[thirdparty/systemd.git] / src / resolve / resolved-dns-stub.c

/* SPDX-License-Identifier: LGPL-2.1+ */

#include "fd-util.h"
#include "resolved-dns-stub.h"
#include "socket-util.h"

/* The MTU of the loopback device is 64K on Linux, advertise that as maximum datagram size, but subtract the Ethernet,
 * IP and UDP header sizes */
#define ADVERTISE_DATAGRAM_SIZE_MAX (65536U-14U-20U-8U)

static int manager_dns_stub_udp_fd(Manager *m);
static int manager_dns_stub_tcp_fd(Manager *m);

static int dns_stub_make_reply_packet(
                DnsPacket **p,
                size_t max_size,
                DnsQuestion *q,
                DnsAnswer *answer,
                bool *ret_truncated) {

        bool truncated = false;
        DnsResourceRecord *rr;
        unsigned c = 0;
        int r;

        assert(p);

        /* Note that we don't bother with any additional RRs, as this is stub is for local lookups only, and hence
         * roundtrips aren't expensive. */

        if (!*p) {
                r = dns_packet_new(p, DNS_PROTOCOL_DNS, 0, max_size);
                if (r < 0)
                        return r;

                r = dns_packet_append_question(*p, q);
                if (r < 0)
                        return r;

                DNS_PACKET_HEADER(*p)->qdcount = htobe16(dns_question_size(q));
        }

        DNS_ANSWER_FOREACH(rr, answer) {

                r = dns_question_matches_rr(q, rr, NULL);
                if (r < 0)
                        return r;
                if (r > 0)
                        goto add;

                r = dns_question_matches_cname_or_dname(q, rr, NULL);
                if (r < 0)
                        return r;
                if (r > 0)
                        goto add;

                continue;
        add:
                r = dns_packet_append_rr(*p, rr, 0, NULL, NULL);
                if (r == -EMSGSIZE) {
                        truncated = true;
                        break;
                }
                if (r < 0)
                        return r;

                c++;
        }

        if (ret_truncated)
                *ret_truncated = truncated;
        else if (truncated)
                return -EMSGSIZE;

        DNS_PACKET_HEADER(*p)->ancount = htobe16(be16toh(DNS_PACKET_HEADER(*p)->ancount) + c);

        return 0;
}

static int dns_stub_finish_reply_packet(
                DnsPacket *p,
                uint16_t id,
                int rcode,
                bool tc,        /* set the Truncated bit? */
                bool add_opt,   /* add an OPT RR to this packet? */
                bool edns0_do,  /* set the EDNS0 DNSSEC OK bit? */
                bool ad) {      /* set the DNSSEC authenticated data bit? */

        int r;

        assert(p);

        if (!add_opt) {
                /* If the client can't to EDNS0, don't do DO either */
                edns0_do = false;

                /* If the client didn't do EDNS, clamp the rcode to 4 bit */
                if (rcode > 0xF)
                        rcode = DNS_RCODE_SERVFAIL;
        }

        /* Don't set the AD bit unless DO is on, too */
        if (!edns0_do)
                ad = false;

        DNS_PACKET_HEADER(p)->id = id;

        DNS_PACKET_HEADER(p)->flags = htobe16(DNS_PACKET_MAKE_FLAGS(
                                                              1  /* qr */,
                                                              0  /* opcode */,
                                                              0  /* aa */,
                                                              tc /* tc */,
                                                              1  /* rd */,
                                                              1  /* ra */,
                                                              ad /* ad */,
                                                              0  /* cd */,
                                                              rcode));

        if (add_opt) {
                r = dns_packet_append_opt(p, ADVERTISE_DATAGRAM_SIZE_MAX, edns0_do, rcode, NULL);
                if (r < 0)
                        return r;
        }

        return 0;
}

static void dns_stub_detach_stream(DnsStream *s) {
        assert(s);

        s->complete = NULL;
        s->on_packet = NULL;
        s->query = NULL;
}

static int dns_stub_send(Manager *m, DnsStream *s, DnsPacket *p, DnsPacket *reply) {
        int r;

        assert(m);
        assert(p);
        assert(reply);

        if (s)
                r = dns_stream_write_packet(s, reply);
        else {
                int fd;

                fd = manager_dns_stub_udp_fd(m);
                if (fd < 0)
                        return log_debug_errno(fd, "Failed to get reply socket: %m");

                /* Note that it is essential here that we explicitly choose the source IP address for this packet. This
                 * is because otherwise the kernel will choose it automatically based on the routing table and will
                 * thus pick 127.0.0.1 rather than 127.0.0.53. */

                r = manager_send(m, fd, LOOPBACK_IFINDEX, p->family, &p->sender, p->sender_port, &p->destination, reply);
        }
        if (r < 0)
                return log_debug_errno(r, "Failed to send reply packet: %m");

        return 0;
}

static int dns_stub_send_failure(Manager *m, DnsStream *s, DnsPacket *p, int rcode, bool authenticated) {
        _cleanup_(dns_packet_unrefp) DnsPacket *reply = NULL;
        int r;

        assert(m);
        assert(p);

        r = dns_stub_make_reply_packet(&reply, DNS_PACKET_PAYLOAD_SIZE_MAX(p), p->question, NULL, NULL);
        if (r < 0)
                return log_debug_errno(r, "Failed to make failure packet: %m");

        r = dns_stub_finish_reply_packet(reply, DNS_PACKET_ID(p), rcode, false, !!p->opt, DNS_PACKET_DO(p), authenticated);
        if (r < 0)
                return log_debug_errno(r, "Failed to build failure packet: %m");

        return dns_stub_send(m, s, p, reply);
}

static void dns_stub_query_complete(DnsQuery *q) {
        int r;

        assert(q);
        assert(q->request_dns_packet);

        switch (q->state) {

        case DNS_TRANSACTION_SUCCESS: {
                bool truncated;

