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, 694 insertions, 123 deletions

diff --git a/src/resolve/resolved-manager.c b/src/resolve/resolved-manager.c
index b4f4d07147..dc6deeb7e5 100644
--- a/src/resolve/resolved-manager.c
+++ b/src/resolve/resolved-manager.c
@@ -22,16 +22,286 @@
 #include <arpa/inet.h>
 #include <resolv.h>
 #include <linux/if.h>
+#include <sys/ioctl.h>
+#include <sys/poll.h>
+#include <netinet/in.h>
 
-#include "resolved.h"
+#include "rtnl-util.h"
 #include "event-util.h"
 #include "network-util.h"
 #include "sd-dhcp-lease.h"
 #include "dhcp-lease-internal.h"
 #include "network-internal.h"
 #include "conf-parser.h"
+#include "socket-util.h"
+#include "resolved.h"
+
+#define SEND_TIMEOUT_USEC (200 * USEC_PER_MSEC)
+
+static int manager_process_link(sd_rtnl *rtnl, sd_rtnl_message *mm, void *userdata) {
+        Manager *m = userdata;
+        uint16_t type;
+        Link *l;
+        int ifindex, r;
+
+        assert(rtnl);
+        assert(m);
+        assert(mm);
+
+        r = sd_rtnl_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:
+                if (!l) {
+                        log_debug("Found link %i", ifindex);
+
+                        r = link_new(m, &l, ifindex);
+                        if (r < 0)
+                                goto fail;
+                }
+
+                r = link_update_rtnl(l, mm);
+                if (r < 0)
+                        goto fail;
+
+                break;
+
+        case RTM_DELLINK:
+                if (l) {
+                        log_debug("Removing link %i", l->ifindex);
+                        link_free(l);
+                }
+
+                break;
+        }
+
+        return 0;
+
+fail:
+        log_warning("Failed to process RTNL link message: %s", strerror(-r));
+        return 0;
+}
+
+static int manager_process_address(sd_rtnl *rtnl, sd_rtnl_message *mm, void *userdata) {
+        Manager *m = userdata;
+        union in_addr_union address;
+        unsigned char family;
+        uint16_t type;
+        int r, ifindex;
+        LinkAddress *a;
+        Link *l;
+
+        assert(rtnl);
+        assert(mm);
+        assert(m);
+
+        r = sd_rtnl_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_rtnl_message_read_in_addr(mm, IFA_LOCAL, &address.in);
+                if (r < 0) {
+                        r = sd_rtnl_message_read_in_addr(mm, IFA_ADDRESS, &address.in);
+                        if (r < 0)
+                                goto fail;
+                }
+
+                break;
+
+        case AF_INET6:
+                r = sd_rtnl_message_read_in6_addr(mm, IFA_LOCAL, &address.in6);
+                if (r < 0) {
+                        r = sd_rtnl_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:
+                if (a)
+                        link_address_free(a);
+                break;
+        }
+
+        return 0;
+
+fail:
+        log_warning("Failed to process RTNL address message: %s", strerror(-r));
+        return 0;
+}
+
+
+static int manager_rtnl_listen(Manager *m) {
+        _cleanup_rtnl_message_unref_ sd_rtnl_message *req = NULL, *reply = NULL;
+        sd_rtnl_message *i;
+        int r;
+
+        assert(m);
+
+        /* First, subscibe to interfaces coming and going */
+        r = sd_rtnl_open(&m->rtnl, 3, RTNLGRP_LINK, RTNLGRP_IPV4_IFADDR, RTNLGRP_IPV6_IFADDR);
+        if (r < 0)
+                return r;
+
+        r = sd_rtnl_attach_event(m->rtnl, m->event, 0);
+        if (r < 0)
+                return r;
+
+        r = sd_rtnl_add_match(m->rtnl, RTM_NEWLINK, manager_process_link, m);
+        if (r < 0)
+                return r;
+
+        r = sd_rtnl_add_match(m->rtnl, RTM_DELLINK, manager_process_link, m);
+        if (r < 0)
+                return r;
+
+        r = sd_rtnl_add_match(m->rtnl, RTM_NEWADDR, manager_process_address, m);
+        if (r < 0)
+                return r;
 
