networkd: start a DBus interface for the DHCP server

Add a "org.freedesktop.network1.DHCPServer" DBus interface that will be
added on a link path where a DHCP server is provided.

Currently, it only exposes a "Leases" property, although there are plans
to expand it further. The property is updated thanks to the
dhcp_server_callback().

src/network/meson.build

@@ -61,6 +61,8 @@ sources = files('''
         networkd-conf.h
         networkd-dhcp-common.c
         networkd-dhcp-common.h
+        networkd-dhcp-server-bus.c
+        networkd-dhcp-server-bus.h
         networkd-dhcp-server.c
         networkd-dhcp-server.h
         networkd-dhcp4.c

src/network/networkd-dhcp-server-bus.c

@@ -0,0 +1,111 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+
+#include "sd-dhcp-server.h"
+
+#include "alloc-util.h"
+#include "bus-common-errors.h"
+#include "bus-util.h"
+#include "dhcp-server-internal.h"
+#include "networkd-dhcp-server-bus.h"
+#include "networkd-link-bus.h"
+#include "networkd-manager.h"
+#include "strv.h"
+
+static int property_get_leases(
+                sd_bus *bus,
+                const char *path,
+                const char *interface,
+                const char *property,
+                sd_bus_message *reply,
+                void *userdata,
+                sd_bus_error *error) {
+        Link *l = userdata;
+        sd_dhcp_server *s;
+        DHCPLease *lease;
+        Iterator i;
+        int r;
+
+        assert(reply);
+        assert(l);
+
+        s = l->dhcp_server;
+        if (!s)
+                return sd_bus_error_setf(error, SD_BUS_ERROR_NOT_SUPPORTED, "Link %s has no DHCP server.", l->ifname);
+
+        r = sd_bus_message_open_container(reply, 'a', "(uayayayayt)");
+        if (r < 0)
+                return r;
+
+        HASHMAP_FOREACH(lease, s->leases_by_client_id, i) {
+                r = sd_bus_message_open_container(reply, 'r', "uayayayayt");
+                if (r < 0)
+                        return r;
+
+                r = sd_bus_message_append(reply, "u", (uint32_t)AF_INET);
+                if (r < 0)
+                        return r;
+
+                r = sd_bus_message_append_array(reply, 'y', lease->client_id.data, lease->client_id.length);
+                if (r < 0)
+                        return r;
+
+                r = sd_bus_message_append_array(reply, 'y', &lease->address, sizeof(lease->address));
+                if (r < 0)
+                        return r;
+
+                r = sd_bus_message_append_array(reply, 'y', &lease->gateway, sizeof(lease->gateway));
+                if (r < 0)
+                        return r;
+
+                r = sd_bus_message_append_array(reply, 'y', &lease->chaddr, sizeof(lease->chaddr));
+                if (r < 0)
+                        return r;
+
+                r = sd_bus_message_append_basic(reply, 't', &lease->expiration);
+                if (r < 0)
+                        return r;
+
+                r = sd_bus_message_close_container(reply);
+                if (r < 0)
+                        return r;
+        }
+
+        return sd_bus_message_close_container(reply);
+}
+
+static int dhcp_server_emit_changed(Link *link, const char *property, ...) {
+        _cleanup_free_ char *path = NULL;
+        char **l;
+
+        assert(link);
+
+        path = link_bus_path(link);
+        if (!path)
+                return log_oom();
+
+        l = strv_from_stdarg_alloca(property);
+
+        return sd_bus_emit_properties_changed_strv(
+                        link->manager->bus,
+                        path,
+                        "org.freedesktop.network1.DHCPServer",
+                        l);
+}
+
+void dhcp_server_callback(sd_dhcp_server *s, uint64_t event, void *data) {
+        Link *l = data;
+
+        assert(l);
+
+        if (event & SD_DHCP_SERVER_EVENT_LEASE_CHANGED)
+                (void) dhcp_server_emit_changed(l, "Leases", NULL);
+}
+
+
+const sd_bus_vtable dhcp_server_vtable[] = {
+        SD_BUS_VTABLE_START(0),
+
+        SD_BUS_PROPERTY("Leases", "a(uayayayayt)", property_get_leases, 0, SD_BUS_VTABLE_PROPERTY_EMITS_CHANGE),
+
+        SD_BUS_VTABLE_END
+};

src/network/networkd-dhcp-server-bus.h

@@ -0,0 +1,9 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+#pragma once
+
+#include "sd-bus.h"
+#include "networkd-link.h"
+
+extern const sd_bus_vtable dhcp_server_vtable[];
+
+void dhcp_server_callback(sd_dhcp_server *server, uint64_t event, void *data);