                r = dns_stub_make_reply_packet(&q->reply_dns_packet, DNS_PACKET_PAYLOAD_SIZE_MAX(q->request_dns_packet), q->question_idna, q->answer, &truncated);
                if (r < 0) {
                        log_debug_errno(r, "Failed to build reply packet: %m");
                        break;
                }

                r = dns_query_process_cname(q);
                if (r == -ELOOP) {
                        (void) dns_stub_send_failure(q->manager, q->request_dns_stream, q->request_dns_packet, DNS_RCODE_SERVFAIL, false);
                        break;
                }
                if (r < 0) {
                        log_debug_errno(r, "Failed to process CNAME: %m");
                        break;
                }
                if (r == DNS_QUERY_RESTARTED)
                        return;

                r = dns_stub_finish_reply_packet(
                                q->reply_dns_packet,
                                DNS_PACKET_ID(q->request_dns_packet),
                                q->answer_rcode,
                                truncated,
                                !!q->request_dns_packet->opt,
                                DNS_PACKET_DO(q->request_dns_packet),
                                dns_query_fully_authenticated(q));
                if (r < 0) {
                        log_debug_errno(r, "Failed to finish reply packet: %m");
                        break;
                }

                (void) dns_stub_send(q->manager, q->request_dns_stream, q->request_dns_packet, q->reply_dns_packet);
                break;
        }

        case DNS_TRANSACTION_RCODE_FAILURE:
                (void) dns_stub_send_failure(q->manager, q->request_dns_stream, q->request_dns_packet, q->answer_rcode, dns_query_fully_authenticated(q));
                break;

        case DNS_TRANSACTION_NOT_FOUND:
                (void) dns_stub_send_failure(q->manager, q->request_dns_stream, q->request_dns_packet, DNS_RCODE_NXDOMAIN, dns_query_fully_authenticated(q));
                break;

        case DNS_TRANSACTION_TIMEOUT:
        case DNS_TRANSACTION_ATTEMPTS_MAX_REACHED:
                /* Propagate a timeout as a no packet, i.e. that the client also gets a timeout */
                break;

        case DNS_TRANSACTION_NO_SERVERS:
        case DNS_TRANSACTION_INVALID_REPLY:
        case DNS_TRANSACTION_ERRNO:
        case DNS_TRANSACTION_ABORTED:
        case DNS_TRANSACTION_DNSSEC_FAILED:
        case DNS_TRANSACTION_NO_TRUST_ANCHOR:
        case DNS_TRANSACTION_RR_TYPE_UNSUPPORTED:
        case DNS_TRANSACTION_NETWORK_DOWN:
                (void) dns_stub_send_failure(q->manager, q->request_dns_stream, q->request_dns_packet, DNS_RCODE_SERVFAIL, false);
                break;

        case DNS_TRANSACTION_NULL:
        case DNS_TRANSACTION_PENDING:
        case DNS_TRANSACTION_VALIDATING:
        default:
                assert_not_reached("Impossible state");
        }

        /* If there's a packet to write set, let's leave the stream around */
        if (q->request_dns_stream && DNS_STREAM_QUEUED(q->request_dns_stream)) {

                /* Detach the stream from our query (make it an orphan), but do not drop the reference to it. The
                 * default completion action of the stream will drop the reference. */

                dns_stub_detach_stream(q->request_dns_stream);
                q->request_dns_stream = NULL;
        }

        dns_query_free(q);
}

static int dns_stub_stream_complete(DnsStream *s, int error) {
        assert(s);

        log_debug_errno(error, "DNS TCP connection terminated, destroying query: %m");

        assert(s->query);
        dns_query_free(s->query);

        return 0;
}

static void dns_stub_process_query(Manager *m, DnsStream *s, DnsPacket *p) {
        DnsQuery *q = NULL;
        int r;

        assert(m);
        assert(p);
        assert(p->protocol == DNS_PROTOCOL_DNS);

        /* Takes ownership of the *s stream object */

        if (in_addr_is_localhost(p->family, &p->sender) <= 0 ||
            in_addr_is_localhost(p->family, &p->destination) <= 0) {
                log_error("Got packet on unexpected IP range, refusing.");
                dns_stub_send_failure(m, s, p, DNS_RCODE_SERVFAIL, false);
                goto fail;
        }

        r = dns_packet_extract(p);
        if (r < 0) {
                log_debug_errno(r, "Failed to extract resources from incoming packet, ignoring packet: %m");
                dns_stub_send_failure(m, s, p, DNS_RCODE_FORMERR, false);
                goto fail;
        }

        if (!DNS_PACKET_VERSION_SUPPORTED(p)) {
                log_debug("Got EDNS OPT field with unsupported version number.");
                dns_stub_send_failure(m, s, p, DNS_RCODE_BADVERS, false);
                goto fail;
        }

        if (dns_type_is_obsolete(p->question->keys[0]->type)) {
                log_debug("Got message with obsolete key type, refusing.");
                dns_stub_send_failure(m, s, p, DNS_RCODE_NOTIMP, false);
                goto fail;
        }

        if (dns_type_is_zone_transer(p->question->keys[0]->type)) {
                log_debug("Got request for zone transfer, refusing.");
                dns_stub_send_failure(m, s, p, DNS_RCODE_NOTIMP, false);
                goto fail;
        }

        if (!DNS_PACKET_RD(p))  {
                /* If the "rd" bit is off (i.e. recursion was not requested), then refuse operation */
                log_debug("Got request with recursion disabled, refusing.");
                dns_stub_send_failure(m, s, p, DNS_RCODE_REFUSED, false);
                goto fail;
        }

        if (DNS_PACKET_DO(p) && DNS_PACKET_CD(p)) {
                log_debug("Got request with DNSSEC CD bit set, refusing.");
                dns_stub_send_failure(m, s, p, DNS_RCODE_NOTIMP, false);
                goto fail;
        }

        r = dns_query_new(m, &q, p->question, p->question, 0, SD_RESOLVED_PROTOCOLS_ALL|SD_RESOLVED_NO_SEARCH);
        if (r < 0) {
                log_error_errno(r, "Failed to generate query object: %m");
                dns_stub_send_failure(m, s, p, DNS_RCODE_SERVFAIL, false);
                goto fail;
        }

