Refactor acceptance of new local connections

The various cases of success or failure are quite intricate.  Since we
plan to intricate it further in an upcoming commit, it's better to
refactor it now.

babeld.c

@@ -89,6 +89,7 @@ struct timeval check_neighbours_timeout, check_interfaces_timeout;
 
 static volatile sig_atomic_t exiting = 0, dumping = 0, reopening = 0;
 
+static int accept_local_connections(fd_set *readfds);
 static int kernel_routes_callback(int changed, void *closure);
 static void init_signals(void);
 static void dump_tables(FILE *out);
@@ -621,23 +622,7 @@ main(int argc, char **argv)
         }
 
 #ifndef NO_LOCAL_INTERFACE
-        if(local_server_socket >= 0 &&
-           FD_ISSET(local_server_socket, &readfds)) {
-            int s;
-            s = accept(local_server_socket, NULL, NULL);
-            if(s < 0) {
-                if(errno != EINTR && errno != EAGAIN)
-                    perror("accept(local_server_socket)");
-            } else if(num_local_sockets >= MAX_LOCAL_SOCKETS) {
-                /* This should never happen, since we don't select for
-                   the server socket in this case.  But I'm paranoid. */
-                fprintf(stderr, "Internal error: too many local sockets.\n");
-                close(s);
-            } else {
-                local_sockets[num_local_sockets++] = s;
-                local_notify_all_1(s);
-            }
-        }
+        accept_local_connections(&readfds);
 
         i = 0;
         while(i < num_local_sockets) {
@@ -839,6 +824,36 @@ main(int argc, char **argv)
     exit(1);
 }
 
+static int
+accept_local_connections(fd_set *readfds)
+{
+    if(local_server_socket < 0 || !FD_ISSET(local_server_socket, readfds))
+        return 0;
+
+    int s;
+    s = accept(local_server_socket, NULL, NULL);
+
+    if(s < 0) {
+        if(errno != EINTR && errno != EAGAIN) {
+            perror("accept(local_server_socket)");
+            return -1;
+        }
+        return 0;
+    }
+
+    if(num_local_sockets >= MAX_LOCAL_SOCKETS) {
+        /* This should never happen, since we don't select for
+           the server socket in this case.  But I'm paranoid. */
+        fprintf(stderr, "Internal error: too many local sockets.\n");
+        close(s);
+        return -1;
+    }
+
+    local_sockets[num_local_sockets++] = s;
+    local_notify_all_1(s);
+    return 1;
+}
+
 void
 schedule_neighbours_check(int msecs, int override)
 {