sd-dhcp-client/networkd: add transient hostname support

src/network/networkd-gperf.gperf

@@ -32,5 +32,6 @@ Route.Gateway,           config_parse_gateway,          0,       0
 Route.Destination,       config_parse_destination,      0,       0
 DHCPv4.UseDNS,           config_parse_bool,             0,       offsetof(Network, dhcp_dns)
 DHCPv4.UseMTU,           config_parse_bool,             0,       offsetof(Network, dhcp_mtu)
+DHCPv4.UseHostname,      config_parse_bool,             0,       offsetof(Network, dhcp_hostname)
 Bridge.Description,      config_parse_string,           0,       offsetof(Bridge, description)
 Bridge.Name,             config_parse_ifname,           0,       offsetof(Bridge, name)

src/network/networkd-link.c

@@ -25,6 +25,7 @@
 #include "networkd.h"
 #include "libudev-private.h"
 #include "util.h"
+#include "bus-util.h"
 
 int link_new(Manager *manager, struct udev_device *device, Link **ret) {
         _cleanup_link_free_ Link *link = NULL;
@@ -310,6 +311,46 @@ static int address_drop_handler(sd_rtnl *rtnl, sd_rtnl_message *m, void *userdat
         return 1;
 }
 
+static int set_hostname_handler(sd_bus *bus, sd_bus_message *m, void *userdata, sd_bus_error *ret_error) {
+        int r;
+
+        r = sd_bus_message_get_errno(m);
+        if (r < 0)
+                log_warning("Could not set hostname: %s", strerror(-r));
+
+        return 1;
+}
+
+static int set_hostname(sd_bus *bus, const char *hostname) {
+        _cleanup_bus_message_unref_ sd_bus_message *m = NULL;
+        int r = 0;
+
+        assert(bus);
+        assert(hostname);
+
+        log_debug("Setting transient hostname: '%s'", hostname);
+
+        r = sd_bus_message_new_method_call(
+                        bus,
+                        "org.freedesktop.hostname1",
+                        "/org/freedesktop/hostname1",
+                        "org.freedesktop.hostname1",
+                        "SetHostname",
+                        &m);
+        if (r < 0)
+                return r;
+
+        r = sd_bus_message_append(m, "sb", hostname, false);
+        if (r < 0)
+                return r;
+
+        r = sd_bus_call_async(bus, m, set_hostname_handler, NULL, 0, NULL);
+        if (r < 0)
+                log_error("Could not set transient hostname: %s", strerror(-r));
+
+        return r;
+}
+
 static int set_mtu_handler(sd_rtnl *rtnl, sd_rtnl_message *m, void *userdata) {
         Link *link = userdata;
         int r;
@@ -370,6 +411,7 @@ static void dhcp_handler(sd_dhcp_client *client, int event, void *userdata) {
 
         assert(link);
         assert(link->network);
+        assert(link->manager);
 
         if (link->state == LINK_STATE_FAILED)
                 return;
@@ -410,6 +452,12 @@ static void dhcp_handler(sd_dhcp_client *client, int event, void *userdata) {
                                 }
                         }
                 }
+
+                if (link->network->dhcp_hostname) {
+                        r = set_hostname(link->manager->bus, "");
+                        if (r < 0)
+                                log_error("Failed to reset transient hostname");
+                }
         }
 
         r = sd_dhcp_client_get_address(client, &address);
@@ -507,6 +555,18 @@ static void dhcp_handler(sd_dhcp_client *client, int event, void *userdata) {
                         }
                 }
 
+                if (link->network->dhcp_hostname) {
+                        const char *hostname;
+
+                        r = sd_dhcp_client_get_hostname(client, &hostname);
+                        if (r >= 0) {
+                                r = set_hostname(link->manager->bus, hostname);
+                                if (r < 0)
+                                        log_error("Failed to set transient hostname "
+                                                  "to '%s'", hostname);
+                        }
+                }
+
                 link_enter_set_addresses(link);
         }
 

src/network/networkd-manager.c

@@ -54,6 +54,10 @@ int manager_new(Manager **ret) {
         if (r < 0)
                 return r;
 
+        r = sd_bus_default_system(&m->bus);
+        if (r < 0)
+                return r;
+
         m->udev = udev_new();
         if (!m->udev)
                 return -ENOMEM;
@@ -85,6 +89,7 @@ void manager_free(Manager *m) {
 
         udev_monitor_unref(m->udev_monitor);
         udev_unref(m->udev);
+        sd_bus_unref(m->bus);
         sd_event_source_unref(m->udev_event_source);
         sd_event_unref(m->event);
 
@@ -280,6 +285,16 @@ int manager_rtnl_listen(Manager *m) {
         return 0;
 }
 
+int manager_bus_listen(Manager *m) {
+        int r;
+
+        r = sd_bus_attach_event(m->bus, m->event, 0);
+        if (r < 0)
+                return r;
+
+        return 0;
+}
+
 static void append_dns(FILE *f, struct in_addr *dns, unsigned char family, unsigned *count) {
         char buf[INET6_ADDRSTRLEN];
         const char *address;

src/network/networkd-network.c

@@ -67,6 +67,7 @@ static int network_load_one(Manager *manager, const char *filename) {
 
         network->dhcp_dns = true;
         network->dhcp_mtu = true;
+        network->dhcp_hostname = true;
 
         r = config_parse(NULL, filename, file, "Match\0Network\0Address\0Route\0DHCPv4\0", config_item_perf_lookup,
                         (void*) network_gperf_lookup, false, false, network);

src/network/networkd.c

@@ -70,6 +70,12 @@ int main(int argc, char *argv[]) {
                 goto out;
         }
 
+        r = manager_bus_listen(m);
+        if (r < 0) {
+                log_error("Could not connect to system bus: %s", strerror(-r));
+                goto out;
+        }
+
         /* write out empty resolv.conf to avoid a
          * dangling symlink */
         r = manager_update_resolv_conf(m);

src/network/networkd.h

@@ -26,6 +26,7 @@
 
 #include "sd-event.h"
 #include "sd-rtnl.h"
+#include "sd-bus.h"
 #include "sd-dhcp-client.h"
 #include "udev.h"
 
@@ -87,6 +88,7 @@ struct Network {
         bool dhcp;
         bool dhcp_dns;
         bool dhcp_mtu;
+        bool dhcp_hostname;
 
         LIST_HEAD(Address, static_addresses);
         LIST_HEAD(Route, static_routes);
@@ -174,6 +176,7 @@ struct Link {
 struct Manager {
         sd_rtnl *rtnl;
         sd_event *event;
+        sd_bus *bus;
         struct udev *udev;
         struct udev_monitor *udev_monitor;
         sd_event_source *udev_event_source;
@@ -199,6 +202,7 @@ int manager_udev_enumerate_links(Manager *m);
 int manager_udev_listen(Manager *m);
 
 int manager_rtnl_listen(Manager *m);
+int manager_bus_listen(Manager *m);
 
 int manager_update_resolv_conf(Manager *m);