/* SPDX-License-Identifier: LGPL-2.1-or-later */ #include #include #include #include #include #include #include #include "af-list.h" #include "alloc-util.h" #include "bus-polkit.h" #include "dirent-util.h" #include "dns-domain.h" #include "event-util.h" #include "fd-util.h" #include "fileio.h" #include "hostname-util.h" #include "idn-util.h" #include "io-util.h" #include "missing_network.h" #include "missing_socket.h" #include "netlink-util.h" #include "ordered-set.h" #include "parse-util.h" #include "random-util.h" #include "resolved-bus.h" #include "resolved-conf.h" #include "resolved-dns-stub.h" #include "resolved-dnssd.h" #include "resolved-etc-hosts.h" #include "resolved-llmnr.h" #include "resolved-manager.h" #include "resolved-mdns.h" #include "resolved-resolv-conf.h" #include "resolved-util.h" #include "resolved-varlink.h" #include "socket-util.h" #include "string-table.h" #include "string-util.h" #include "utf8.h" #define SEND_TIMEOUT_USEC (200 * USEC_PER_MSEC) static int manager_process_link(sd_netlink *rtnl, sd_netlink_message *mm, void *userdata) { Manager *m = userdata; uint16_t type; Link *l; int ifindex, r; assert(rtnl); assert(m); assert(mm); r = sd_netlink_message_get_type(mm, &type); if (r < 0) goto fail; r = sd_rtnl_message_link_get_ifindex(mm, &ifindex); if (r < 0) goto fail; l = hashmap_get(m->links, INT_TO_PTR(ifindex)); switch (type) { case RTM_NEWLINK:{ bool is_new = !l; if (!l) { r = link_new(m, &l, ifindex); if (r < 0) goto fail; } r = link_process_rtnl(l, mm); if (r < 0) goto fail; r = link_update(l); if (r < 0) goto fail; if (is_new) log_debug("Found new link %i/%s", ifindex, l->ifname); break; } case RTM_DELLINK: if (l) { log_debug("Removing link %i/%s", l->ifindex, l->ifname); link_remove_user(l); link_free(l); } break; } return 0; fail: log_warning_errno(r, "Failed to process RTNL link message: %m"); return 0; } static int manager_process_address(sd_netlink *rtnl, sd_netlink_message *mm, void *userdata) { Manager *m = userdata; union in_addr_union address; uint16_t type; int r, ifindex, family; LinkAddress *a; Link *l; assert(rtnl); assert(mm); assert(m); r = sd_netlink_message_get_type(mm, &type); if (r < 0) goto fail; r = sd_rtnl_message_addr_get_ifindex(mm, &ifindex); if (r < 0) goto fail; l = hashmap_get(m->links, INT_TO_PTR(ifindex)); if (!l) return 0; r = sd_rtnl_message_addr_get_family(mm, &family); if (r < 0) goto fail; switch (family) { case AF_INET: r = sd_netlink_message_read_in_addr(mm, IFA_LOCAL, &address.in); if (r < 0) { r = sd_netlink_message_read_in_addr(mm, IFA_ADDRESS, &address.in); if (r < 0) goto fail; } break; case AF_INET6: r = sd_netlink_message_read_in6_addr(mm, IFA_LOCAL, &address.in6); if (r < 0) { r = sd_netlink_message_read_in6_addr(mm, IFA_ADDRESS, &address.in6); if (r < 0) goto fail; } break; default: return 0; } a = link_find_address(l, family, &address); switch (type) { case RTM_NEWADDR: if (!a) { r = link_address_new(l, &a, family, &address); if (r < 0) return r; } r = link_address_update_rtnl(a, mm); if (r < 0) return r; break; case RTM_DELADDR: link_address_free(a); break; } return 0; fail: log_warning_errno(r, "Failed to process RTNL address message: %m"); return 0; } static int manager_rtnl_listen(Manager *m) { _cleanup_(sd_netlink_message_unrefp) sd_netlink_message *req = NULL, *reply = NULL; sd_netlink_message *i; int r; assert(m); /* First, subscribe to interfaces coming and going */ r = sd_netlink_open(&m->rtnl); if (r < 0) return r; r = sd_netlink_attach_event(m->rtnl, m->event, SD_EVENT_PRIORITY_IMPORTANT); if (r < 0) return r; r = sd_netlink_add_match(m->rtnl, NULL, RTM_NEWLINK, manager_process_link, NULL, m, "resolve-NEWLINK"); if (r < 0) return r; r = sd_netlink_add_match(m->rtnl, NULL, RTM_DELLINK, manager_process_link, NULL, m, "resolve-DELLINK"); if (r < 0) return r; r = sd_netlink_add_match(m->rtnl, NULL, RTM_NEWADDR, manager_process_address, NULL, m, "resolve-NEWADDR"); if (r < 0) return r; r = sd_netlink_add_match(m->rtnl, NULL, RTM_DELADDR, manager_process_address, NULL, m, "resolve-DELADDR"); if (r < 0) return r; /* Then, enumerate all links */ r = sd_rtnl_message_new_link(m->rtnl, &req, RTM_GETLINK, 0); if (r < 0) return r; r = sd_netlink_message_request_dump(req, true); if (r < 0) return r; r = sd_netlink_call(m->rtnl, req, 0, &reply); if (r < 0) return r; for (i = reply; i; i = sd_netlink_message_next(i)) { r = manager_process_link(m->rtnl, i, m); if (r < 0) return r; } req = sd_netlink_message_unref(req); reply = sd_netlink_message_unref(reply); /* Finally, enumerate all addresses, too */ r = sd_rtnl_message_new_addr(m->rtnl, &req, RTM_GETADDR, 0, AF_UNSPEC); if (r < 0) return r; r = sd_netlink_message_request_dump(req, true); if (r < 0) return r; r = sd_netlink_call(m->rtnl, req, 0, &reply); if (r < 0) return r; for (i = reply; i; i = sd_netlink_message_next(i)) { r = manager_process_address(m->rtnl, i, m); if (r < 0) return r; } return r; } static int on_network_event(sd_event_source *s, int fd, uint32_t revents, void *userdata) { Manager *m = userdata; Link *l; int r; assert(m); sd_network_monitor_flush(m->network_monitor); HASHMAP_FOREACH(l, m->links) { r = link_update(l); if (r < 0) log_warning_errno(r, "Failed to update monitor information for %i: %m", l->ifindex); } (void) manager_write_resolv_conf(m); (void) manager_send_changed(m, "DNS"); return 0; } static int manager_network_monitor_listen(Manager *m) { int r, fd, events; assert(m); r = sd_network_monitor_new(&m->network_monitor, NULL); if (r < 0) return r; fd = sd_network_monitor_get_fd(m->network_monitor); if (fd < 0) return fd; events = sd_network_monitor_get_events(m->network_monitor); if (events < 0) return events; r = sd_event_add_io(m->event, &m->network_event_source, fd, events, &on_network_event, m); if (r < 0) return r; r = sd_event_source_set_priority(m->network_event_source, SD_EVENT_PRIORITY_IMPORTANT+5); if (r < 0) return r; (void) sd_event_source_set_description(m->network_event_source, "network-monitor"); return 0; } static int manager_clock_change_listen(Manager *m); static int on_clock_change(sd_event_source *source, int fd, uint32_t revents, void *userdata) { Manager *m = userdata; assert(m); /* The clock has changed, let's flush all caches. Why that? That's because DNSSEC validation takes * the system clock into consideration, and if the clock changes the old validations might have been * wrong. Let's redo all validation with the new, correct time. * * (Also, this is triggered after system suspend, which is also a good reason to drop caches, since * we might be connected to a different network now without this being visible in a dropped link * carrier or so.) */ log_info("Clock change detected. Flushing caches."); manager_flush_caches(m, LOG_DEBUG /* downgrade the functions own log message, since we already logged here at LOG_INFO level */); /* The clock change timerfd is unusable after it triggered once, create a new one. */ return manager_clock_change_listen(m); } static int manager_clock_change_listen(Manager *m) { int r; assert(m); m->clock_change_event_source = sd_event_source_disable_unref(m->clock_change_event_source); r = event_add_time_change(m->event, &m->clock_change_event_source, on_clock_change, m); if (r < 0) return log_error_errno(r, "Failed to create clock change event source: %m"); return 0; } static int determine_hostnames(char **full_hostname, char **llmnr_hostname, char **mdns_hostname) { _cleanup_free_ char *h = NULL, *n = NULL; int r; assert(full_hostname); assert(llmnr_hostname); assert(mdns_hostname); r = resolve_system_hostname(&h, &n); if (r < 0) return r; r = dns_name_concat(n, "local", 0, mdns_hostname); if (r < 0) return log_error_errno(r, "Failed to determine mDNS hostname: %m"); *llmnr_hostname = TAKE_PTR(n); *full_hostname = TAKE_PTR(h); return 0; } static char* fallback_hostname(void) { /* Determine the fall back hostname. For exposing this system to the outside world, we cannot have it * to be "localhost" even if that's the default hostname. In this case, let's revert to "linux" * instead. */ _cleanup_free_ char *n = get_default_hostname(); if (!n) return NULL; if (is_localhost(n)) return strdup("linux"); return TAKE_PTR(n); } static int make_fallback_hostnames(char **full_hostname, char **llmnr_hostname, char **mdns_hostname) { _cleanup_free_ char *h = NULL, *n = NULL, *m = NULL; char label[DNS_LABEL_MAX]; const char *p; int r; assert(full_hostname); assert(llmnr_hostname); assert(mdns_hostname); p = h = fallback_hostname(); if (!h) return log_oom(); r = dns_label_unescape(&p, label, sizeof label, 0); if (r < 0) return log_error_errno(r, "Failed to unescape fallback hostname: %m"); assert(r > 0); /* The fallback hostname must have at least one label */ r = dns_label_escape_new(label, r, &n); if (r < 0) return log_error_errno(r, "Failed to escape fallback hostname: %m"); r = dns_name_concat(n, "local", 0, &m); if (r < 0) return log_error_errno(r, "Failed to concatenate mDNS hostname: %m"); *llmnr_hostname = TAKE_PTR(n); *mdns_hostname = TAKE_PTR(m); *full_hostname = TAKE_PTR(h); return 0; } static int on_hostname_change(sd_event_source *es, int fd, uint32_t revents, void *userdata) { _cleanup_free_ char *full_hostname = NULL, *llmnr_hostname = NULL, *mdns_hostname = NULL; Manager *m = userdata; bool llmnr_hostname_changed; int r; assert(m); r = determine_hostnames(&full_hostname, &llmnr_hostname, &mdns_hostname); if (r < 0) { log_warning_errno(r, "Failed to determine the local hostname and LLMNR/mDNS names, ignoring: %m"); return 0; /* ignore invalid hostnames */ } llmnr_hostname_changed = !streq(llmnr_hostname, m->llmnr_hostname); if (streq(full_hostname, m->full_hostname) && !llmnr_hostname_changed && streq(mdns_hostname, m->mdns_hostname)) return 0; log_info("System hostname changed to '%s'.", full_hostname); free_and_replace(m->full_hostname, full_hostname); free_and_replace(m->llmnr_hostname, llmnr_hostname); free_and_replace(m->mdns_hostname, mdns_hostname); manager_refresh_rrs(m); (void) manager_send_changed(m, "LLMNRHostname"); return 0; } static int manager_watch_hostname(Manager *m) { int r; assert(m); m->hostname_fd = open("/proc/sys/kernel/hostname", O_RDONLY|O_CLOEXEC|O_NONBLOCK|O_NOCTTY); if (m->hostname_fd < 0) { log_warning_errno(errno, "Failed to watch hostname: %m"); return 0; } r = sd_event_add_io(m->event, &m->hostname_event_source, m->hostname_fd, 0, on_hostname_change, m); if (r < 0) { if (r == -EPERM) /* kernels prior to 3.2 don't support polling this file. Ignore the failure. */ m->hostname_fd = safe_close(m->hostname_fd); else return log_error_errno(r, "Failed to add hostname event source: %m"); } (void) sd_event_source_set_description(m->hostname_event_source, "hostname"); r = determine_hostnames(&m->full_hostname, &m->llmnr_hostname, &m->mdns_hostname); if (r < 0) { _cleanup_free_ char *d = NULL; d = fallback_hostname(); if (!d) return log_oom(); log_info("Defaulting to hostname '%s'.", d); r = make_fallback_hostnames(&m->full_hostname, &m->llmnr_hostname, &m->mdns_hostname); if (r < 0) return r; } else log_info("Using system hostname '%s'.", m->full_hostname); return 0; } static int manager_sigusr1(sd_event_source *s, const struct signalfd_siginfo *si, void *userdata) { _cleanup_free_ char *buffer = NULL; _cleanup_fclose_ FILE *f = NULL; Manager *m = userdata; size_t size = 0; Link *l; assert(s); assert(si); assert(m); f = open_memstream_unlocked(&buffer, &size); if (!f) return log_oom(); LIST_FOREACH(scopes, scope, m->dns_scopes) dns_scope_dump(scope, f); LIST_FOREACH(servers, server, m->dns_servers) dns_server_dump(server, f); LIST_FOREACH(servers, server, m->fallback_dns_servers) dns_server_dump(server, f); HASHMAP_FOREACH(l, m->links) LIST_FOREACH(servers, server, l->dns_servers) dns_server_dump(server, f); if (fflush_and_check(f) < 0) return log_oom(); log_dump(LOG_INFO, buffer); return 0; } static int manager_sigusr2(sd_event_source *s, const struct signalfd_siginfo *si, void *userdata) { Manager *m = userdata; assert(s); assert(si); assert(m); manager_flush_caches(m, LOG_INFO); return 0; } static int manager_sigrtmin1(sd_event_source *s, const struct signalfd_siginfo *si, void *userdata) { Manager *m = userdata; assert(s); assert(si); assert(m); manager_reset_server_features(m); return 0; } int manager_new(Manager **ret) { _cleanup_(manager_freep) Manager *m = NULL; int r; assert(ret); m = new(Manager, 1); if (!m) return -ENOMEM; *m = (Manager) { .llmnr_ipv4_udp_fd = -1, .llmnr_ipv6_udp_fd = -1, .llmnr_ipv4_tcp_fd = -1, .llmnr_ipv6_tcp_fd = -1, .mdns_ipv4_fd = -1, .mdns_ipv6_fd = -1, .hostname_fd = -1, .llmnr_support = DEFAULT_LLMNR_MODE, .mdns_support = DEFAULT_MDNS_MODE, .dnssec_mode = DEFAULT_DNSSEC_MODE, .dns_over_tls_mode = DEFAULT_DNS_OVER_TLS_MODE, .enable_cache = DNS_CACHE_MODE_YES, .dns_stub_listener_mode = DNS_STUB_LISTENER_YES, .read_resolv_conf = true, .need_builtin_fallbacks = true, .etc_hosts_last = USEC_INFINITY, .read_etc_hosts = true, }; r = dns_trust_anchor_load(&m->trust_anchor); if (r < 0) return r; r = manager_parse_config_file(m); if (r < 0) log_warning_errno(r, "Failed to parse configuration file: %m"); #if ENABLE_DNS_OVER_TLS r = dnstls_manager_init(m); if (r < 0) return r; #endif r = sd_event_default(&m->event); if (r < 0) return r; (void) sd_event_add_signal(m->event, NULL, SIGTERM, NULL, NULL); (void) sd_event_add_signal(m->event, NULL, SIGINT, NULL, NULL); (void) sd_event_set_watchdog(m->event, true); r = manager_watch_hostname(m); if (r < 0) return r; r = dnssd_load(m); if (r < 0) log_warning_errno(r, "Failed to load DNS-SD configuration files: %m"); r = dns_scope_new(m, &m->unicast_scope, NULL, DNS_PROTOCOL_DNS, AF_UNSPEC); if (r < 0) return r; r = manager_network_monitor_listen(m); if (r < 0) return r; r = manager_rtnl_listen(m); if (r < 0) return r; r = manager_clock_change_listen(m); if (r < 0) return r; r = manager_connect_bus(m); if (r < 0) return r; (void) sd_event_add_signal(m->event, &m->sigusr1_event_source, SIGUSR1, manager_sigusr1, m); (void) sd_event_add_signal(m->event, &m->sigusr2_event_source, SIGUSR2, manager_sigusr2, m); (void) sd_event_add_signal(m->event, &m->sigrtmin1_event_source, SIGRTMIN+1, manager_sigrtmin1, m); manager_cleanup_saved_user(m); *ret = TAKE_PTR(m); return 0; } int manager_start(Manager *m) { int r; assert(m); r = manager_dns_stub_start(m); if (r < 0) return r; r = manager_varlink_init(m); if (r < 0) return r; return 0; } Manager *manager_free(Manager *m) { Link *l; DnssdService *s; if (!m) return NULL; dns_server_unlink_all(m->dns_servers); dns_server_unlink_all(m->fallback_dns_servers); dns_search_domain_unlink_all(m->search_domains); while ((l = hashmap_first(m->links))) link_free(l); while (m->dns_queries) dns_query_free(m->dns_queries); m->stub_queries_by_packet = hashmap_free(m->stub_queries_by_packet); dns_scope_free(m->unicast_scope); /* At this point only orphaned streams should remain. All others should have been freed already by their * owners */ while (m->dns_streams) dns_stream_unref(m->dns_streams); #if ENABLE_DNS_OVER_TLS dnstls_manager_free(m); #endif hashmap_free(m->links); hashmap_free(m->dns_transactions); sd_event_source_unref(m->network_event_source); sd_network_monitor_unref(m->network_monitor); sd_netlink_unref(m->rtnl); sd_event_source_unref(m->rtnl_event_source); sd_event_source_unref(m->clock_change_event_source); manager_llmnr_stop(m); manager_mdns_stop(m); manager_dns_stub_stop(m); manager_varlink_done(m); manager_socket_graveyard_clear(m); ordered_set_free(m->dns_extra_stub_listeners); bus_verify_polkit_async_registry_free(m->polkit_registry); sd_bus_flush_close_unref(m->bus); sd_event_source_unref(m->sigusr1_event_source); sd_event_source_unref(m->sigusr2_event_source); sd_event_source_unref(m->sigrtmin1_event_source); dns_resource_key_unref(m->llmnr_host_ipv4_key); dns_resource_key_unref(m->llmnr_host_ipv6_key); dns_resource_key_unref(m->mdns_host_ipv4_key); dns_resource_key_unref(m->mdns_host_ipv6_key); sd_event_source_unref(m->hostname_event_source); safe_close(m->hostname_fd); sd_event_unref(m->event); free(m->full_hostname); free(m->llmnr_hostname); free(m->mdns_hostname); while ((s = hashmap_first(m->dnssd_services))) dnssd_service_free(s); hashmap_free(m->dnssd_services); dns_trust_anchor_flush(&m->trust_anchor); manager_etc_hosts_flush(m); return mfree(m); } int manager_recv(Manager *m, int fd, DnsProtocol protocol, DnsPacket **ret) { _cleanup_(dns_packet_unrefp) DnsPacket *p = NULL; CMSG_BUFFER_TYPE(CMSG_SPACE(MAXSIZE(struct in_pktinfo, struct in6_pktinfo)) + CMSG_SPACE(int) /* ttl/hoplimit */ + EXTRA_CMSG_SPACE /* kernel appears to require extra buffer space */) control; union sockaddr_union sa; struct iovec iov; struct msghdr mh = { .msg_name = &sa.sa, .msg_namelen = sizeof(sa), .msg_iov = &iov, .msg_iovlen = 1, .msg_control = &control, .msg_controllen = sizeof(control), }; struct cmsghdr *cmsg; ssize_t ms, l; int r; assert(m); assert(fd >= 0); assert(ret); ms = next_datagram_size_fd(fd); if (ms < 0) return ms; r = dns_packet_new(&p, protocol, ms, DNS_PACKET_SIZE_MAX); if (r < 0) return r; iov = IOVEC_MAKE(DNS_PACKET_DATA(p), p->allocated); l = recvmsg_safe(fd, &mh, 0); if (l < 0) { if (ERRNO_IS_TRANSIENT(l)) return 0; return l; } if (l == 0) return 0; assert(!(mh.msg_flags & MSG_TRUNC)); p->size = (size_t) l; p->family = sa.sa.sa_family; p->ipproto = IPPROTO_UDP; if (p->family == AF_INET) { p->sender.in = sa.in.sin_addr; p->sender_port = be16toh(sa.in.sin_port); } else if (p->family == AF_INET6) { p->sender.in6 = sa.in6.sin6_addr; p->sender_port = be16toh(sa.in6.sin6_port); p->ifindex = sa.in6.sin6_scope_id; } else return -EAFNOSUPPORT; p->timestamp = now(CLOCK_BOOTTIME); CMSG_FOREACH(cmsg, &mh) { if (cmsg->cmsg_level == IPPROTO_IPV6) { assert(p->family == AF_INET6); switch (cmsg->cmsg_type) { case IPV6_PKTINFO: { struct in6_pktinfo *i = (struct in6_pktinfo*) CMSG_DATA(cmsg); if (p->ifindex <= 0) p->ifindex = i->ipi6_ifindex; p->destination.in6 = i->ipi6_addr; break; } case IPV6_HOPLIMIT: p->ttl = *(int *) CMSG_DATA(cmsg); break; case IPV6_RECVFRAGSIZE: p->fragsize = *(int *) CMSG_DATA(cmsg); break; } } else if (cmsg->cmsg_level == IPPROTO_IP) { assert(p->family == AF_INET); switch (cmsg->cmsg_type) { case IP_PKTINFO: { struct in_pktinfo *i = (struct in_pktinfo*) CMSG_DATA(cmsg); if (p->ifindex <= 0) p->ifindex = i->ipi_ifindex; p->destination.in = i->ipi_addr; break; } case IP_TTL: p->ttl = *(int *) CMSG_DATA(cmsg); break; case IP_RECVFRAGSIZE: p->fragsize = *(int *) CMSG_DATA(cmsg); break; } } } /* The Linux kernel sets the interface index to the loopback * device if the packet came from the local host since it * avoids the routing table in such a case. Let's unset the * interface index in such a case. */ if (p->ifindex == LOOPBACK_IFINDEX) p->ifindex = 0; if (protocol != DNS_PROTOCOL_DNS) { /* If we don't know the interface index still, we look for the * first local interface with a matching address. Yuck! */ if (p->ifindex <= 0) p->ifindex = manager_find_ifindex(m, p->family, &p->destination); } if (DEBUG_LOGGING) { _cleanup_free_ char *sender_address = NULL, *destination_address = NULL; (void) in_addr_to_string(p->family, &p->sender, &sender_address); (void) in_addr_to_string(p->family, &p->destination, &destination_address); log_debug("Received %s UDP packet of size %zu, ifindex=%i, ttl=%i, fragsize=%zu, sender=%s, destination=%s", dns_protocol_to_string(protocol), p->size, p->ifindex, p->ttl, p->fragsize, strna(sender_address), strna(destination_address)); } *ret = TAKE_PTR(p); return 1; } static int sendmsg_loop(int fd, struct msghdr *mh, int flags) { int r; assert(fd >= 0); assert(mh); for (;;) { if (sendmsg(fd, mh, flags) >= 0) return 0; if (errno == EINTR) continue; if (errno != EAGAIN) return -errno; r = fd_wait_for_event(fd, POLLOUT, SEND_TIMEOUT_USEC); if (r < 0) return r; if (r == 0) return -ETIMEDOUT; } } static int write_loop(int fd, void *message, size_t length) { int r; assert(fd >= 0); assert(message); for (;;) { if (write(fd, message, length) >= 0) return 0; if (errno == EINTR) continue; if (errno != EAGAIN) return -errno; r = fd_wait_for_event(fd, POLLOUT, SEND_TIMEOUT_USEC); if (r < 0) return r; if (r == 0) return -ETIMEDOUT; } } int manager_write(Manager *m, int fd, DnsPacket *p) { int r; log_debug("Sending %s%s packet with id %" PRIu16 " of size %zu.", DNS_PACKET_TC(p) ? "truncated (!) " : "", DNS_PACKET_QR(p) ? "response" : "query", DNS_PACKET_ID(p), p->size); r = write_loop(fd, DNS_PACKET_DATA(p), p->size); if (r < 0) return r; return 0; } static int manager_ipv4_send( Manager *m, int fd, int ifindex, const struct in_addr *destination, uint16_t port, const struct in_addr *source, DnsPacket *p) { CMSG_BUFFER_TYPE(CMSG_SPACE(sizeof(struct in_pktinfo))) control = {}; union sockaddr_union sa; struct iovec iov; struct msghdr mh = { .msg_iov = &iov, .msg_iovlen = 1, .msg_name = &sa.sa, .msg_namelen = sizeof(sa.in), }; assert(m); assert(fd >= 0); assert(destination); assert(port > 0); assert(p); iov = IOVEC_MAKE(DNS_PACKET_DATA(p), p->size); sa = (union sockaddr_union) { .in.sin_family = AF_INET, .in.sin_addr = *destination, .in.sin_port = htobe16(port), }; if (ifindex > 0) { struct cmsghdr *cmsg; struct in_pktinfo *pi; mh.msg_control = &control; mh.msg_controllen = sizeof(control); cmsg = CMSG_FIRSTHDR(&mh); cmsg->cmsg_len = CMSG_LEN(sizeof(struct in_pktinfo)); cmsg->cmsg_level = IPPROTO_IP; cmsg->cmsg_type = IP_PKTINFO; pi = (struct in_pktinfo*) CMSG_DATA(cmsg); pi->ipi_ifindex = ifindex; if (source) pi->ipi_spec_dst = *source; } return sendmsg_loop(fd, &mh, 0); } static int manager_ipv6_send( Manager *m, int fd, int ifindex, const struct in6_addr *destination, uint16_t port, const struct in6_addr *source, DnsPacket *p) { CMSG_BUFFER_TYPE(CMSG_SPACE(sizeof(struct in6_pktinfo))) control = {}; union sockaddr_union sa; struct iovec iov; struct msghdr mh = { .msg_iov = &iov, .msg_iovlen = 1, .msg_name = &sa.sa, .msg_namelen = sizeof(sa.in6), }; assert(m); assert(fd >= 0); assert(destination); assert(port > 0); assert(p); iov = IOVEC_MAKE(DNS_PACKET_DATA(p), p->size); sa = (union sockaddr_union) { .in6.sin6_family = AF_INET6, .in6.sin6_addr = *destination, .in6.sin6_port = htobe16(port), .in6.sin6_scope_id = ifindex, }; if (ifindex > 0) { struct cmsghdr *cmsg; struct in6_pktinfo *pi; mh.msg_control = &control; mh.msg_controllen = sizeof(control); cmsg = CMSG_FIRSTHDR(&mh); cmsg->cmsg_len = CMSG_LEN(sizeof(struct in6_pktinfo)); cmsg->cmsg_level = IPPROTO_IPV6; cmsg->cmsg_type = IPV6_PKTINFO; pi = (struct in6_pktinfo*) CMSG_DATA(cmsg); pi->ipi6_ifindex = ifindex; if (source) pi->ipi6_addr = *source; } return sendmsg_loop(fd, &mh, 0); } int manager_send( Manager *m, int fd, int ifindex, int family, const union in_addr_union *destination, uint16_t port, const union in_addr_union *source, DnsPacket *p) { assert(m); assert(fd >= 0); assert(destination); assert(port > 0); assert(p); log_debug("Sending %s%s packet with id %" PRIu16 " on interface %i/%s of size %zu.", DNS_PACKET_TC(p) ? "truncated (!) " : "", DNS_PACKET_QR(p) ? "response" : "query", DNS_PACKET_ID(p), ifindex, af_to_name(family), p->size); if (family == AF_INET) return manager_ipv4_send(m, fd, ifindex, &destination->in, port, source ? &source->in : NULL, p); if (family == AF_INET6) return manager_ipv6_send(m, fd, ifindex, &destination->in6, port, source ? &source->in6 : NULL, p); return -EAFNOSUPPORT; } uint32_t manager_find_mtu(Manager *m) { uint32_t mtu = 0; Link *l; /* If we don't know on which link a DNS packet would be delivered, let's find the largest MTU that * works on all interfaces we know of that have an IP address associated */ HASHMAP_FOREACH(l, m->links) { /* Let's filter out links without IP addresses (e.g. AF_CAN links and suchlike) */ if (!l->addresses) continue; /* Safety check: MTU shorter than what we need for the absolutely shortest DNS request? Then * let's ignore this link. */ if (l->mtu < MIN(UDP4_PACKET_HEADER_SIZE + DNS_PACKET_HEADER_SIZE, UDP6_PACKET_HEADER_SIZE + DNS_PACKET_HEADER_SIZE)) continue; if (mtu <= 0 || l->mtu < mtu) mtu = l->mtu; } if (mtu == 0) /* found nothing? then let's assume the typical Ethernet MTU for lack of anything more precise */ return 1500; return mtu; } int manager_find_ifindex(Manager *m, int family, const union in_addr_union *in_addr) { LinkAddress *a; assert(m); if (!IN_SET(family, AF_INET, AF_INET6)) return 0; if (!in_addr) return 0; a = manager_find_link_address(m, family, in_addr); if (a) return a->link->ifindex; return 0; } void manager_refresh_rrs(Manager *m) { Link *l; DnssdService *s; assert(m); m->llmnr_host_ipv4_key = dns_resource_key_unref(m->llmnr_host_ipv4_key); m->llmnr_host_ipv6_key = dns_resource_key_unref(m->llmnr_host_ipv6_key); m->mdns_host_ipv4_key = dns_resource_key_unref(m->mdns_host_ipv4_key); m->mdns_host_ipv6_key = dns_resource_key_unref(m->mdns_host_ipv6_key); HASHMAP_FOREACH(l, m->links) link_add_rrs(l, true); if (m->mdns_support == RESOLVE_SUPPORT_YES) HASHMAP_FOREACH(s, m->dnssd_services) if (dnssd_update_rrs(s) < 0) log_warning("Failed to refresh DNS-SD service '%s'", s->name); HASHMAP_FOREACH(l, m->links) link_add_rrs(l, false); } static int manager_next_random_name(const char *old, char **ret_new) { const char *p; uint64_t u, a; char *n; p = strchr(old, 0); assert(p); while (p > old) { if (!strchr(DIGITS, p[-1])) break; p--; } if (*p == 0 || safe_atou64(p, &u) < 0 || u <= 0) u = 1; /* Add a random number to the old value. This way we can avoid * that two hosts pick the same hostname, win on IPv4 and lose * on IPv6 (or vice versa), and pick the same hostname * replacement hostname, ad infinitum. We still want the * numbers to go up monotonically, hence we just add a random * value 1..10 */ random_bytes(&a, sizeof(a)); u += 1 + a % 10; if (asprintf(&n, "%.*s%" PRIu64, (int) (p - old), old, u) < 0) return -ENOMEM; *ret_new = n; return 0; } int manager_next_hostname(Manager *m) { _cleanup_free_ char *h = NULL, *k = NULL; int r; assert(m); r = manager_next_random_name(m->llmnr_hostname, &h); if (r < 0) return r; r = dns_name_concat(h, "local", 0, &k); if (r < 0) return r; log_info("Hostname conflict, changing published hostname from '%s' to '%s'.", m->llmnr_hostname, h); free_and_replace(m->llmnr_hostname, h); free_and_replace(m->mdns_hostname, k); manager_refresh_rrs(m); (void) manager_send_changed(m, "LLMNRHostname"); return 0; } LinkAddress* manager_find_link_address(Manager *m, int family, const union in_addr_union *in_addr) { Link *l; assert(m); if (!IN_SET(family, AF_INET, AF_INET6)) return NULL; if (!in_addr) return NULL; HASHMAP_FOREACH(l, m->links) { LinkAddress *a; a = link_find_address(l, family, in_addr); if (a) return a; } return NULL; } bool manager_packet_from_local_address(Manager *m, DnsPacket *p) { assert(m); assert(p); /* Let's see if this packet comes from an IP address we have on any local interface */ return !!manager_find_link_address(m, p->family, &p->sender); } bool manager_packet_from_our_transaction(Manager *m, DnsPacket *p) { DnsTransaction *t; assert(m); assert(p); /* Let's see if we have a transaction with a query message with the exact same binary contents as the * one we just got. If so, it's almost definitely a packet loop of some kind. */ t = hashmap_get(m->dns_transactions, UINT_TO_PTR(DNS_PACKET_ID(p))); if (!t) return false; return t->sent && dns_packet_equal(t->sent, p); } DnsScope* manager_find_scope(Manager *m, DnsPacket *p) { Link *l; assert(m); assert(p); l = hashmap_get(m->links, INT_TO_PTR(p->ifindex)); if (!l) return NULL; switch (p->protocol) { case DNS_PROTOCOL_LLMNR: if (p->family == AF_INET) return l->llmnr_ipv4_scope; else if (p->family == AF_INET6) return l->llmnr_ipv6_scope; break; case DNS_PROTOCOL_MDNS: if (p->family == AF_INET) return l->mdns_ipv4_scope; else if (p->family == AF_INET6) return l->mdns_ipv6_scope; break; default: break; } return NULL; } void manager_verify_all(Manager *m) { assert(m); LIST_FOREACH(scopes, s, m->dns_scopes) dns_zone_verify_all(&s->zone); } int manager_is_own_hostname(Manager *m, const char *name) { int r; assert(m); assert(name); if (m->llmnr_hostname) { r = dns_name_equal(name, m->llmnr_hostname); if (r != 0) return r; } if (m->mdns_hostname) { r = dns_name_equal(name, m->mdns_hostname); if (r != 0) return r; } if (m->full_hostname) return dns_name_equal(name, m->full_hostname); return 0; } int manager_compile_dns_servers(Manager *m, OrderedSet **dns) { Link *l; int r; assert(m); assert(dns); r = ordered_set_ensure_allocated(dns, &dns_server_hash_ops); if (r < 0) return r; /* First add the system-wide servers and domains */ LIST_FOREACH(servers, s, m->dns_servers) { r = ordered_set_put(*dns, s); if (r == -EEXIST) continue; if (r < 0) return r; } /* Then, add the per-link servers */ HASHMAP_FOREACH(l, m->links) { LIST_FOREACH(servers, s, l->dns_servers) { r = ordered_set_put(*dns, s); if (r == -EEXIST) continue; if (r < 0) return r; } } /* If we found nothing, add the fallback servers */ if (ordered_set_isempty(*dns)) { LIST_FOREACH(servers, s, m->fallback_dns_servers) { r = ordered_set_put(*dns, s); if (r == -EEXIST) continue; if (r < 0) return r; } } return 0; } /* filter_route is a tri-state: * < 0: no filtering * = 0 or false: return only domains which should be used for searching * > 0 or true: return only domains which are for routing only */ int manager_compile_search_domains(Manager *m, OrderedSet **domains, int filter_route) { Link *l; int r; assert(m); assert(domains); r = ordered_set_ensure_allocated(domains, &dns_name_hash_ops); if (r < 0) return r; LIST_FOREACH(domains, d, m->search_domains) { if (filter_route >= 0 && d->route_only != !!filter_route) continue; r = ordered_set_put(*domains, d->name); if (r == -EEXIST) continue; if (r < 0) return r; } HASHMAP_FOREACH(l, m->links) { LIST_FOREACH(domains, d, l->search_domains) { if (filter_route >= 0 && d->route_only != !!filter_route) continue; r = ordered_set_put(*domains, d->name); if (r == -EEXIST) continue; if (r < 0) return r; } } return 0; } DnssecMode manager_get_dnssec_mode(Manager *m) { assert(m); if (m->dnssec_mode != _DNSSEC_MODE_INVALID) return m->dnssec_mode; return DNSSEC_NO; } bool manager_dnssec_supported(Manager *m) { DnsServer *server; Link *l; assert(m); if (manager_get_dnssec_mode(m) == DNSSEC_NO) return false; server = manager_get_dns_server(m); if (server && !dns_server_dnssec_supported(server)) return false; HASHMAP_FOREACH(l, m->links) if (!link_dnssec_supported(l)) return false; return true; } DnsOverTlsMode manager_get_dns_over_tls_mode(Manager *m) { assert(m); if (m->dns_over_tls_mode != _DNS_OVER_TLS_MODE_INVALID) return m->dns_over_tls_mode; return DNS_OVER_TLS_NO; } void manager_dnssec_verdict(Manager *m, DnssecVerdict verdict, const DnsResourceKey *key) { assert(verdict >= 0); assert(verdict < _DNSSEC_VERDICT_MAX); if (DEBUG_LOGGING) { char s[DNS_RESOURCE_KEY_STRING_MAX]; log_debug("Found verdict for lookup %s: %s", dns_resource_key_to_string(key, s, sizeof s), dnssec_verdict_to_string(verdict)); } m->n_dnssec_verdict[verdict]++; } bool manager_routable(Manager *m) { Link *l; assert(m); /* Returns true if the host has at least one interface with a routable address (regardless if IPv4 or IPv6) */ HASHMAP_FOREACH(l, m->links) if (link_relevant(l, AF_UNSPEC, false)) return true; return false; } void manager_flush_caches(Manager *m, int log_level) { assert(m); LIST_FOREACH(scopes, scope, m->dns_scopes) dns_cache_flush(&scope->cache); log_full(log_level, "Flushed all caches."); } void