Add support for listening on kernel sockets.

babel.c

@@ -71,6 +71,7 @@ char *state_file = "/var/lib/babel-state";
 int protocol_port;
 unsigned char protocol_group[16];
 int protocol_socket = -1;
+int kernel_socket = -1;
 
 static volatile sig_atomic_t exiting = 0, dumping = 0;
 
@@ -389,7 +390,10 @@ main(int argc, char **argv)
         if(timeval_compare(&tv, &now) > 0) {
             timeval_minus(&tv, &tv, &now);
             FD_SET(protocol_socket, &readfds);
-            rc = select(protocol_socket + 1, &readfds, NULL, NULL, &tv);
+            if(kernel_socket >= 0)
+                FD_SET(kernel_socket, &readfds);
+            rc = select(MAX(protocol_socket, kernel_socket) + 1,
+                        &readfds, NULL, NULL, &tv);
             if(rc < 0 && errno != EINTR) {
                 perror("select");
                 sleep(1);
@@ -402,6 +406,10 @@ main(int argc, char **argv)
         if(exiting)
             break;
 
+        if(kernel_socket >= 0 && FD_ISSET(kernel_socket, &readfds)) {
+            kernel_callback();
+        }
+
         if(FD_ISSET(protocol_socket, &readfds)) {
             rc = babel_recv(protocol_socket, buf, maxmtu,
                               (struct sockaddr*)&sin6, sizeof(sin6));

babel.h

@@ -30,6 +30,10 @@ THE SOFTWARE.
 
 #define INFINITY ((unsigned short)(~0))
 
+#ifndef RTPROT_BABEL
+#define RTPROT_BABEL 42
+#endif
+
 #undef MAX
 #undef MIN
 
@@ -90,3 +94,4 @@ extern int numnets;
 extern int protocol_port;
 extern unsigned char protocol_group[16];
 extern int protocol_socket;
+extern int kernel_socket;