-static int set_fallback_dns(Manager *m, const char *string) {
+        r = sd_rtnl_add_match(m->rtnl, RTM_DELADDR, manager_process_address, m);
+        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_rtnl_message_request_dump(req, true);
+        if (r < 0)
+                return r;
+
+        r = sd_rtnl_call(m->rtnl, req, 0, &reply);
+        if (r < 0)
+                return r;
+
+        for (i = reply; i; i = sd_rtnl_message_next(i)) {
+                r = manager_process_link(m->rtnl, i, m);
+                if (r < 0)
+                        return r;
+        }
+
+        req = sd_rtnl_message_unref(req);
+        reply = sd_rtnl_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_rtnl_message_request_dump(req, true);
+        if (r < 0)
+                return r;
+
+        r = sd_rtnl_call(m->rtnl, req, 0, &reply);
+        if (r < 0)
+                return r;
+
+        for (i = reply; i; i = sd_rtnl_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;
+        Iterator i;
+        Link *l;
+        int r;
+
+        assert(m);
+
+        sd_network_monitor_flush(m->network_monitor);
+
+        HASHMAP_FOREACH(l, m->links, i) {
+                r = link_update_monitor(l);
+                if (r < 0)
+                        log_warning("Failed to update monitor information for %i: %s", l->ifindex, strerror(-r));
+        }
+
+        r = manager_write_resolv_conf(m);
+        if (r < 0)
+                log_warning("Could not update resolv.conf: %s", strerror(-r));
+
+        return 0;
+}
+
+static int manager_network_monitor_listen(Manager *m) {
+        int r, fd, events;
+
+        assert(m);
+
+        r = sd_network_monitor_new(NULL, &m->network_monitor);
+        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;
+
+        return 0;
+}
+
+static int parse_dns_server_string(Manager *m, const char *string) {
         char *word, *state;
         size_t length;
         int r;
@@ -40,27 +310,26 @@ static int set_fallback_dns(Manager *m, const char *string) {
         assert(string);
 
         FOREACH_WORD_QUOTED(word, length, string, state) {
-                _cleanup_free_ Address *address = NULL;
-                Address *tail;
-                _cleanup_free_ char *addrstr = NULL;
-
-                address = new0(Address, 1);
-                if (!address)
-                        return -ENOMEM;
+                char buffer[length+1];
+                unsigned family;
+                union in_addr_union addr;
 
-                addrstr = strndup(word, length);
-                if (!addrstr)
-                        return -ENOMEM;
+                memcpy(buffer, word, length);
+                buffer[length] = 0;
 
-                r = net_parse_inaddr(addrstr, &address->family, &address->in_addr);
+                r = in_addr_from_string_auto(buffer, &family, &addr);
                 if (r < 0) {
-                        log_debug("Ignoring invalid DNS address '%s'", addrstr);
+                        log_warning("Ignoring invalid DNS address '%s'", buffer);
                         continue;
                 }
 
-                LIST_FIND_TAIL(addresses, m->fallback_dns, tail);
-                LIST_INSERT_AFTER(addresses, m->fallback_dns, tail, address);
-                address = NULL;
+                /* filter out duplicates */
+                if (manager_find_dns_server(m, family, &addr))
+                        continue;
+
+                r = dns_server_new(m, NULL, DNS_SERVER_SYSTEM, NULL, family, &addr);
+                if (r < 0)
+                        return r;
         }
 
         return 0;
@@ -79,39 +348,48 @@ int config_parse_dnsv(
                 void *userdata) {
 
         Manager *m = userdata;
-        Address *address;
+        int r;
 
         assert(filename);
         assert(lvalue);
         assert(rvalue);
         assert(m);
 
-        while ((address = m->fallback_dns)) {
-                LIST_REMOVE(addresses, m->fallback_dns, address);
-                free(address);
+        /* Empty assignment means clear the list */
+        if (isempty(rvalue)) {
+                while (m->dns_servers)
+                        dns_server_free(m->dns_servers);
+
+                return 0;
         }
 
-        set_fallback_dns(m, rvalue);
+        r = parse_dns_server_string(m, rvalue);
+        if (r < 0) {
+                log_error("Failed to parse DNS server string");
+                return r;
+        }
 
         return 0;
 }
 
-static int manager_parse_config_file(Manager *m) {
+int manager_parse_config_file(Manager *m) {
         int r;
 
         assert(m);
 
-        r = config_parse(NULL, "/etc/systemd/resolved.conf", NULL,
-                         "Resolve\0", config_item_perf_lookup, (void*) resolved_gperf_lookup,
+        r = config_parse(NULL,
+                         "/etc/systemd/resolved.conf", NULL,
+                         "Resolve\0",
+                         config_item_perf_lookup, (void*) resolved_gperf_lookup,
                          false, false, m);
         if (r < 0)
                 log_warning("Failed to parse configuration file: %s", strerror(-r));
 