        /* Request that the TTL is corrected by the cached time for this lookup, so that we return vaguely useful TTLs */
        q->clamp_ttl = true;

        q->request_dns_packet = dns_packet_ref(p);
        q->request_dns_stream = dns_stream_ref(s); /* make sure the stream stays around until we can send a reply through it */
        q->complete = dns_stub_query_complete;

        if (s) {
                s->on_packet = NULL;
                s->complete = dns_stub_stream_complete;
                s->query = q;
        }

        r = dns_query_go(q);
        if (r < 0) {
                log_error_errno(r, "Failed to start query: %m");
                dns_stub_send_failure(m, s, p, DNS_RCODE_SERVFAIL, false);
                goto fail;
        }

        log_debug("Processing query...");
        return;

fail:
        if (s && DNS_STREAM_QUEUED(s))
                dns_stub_detach_stream(s);

        dns_query_free(q);
}

static int on_dns_stub_packet(sd_event_source *s, int fd, uint32_t revents, void *userdata) {
        _cleanup_(dns_packet_unrefp) DnsPacket *p = NULL;
        Manager *m = userdata;
        int r;

        r = manager_recv(m, fd, DNS_PROTOCOL_DNS, &p);
        if (r <= 0)
                return r;

        if (dns_packet_validate_query(p) > 0) {
                log_debug("Got DNS stub UDP query packet for id %u", DNS_PACKET_ID(p));

                dns_stub_process_query(m, NULL, p);
        } else
                log_debug("Invalid DNS stub UDP packet, ignoring.");

        return 0;
}

static int manager_dns_stub_udp_fd(Manager *m) {
        union sockaddr_union sa = {
                .in.sin_family = AF_INET,
                .in.sin_port = htobe16(53),
                .in.sin_addr.s_addr = htobe32(INADDR_DNS_STUB),
        };
        _cleanup_close_ int fd = -1;
        int r;

        if (m->dns_stub_udp_fd >= 0)
                return m->dns_stub_udp_fd;

        fd = socket(AF_INET, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
        if (fd < 0)
                return -errno;

        r = setsockopt_int(fd, SOL_SOCKET, SO_REUSEADDR, true);
        if (r < 0)
                return r;

        r = setsockopt_int(fd, IPPROTO_IP, IP_PKTINFO, true);
        if (r < 0)
                return r;

        r = setsockopt_int(fd, IPPROTO_IP, IP_RECVTTL, true);
        if (r < 0)
                return r;

        /* Make sure no traffic from outside the local host can leak to onto this socket */
        if (setsockopt(fd, SOL_SOCKET, SO_BINDTODEVICE, "lo", 3) < 0)
                return -errno;

        if (bind(fd, &sa.sa, sizeof(sa.in)) < 0)
                return -errno;

        r = sd_event_add_io(m->event, &m->dns_stub_udp_event_source, fd, EPOLLIN, on_dns_stub_packet, m);
        if (r < 0)
                return r;

        (void) sd_event_source_set_description(m->dns_stub_udp_event_source, "dns-stub-udp");

        return m->dns_stub_udp_fd = TAKE_FD(fd);
}

static int on_dns_stub_stream_packet(DnsStream *s) {
        assert(s);
        assert(s->read_packet);

        if (dns_packet_validate_query(s->read_packet) > 0) {
                log_debug("Got DNS stub TCP query packet for id %u", DNS_PACKET_ID(s->read_packet));

                dns_stub_process_query(s->manager, s, s->read_packet);
        } else
                log_debug("Invalid DNS stub TCP packet, ignoring.");

        /* Drop the reference to the stream. Either a query was created and added its own reference to the stream now,
         * or that didn't happen in which case we want to free the stream */
        dns_stream_unref(s);

        return 0;
}

static int on_dns_stub_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 (IN_SET(errno, EAGAIN, EINTR))
                        return 0;

                return -errno;
        }

        r = dns_stream_new(m, &stream, DNS_PROTOCOL_DNS, cfd, NULL);
        if (r < 0) {
                safe_close(cfd);
                return r;
        }

        stream->on_packet = on_dns_stub_stream_packet;

        /* We let the reference to the stream dangling here, it will either be dropped by the default "complete" action
         * of the stream, or by our packet callback, or when the manager is shut down. */

        return 0;
}

static int manager_dns_stub_tcp_fd(Manager *m) {
        union sockaddr_union sa = {
                .in.sin_family = AF_INET,
                .in.sin_addr.s_addr = htobe32(INADDR_DNS_STUB),
                .in.sin_port = htobe16(53),
        };
        _cleanup_close_ int fd = -1;
        int r;

        if (m->dns_stub_tcp_fd >= 0)
                return m->dns_stub_tcp_fd;

        fd = socket(AF_INET, SOCK_STREAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
        if (fd < 0)
                return -errno;

        r = setsockopt_int(fd, IPPROTO_IP, IP_TTL, true);
        if (r < 0)
                return r;

        r = setsockopt_int(fd, SOL_SOCKET, SO_REUSEADDR, true);
        if (r < 0)
                return r;

        r = setsockopt_int(fd, IPPROTO_IP, IP_PKTINFO, true);
        if (r < 0)
                return r;

        r = setsockopt_int(fd, IPPROTO_IP, IP_RECVTTL, true);
        if (r < 0)
                return r;

        /* Make sure no traffic from outside the local host can leak to onto this socket */
        if (setsockopt(fd, SOL_SOCKET, SO_BINDTODEVICE, "lo", 3) < 0)
                return -errno;

        if (bind(fd, &sa.sa, sizeof(sa.in)) < 0)
                return -errno;

        if (listen(fd, SOMAXCONN) < 0)
                return -errno;

        r = sd_event_add_io(m->event, &m->dns_stub_tcp_event_source, fd, EPOLLIN, on_dns_stub_stream, m);
        if (r < 0)
                return r;

