Implement link status detection.

babel.c

@@ -61,7 +61,7 @@ static int maxmtu;
 int reboot_time;
 
 int idle_time = 320;
-
+int link_detect = 0;
 int wireless_hello_interval = -1;
 int wired_hello_interval = -1;
 int idle_hello_interval = -1;
@@ -188,6 +188,8 @@ main(int argc, char **argv)
             debug = atoi(*arg);
         } else if(strcmp(*arg, "-4") == 0) {
             do_ipv4 = 1;
+        } else if(strcmp(*arg, "-l") == 0) {
+            link_detect = 1;
         } else {
             goto syntax;
         }

babel.h

@@ -66,6 +66,7 @@ extern int reboot_time;
 extern int do_ipv4;
 extern int wireless_hello_interval, wired_hello_interval, idle_hello_interval;
 extern int idle_time;
+extern int link_detect;
 
 extern unsigned char myid[16];
 

kernel_netlink.c

@@ -545,6 +545,7 @@ kernel_interface_operational(const char *ifname, int ifindex)
 {
     struct ifreq req;
     int rc;
+    int flags = link_detect ? (IFF_UP | IFF_RUNNING) : IFF_UP;
 
     memset(&req, 0, sizeof(req));
     memset(&req, 0, sizeof(req));
@@ -552,7 +553,7 @@ kernel_interface_operational(const char *ifname, int ifindex)
     rc = ioctl(dgram_socket, SIOCGIFFLAGS, &req);
     if(rc < 0)
         return -1;
-    return ((req.ifr_flags & IFF_UP) != 0);
+    return ((req.ifr_flags & flags) == flags);
 }
 
 int