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, 378 insertions, 0 deletions

diff --git a/src/resolve/resolved-link.c b/src/resolve/resolved-link.c
new file mode 100644
index 0000000000..27477de7b5
--- /dev/null
+++ b/src/resolve/resolved-link.c
@@ -0,0 +1,378 @@
+/*-*- 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 <net/if.h>
+
+#include "sd-network.h"
+#include "dhcp-lease-internal.h"
+#include "strv.h"
+#include "resolved-link.h"
+
+int link_new(Manager *m, Link **ret, int ifindex) {
+        _cleanup_(link_freep) Link *l = NULL;
+        int r;
+
+        assert(m);
+        assert(ifindex > 0);
+
+        r = hashmap_ensure_allocated(&m->links, NULL, NULL);
+        if (r < 0)
+                return r;
+
+        l = new0(Link, 1);
+        if (!l)
+                return -ENOMEM;
+
+        l->ifindex = ifindex;
+
+        r = hashmap_put(m->links, INT_TO_PTR(ifindex), l);
+        if (r < 0)
+                return r;
+
+        l->manager = m;
+
+        if (ret)
+                *ret = l;
+        l = NULL;
+
+        return 0;
+}
+
+Link *link_free(Link *l) {
+
+        if (!l)
+                return NULL;
+
+        while (l->addresses)
+                link_address_free(l->addresses);
+
+        if (l->manager)
+                hashmap_remove(l->manager->links, INT_TO_PTR(l->ifindex));
+
+        dns_scope_free(l->unicast_scope);
+        dns_scope_free(l->mdns_ipv4_scope);
+        dns_scope_free(l->mdns_ipv6_scope);
+
+        while (l->dhcp_dns_servers)
+                dns_server_free(l->dhcp_dns_servers);
+
+        while (l->link_dns_servers)
+                dns_server_free(l->link_dns_servers);
+
+        free(l);
+        return NULL;
+ }
+
+int link_update_rtnl(Link *l, sd_rtnl_message *m) {
+        int r;
+
+        assert(l);
+        assert(m);
+
+        r = sd_rtnl_message_link_get_flags(m, &l->flags);
+        if (r < 0)
+                return r;
+
+        return 0;
+}
+
+static int update_dhcp_dns_servers(Link *l) {
+        _cleanup_dhcp_lease_unref_ sd_dhcp_lease *lease = NULL;
+        _cleanup_free_ struct in_addr *nameservers = NULL;
+        DnsServer *s, *nx;
+        unsigned i;
+        size_t n;
+        int r;
+
+        assert(l);
+
+        r = sd_network_dhcp_use_dns(l->ifindex);
+        if (r <= 0)
+                goto clear;
+
+        r = sd_network_get_dhcp_lease(l->ifindex, &lease);
+        if (r < 0)
+                goto clear;
+
+        LIST_FOREACH(servers, s, l->dhcp_dns_servers)
+                s->marked = true;
+
+        r = sd_dhcp_lease_get_dns(lease, &nameservers, &n);
+        if (r < 0)
+                goto clear;
+
+        for (i = 0; i < n; i++) {
+                union in_addr_union a = { .in = nameservers[i] };
+
+                s = link_find_dns_server(l, DNS_SERVER_DHCP, AF_INET, &a);
+                if (s)
+                        s->marked = false;
+                else {
+                        r = dns_server_new(l->manager, NULL, DNS_SERVER_DHCP, l, AF_INET, &a);
+                        if (r < 0)
+                                goto clear;
+                }
+        }
+
+        LIST_FOREACH_SAFE(servers, s, nx, l->dhcp_dns_servers)
+                if (s->marked)
+                        dns_server_free(s);
+
+        return 0;
+
+clear:
+        while (l->dhcp_dns_servers)
+                dns_server_free(l->dhcp_dns_servers);
+
+        return r;
+}
+
+static int update_link_dns_servers(Link *l) {
+        _cleanup_free_ struct in_addr *nameservers = NULL;
+        _cleanup_free_ struct in6_addr *nameservers6 = NULL;
+        DnsServer *s, *nx;
+        unsigned i;
+        size_t n;
+        int r;
+
+        assert(l);
+
+        LIST_FOREACH(servers, s, l->link_dns_servers)
+                s->marked = true;
+
+        r = sd_network_get_dns(l->ifindex, &nameservers, &n);
+        if (r < 0)
+                goto clear;
+
+        for (i = 0; i < n; i++) {
+                union in_addr_union a = { .in = nameservers[i] };
+
+                s = link_find_dns_server(l, DNS_SERVER_LINK, AF_INET, &a);
+                if (s)
+                        s->marked = false;
+                else {
+                        r = dns_server_new(l->manager, NULL, DNS_SERVER_LINK, l, AF_INET, &a);
+                        if (r < 0)
+                                goto clear;
+                }
+        }
+
+        r = sd_network_get_dns6(l->ifindex, &nameservers6, &n);
+        if (r < 0)
+                goto clear;
+
+        for (i = 0; i < n; i++) {
+                union in_addr_union a = { .in6 = nameservers6[i] };
+
+                s = link_find_dns_server(l, DNS_SERVER_LINK, AF_INET6, &a);
+                if (s)
+                        s->marked = false;
+                else {
+                        r = dns_server_new(l->manager, NULL, DNS_SERVER_LINK, l, AF_INET6, &a);
