diff options
Diffstat (limited to 'src/resolve/resolved-llmnr.c')
| -rw-r--r-- | src/resolve/resolved-llmnr.c | 471 |
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); +} |