        (void) sd_event_source_set_description(m->dns_stub_tcp_event_source, "dns-stub-tcp");

        return m->dns_stub_tcp_fd = TAKE_FD(fd);
}

int manager_dns_stub_start(Manager *m) {
        const char *t = "UDP";
        int r = 0;

        assert(m);

        if (m->dns_stub_listener_mode == DNS_STUB_LISTENER_NO)
                log_debug("Not creating stub listener.");
        else
                log_debug("Creating stub listener using %s.",
                          m->dns_stub_listener_mode == DNS_STUB_LISTENER_UDP ? "UDP" :
                          m->dns_stub_listener_mode == DNS_STUB_LISTENER_TCP ? "TCP" :
                          "UDP/TCP");

        if (IN_SET(m->dns_stub_listener_mode, DNS_STUB_LISTENER_YES, DNS_STUB_LISTENER_UDP))
                r = manager_dns_stub_udp_fd(m);

        if (r >= 0 &&
            IN_SET(m->dns_stub_listener_mode, DNS_STUB_LISTENER_YES, DNS_STUB_LISTENER_TCP)) {
                t = "TCP";
                r = manager_dns_stub_tcp_fd(m);
        }

        if (IN_SET(r, -EADDRINUSE, -EPERM)) {
                if (r == -EADDRINUSE)
                        log_warning_errno(r,
                                          "Another process is already listening on %s socket 127.0.0.53:53.\n"
                                          "Turning off local DNS stub support.", t);
                else
                        log_warning_errno(r,
                                          "Failed to listen on %s socket 127.0.0.53:53: %m.\n"
                                          "Turning off local DNS stub support.", t);
                manager_dns_stub_stop(m);
        } else if (r < 0)
                return log_error_errno(r, "Failed to listen on %s socket 127.0.0.53:53: %m", t);

        return 0;
}

void manager_dns_stub_stop(Manager *m) {
        assert(m);

        m->dns_stub_udp_event_source = sd_event_source_unref(m->dns_stub_udp_event_source);
        m->dns_stub_tcp_event_source = sd_event_source_unref(m->dns_stub_tcp_event_source);

