Add ability to specify router-id explicitly on the command-line.

There is no equivalent config-file option, since I'm worried about config
files being copied between nodes.

CHANGES

 babeld-1.6.2 (unreleased)
 
+  * Added the ability to specify a router-id explicitly (-R).
   * Changed router-id computation to use all interfaces, which increases
     the chances of a stable id.
   * Changed the format of babel-state to only contain the seqno -- the

babeld.c

@@ -56,6 +56,7 @@ THE SOFTWARE.
 struct timeval now;
 
 unsigned char myid[8];
+int have_id = 0;
 int debug = 0;
 
 int link_detect = 0;
@@ -126,7 +127,8 @@ main(int argc, char **argv)
     has_ipv6_subtrees = kernel_has_ipv6_subtrees();
 
     while(1) {
-        opt = getopt(argc, argv, "m:p:h:H:i:k:A:sruS:d:g:lwz:M:t:T:c:C:DL:I:");
+        opt = getopt(argc, argv,
+                     "m:p:h:H:i:k:A:srR:uS:d:g:lwz:M:t:T:c:C:DL:I:");
         if(opt < 0)
             break;
 
@@ -179,6 +181,12 @@ main(int argc, char **argv)
         case 'r':
             random_id = 1;
             break;
+        case 'R':
+            rc = parse_eui64(optarg, myid);
+            if(rc < 0)
+                goto usage;
+            have_id = 1;
+            break;
         case 'u':
             keep_unfeasible = 1;
             break;
@@ -395,9 +403,7 @@ main(int argc, char **argv)
         goto fail;
     }
 
-    if(random_id)
-        goto random_id;
-
+    if(!have_id && !random_id) {
         /* We use all available interfaces here, since this increases the
            chances of getting a stable router-id in case the set of Babel
            interfaces changes. */
@@ -412,13 +418,16 @@ main(int argc, char **argv)
             if(rc < 0)
                 continue;
             memcpy(myid, eui, 8);
-        goto have_id;
+            have_id = 1;
+            break;
+        }
     }
 
+    if(!have_id) {
+        if(!random_id)
             fprintf(stderr,
-            "Warning: couldn't find router id -- using random value.\n");
-
- random_id:
+                    "Warning: couldn't find router id -- "
+                    "using random value.\n");
         rc = read_random_bytes(myid, 8);
         if(rc < 0) {
             perror("read(random)");
@@ -426,8 +435,8 @@ main(int argc, char **argv)
         }
         /* Clear group and global bits */
         myid[0] &= ~3;
+    }
 
- have_id:
     myseqno = (random() & 0xFFFF);
 
     fd = open(state_file, O_RDONLY);

babeld.man

@@ -94,6 +94,11 @@ derived from the MAC address of the first interface, which is easier
 to debug and more reliably prevents routing loops but may sometimes
 cause a node to be unreachable for 120 seconds just after boot.
 .TP
+.BI \-R " router-id"
+Specify the router-id explicitly, as a modified EUI-64 or a MAC-48
+address.  If two nodes have the same router-id, bad things will happen.
+Don't use this option unless you know what you are doing.
+.TP
 .B \-u
 Do not flush unfeasible (useless) routes.  This is useful in order to
 announce more information to a front-end (see