-        return r;
+        return 0;
 }
 
 int manager_new(Manager **ret) {
-        _cleanup_manager_free_ Manager *m = NULL;
+        _cleanup_(manager_freep) Manager *m = NULL;
         int r;
 
         assert(ret);
@@ -120,11 +398,9 @@ int manager_new(Manager **ret) {
         if (!m)
                 return -ENOMEM;
 
-        r = set_fallback_dns(m, DNS_SERVERS);
-        if (r < 0)
-                return r;
+        m->dns_ipv4_fd = m->dns_ipv6_fd = -1;
 
-        r = manager_parse_config_file(m);
+        r = parse_dns_server_string(m, /* "172.31.0.125 2001:4860:4860::8888 2001:4860:4860::8889" */ DNS_SERVERS);
         if (r < 0)
                 return r;
 
@@ -137,61 +413,96 @@ int manager_new(Manager **ret) {
 
         sd_event_set_watchdog(m->event, true);
 
+        r = dns_scope_new(m, &m->unicast_scope, DNS_SCOPE_DNS);
+        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_connect_bus(m);
+        if (r < 0)
+                return r;
+
         *ret = m;
         m = NULL;
 
         return 0;
 }
 
-void manager_free(Manager *m) {
-        Address *address;
+Manager *manager_free(Manager *m) {
+        Link *l;
 
         if (!m)
-                return;
+                return NULL;
+
+        while (m->dns_queries)
+                dns_query_free(m->dns_queries);
+
+        hashmap_free(m->dns_query_transactions);
+
+        while ((l = hashmap_first(m->links)))
+               link_free(l);
+        hashmap_free(m->links);
+
+        dns_scope_free(m->unicast_scope);
+
+        while (m->dns_servers)
+                dns_server_free(m->dns_servers);
 
         sd_event_source_unref(m->network_event_source);
         sd_network_monitor_unref(m->network_monitor);
-        sd_event_unref(m->event);
 
-        while ((address = m->fallback_dns)) {
-                LIST_REMOVE(addresses, m->fallback_dns, address);
-                free(address);
-        }
+        sd_event_source_unref(m->dns_ipv4_event_source);
+        sd_event_source_unref(m->dns_ipv6_event_source);
+
+        safe_close(m->dns_ipv4_fd);
+        safe_close(m->dns_ipv6_fd);
+
+        sd_event_source_unref(m->bus_retry_event_source);
+        sd_bus_unref(m->bus);
 
+        sd_event_unref(m->event);
         free(m);
+
+        return NULL;
 }
 
-static void append_dns(FILE *f, void *dns, unsigned char family, unsigned *count) {
-        char buf[INET6_ADDRSTRLEN];
-        const char *address;
+static void write_resolve_conf_server(DnsServer *s, FILE *f, unsigned *count) {
+        _cleanup_free_ char *t  = NULL;
+        int r;
 
+        assert(s);
         assert(f);
-        assert(dns);
         assert(count);
 
-        address = inet_ntop(family, dns, buf, INET6_ADDRSTRLEN);
-        if (!address) {
+        r = in_addr_to_string(s->family, &s->address, &t);
+        if (r < 0) {
                 log_warning("Invalid DNS address. Ignoring.");
                 return;
         }
 
         if (*count == MAXNS)
-                fputs("# Too many DNS servers configured, the following entries "
-                      "may be ignored\n", f);
-
-        fprintf(f, "nameserver %s\n", address);
+                fputs("# Too many DNS servers configured, the following entries may be ignored\n", f);
 
+        fprintf(f, "nameserver %s\n", t);
         (*count) ++;
 }
 
-int manager_update_resolv_conf(Manager *m) {
+int manager_write_resolv_conf(Manager *m) {
         const char *path = "/run/systemd/resolve/resolv.conf";
         _cleanup_free_ char *temp_path = NULL;
         _cleanup_fclose_ FILE *f = NULL;
-         _cleanup_free_ unsigned *indices = NULL;
-        Address *address;
         unsigned count = 0;
-        int n, r, i;
+        DnsServer *s;
+        Iterator i;
+        Link *l;
+        int r;
 
         assert(m);
 
@@ -207,108 +518,368 @@ int manager_update_resolv_conf(Manager *m) {
               "# resolv.conf(5) in a different way, replace the symlink by a\n"
               "# static file or a different symlink.\n\n", f);
 
