[Dnsmasq-discuss] [PATCH V2] Add new extensible D-Bus signal

Victorien Molle victorien.molle at wifirst.fr
Thu Jan 23 11:00:37 GMT 2020


For our usage, we need to have more informations sent over D-Bus such as the interface
name, the vendor class identifier and the lease expiration time.

To achieve this, we add a new D-Bus signal "DhcpLeaseNotification" which exports the
requested informations as a dictionnary.
It also has the advantage to be flexible if someone wants to add a new entry in the
future.

Note: in order to get leases extradata be populated, we enabled this feature if D-Bus
is enabled in configuration file (this was enabled in the past only if a script was
ran on leases updates).

Here is an example of the obtained result with a Python3 program:

''' Define our D-Bus callback '''
def cb(action, ipaddr, hwaddr, hostname, info):
    print(f'Action: {action}')
    print(f'IP: {ipaddr}')
    print(f'Hostname: {hostname}')
    for k in info:
        print(f'{k}: {info.get(k)}')

''' Connect to signal DhcpLeaseNotification on interface uk.org.thekelleys.dnsmasq '''
DNSMasq.listen('DhcpLeaseNotification', callback=cb)

''' Run GLib loop '''
GLib.MainLoop().run()

''' When DNSMasq receives a DHCP request, here is the result: '''

Action: 3
IP: 192.168.1.100
Hostname: Nucleus.nucle.us
interface: br-mgmt
vendor_class: LaGrosseBiche
expiration: 1575667431

Signed-off-by: Victorien Molle <victorien.molle at wifirst.fr>
Signed-off-by: Florent Fourcot <florent.fourcot at wifirst.fr>
---
 dbus/DBus-interface |   9 ++++
 src/dbus.c          | 118 +++++++++++++++++++++++++++++++++++++++++++-
 src/dnsmasq.h       |   2 +-
 src/lease.c         |   2 +-
 src/rfc2131.c       |  12 ++---
 5 files changed, 134 insertions(+), 9 deletions(-)

diff --git a/dbus/DBus-interface b/dbus/DBus-interface
index 954c5b9..ed42551 100644
--- a/dbus/DBus-interface
+++ b/dbus/DBus-interface
@@ -273,14 +273,23 @@ DhcpLeaseAdded
 ---------------
 
 This signal is emitted when a DHCP lease for a given IP address is created.
+This will also trigger the DhcpLeaseNotification signal.
 
 DhcpLeaseDeleted
 ----------------
 
 This signal is emitted when a DHCP lease for a given IP address is deleted.
+This will also trigger the DhcpLeaseNotification signal.
 
 DhcpLeaseUpdated
 ----------------
 
 This signal is emitted when a DHCP lease for a given IP address is updated.
+This will also trigger the DhcpLeaseNotification signal.
+
+DhcpLeaseNotification
+---------------------
+
+This signal is emitted when a DHCP lease action is triggered. It exports,
+as a dictionnary, more informations than the other signals.
  
diff --git a/src/dbus.c b/src/dbus.c
index c0ce903..c906e11 100644
--- a/src/dbus.c
+++ b/src/dbus.c
@@ -55,6 +55,7 @@ const char* introspection_xml_template =
 "    <method name=\"SetBogusPrivOption\">\n"
 "      <arg name=\"boguspriv\" direction=\"in\" type=\"b\"/>\n"
 "    </method>\n"
+#ifdef HAVE_DHCP
 "    <signal name=\"DhcpLeaseAdded\">\n"
 "      <arg name=\"ipaddr\" type=\"s\"/>\n"
 "      <arg name=\"hwaddr\" type=\"s\"/>\n"
@@ -70,7 +71,13 @@ const char* introspection_xml_template =
 "      <arg name=\"hwaddr\" type=\"s\"/>\n"
 "      <arg name=\"hostname\" type=\"s\"/>\n"
 "    </signal>\n"
-#ifdef HAVE_DHCP
+"    <signal name=\"DhcpLeaseNotification\">\n"
+"      <arg name=\"notification_type\" type=\"i\"/>\n"
+"      <arg name=\"ipaddr\" type=\"s\"/>\n"
+"      <arg name=\"hwaddr\" type=\"s\"/>\n"
+"      <arg name=\"hostname\" type=\"s\"/>\n"
+"      <arg name=\"lease_info\" type=\"a{sv}\"/>\n"
+"    </signal>\n"
 "    <method name=\"AddDhcpLease\">\n"
 "       <arg name=\"ipaddr\" type=\"s\"/>\n"
 "       <arg name=\"hwaddr\" type=\"s\"/>\n"
@@ -98,6 +105,12 @@ struct watch {
   struct watch *next;
 };
 
