resolved: add a DNS client stub resolver

Let's turn resolved into a something truly useful: a fully asynchronous
DNS stub resolver that subscribes to network changes.

(More to come: caching, LLMNR, mDNS/DNS-SD, DNSSEC, IDN, NSS module)

1 files changed, 468 insertions, 0 deletions

diff --git a/src/resolve/resolved-bus.c b/src/resolve/resolved-bus.c
new file mode 100644
index 0000000000..4a011efc4d
--- /dev/null
+++ b/src/resolve/resolved-bus.c
@@ -0,0 +1,468 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+/***
+  This file is part of systemd.
+
+  Copyright 2014 Lennart Poettering
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU Lesser General Public License as published by
+  the Free Software Foundation; either version 2.1 of the License, or
+  (at your option) any later version.
+
+  systemd is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include "bus-errors.h"
+#include "bus-util.h"
+
+#include "resolved.h"
+#include "resolved-dns-domain.h"
+
+static void bus_method_resolve_hostname_complete(DnsQuery *q) {
+        int r;
+
+        assert(q);
+
+        switch(q->state) {
+
+        case DNS_QUERY_SKIPPED:
+                r = sd_bus_reply_method_errorf(q->request, BUS_ERROR_NO_NAME_SERVERS, "Not appropriate name servers or networks found");
+                break;
+
+        case DNS_QUERY_TIMEOUT:
+                r = sd_bus_reply_method_errorf(q->request, SD_BUS_ERROR_TIMEOUT, "Query timed out");
+                break;
+
+        case DNS_QUERY_ATTEMPTS_MAX:
+                r = sd_bus_reply_method_errorf(q->request, SD_BUS_ERROR_TIMEOUT, "All attempts to contact name servers or networks failed");
+                break;
+
+        case DNS_QUERY_FAILURE: {
+                _cleanup_bus_error_free_ sd_bus_error error = SD_BUS_ERROR_NULL;
+
+                if (q->rcode == DNS_RCODE_NXDOMAIN)
+                        sd_bus_error_setf(&error, _BUS_ERROR_DNS "NXDOMAIN", "Hostname %s does not exist", q->request_hostname);
+                else {
+                        const char *rc, *n;
+                        char p[DECIMAL_STR_MAX(q->rcode)];
+
+                        rc = dns_rcode_to_string(q->rcode);
+                        if (!rc) {
+                                sprintf(p, "%i", q->rcode);
+                                rc = p;
+                        }
+
+                        n = strappenda(_BUS_ERROR_DNS, rc);
+
+                        sd_bus_error_setf(&error, n, "Could not resolve hostname %s, server or network returned error %s", q->request_hostname, rc);
+                }
+
+                r = sd_bus_reply_method_error(q->request, &error);
+                break;
+        }
+
+        case DNS_QUERY_SUCCESS: {
+                _cleanup_bus_message_unref_ sd_bus_message *reply = NULL;
+                unsigned i, n, added = 0;
+
+                assert(q->packet);
+
+                r = dns_packet_skip_question(q->packet);
+                if (r < 0)
+                        goto parse_fail;
+
+                r = sd_bus_message_new_method_return(q->request, &reply);
+                if (r < 0)
+                        goto finish;
+
+                r = sd_bus_message_open_container(reply, 'a', "(yayi)");
+                if (r < 0)
+                        goto finish;
+
+                n = be16toh(DNS_PACKET_HEADER(q->packet)->ancount) +
+                    be16toh(DNS_PACKET_HEADER(q->packet)->nscount) +
+                    be16toh(DNS_PACKET_HEADER(q->packet)->arcount);
+
+                for (i = 0; i < n; i++) {
+                        _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL;
+
+                        r = dns_packet_read_rr(q->packet, &rr, NULL);
+                        if (r < 0)
+                                goto parse_fail;
+
+                        if (rr->key.class != DNS_CLASS_IN)
+                                continue;
+
+                        if (!(q->request_family != AF_INET6 && rr->key.type == DNS_TYPE_A) &&
+                            !(q->request_family != AF_INET && rr->key.type == DNS_TYPE_AAAA))
+                                continue;
+