        m->dns_stub_udp_fd = safe_close(m->dns_stub_udp_fd);
        m->dns_stub_tcp_fd = safe_close(m->dns_stub_tcp_fd);
}
Commit	Line	Data
53e1b683	1	/* SPDX-License-Identifier: LGPL-2.1+ */
b30bf55d LP	2
	3	#include "fd-util.h"
	4	#include "resolved-dns-stub.h"
	5	#include "socket-util.h"
	6
	7	/* The MTU of the loopback device is 64K on Linux, advertise that as maximum datagram size, but subtract the Ethernet,
	8	* IP and UDP header sizes */
	9	#define ADVERTISE_DATAGRAM_SIZE_MAX (65536U-14U-20U-8U)
	10
424e490b ZJS	11	static int manager_dns_stub_udp_fd(Manager *m);
	12	static int manager_dns_stub_tcp_fd(Manager *m);
	13
b30bf55d	14	static int dns_stub_make_reply_packet(
e8d23f92	15	DnsPacket **p,
51027656	16	size_t max_size,
b30bf55d	17	DnsQuestion *q,
51027656 LP	18	DnsAnswer *answer,
51027656 LP	19	bool *ret_truncated) {
b30bf55d	20
51027656	21	bool truncated = false;
b30bf55d LP	22	DnsResourceRecord *rr;
	23	unsigned c = 0;
	24	int r;
	25
e8d23f92 LP	26	assert(p);
e8d23f92 LP	27
b30bf55d LP	28	/* Note that we don't bother with any additional RRs, as this is stub is for local lookups only, and hence
	29	* roundtrips aren't expensive. */
	30
e8d23f92	31	if (!*p) {
51027656	32	r = dns_packet_new(p, DNS_PROTOCOL_DNS, 0, max_size);
e8d23f92 LP	33	if (r < 0)
e8d23f92 LP	34	return r;
b30bf55d	35
e8d23f92 LP	36	r = dns_packet_append_question(*p, q);
	37	if (r < 0)
	38	return r;
b30bf55d	39
e8d23f92 LP	40	DNS_PACKET_HEADER(*p)->qdcount = htobe16(dns_question_size(q));
e8d23f92 LP	41	}
b30bf55d LP	42
b30bf55d LP	43	DNS_ANSWER_FOREACH(rr, answer) {
e8d23f92	44
b30bf55d LP	45	r = dns_question_matches_rr(q, rr, NULL);
	46	if (r < 0)
	47	return r;
	48	if (r > 0)
	49	goto add;
	50
	51	r = dns_question_matches_cname_or_dname(q, rr, NULL);
	52	if (r < 0)
	53	return r;
	54	if (r > 0)
	55	goto add;
	56
	57	continue;
	58	add:
01c901e2	59	r = dns_packet_append_rr(*p, rr, 0, NULL, NULL);
51027656 LP	60	if (r == -EMSGSIZE) {
	61	truncated = true;
	62	break;
	63	}
b30bf55d LP	64	if (r < 0)
	65	return r;
	66
	67	c++;
	68	}
e8d23f92	69
51027656 LP	70	if (ret_truncated)
	71	*ret_truncated = truncated;
	72	else if (truncated)
	73	return -EMSGSIZE;
	74
e8d23f92 LP	75	DNS_PACKET_HEADER(p)->ancount = htobe16(be16toh(DNS_PACKET_HEADER(p)->ancount) + c);
	76
	77	return 0;
	78	}
	79
	80	static int dns_stub_finish_reply_packet(
	81	DnsPacket *p,
	82	uint16_t id,
	83	int rcode,
51027656	84	bool tc, /* set the Truncated bit? */
e8d23f92 LP	85	bool add_opt, /* add an OPT RR to this packet? */
	86	bool edns0_do, /* set the EDNS0 DNSSEC OK bit? */
	87	bool ad) { /* set the DNSSEC authenticated data bit? */
	88
	89	int r;
	90
	91	assert(p);
	92
941dd294 LP	93	if (!add_opt) {
	94	/* If the client can't to EDNS0, don't do DO either */
	95	edns0_do = false;
	96
	97	/* If the client didn't do EDNS, clamp the rcode to 4 bit */
	98	if (rcode > 0xF)
	99	rcode = DNS_RCODE_SERVFAIL;
	100	}
	101
	102	/* Don't set the AD bit unless DO is on, too */
	103	if (!edns0_do)
	104	ad = false;
e8d23f92 LP	105
	106	DNS_PACKET_HEADER(p)->id = id;
	107
	108	DNS_PACKET_HEADER(p)->flags = htobe16(DNS_PACKET_MAKE_FLAGS(
51027656 LP	109	1 /* qr */,
	110	0 /* opcode */,
	111	0 /* aa */,
	112	tc /* tc */,
	113	1 /* rd */,
	114	1 /* ra */,
e8d23f92	115	ad /* ad */,
51027656	116	0 /* cd */,
e8d23f92	117	rcode));
b30bf55d LP	118
	119	if (add_opt) {
	120	r = dns_packet_append_opt(p, ADVERTISE_DATAGRAM_SIZE_MAX, edns0_do, rcode, NULL);
	121	if (r < 0)
	122	return r;
	123	}
	124
b30bf55d LP	125	return 0;
	126	}
	127
	128	static void dns_stub_detach_stream(DnsStream *s) {
	129	assert(s);
	130
	131	s->complete = NULL;
	132	s->on_packet = NULL;
	133	s->query = NULL;
	134	}
	135
	136	static int dns_stub_send(Manager m, DnsStream s, DnsPacket p, DnsPacket reply) {
	137	int r;
	138
	139	assert(m);
	140	assert(p);
	141	assert(reply);
	142
	143	if (s)
	144	r = dns_stream_write_packet(s, reply);
	145	else {
	146	int fd;
	147
b30bf55d LP	148	fd = manager_dns_stub_udp_fd(m);
	149	if (fd < 0)
	150	return log_debug_errno(fd, "Failed to get reply socket: %m");
	151
	152	/* Note that it is essential here that we explicitly choose the source IP address for this packet. This
	153	* is because otherwise the kernel will choose it automatically based on the routing table and will
	154	* thus pick 127.0.0.1 rather than 127.0.0.53. */
	155
	156	r = manager_send(m, fd, LOOPBACK_IFINDEX, p->family, &p->sender, p->sender_port, &p->destination, reply);
	157	}
	158	if (r < 0)
	159	return log_debug_errno(r, "Failed to send reply packet: %m");
	160
	161	return 0;
	162	}
	163
2b2d98c1	164	static int dns_stub_send_failure(Manager m, DnsStream s, DnsPacket *p, int rcode, bool authenticated) {
b30bf55d LP	165	_cleanup_(dns_packet_unrefp) DnsPacket *reply = NULL;
	166	int r;
	167
	168	assert(m);
	169	assert(p);
	170