+struct lease_info {
+  char *key;
+  char *fmt;
+  char dbus_type;
+  DBusBasicValue value;
+};
 
 static dbus_bool_t add_watch(DBusWatch *watch, void *data)
 {
@@ -828,6 +841,106 @@ void check_dbus_listeners()
 }
 
 #ifdef HAVE_DHCP
+/*
+  As this function is called by emit_dbus_signal, we already have access to ipaddr, hwaddr and hostname attributes
+  NOTE: connection attribute is currently not NULL as it is verified by emit_dbus_signal
+*/
+void emit_dhcplease_notification(DBusConnection *connection, int action, struct dhcp_lease *lease, char *ipaddr, char *hwaddr, char *hostname)
+{
+  DBusMessageIter array, dict, iter, variant;
+  dbus_uint64_t expires = lease->expires;
+  unsigned char *buf = lease->extradata;
+  dbus_int32_t act_type = action;
+  char interface[IF_NAMESIZE];
+  DBusMessage* message = NULL;
+  struct lease_info *info;
+  int fd = daemon->dhcpfd;
+#if defined(HAVE_SCRIPT) || defined(HAVE_DBUS)
+  char *vendor_class;
+  int allocated = 0;
+#endif
+
+#ifdef HAVE_DHCP6
+  if (!daemon->dhcp)
+    fd = daemon->dhcp6fd;
+#endif
+
+  /* Get interface name */
+  if (!indextoname(fd, lease->last_interface, interface))
+    interface[0] = 0;
+
+#if defined(HAVE_SCRIPT) || defined(HAVE_DBUS)
+  vendor_class = "";
+  /* As defined in rfc2131.c, the first data is the vendor class even if it is empty */
+  if (buf && *buf != 0)
+    {
+      vendor_class = (char*)whine_malloc(lease->extradata_len + 1);
+      if (vendor_class)
+        {
+          allocated = 1;
+          strncpy(vendor_class, (const char*)buf, (lease->extradata_len));
+        }
+      else
+        {
+          vendor_class = "";
+        }
+    }
+#endif
+
+  struct lease_info infos[] = {{.key = "interface", .fmt = "s", .dbus_type = DBUS_TYPE_STRING, .value.str = interface},
+#if defined(HAVE_SCRIPT) || defined(HAVE_DBUS)
+                               {.key = "vendor_class", .fmt = "s", .dbus_type = DBUS_TYPE_STRING, .value.str = vendor_class},
+#endif
+                               {.key = "expiration", .fmt = "t", .dbus_type = DBUS_TYPE_UINT64, .value.u64 = expires},
+                               {NULL, NULL, DBUS_TYPE_INVALID, 0}
+                               };
+
+  if (!(message = dbus_message_new_signal(DNSMASQ_PATH, daemon->dbus_name, "DhcpLeaseNotification")))
+    goto out;
+
+  dbus_message_iter_init_append(message, &iter);
+  dbus_message_iter_append_basic(&iter, DBUS_TYPE_INT32, &act_type);
+  dbus_message_iter_append_basic(&iter, DBUS_TYPE_STRING, &ipaddr);
+  dbus_message_iter_append_basic(&iter, DBUS_TYPE_STRING, &hwaddr);
+  dbus_message_iter_append_basic(&iter, DBUS_TYPE_STRING, &hostname);
+  dbus_message_iter_open_container(&iter, DBUS_TYPE_ARRAY, "{sv}", &array);
+  for (info = infos; info->key; info++) {
+    dbus_message_iter_open_container(&array, DBUS_TYPE_DICT_ENTRY, NULL, &dict);
+    dbus_message_iter_append_basic(&dict, DBUS_TYPE_STRING, &info->key);
+    dbus_message_iter_open_container(&dict, DBUS_TYPE_VARIANT, info->fmt, &variant);
+    switch (info->dbus_type)
+      {
+      case DBUS_TYPE_STRING:
+        dbus_message_iter_append_basic(&variant, info->dbus_type, &info->value.str);
+        break;
+
+      case DBUS_TYPE_UINT64:
+        dbus_message_iter_append_basic(&variant, info->dbus_type, &info->value.u64);
+        break;
+
+      default:
+        dbus_message_iter_abandon_container(&dict, &variant);
+        dbus_message_iter_abandon_container_if_open(&array, &dict);
+        dbus_message_iter_abandon_container_if_open(&iter, &array);
+        dbus_message_unref(message);
+        my_syslog(LOG_WARNING, _("Unknown D-Bus type specified for key '%s'. This will completely disable 'DhcpLeaseNotification' signal"),
+                                 info->key);
+        goto out;
+      }
+    dbus_message_iter_close_container(&dict, &variant);
+    dbus_message_iter_close_container(&array, &dict);
+  }
+  dbus_message_iter_close_container(&iter, &array);
+  dbus_connection_send(connection, message, NULL);
+  dbus_message_unref(message);
+
+out:
+#if defined(HAVE_SCRIPT) || defined(HAVE_DBUS)
+  if (vendor_class && allocated)
+    free(vendor_class);
+#endif
+}
+
 void emit_dbus_signal(int action, struct dhcp_lease *lease, char *hostname)
 {
   DBusConnection *connection = (DBusConnection *)daemon->dbus;
@@ -878,6 +991,9 @@ void emit_dbus_signal(int action, struct dhcp_lease *lease, char *hostname)
     dbus_connection_send(connection, message, NULL);
   