+                        if (!dns_name_equal(rr->key.name, q->request_hostname))
+                                continue;
+
+                        r = sd_bus_message_open_container(reply, 'r', "yayi");
+                        if (r < 0)
+                                goto finish;
+
+                        if (rr->key.type == DNS_TYPE_A) {
+                                r = sd_bus_message_append(reply, "y", AF_INET);
+                                if (r < 0)
+                                        goto finish;
+
+                                r = sd_bus_message_append_array(reply, 'y', &rr->a.in_addr, sizeof(struct in_addr));
+                        } else {
+                                r = sd_bus_message_append(reply, "y", AF_INET6);
+                                if (r < 0)
+                                        goto finish;
+
+                                r = sd_bus_message_append_array(reply, 'y', &rr->aaaa.in6_addr, sizeof(struct in6_addr));
+                        }
+                        if (r < 0)
+                                goto finish;
+
+                        r = sd_bus_message_append(reply, "i", q->packet->ifindex);
+                        if (r < 0)
+                                goto finish;
+
+                        r = sd_bus_message_close_container(reply);
+                        if (r < 0)
+                                goto finish;
+
+                        added ++;
+                }
+
+                if (added <= 0)
+                        goto parse_fail;
+
+                r = sd_bus_message_close_container(reply);
+                if (r < 0)
+                        goto finish;
+
+                r = sd_bus_send(q->manager->bus, reply, NULL);
+                break;
+        }
+
+        parse_fail:
+        case DNS_QUERY_INVALID_REPLY:
+                r = sd_bus_reply_method_errorf(q->request, BUS_ERROR_INVALID_REPLY, "Received invalid reply");
+                break;
+
+        case DNS_QUERY_NULL:
+        case DNS_QUERY_SENT:
+                assert_not_reached("Unexpected query state");
+        }
+
+finish:
+        if (r < 0)
+                log_error("Failed to send bus reply: %s", strerror(-r));
+
+        dns_query_free(q);
+}
+
+static int bus_method_resolve_hostname(sd_bus *bus, sd_bus_message *message, void *userdata, sd_bus_error *error) {
+        Manager *m = userdata;
+        const char *hostname;
+        uint8_t family;
+        DnsResourceKey keys[2];
+        DnsQuery *q;
+        unsigned n = 0;
+        int r;
+
+        assert(bus);
+        assert(message);
+        assert(m);
+
+        r = sd_bus_message_read(message, "sy", &hostname, &family);
+        if (r < 0)
+                return r;
+
+        if (!IN_SET(family, AF_INET, AF_INET6, AF_UNSPEC))
+                return sd_bus_error_setf(error, SD_BUS_ERROR_INVALID_ARGS, "Unknown address family %u", family);
+
+        if (!hostname_is_valid(hostname))
+                return sd_bus_error_setf(error, SD_BUS_ERROR_INVALID_ARGS, "Invalid hostname '%s'", hostname);
+
+        if (family != AF_INET6) {
+                keys[n].class = DNS_CLASS_IN;
+                keys[n].type = DNS_TYPE_A;
+                keys[n].name = (char*) hostname;
+                n++;
+        }
+
+        if (family != AF_INET) {
+                keys[n].class = DNS_CLASS_IN;
+                keys[n].type = DNS_TYPE_AAAA;
+                keys[n].name = (char*) hostname;
+                n++;
+        }
+
+        r = dns_query_new(m, &q, keys, n);
+        if (r < 0)
+                return r;
+
+        q->request = sd_bus_message_ref(message);
+        q->request_family = family;
+        q->request_hostname = hostname;
+        q->complete = bus_method_resolve_hostname_complete;
+
+        r = dns_query_start(q);
+        if (r < 0) {
+                dns_query_free(q);
+                return r;
+        }
+
+        return 1;
+}
+
+static void bus_method_resolve_address_complete(DnsQuery *q) {
+        _cleanup_free_ char *ip = NULL;
+        int r;
+
+        assert(q);
+
+        in_addr_to_string(q->request_family, &q->request_address, &ip);