-        n = sd_network_get_ifindices(&indices);
-        if (n < 0)
-                n = 0;
-
-        for (i = 0; i < n; i++) {
-                _cleanup_dhcp_lease_unref_ sd_dhcp_lease *lease = NULL;
-                struct in_addr *nameservers;
-                struct in6_addr *nameservers6;
-                size_t nameservers_size;
-
-                r = sd_network_dhcp_use_dns(indices[i]);
-                if (r > 0) {
-                        r = sd_network_get_dhcp_lease(indices[i], &lease);
-                        if (r >= 0) {
-                                r = sd_dhcp_lease_get_dns(lease, &nameservers, &nameservers_size);
-                                if (r >= 0) {
-                                        unsigned j;
-
-                                        for (j = 0; j < nameservers_size; j++)
-                                                append_dns(f, &nameservers[j], AF_INET, &count);
-                                }
-                        }
-                }
+        HASHMAP_FOREACH(l, m->links, i) {
+                LIST_FOREACH(servers, s, l->link_dns_servers)
+                        write_resolve_conf_server(s, f, &count);
 
-                r = sd_network_get_dns(indices[i], &nameservers, &nameservers_size);
-                if (r >= 0) {
-                        unsigned j;
+                LIST_FOREACH(servers, s, l->dhcp_dns_servers)
+                        write_resolve_conf_server(s, f, &count);
+        }
 
-                        for (j = 0; j < nameservers_size; j++)
-                                append_dns(f, &nameservers[j], AF_INET, &count);
+        LIST_FOREACH(servers, s, m->dns_servers)
+                write_resolve_conf_server(s, f, &count);
 
-                        free(nameservers);
-                }
+        r = fflush_and_check(f);
+        if (r < 0)
+                goto fail;
+
+        if (rename(temp_path, path) < 0) {
+                r = -errno;
+                goto fail;
+        }
 
-                r = sd_network_get_dns6(indices[i], &nameservers6, &nameservers_size);
-                if (r >= 0) {
-                        unsigned j;
+        return 0;
 
-                        for (j = 0; j < nameservers_size; j++)
-                                append_dns(f, &nameservers6[j], AF_INET6, &count);
+fail:
+        unlink(path);
+        unlink(temp_path);
+        return r;
+}
 
-                        free(nameservers6);
-                }
+int manager_dns_ipv4_recv(Manager *m, DnsPacket **ret) {
+        _cleanup_(dns_packet_unrefp) DnsPacket *p = NULL;
+        struct msghdr mh = {};
+        int fd, ms = 0, r;
+        struct iovec iov;
+        ssize_t l;
+
+        assert(m);
+        assert(ret);
+
+        fd = manager_dns_ipv4_fd(m);
+        if (fd < 0)
+                return fd;
+
+        r = ioctl(fd, FIONREAD, &ms);
+        if (r < 0)
+                return -errno;
+        if (ms < 0)
+                return -EIO;
+
+        r = dns_packet_new(&p, ms);
+        if (r < 0)
+                return r;
+
+        iov.iov_base = DNS_PACKET_DATA(p);
+        iov.iov_len = p->allocated;
+
+        mh.msg_iov = &iov;
+        mh.msg_iovlen = 1;
+
+        l = recvmsg(fd, &mh, 0);
+        if (l < 0) {
+                if (errno == EAGAIN)
+                        return 0;
+
+                return -errno;
         }
 
-        LIST_FOREACH(addresses, address, m->fallback_dns)
-                append_dns(f, &address->in_addr, address->family, &count);
+        if (l <= 0)
+                return -EIO;
 
-        fflush(f);
+        p->size = (size_t) l;
 
-        if (ferror(f) || rename(temp_path, path) < 0) {
-                r = -errno;
-                unlink(path);
-                unlink(temp_path);
+        *ret = p;
+        p = NULL;
+
+        return 1;
+}
+
+int manager_dns_ipv6_recv(Manager *m, DnsPacket **ret) {
+        _cleanup_(dns_packet_unrefp) DnsPacket *p = NULL;
+        struct msghdr mh = {};
+        struct iovec iov;
+        int fd, ms = 0, r;
+        ssize_t l;
+
+        assert(m);
+        assert(ret);
+
+        fd = manager_dns_ipv6_fd(m);
+        if (fd < 0)
+                return fd;
+
+        r = ioctl(fd, FIONREAD, &ms);
+        if (r < 0)
+                return -errno;
+        if (ms < 0)
+                return -EIO;
+
+        r = dns_packet_new(&p, ms);
+        if (r < 0)
                 return r;
+
+        iov.iov_base = DNS_PACKET_DATA(p);
+        iov.iov_len = p->allocated;
+
+        mh.msg_iov = &iov;
+        mh.msg_iovlen = 1;
+
+        l = recvmsg(fd, &mh, 0);
+        if (l < 0) {
+                if (errno == EAGAIN)
+                        return 0;
+
+                return -errno;
         }
 