51027656	171	r = dns_stub_make_reply_packet(&reply, DNS_PACKET_PAYLOAD_SIZE_MAX(p), p->question, NULL, NULL);
e8d23f92 LP	172	if (r < 0)
	173	return log_debug_errno(r, "Failed to make failure packet: %m");
	174
51027656	175	r = dns_stub_finish_reply_packet(reply, DNS_PACKET_ID(p), rcode, false, !!p->opt, DNS_PACKET_DO(p), authenticated);
b30bf55d LP	176	if (r < 0)
	177	return log_debug_errno(r, "Failed to build failure packet: %m");
	178
	179	return dns_stub_send(m, s, p, reply);
	180	}
	181
	182	static void dns_stub_query_complete(DnsQuery *q) {
	183	int r;
	184
	185	assert(q);
	186	assert(q->request_dns_packet);
	187
	188	switch (q->state) {
	189
51027656 LP	190	case DNS_TRANSACTION_SUCCESS: {
51027656 LP	191	bool truncated;
e8d23f92	192
51027656	193	r = dns_stub_make_reply_packet(&q->reply_dns_packet, DNS_PACKET_PAYLOAD_SIZE_MAX(q->request_dns_packet), q->question_idna, q->answer, &truncated);
e8d23f92 LP	194	if (r < 0) {
	195	log_debug_errno(r, "Failed to build reply packet: %m");
	196	break;
	197	}
b30bf55d	198
e8d23f92 LP	199	r = dns_query_process_cname(q);
e8d23f92 LP	200	if (r == -ELOOP) {
2b2d98c1	201	(void) dns_stub_send_failure(q->manager, q->request_dns_stream, q->request_dns_packet, DNS_RCODE_SERVFAIL, false);
e8d23f92 LP	202	break;
	203	}
	204	if (r < 0) {
	205	log_debug_errno(r, "Failed to process CNAME: %m");
	206	break;
	207	}
	208	if (r == DNS_QUERY_RESTARTED)
	209	return;
	210
	211	r = dns_stub_finish_reply_packet(
	212	q->reply_dns_packet,
b30bf55d LP	213	DNS_PACKET_ID(q->request_dns_packet),
b30bf55d LP	214	q->answer_rcode,
51027656	215	truncated,
b30bf55d LP	216	!!q->request_dns_packet->opt,
b30bf55d LP	217	DNS_PACKET_DO(q->request_dns_packet),
941dd294	218	dns_query_fully_authenticated(q));
b30bf55d	219	if (r < 0) {
e8d23f92	220	log_debug_errno(r, "Failed to finish reply packet: %m");
b30bf55d LP	221	break;
	222	}
	223
e8d23f92	224	(void) dns_stub_send(q->manager, q->request_dns_stream, q->request_dns_packet, q->reply_dns_packet);
b30bf55d	225	break;
51027656	226	}
b30bf55d LP	227
b30bf55d LP	228	case DNS_TRANSACTION_RCODE_FAILURE:
2b2d98c1	229	(void) dns_stub_send_failure(q->manager, q->request_dns_stream, q->request_dns_packet, q->answer_rcode, dns_query_fully_authenticated(q));
b30bf55d LP	230	break;
	231
	232	case DNS_TRANSACTION_NOT_FOUND:
2b2d98c1	233	(void) dns_stub_send_failure(q->manager, q->request_dns_stream, q->request_dns_packet, DNS_RCODE_NXDOMAIN, dns_query_fully_authenticated(q));
b30bf55d LP	234	break;
	235
	236	case DNS_TRANSACTION_TIMEOUT:
	237	case DNS_TRANSACTION_ATTEMPTS_MAX_REACHED:
	238	/* Propagate a timeout as a no packet, i.e. that the client also gets a timeout */
	239	break;
	240
	241	case DNS_TRANSACTION_NO_SERVERS:
	242	case DNS_TRANSACTION_INVALID_REPLY:
	243	case DNS_TRANSACTION_ERRNO:
	244	case DNS_TRANSACTION_ABORTED:
	245	case DNS_TRANSACTION_DNSSEC_FAILED:
	246	case DNS_TRANSACTION_NO_TRUST_ANCHOR:
	247	case DNS_TRANSACTION_RR_TYPE_UNSUPPORTED:
	248	case DNS_TRANSACTION_NETWORK_DOWN:
2b2d98c1	249	(void) dns_stub_send_failure(q->manager, q->request_dns_stream, q->request_dns_packet, DNS_RCODE_SERVFAIL, false);
b30bf55d LP	250	break;
	251
	252	case DNS_TRANSACTION_NULL:
	253	case DNS_TRANSACTION_PENDING:
	254	case DNS_TRANSACTION_VALIDATING:
	255	default:
	256	assert_not_reached("Impossible state");
	257	}
	258
	259	/* If there's a packet to write set, let's leave the stream around */
	260	if (q->request_dns_stream && DNS_STREAM_QUEUED(q->request_dns_stream)) {
	261
	262	/* Detach the stream from our query (make it an orphan), but do not drop the reference to it. The
	263	* default completion action of the stream will drop the reference. */
	264
	265	dns_stub_detach_stream(q->request_dns_stream);
	266	q->request_dns_stream = NULL;
	267	}
	268
	269	dns_query_free(q);
	270	}
	271
	272	static int dns_stub_stream_complete(DnsStream *s, int error) {
	273	assert(s);
	274
	275	log_debug_errno(error, "DNS TCP connection terminated, destroying query: %m");
	276
	277	assert(s->query);
	278	dns_query_free(s->query);
	279
	280	return 0;
	281	}
	282
	283	static void dns_stub_process_query(Manager m, DnsStream s, DnsPacket *p) {
	284	DnsQuery *q = NULL;
	285	int r;
	286
	287	assert(m);
	288	assert(p);
	289	assert(p->protocol == DNS_PROTOCOL_DNS);
	290
	291	/* Takes ownership of the s stream object /
	292
	293	if (in_addr_is_localhost(p->family, &p->sender) <= 0 \|\|
	294	in_addr_is_localhost(p->family, &p->destination) <= 0) {
	295	log_error("Got packet on unexpected IP range, refusing.");
2b2d98c1	296	dns_stub_send_failure(m, s, p, DNS_RCODE_SERVFAIL, false);
b30bf55d LP	297	goto fail;
	298	}
	299
	300	r = dns_packet_extract(p);
	301	if (r < 0) {
	302	log_debug_errno(r, "Failed to extract resources from incoming packet, ignoring packet: %m");