+
+        switch(q->state) {
+
+        case DNS_QUERY_SKIPPED:
+                r = sd_bus_reply_method_errorf(q->request, BUS_ERROR_NO_NAME_SERVERS, "Not appropriate name servers or networks found");
+                break;
+
+        case DNS_QUERY_TIMEOUT:
+                r = sd_bus_reply_method_errorf(q->request, SD_BUS_ERROR_TIMEOUT, "Query timed out");
+                break;
+
+        case DNS_QUERY_ATTEMPTS_MAX:
+                r = sd_bus_reply_method_errorf(q->request, SD_BUS_ERROR_TIMEOUT, "All attempts to contact name servers or networks failed");
+                break;
+
+        case DNS_QUERY_FAILURE: {
+                _cleanup_bus_error_free_ sd_bus_error error = SD_BUS_ERROR_NULL;
+
+                if (q->rcode == DNS_RCODE_NXDOMAIN)
+                        sd_bus_error_setf(&error, _BUS_ERROR_DNS "NXDOMAIN", "No hostname known for address %s ", ip);
+                else {
+                        const char *rc, *n;
+                        char p[DECIMAL_STR_MAX(q->rcode)];
+
+                        rc = dns_rcode_to_string(q->rcode);
+                        if (!rc) {
+                                sprintf(p, "%i", q->rcode);
+                                rc = p;
+                        }
+
+                        n = strappenda(_BUS_ERROR_DNS, rc);
+
+                        sd_bus_error_setf(&error, n, "Could not resolve address %s, server or network returned error %s", ip, rc);
+                }
+
+                r = sd_bus_reply_method_error(q->request, &error);
+                break;
+        }
+
+        case DNS_QUERY_SUCCESS: {
+                _cleanup_bus_message_unref_ sd_bus_message *reply = NULL;
+                unsigned i, n, added = 0;
+                _cleanup_free_ char *reverse = NULL;
+
+                assert(q->packet);
+
+                r = dns_name_reverse(q->request_family, &q->request_address, &reverse);
+                if (r < 0)
+                        goto finish;
+
+                r = dns_packet_skip_question(q->packet);
+                if (r < 0)
+                        goto parse_fail;
+
+                r = sd_bus_message_new_method_return(q->request, &reply);
+                if (r < 0)
+                        goto finish;
+
+                r = sd_bus_message_open_container(reply, 'a', "s");
+                if (r < 0)
+                        goto finish;
+
+                n = be16toh(DNS_PACKET_HEADER(q->packet)->ancount) +
+                    be16toh(DNS_PACKET_HEADER(q->packet)->nscount) +
+                    be16toh(DNS_PACKET_HEADER(q->packet)->arcount);
+
+                for (i = 0; i < n; i++) {
+                        _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL;
+
+                        r = dns_packet_read_rr(q->packet, &rr, NULL);
+                        if (r < 0)
+                                goto parse_fail;
+
+                        if (rr->key.class != DNS_CLASS_IN)
+                                continue;
+                        if (rr->key.type != DNS_TYPE_PTR)
+                                continue;
+                        if (!dns_name_equal(rr->key.name, reverse))
+                                continue;
+
+                        r = sd_bus_message_append(reply, "s", rr->ptr.name);
+                        if (r < 0)
+                                goto finish;
+
+                        added ++;
+                }
+
+                if (added <= 0)
+                        goto parse_fail;
+
+                r = sd_bus_message_close_container(reply);
+                if (r < 0)
+                        goto finish;
+
+                r = sd_bus_send(q->manager->bus, reply, NULL);
+                break;
+        }
+
+        parse_fail:
+        case DNS_QUERY_INVALID_REPLY:
+                r = sd_bus_reply_method_errorf(q->request, BUS_ERROR_INVALID_REPLY, "Received invalid reply");
+                break;
+
+        case DNS_QUERY_NULL:
+        case DNS_QUERY_SENT:
+                assert_not_reached("Unexpected query state");
+        }
+
+finish:
+        if (r < 0)
+                log_error("Failed to send bus reply: %s", strerror(-r));