-        return 0;
+        if (l <= 0)
+                return -EIO;
+
+        p->size = (size_t) l;
+
+        *ret = p;
+        p = NULL;
+
+        return 1;
+}
+
+static int on_dns_ipv4_packet(sd_event_source *s, int fd, uint32_t revents, void *userdata) {
+        _cleanup_(dns_packet_unrefp) DnsPacket *p = NULL;
+        DnsQueryTransaction *t = NULL;
+        Manager *m = userdata;
+        int r;
+
+        r = manager_dns_ipv4_recv(m, &p);
+        if (r <= 0)
+                return r;
+
+        t = hashmap_get(m->dns_query_transactions, UINT_TO_PTR(DNS_PACKET_HEADER(p)->id));
+        if (!t)
+                return 0;
+
+        return dns_query_transaction_reply(t, p);
 }
 
-static int manager_network_event_handler(sd_event_source *s, int fd, uint32_t revents,
-                                         void *userdata) {
+static int on_dns_ipv6_packet(sd_event_source *s, int fd, uint32_t revents, void *userdata) {
+        _cleanup_(dns_packet_unrefp) DnsPacket *p = NULL;
+        DnsQueryTransaction *t = NULL;
         Manager *m = userdata;
         int r;
 
+        r = manager_dns_ipv6_recv(m, &p);
+        if (r <= 0)
+                return r;
+
+        t = hashmap_get(m->dns_query_transactions, UINT_TO_PTR(DNS_PACKET_HEADER(p)->id));
+        if (!t)
+                return 0;
+
+        return dns_query_transaction_reply(t, p);
+}
+
+int manager_dns_ipv4_fd(Manager *m) {
+        int r;
+
         assert(m);
 
-        r = manager_update_resolv_conf(m);
-        if (r < 0)
-                log_warning("Could not update resolv.conf: %s", strerror(-r));
+        if (m->dns_ipv4_fd >= 0)
+                return m->dns_ipv4_fd;
 
-        sd_network_monitor_flush(m->network_monitor);
+        m->dns_ipv4_fd = socket(AF_INET, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
+        if (m->dns_ipv4_fd < 0)
+                return -errno;
 
-        return 0;
+        r = sd_event_add_io(m->event, &m->dns_ipv4_event_source, m->dns_ipv4_fd, EPOLLIN, on_dns_ipv4_packet, m);
+        if (r < 0)
+                return r;
+
+        return m->dns_ipv4_fd;
 }
 
-int manager_network_monitor_listen(Manager *m) {
-        _cleanup_event_source_unref_ sd_event_source *event_source = NULL;
-        _cleanup_network_monitor_unref_ sd_network_monitor *monitor = NULL;
-        int r, fd, events;
+int manager_dns_ipv6_fd(Manager *m) {
+        int r;
+
+        assert(m);
 
-        r = sd_network_monitor_new(NULL, &monitor);
+        if (m->dns_ipv6_fd >= 0)
+                return m->dns_ipv6_fd;
+
+        m->dns_ipv6_fd = socket(AF_INET6, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
+        if (m->dns_ipv6_fd < 0)
+                return -errno;
+
+        r = sd_event_add_io(m->event, &m->dns_ipv6_event_source, m->dns_ipv6_fd, EPOLLIN, on_dns_ipv6_packet, m);
         if (r < 0)
                 return r;
 
-        fd = sd_network_monitor_get_fd(monitor);
+        return m->dns_ipv6_fd;
+}
+
+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;
+        }
+}
+
+int manager_dns_ipv4_send(Manager *m, DnsServer *srv, int ifindex, DnsPacket *p) {
+        union sockaddr_union sa = {
+                .in.sin_family = AF_INET,
+                .in.sin_port = htobe16(53),
+        };
+        struct msghdr mh = {};
+        struct iovec iov;
+        uint8_t control[CMSG_SPACE(sizeof(struct in_pktinfo))];
+        int fd;
+
+        assert(m);
+        assert(srv);
+        assert(p);
+
+        fd = manager_dns_ipv4_fd(m);
         if (fd < 0)
                 return fd;
 