2b2d98c1	303	dns_stub_send_failure(m, s, p, DNS_RCODE_FORMERR, false);
b30bf55d LP	304	goto fail;
	305	}
	306
	307	if (!DNS_PACKET_VERSION_SUPPORTED(p)) {
	308	log_debug("Got EDNS OPT field with unsupported version number.");
2b2d98c1	309	dns_stub_send_failure(m, s, p, DNS_RCODE_BADVERS, false);
b30bf55d LP	310	goto fail;
	311	}
	312
	313	if (dns_type_is_obsolete(p->question->keys[0]->type)) {
	314	log_debug("Got message with obsolete key type, refusing.");
2b2d98c1	315	dns_stub_send_failure(m, s, p, DNS_RCODE_NOTIMP, false);
b30bf55d LP	316	goto fail;
	317	}
	318
	319	if (dns_type_is_zone_transer(p->question->keys[0]->type)) {
	320	log_debug("Got request for zone transfer, refusing.");
2b2d98c1	321	dns_stub_send_failure(m, s, p, DNS_RCODE_NOTIMP, false);
b30bf55d LP	322	goto fail;
	323	}
	324
	325	if (!DNS_PACKET_RD(p)) {
	326	/* If the "rd" bit is off (i.e. recursion was not requested), then refuse operation */
	327	log_debug("Got request with recursion disabled, refusing.");
2b2d98c1	328	dns_stub_send_failure(m, s, p, DNS_RCODE_REFUSED, false);
b30bf55d LP	329	goto fail;
	330	}
	331
	332	if (DNS_PACKET_DO(p) && DNS_PACKET_CD(p)) {
	333	log_debug("Got request with DNSSEC CD bit set, refusing.");
2b2d98c1	334	dns_stub_send_failure(m, s, p, DNS_RCODE_NOTIMP, false);
b30bf55d LP	335	goto fail;
	336	}
	337
e8d23f92	338	r = dns_query_new(m, &q, p->question, p->question, 0, SD_RESOLVED_PROTOCOLS_ALL\|SD_RESOLVED_NO_SEARCH);
b30bf55d LP	339	if (r < 0) {
b30bf55d LP	340	log_error_errno(r, "Failed to generate query object: %m");
2b2d98c1	341	dns_stub_send_failure(m, s, p, DNS_RCODE_SERVFAIL, false);
b30bf55d LP	342	goto fail;
	343	}
	344
	345	/* Request that the TTL is corrected by the cached time for this lookup, so that we return vaguely useful TTLs */
	346	q->clamp_ttl = true;
	347
	348	q->request_dns_packet = dns_packet_ref(p);
	349	q->request_dns_stream = dns_stream_ref(s); /* make sure the stream stays around until we can send a reply through it */
	350	q->complete = dns_stub_query_complete;
	351
	352	if (s) {
	353	s->on_packet = NULL;
	354	s->complete = dns_stub_stream_complete;
	355	s->query = q;
	356	}
	357
	358	r = dns_query_go(q);
	359	if (r < 0) {
	360	log_error_errno(r, "Failed to start query: %m");
2b2d98c1	361	dns_stub_send_failure(m, s, p, DNS_RCODE_SERVFAIL, false);
b30bf55d LP	362	goto fail;
	363	}
	364
52e63427	365	log_debug("Processing query...");
b30bf55d LP	366	return;
	367
	368	fail:
	369	if (s && DNS_STREAM_QUEUED(s))
	370	dns_stub_detach_stream(s);
	371
	372	dns_query_free(q);
	373	}
	374
	375	static int on_dns_stub_packet(sd_event_source s, int fd, uint32_t revents, void userdata) {
	376	_cleanup_(dns_packet_unrefp) DnsPacket *p = NULL;
	377	Manager *m = userdata;
	378	int r;
	379
	380	r = manager_recv(m, fd, DNS_PROTOCOL_DNS, &p);
	381	if (r <= 0)
	382	return r;
	383
	384	if (dns_packet_validate_query(p) > 0) {
	385	log_debug("Got DNS stub UDP query packet for id %u", DNS_PACKET_ID(p));
	386
	387	dns_stub_process_query(m, NULL, p);
	388	} else
	389	log_debug("Invalid DNS stub UDP packet, ignoring.");
	390
	391	return 0;
	392	}
	393
424e490b	394	static int manager_dns_stub_udp_fd(Manager *m) {
b30bf55d LP	395	union sockaddr_union sa = {
	396	.in.sin_family = AF_INET,
	397	.in.sin_port = htobe16(53),
	398	.in.sin_addr.s_addr = htobe32(INADDR_DNS_STUB),
	399	};
424e490b	400	_cleanup_close_ int fd = -1;
b30bf55d LP	401	int r;
	402
	403	if (m->dns_stub_udp_fd >= 0)
	404	return m->dns_stub_udp_fd;
	405
424e490b ZJS	406	fd = socket(AF_INET, SOCK_DGRAM\|SOCK_CLOEXEC\|SOCK_NONBLOCK, 0);
424e490b ZJS	407	if (fd < 0)
b30bf55d LP	408	return -errno;
b30bf55d LP	409
2ff48e98 LP	410	r = setsockopt_int(fd, SOL_SOCKET, SO_REUSEADDR, true);
	411	if (r < 0)
	412	return r;
b30bf55d	413
2ff48e98 LP	414	r = setsockopt_int(fd, IPPROTO_IP, IP_PKTINFO, true);
	415	if (r < 0)
	416	return r;
b30bf55d	417
2ff48e98 LP	418	r = setsockopt_int(fd, IPPROTO_IP, IP_RECVTTL, true);
	419	if (r < 0)
	420	return r;
b30bf55d LP	421
b30bf55d LP	422	/* Make sure no traffic from outside the local host can leak to onto this socket */
424e490b ZJS	423	if (setsockopt(fd, SOL_SOCKET, SO_BINDTODEVICE, "lo", 3) < 0)
424e490b ZJS	424	return -errno;
b30bf55d	425
424e490b ZJS	426	if (bind(fd, &sa.sa, sizeof(sa.in)) < 0)
424e490b ZJS	427	return -errno;
b30bf55d	428
424e490b	429	r = sd_event_add_io(m->event, &m->dns_stub_udp_event_source, fd, EPOLLIN, on_dns_stub_packet, m);
b30bf55d	430	if (r < 0)
424e490b	431	return r;
b30bf55d LP	432
	433	(void) sd_event_source_set_description(m->dns_stub_udp_event_source, "dns-stub-udp");
	434
c10d6bdb	435	return m->dns_stub_udp_fd = TAKE_FD(fd);
b30bf55d LP	436	}
	437
	438	static int on_dns_stub_stream_packet(DnsStream *s) {
	439	assert(s);
	440	assert(s->read_packet);
	441
	442	if (dns_packet_validate_query(s->read_packet) > 0) {