manager_reset_server_features(Manager *m) { Link *l; dns_server_reset_features_all(m->dns_servers); dns_server_reset_features_all(m->fallback_dns_servers); HASHMAP_FOREACH(l, m->links) dns_server_reset_features_all(l->dns_servers); log_info("Resetting learnt feature levels on all servers."); } void manager_cleanup_saved_user(Manager *m) { _cleanup_closedir_ DIR *d = NULL; assert(m); /* Clean up all saved per-link files in /run/systemd/resolve/netif/ that don't have a matching interface * anymore. These files are created to persist settings pushed in by the user via the bus, so that resolved can * be restarted without losing this data. */ d = opendir("/run/systemd/resolve/netif/"); if (!d) { if (errno == ENOENT) return; log_warning_errno(errno, "Failed to open interface directory: %m"); return; } FOREACH_DIRENT_ALL(de, d, log_error_errno(errno, "Failed to read interface directory: %m")) { _cleanup_free_ char *p = NULL; int ifindex; Link *l; if (!IN_SET(de->d_type, DT_UNKNOWN, DT_REG)) continue; if (dot_or_dot_dot(de->d_name)) continue; ifindex = parse_ifindex(de->d_name); if (ifindex < 0) /* Probably some temporary file from a previous run. Delete it */ goto rm; l = hashmap_get(m->links, INT_TO_PTR(ifindex)); if (!l) /* link vanished */ goto rm; if (l->is_managed) /* now managed by networkd, hence the bus settings are useless */ goto rm; continue; rm: p = path_join("/run/systemd/resolve/netif", de->d_name); if (!p) { log_oom(); return; } (void) unlink(p); } } bool manager_next_dnssd_names(Manager *m) { DnssdService *s; bool tried = false; int r; assert(m); HASHMAP_FOREACH(s, m->dnssd_services) { _cleanup_free_ char * new_name = NULL; if (!s->withdrawn) continue; r = manager_next_random_name(s->name_template, &new_name); if (r < 0) { log_warning_errno(r, "Failed to get new name for service '%s': %m", s->name); continue; } free_and_replace(s->name_template, new_name); s->withdrawn = false; tried = true; } if (tried) manager_refresh_rrs(m); return tried; } bool manager_server_is_stub(Manager *m, DnsServer *s) { DnsStubListenerExtra *l; assert(m); assert(s); /* Safety check: we generally already skip the main stub when parsing configuration. But let's be * extra careful, and check here again */ if (s->family == AF_INET && s->address.in.s_addr == htobe32(INADDR_DNS_STUB) && dns_server_port(s) == 53) return true; /* Main reason to call this is to check server data against the extra listeners, and filter things * out. */ ORDERED_SET_FOREACH(l, m->dns_extra_stub_listeners) if (s->family == l->family && in_addr_equal(s->family, &s->address, &l->address) && dns_server_port(s) == dns_stub_listener_extra_port(l)) return true; return false; } int socket_disable_pmtud(int fd, int af) { int r; assert(fd >= 0); if (af == AF_UNSPEC) { r = socket_get_family(fd, &af); if (r < 0) return r; } switch (af) { case AF_INET: { /* Turn off path MTU discovery, let's rather fragment on the way than to open us up against * PMTU forgery vulnerabilities. * * There appears to be no documentation about IP_PMTUDISC_OMIT, but it has the effect that * the "Don't Fragment" bit in the IPv4 header is turned off, thus enforcing fragmentation if * our datagram size exceeds the MTU of a router in the path, and turning off path MTU * discovery. * * This helps mitigating the PMTUD vulnerability described here: * * https://blog.apnic.net/2019/07/12/its-time-to-consider-avoiding-ip-fragmentation-in-the-dns/ * * Similar logic is in place in most DNS servers. * * There are multiple conflicting goals: we want to allow the largest datagrams possible (for * efficiency reasons), but not have fragmentation (for security reasons), nor use PMTUD (for * security reasons, too). Our strategy to deal with this is: use large packets, turn off * PMTUD, but watch fragmentation taking place, and then size our packets to the max of the * fragments seen — and if we need larger packets always go to TCP. */ r = setsockopt_int(fd, IPPROTO_IP, IP_MTU_DISCOVER, IP_PMTUDISC_OMIT); if (r < 0) return r; return 0; } case AF_INET6: { /* On IPv6 fragmentation only is done by the sender — never by routers on the path. PMTUD is * mandatory. If we want to turn off PMTUD, the only way is by sending with minimal MTU only, * so that we apply maximum fragmentation locally already, and thus PMTUD doesn't happen * because there's nothing that could be fragmented further anymore. */ r = setsockopt_int(fd, IPPROTO_IPV6, IPV6_MTU, IPV6_MIN_MTU); if (r < 0) return r; return 0; } default: return -EAFNOSUPPORT; } }