-        events = sd_network_monitor_get_events(monitor);
-        if (events < 0)
-                return events;
+        iov.iov_base = DNS_PACKET_DATA(p);
+        iov.iov_len = p->size;
 
-        r = sd_event_add_io(m->event, &event_source, fd, events,
-                            &manager_network_event_handler, m);
-        if (r < 0)
-                return r;
+        sa.in.sin_addr = srv->address.in;
 
-        m->network_monitor = monitor;
-        m->network_event_source = event_source;
-        monitor = NULL;
-        event_source = NULL;
+        mh.msg_iov = &iov;
+        mh.msg_iovlen = 1;
+        mh.msg_name = &sa.sa;
+        mh.msg_namelen = sizeof(sa.in);
 
-        return 0;
+        if (ifindex > 0) {
+                struct cmsghdr *cmsg;
+                struct in_pktinfo *pi;
+
+                zero(control);
+
+                mh.msg_control = control;
+                mh.msg_controllen = CMSG_LEN(sizeof(struct in_pktinfo));
+
+                cmsg = CMSG_FIRSTHDR(&mh);
+                cmsg->cmsg_len = mh.msg_controllen;
+                cmsg->cmsg_level = IPPROTO_IP;
+                cmsg->cmsg_type = IP_PKTINFO;
+
+                pi = (struct in_pktinfo*) CMSG_DATA(cmsg);
+                pi->ipi_ifindex = ifindex;
+        }
+
+        return sendmsg_loop(fd, &mh, 0);
+}
+
+int manager_dns_ipv6_send(Manager *m, DnsServer *srv, int ifindex, DnsPacket *p) {
+        union sockaddr_union sa = {
+                .in6.sin6_family = AF_INET6,
+                .in6.sin6_port = htobe16(53),
+        };
+
+        struct msghdr mh = {};
+        struct iovec iov;
+        uint8_t control[CMSG_SPACE(sizeof(struct in6_pktinfo))];
+        int fd;
+
+        assert(m);
+        assert(srv);
+        assert(p);
+
+        fd = manager_dns_ipv6_fd(m);
+        if (fd < 0)
+                return fd;
+
+        iov.iov_base = DNS_PACKET_DATA(p);
+        iov.iov_len = p->size;
+
+        sa.in6.sin6_addr = srv->address.in6;
+        sa.in6.sin6_scope_id = ifindex;
+
+        mh.msg_iov = &iov;
+        mh.msg_iovlen = 1;
+        mh.msg_name = &sa.sa;
+        mh.msg_namelen = sizeof(sa.in6);
+
+        if (ifindex > 0) {
+                struct cmsghdr *cmsg;
+                struct in6_pktinfo *pi;
+
+                zero(control);
+
+                mh.msg_control = control;
+                mh.msg_controllen = CMSG_LEN(sizeof(struct in6_pktinfo));
+
+                cmsg = CMSG_FIRSTHDR(&mh);
+                cmsg->cmsg_len = mh.msg_controllen;
+                cmsg->cmsg_level = IPPROTO_IPV6;
+                cmsg->cmsg_type = IPV6_PKTINFO;
+
+                pi = (struct in6_pktinfo*) CMSG_DATA(cmsg);
+                pi->ipi6_ifindex = ifindex;
+        }
+
+        return sendmsg_loop(fd, &mh, 0);
+}
+
+DnsServer* manager_find_dns_server(Manager *m, unsigned char family, union in_addr_union *in_addr) {
+        DnsServer *s;
+
+        assert(m);
+        assert(in_addr);
+
+        LIST_FOREACH(servers, s, m->dns_servers) {
+
+                if (s->family == family &&
+                    in_addr_equal(family, &s->address, in_addr))
+                        return s;
+        }
+
+        return NULL;
+}
+
+DnsServer *manager_get_dns_server(Manager *m) {
+        assert(m);
+
+        if (!m->current_dns_server)
+                m->current_dns_server = m->dns_servers;
+
+        return m->current_dns_server;
+}
+
+void manager_next_dns_server(Manager *m) {
+        assert(m);
+
+        if (!m->current_dns_server) {
+                m->current_dns_server = m->dns_servers;
+                return;
+        }
+
+        if (!m->current_dns_server)
+                return;
+
+        if (m->current_dns_server->servers_next) {
+                m->current_dns_server = m->current_dns_server->servers_next;
+                return;
+        }
+
+        m->current_dns_server = m->dns_servers;
 }