	443	log_debug("Got DNS stub TCP query packet for id %u", DNS_PACKET_ID(s->read_packet));
	444
	445	dns_stub_process_query(s->manager, s, s->read_packet);
	446	} else
	447	log_debug("Invalid DNS stub TCP packet, ignoring.");
	448
	449	/* Drop the reference to the stream. Either a query was created and added its own reference to the stream now,
	450	* or that didn't happen in which case we want to free the stream */
	451	dns_stream_unref(s);
	452
	453	return 0;
	454	}
	455
	456	static int on_dns_stub_stream(sd_event_source s, int fd, uint32_t revents, void userdata) {
	457	DnsStream *stream;
	458	Manager *m = userdata;
	459	int cfd, r;
	460
	461	cfd = accept4(fd, NULL, NULL, SOCK_NONBLOCK\|SOCK_CLOEXEC);
	462	if (cfd < 0) {
3742095b	463	if (IN_SET(errno, EAGAIN, EINTR))
b30bf55d LP	464	return 0;
	465
	466	return -errno;
	467	}
	468
91ccab1e	469	r = dns_stream_new(m, &stream, DNS_PROTOCOL_DNS, cfd, NULL);
b30bf55d LP	470	if (r < 0) {
	471	safe_close(cfd);
	472	return r;
	473	}
	474
	475	stream->on_packet = on_dns_stub_stream_packet;
	476
	477	/* We let the reference to the stream dangling here, it will either be dropped by the default "complete" action
	478	* of the stream, or by our packet callback, or when the manager is shut down. */
	479
	480	return 0;
	481	}
	482
424e490b	483	static int manager_dns_stub_tcp_fd(Manager *m) {
b30bf55d LP	484	union sockaddr_union sa = {
	485	.in.sin_family = AF_INET,
	486	.in.sin_addr.s_addr = htobe32(INADDR_DNS_STUB),
	487	.in.sin_port = htobe16(53),
	488	};
424e490b	489	_cleanup_close_ int fd = -1;
b30bf55d LP	490	int r;
	491
	492	if (m->dns_stub_tcp_fd >= 0)
	493	return m->dns_stub_tcp_fd;
	494
424e490b ZJS	495	fd = socket(AF_INET, SOCK_STREAM\|SOCK_CLOEXEC\|SOCK_NONBLOCK, 0);
424e490b ZJS	496	if (fd < 0)
b30bf55d LP	497	return -errno;
b30bf55d LP	498
2ff48e98 LP	499	r = setsockopt_int(fd, IPPROTO_IP, IP_TTL, true);
	500	if (r < 0)
	501	return r;
b30bf55d	502
2ff48e98 LP	503	r = setsockopt_int(fd, SOL_SOCKET, SO_REUSEADDR, true);
	504	if (r < 0)
	505	return r;
b30bf55d	506
2ff48e98 LP	507	r = setsockopt_int(fd, IPPROTO_IP, IP_PKTINFO, true);
	508	if (r < 0)
	509	return r;
b30bf55d	510
2ff48e98 LP	511	r = setsockopt_int(fd, IPPROTO_IP, IP_RECVTTL, true);
	512	if (r < 0)
	513	return r;
b30bf55d LP	514
b30bf55d LP	515	/* Make sure no traffic from outside the local host can leak to onto this socket */
424e490b ZJS	516	if (setsockopt(fd, SOL_SOCKET, SO_BINDTODEVICE, "lo", 3) < 0)
424e490b ZJS	517	return -errno;
b30bf55d	518
424e490b ZJS	519	if (bind(fd, &sa.sa, sizeof(sa.in)) < 0)
424e490b ZJS	520	return -errno;
b30bf55d	521
424e490b ZJS	522	if (listen(fd, SOMAXCONN) < 0)
424e490b ZJS	523	return -errno;
b30bf55d	524
424e490b	525	r = sd_event_add_io(m->event, &m->dns_stub_tcp_event_source, fd, EPOLLIN, on_dns_stub_stream, m);
b30bf55d	526	if (r < 0)
424e490b	527	return r;
b30bf55d LP	528
	529	(void) sd_event_source_set_description(m->dns_stub_tcp_event_source, "dns-stub-tcp");
	530
c10d6bdb	531	return m->dns_stub_tcp_fd = TAKE_FD(fd);
b30bf55d LP	532	}
	533
	534	int manager_dns_stub_start(Manager *m) {
424e490b	535	const char *t = "UDP";
01b0669e	536	int r = 0;
b30bf55d LP	537
	538	assert(m);
	539
d5da7707 ZJS	540	if (m->dns_stub_listener_mode == DNS_STUB_LISTENER_NO)
	541	log_debug("Not creating stub listener.");
	542	else
	543	log_debug("Creating stub listener using %s.",
	544	m->dns_stub_listener_mode == DNS_STUB_LISTENER_UDP ? "UDP" :
	545	m->dns_stub_listener_mode == DNS_STUB_LISTENER_TCP ? "TCP" :
	546	"UDP/TCP");
	547
424e490b	548	if (IN_SET(m->dns_stub_listener_mode, DNS_STUB_LISTENER_YES, DNS_STUB_LISTENER_UDP))
1ae43295	549	r = manager_dns_stub_udp_fd(m);
b30bf55d	550
424e490b ZJS	551	if (r >= 0 &&
	552	IN_SET(m->dns_stub_listener_mode, DNS_STUB_LISTENER_YES, DNS_STUB_LISTENER_TCP)) {
	553	t = "TCP";
1ae43295	554	r = manager_dns_stub_tcp_fd(m);
1ae43295	555	}
b30bf55d	556
0f4db364 ZJS	557	if (IN_SET(r, -EADDRINUSE, -EPERM)) {
	558	if (r == -EADDRINUSE)
	559	log_warning_errno(r,
	560	"Another process is already listening on %s socket 127.0.0.53:53.\n"
	561	"Turning off local DNS stub support.", t);
	562	else
	563	log_warning_errno(r,
	564	"Failed to listen on %s socket 127.0.0.53:53: %m.\n"
	565	"Turning off local DNS stub support.", t);
424e490b ZJS	566	manager_dns_stub_stop(m);
	567	} else if (r < 0)
	568	return log_error_errno(r, "Failed to listen on %s socket 127.0.0.53:53: %m", t);
b30bf55d LP	569
	570	return 0;
	571	}
	572
	573	void manager_dns_stub_stop(Manager *m) {
	574	assert(m);
	575
	576	m->dns_stub_udp_event_source = sd_event_source_unref(m->dns_stub_udp_event_source);
	577	m->dns_stub_tcp_event_source = sd_event_source_unref(m->dns_stub_tcp_event_source);
	578
	579	m->dns_stub_udp_fd = safe_close(m->dns_stub_udp_fd);
	580	m->dns_stub_tcp_fd = safe_close(m->dns_stub_tcp_fd);
	581	}