   dbus_message_unref(message);
+
+  /* Now emit a notification with more informations */
+  emit_dhcplease_notification(connection, action, lease, daemon->addrbuff, mac, hostname);
 }
 #endif
 
diff --git a/src/dnsmasq.h b/src/dnsmasq.h
index 8e047fc..6b79685 100644
--- a/src/dnsmasq.h
+++ b/src/dnsmasq.h
@@ -1415,7 +1415,7 @@ void lease_update_from_configs(void);
 int do_script_run(time_t now);
 void rerun_scripts(void);
 void lease_find_interfaces(time_t now);
-#ifdef HAVE_SCRIPT
+#if defined(HAVE_SCRIPT) || defined(HAVE_DBUS)
 void lease_add_extradata(struct dhcp_lease *lease, unsigned char *data, 
 			 unsigned int len, int delim);
 #endif
diff --git a/src/lease.c b/src/lease.c
index 081d90e..107b79a 100644
--- a/src/lease.c
+++ b/src/lease.c
@@ -1158,7 +1158,7 @@ int do_script_run(time_t now)
   return 0; /* nothing to do */
 }
 
-#ifdef HAVE_SCRIPT
+#if defined(HAVE_SCRIPT) || defined(HAVE_DBUS)
 /* delim == -1 -> delim = 0, but embedded 0s, creating extra records, are OK. */
 void lease_add_extradata(struct dhcp_lease *lease, unsigned char *data, unsigned int len, int delim)
 {
diff --git a/src/rfc2131.c b/src/rfc2131.c
index 0058747..d4e9802 100644
--- a/src/rfc2131.c
+++ b/src/rfc2131.c
@@ -21,7 +21,7 @@
 #define option_len(opt) ((int)(((unsigned char *)(opt))[1]))
 #define option_ptr(opt, i) ((void *)&(((unsigned char *)(opt))[2u+(unsigned int)(i)]))
 
-#ifdef HAVE_SCRIPT
+#if defined(HAVE_SCRIPT) || defined(HAVE_DBUS)
 static void add_extradata_opt(struct dhcp_lease *lease, unsigned char *opt);
 #endif
 
@@ -97,7 +97,7 @@ size_t dhcp_reply(struct dhcp_context *context, char *iface_name, int int_index,
   struct dhcp_opt *o;
   unsigned char pxe_uuid[17];
   unsigned char *oui = NULL, *serial = NULL;
-#ifdef HAVE_SCRIPT
+#if defined(HAVE_SCRIPT) || defined(HAVE_DBUS)
   unsigned char *class = NULL;
 #endif
 
@@ -163,7 +163,7 @@ size_t dhcp_reply(struct dhcp_context *context, char *iface_name, int int_index,
 		  unsigned char *y = option_ptr(opt, offset + elen + 5);
 		  oui = option_find1(x, y, 1, 1);
 		  serial = option_find1(x, y, 2, 1);
-#ifdef HAVE_SCRIPT
+#if defined(HAVE_SCRIPT) || defined(HAVE_DBUS)
 		  class = option_find1(x, y, 3, 1);		  
 #endif
 		  /* If TR069-id is present set the tag "cpewan-id" to facilitate echoing 
@@ -1365,8 +1365,8 @@ size_t dhcp_reply(struct dhcp_context *context, char *iface_name, int int_index,
 	      /* pick up INIT-REBOOT events. */
 	      lease->flags |= LEASE_CHANGED;
 
-#ifdef HAVE_SCRIPT
-	      if (daemon->lease_change_command)
+#if defined(HAVE_SCRIPT) || defined(HAVE_DBUS)
+	      if (daemon->lease_change_command || daemon->dbus)
 		{
 		  struct dhcp_netid *n;
 		  
@@ -1661,7 +1661,7 @@ static int sanitise(unsigned char *opt, char *buf)
   return 1;
 }
 
-#ifdef HAVE_SCRIPT
+#if defined(HAVE_SCRIPT) || defined(HAVE_DBUS)
 static void add_extradata_opt(struct dhcp_lease *lease, unsigned char *opt)
 {
   if (!opt)
-- 
2.24.0




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