+                        if (r < 0)
+                                goto clear;
+                }
+        }
+
+        LIST_FOREACH_SAFE(servers, s, nx, l->link_dns_servers)
+                if (s->marked)
+                        dns_server_free(s);
+
+        return 0;
+
+clear:
+        while (l->link_dns_servers)
+                dns_server_free(l->link_dns_servers);
+
+        return r;
+}
+
+int link_update_monitor(Link *l) {
+        assert(l);
+
+        free(l->operational_state);
+        l->operational_state = NULL;
+
+        sd_network_get_link_operational_state(l->ifindex, &l->operational_state);
+
+        update_dhcp_dns_servers(l);
+        update_link_dns_servers(l);
+
+        return 0;
+}
+
+bool link_relevant(Link *l) {
+        LinkAddress *a;
+
+        assert(l);
+
+        /* A link is relevant if it isn't a loopback device and has at
+         * least one relevant IP address */
+
+        if (l->flags & IFF_LOOPBACK)
+                return false;
+
+        if (l->operational_state && !STR_IN_SET(l->operational_state, "unknown", "degraded", "routable"))
+                return false;
+
+        LIST_FOREACH(addresses, a, l->addresses)
+                if (link_address_relevant(a))
+                        return true;
+
+        return false;
+}
+
+LinkAddress *link_find_address(Link *l, unsigned char family, union in_addr_union *in_addr) {
+        LinkAddress *a;
+
+        assert(l);
+
+        LIST_FOREACH(addresses, a, l->addresses) {
+
+                if (a->family == family &&
+                    in_addr_equal(family, &a->in_addr, in_addr))
+                        return a;
+        }
+
+        return NULL;
+}
+
+DnsServer* link_find_dns_server(Link *l, DnsServerSource source, unsigned char family, union in_addr_union *in_addr) {
+        DnsServer *first, *s;
+
+        assert(l);
+
+        first = source == DNS_SERVER_DHCP ? l->dhcp_dns_servers : l->link_dns_servers;
+
+        LIST_FOREACH(servers, s, first) {
+
+                if (s->family == family &&
+                    in_addr_equal(family, &s->address, in_addr))
+                        return s;
+        }
+
+        return NULL;
+}
+
+DnsServer *link_get_dns_server(Link *l) {
+        assert(l);
+
+        if (!l->current_dns_server)
+                l->current_dns_server = l->link_dns_servers;
+        if (!l->current_dns_server)
+                l->current_dns_server = l->dhcp_dns_servers;
+
+        return l->current_dns_server;
+}
+
+void link_next_dns_server(Link *l) {
+        assert(l);
+
+        /* Switch to the next DNS server */
+
+        if (!l->current_dns_server) {
+                l->current_dns_server = l->link_dns_servers;
+                if (l->current_dns_server)
+                        return;
+        }
+
+        if (!l->current_dns_server) {
+                l->current_dns_server = l->dhcp_dns_servers;
+                if (l->current_dns_server)
+                        return;
+        }
+
+        if (!l->current_dns_server)
+                return;
+
+        if (l->current_dns_server->servers_next) {
+                l->current_dns_server = l->current_dns_server->servers_next;
+                return;
+        }
+
+        if (l->current_dns_server->source == DNS_SERVER_LINK)
+                l->current_dns_server = l->dhcp_dns_servers;
+        else {
+                assert(l->current_dns_server->source == DNS_SERVER_DHCP);
+                l->current_dns_server = l->link_dns_servers;
+        }
+}
+
+int link_address_new(Link *l, LinkAddress **ret, unsigned char family, union in_addr_union *in_addr) {
+        LinkAddress *a;
+
+        assert(l);
+        assert(in_addr);
+
+        a = new0(LinkAddress, 1);
+        if (!a)
+                return -ENOMEM;
+
+        a->family = family;
+        a->in_addr = *in_addr;
+
+        a->link = l;
+        LIST_PREPEND(addresses, l->addresses, a);
+
+        if (ret)
+                *ret = a;
+
+        return 0;
+}
+
+LinkAddress *link_address_free(LinkAddress *a) {
+        if (!a)
+                return NULL;
+
+        if (a->link)
+                LIST_REMOVE(addresses, a->link->addresses, a);
+
+        free(a);
+        return NULL;
+}
+
+int link_address_update_rtnl(LinkAddress *a, sd_rtnl_message *m) {
+        int r;
+        assert(a);
+        assert(m);
+
+        r = sd_rtnl_message_addr_get_flags(m, &a->flags);
+        if (r < 0)
+                return r;
+
+        r = sd_rtnl_message_addr_get_scope(m, &a->scope);
+        if (r < 0)
+                return r;
+
+        return 0;
+}
+
+bool link_address_relevant(LinkAddress *a) {
+        assert(a);
+
+        if (a->flags & IFA_F_DEPRECATED)
+                return false;
+
+        if (IN_SET(a->scope, RT_SCOPE_HOST, RT_SCOPE_NOWHERE))
+                return false;
+
+        return true;
+}