
+ if (r < 0) {
+ if (errno != EADDRINUSE)
+ return log_error_errno(errno, "LLMNR-IPv4(TCP): Failed to bind socket: %m");
+
+ log_warning("LLMNR-IPv4(TCP): There appears to be another LLMNR responder running, or previously systemd-resolved crashed with some outstanding transfers.");
+
+ /* try again with SO_REUSEADDR */
+ r = setsockopt_int(s, SOL_SOCKET, SO_REUSEADDR, true);
+ if (r < 0)
+ return log_error_errno(r, "LLMNR-IPv4(TCP): Failed to set SO_REUSEADDR: %m");
+
+ r = bind(s, &sa.sa, sizeof(sa.in));
+ if (r < 0)
+ return log_error_errno(errno, "LLMNR-IPv4(TCP): Failed to bind socket: %m");
+ } else {
+ /* enable SO_REUSEADDR for the case that the user really wants multiple LLMNR responders */
+ r = setsockopt_int(s, SOL_SOCKET, SO_REUSEADDR, true);
+ if (r < 0)
+ return log_error_errno(r, "LLMNR-IPv4(TCP): Failed to set SO_REUSEADDR: %m");
+ }
+
+ r = listen(s, SOMAXCONN_DELUXE);
+ if (r < 0)
+ return log_error_errno(errno, "LLMNR-IPv4(TCP): Failed to listen the stream: %m");
+
+ r = sd_event_add_io(m->event, &m->llmnr_ipv4_tcp_event_source, s, EPOLLIN, on_llmnr_stream, m);
+ if (r < 0)
+ return log_error_errno(r, "LLMNR-IPv4(TCP): Failed to create event source: %m");
+
+ (void) sd_event_source_set_description(m->llmnr_ipv4_tcp_event_source, "llmnr-ipv4-tcp");
+
+ return m->llmnr_ipv4_tcp_fd = TAKE_FD(s);
+}
+
+int manager_llmnr_ipv6_tcp_fd(Manager *m) {
+ union sockaddr_union sa = {
+ .in6.sin6_family = AF_INET6,
+ .in6.sin6_port = htobe16(LLMNR_PORT),
+ };
+ _cleanup_close_ int s = -1;
+ int r;
+
+ assert(m);
+
+ if (m->llmnr_ipv6_tcp_fd >= 0)
+ return m->llmnr_ipv6_tcp_fd;
+
+ s = socket(AF_INET6, SOCK_STREAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
+ if (s < 0)
+ return log_error_errno(errno, "LLMNR-IPv6(TCP): Failed to create socket: %m");
+
+ r = setsockopt_int(s, IPPROTO_IPV6, IPV6_V6ONLY, true);
+ if (r < 0)
+ return log_error_errno(r, "LLMNR-IPv6(TCP): Failed to set IPV6_V6ONLY: %m");
+
+ r = set_llmnr_common_socket_options(s, AF_INET6);
+ if (r < 0)
+ return log_error_errno(r, "LLMNR-IPv6(TCP): Failed to set common socket options: %m");
+
+ r = set_llmnr_common_tcp_socket_options(s, AF_INET6);
+ if (r < 0)
+ return log_error_errno(r, "LLMNR-IPv6(TCP): Failed to set common TCP socket options: %m");
+
+ /* first try to bind without SO_REUSEADDR to detect another LLMNR responder */
+ r = bind(s, &sa.sa, sizeof(sa.in6));
+ if (r < 0) {
+ if (errno != EADDRINUSE)
+ return log_error_errno(errno, "LLMNR-IPv6(TCP): Failed to bind socket: %m");
+
+ log_warning("LLMNR-IPv6(TCP): There appears to be another LLMNR responder running, or previously systemd-resolved crashed with some outstanding transfers.");
+
+ /* try again with SO_REUSEADDR */
+ r = setsockopt_int(s, SOL_SOCKET, SO_REUSEADDR, true);
+ if (r < 0)
+ return log_error_errno(r, "LLMNR-IPv6(TCP): Failed to set SO_REUSEADDR: %m");
+
+ r = bind(s, &sa.sa, sizeof(sa.in6));
+ if (r < 0)
+ return log_error_errno(errno, "LLMNR-IPv6(TCP): Failed to bind socket: %m");
+ } else {
+ /* enable SO_REUSEADDR for the case that the user really wants multiple LLMNR responders */
+ r = setsockopt_int(s, SOL_SOCKET, SO_REUSEADDR, true);
+ if (r < 0)
+ return log_error_errno(r, "LLMNR-IPv6(TCP): Failed to set SO_REUSEADDR: %m");
+ }
+
+ r = listen(s, SOMAXCONN_DELUXE);
+ if (r < 0)
+ return log_error_errno(errno, "LLMNR-IPv6(TCP): Failed to listen the stream: %m");
+
+ r = sd_event_add_io(m->event, &m->llmnr_ipv6_tcp_event_source, s, EPOLLIN, on_llmnr_stream, m);
+ if (r < 0)
+ return log_error_errno(r, "LLMNR-IPv6(TCP): Failed to create event source: %m");
+
+ (void) sd_event_source_set_description(m->llmnr_ipv6_tcp_event_source, "llmnr-ipv6-tcp");
+
+ return m->llmnr_ipv6_tcp_fd = TAKE_FD(s);
+}