+
+        dns_query_free(q);
+}
+
+static int bus_method_resolve_address(sd_bus *bus, sd_bus_message *message, void *userdata, sd_bus_error *error) {
+        _cleanup_(dns_resource_key_free) DnsResourceKey key = {};
+        Manager *m = userdata;
+        uint8_t family;
+        const void *d;
+        int ifindex;
+        DnsQuery *q;
+        size_t sz;
+        int r;
+
+        assert(bus);
+        assert(message);
+        assert(m);
+
+        r = sd_bus_message_read(message, "y", &family);
+        if (r < 0)
+                return r;
+
+        if (!IN_SET(family, AF_INET, AF_INET6))
+                return sd_bus_error_setf(error, SD_BUS_ERROR_INVALID_ARGS, "Unknown address family %u", family);
+
+        r = sd_bus_message_read_array(message, 'y', &d, &sz);
+        if (r < 0)
+                return r;
+
+        if ((family == AF_INET && sz != sizeof(struct in_addr)) ||
+            (family == AF_INET6 && sz != sizeof(struct in6_addr)))
+                return sd_bus_error_setf(error, SD_BUS_ERROR_INVALID_ARGS, "Invalid address size");
+
+        r = sd_bus_message_read(message, "i", &ifindex);
+        if (r < 0)
+                return r;
+        if (ifindex < 0)
+                return sd_bus_error_setf(error, SD_BUS_ERROR_INVALID_ARGS, "Invalid interface index");
+
+        key.class = DNS_CLASS_IN;
+        key.type = DNS_TYPE_PTR;
+        r = dns_name_reverse(family, d, &key.name);
+        if (r < 0)
+                return r;
+
+        r = dns_query_new(m, &q, &key, 1);
+        if (r < 0)
+                return r;
+
+        q->request = sd_bus_message_ref(message);
+        q->request_family = family;
+        memcpy(&q->request_address, d, sz);
+        q->complete = bus_method_resolve_address_complete;
+
+        r = dns_query_start(q);
+        if (r < 0) {
+                dns_query_free(q);
+                return r;
+        }
+
+        return 1;
+}
+
+static const sd_bus_vtable resolve_vtable[] = {
+        SD_BUS_VTABLE_START(0),
+        SD_BUS_METHOD("ResolveHostname", "sy", "a(yayi)", bus_method_resolve_hostname, SD_BUS_VTABLE_UNPRIVILEGED),
+        SD_BUS_METHOD("ResolveAddress", "yayi", "as", bus_method_resolve_address, SD_BUS_VTABLE_UNPRIVILEGED),
+        SD_BUS_VTABLE_END,
+};
+
+static int on_bus_retry(sd_event_source *s, usec_t usec, void *userdata) {
+        Manager *m = userdata;
+
+        assert(s);
+        assert(m);
+
+        m->bus_retry_event_source = sd_event_source_unref(m->bus_retry_event_source);
+
+        manager_connect_bus(m);
+        return 0;
+}
+
+int manager_connect_bus(Manager *m) {
+        int r;
+
+        assert(m);
+
+        if (m->bus)
+                return 0;
+
+        r = sd_bus_default_system(&m->bus);
+        if (r < 0) {
+                /* We failed to connect? Yuck, we must be in early
+                 * boot. Let's try in 5s again. As soon as we have
+                 * kdbus we can stop doing this... */
+
+                log_debug("Failed to connect to bus, trying again in 5s: %s", strerror(-r));
+
+                r = sd_event_add_time(m->event, &m->bus_retry_event_source, CLOCK_MONOTONIC, now(CLOCK_MONOTONIC) + 5*USEC_PER_SEC, 0, on_bus_retry, m);
+                if (r < 0) {
+                        log_error("Failed to install bus reconnect time event: %s", strerror(-r));
+                        return r;
+                }
+
+                return 0;
+        }
+
+        r = sd_bus_add_object_vtable(m->bus, NULL, "/org/freedesktop/resolve1", "org.freedesktop.resolve1", resolve_vtable, m);
+        if (r < 0) {
+                log_error("Failed to register object: %s", strerror(-r));
+                return r;
+        }
+
+        r = sd_bus_request_name(m->bus, "org.freedesktop.resolve1", 0);
+        if (r < 0) {
+                log_error("Failed to register name: %s", strerror(-r));
+                return r;
+        }
+
+        r = sd_bus_attach_event(m->bus, m->event, 0);
+        if (r < 0) {
+                log_error("Failed to attach bus to event loop: %s", strerror(-r));
+                return r;
+        }
+
+        return 0;
+}