Default route metric

Define the metric of the default route and only add it if there
is no other default route with the same metric.  With the default
value of -1, the route is only added if there is no default route
at all.

Olivier Mehani <olivier.mehani@nicta.com.au>
Index: ppp-2.4.4/pppd/options.c
===================================================================
--- ppp-2.4.4.orig/pppd/options.c	2006-06-18 21:26:00.000000000 +1000
+++ ppp-2.4.4/pppd/options.c	2010-04-22 17:08:38.000000000 +1000
@@ -119,6 +119,7 @@
 bool	dryrun;			/* print out option values and exit */
 char	*domain;		/* domain name set by domain option */
 int	child_wait = 5;		/* # seconds to wait for children at exit */
+int	dfl_route_metric = -1;	/* metric of the default route to set over the PPP link */
 
 #ifdef MAXOCTETS
 unsigned int  maxoctets = 0;    /* default - no limit */
@@ -281,6 +282,10 @@
       "Number of seconds to wait for child processes at exit",
       OPT_PRIO },
 
+    { "defaultroute-metric", o_int, &dfl_route_metric,
+      "Metric to use for the default route (Linux only; -1 for default behavior)",
+      OPT_PRIV|OPT_LLIMIT|OPT_INITONLY, NULL, 0, -1 },
+
 #ifdef HAVE_MULTILINK
     { "multilink", o_bool, &multilink,
       "Enable multilink operation", OPT_PRIO | 1 },
Index: ppp-2.4.4/pppd/sys-linux.c
===================================================================
--- ppp-2.4.4.orig/pppd/sys-linux.c	2005-08-27 08:44:35.000000000 +1000
+++ ppp-2.4.4/pppd/sys-linux.c	2010-04-22 17:09:44.000000000 +1000
@@ -232,7 +232,7 @@
 static void close_route_table (void);
 static int open_route_table (void);
 static int read_route_table (struct rtentry *rt);
-static int defaultroute_exists (struct rtentry *rt);
+static int defaultroute_exists (struct rtentry *rt, int metric);
 static int get_ether_addr (u_int32_t ipaddr, struct sockaddr *hwaddr,
 			   char *name, int namelen);
 static void decode_version (char *buf, int *version, int *mod, int *patch);
@@ -242,6 +242,8 @@
 
 extern u_char	inpacket_buf[];	/* borrowed from main.c */
 
+extern int dfl_route_metric;
+
 /*
  * SET_SA_FAMILY - set the sa_family field of a struct sockaddr,
  * if it exists.
@@ -1526,9 +1528,10 @@
 /********************************************************************
  *
  * defaultroute_exists - determine if there is a default route
+ * with the given metric (or negative for any)
  */
 
-static int defaultroute_exists (struct rtentry *rt)
+static int defaultroute_exists (struct rtentry *rt, int metric)
 {
     int result = 0;
 
@@ -1541,7 +1544,8 @@
 
 	if (kernel_version > KVERSION(2,1,0) && SIN_ADDR(rt->rt_genmask) != 0)
 	    continue;
-	if (SIN_ADDR(rt->rt_dst) == 0L) {
+	if (SIN_ADDR(rt->rt_dst) == 0L && (metric < 0 ||
+			 (metric >= 0 && (rt->rt_metric + 1) == metric))) {
 	    result = 1;
 	    break;
 	}
@@ -1588,13 +1592,13 @@
 {
     struct rtentry rt;
 
-    if (defaultroute_exists(&rt) && strcmp(rt.rt_dev, ifname) != 0) {
+    if (defaultroute_exists(&rt, dfl_route_metric) && strcmp(rt.rt_dev, ifname) != 0) {
 	if (rt.rt_flags & RTF_GATEWAY)
-	    error("not replacing existing default route via %I",
-		  SIN_ADDR(rt.rt_gateway));
+	    error("not replacing existing default route via %I with metric %d",
+		  SIN_ADDR(rt.rt_gateway), dfl_route_metric);
 	else
-	    error("not replacing existing default route through %s",
-		  rt.rt_dev);
+	    error("not replacing existing default route through %s with metric %d",
+		  rt.rt_dev, dfl_route_metric);
 	return 0;
     }
 
@@ -1602,6 +1606,7 @@
     SET_SA_FAMILY (rt.rt_dst, AF_INET);
 
     rt.rt_dev = ifname;
+    rt.rt_metric = dfl_route_metric + 1; /* +1 for binary compatibility */
 
     if (kernel_version > KVERSION(2,1,0)) {
 	SET_SA_FAMILY (rt.rt_genmask, AF_INET);
@@ -1634,6 +1639,9 @@
     SET_SA_FAMILY (rt.rt_dst,     AF_INET);
     SET_SA_FAMILY (rt.rt_gateway, AF_INET);
 
+    rt.rt_dev = ifname;
+    rt.rt_metric = dfl_route_metric + 1; /* +1 for binary compatibility */
+
     if (kernel_version > KVERSION(2,1,0)) {
 	SET_SA_FAMILY (rt.rt_genmask, AF_INET);
 	SIN_ADDR(rt.rt_genmask) = 0L;
Index: ppp-2.4.4/pppd/pppd.8
===================================================================
--- ppp-2.4.4.orig/pppd/pppd.8	2006-06-16 10:01:23.000000000 +1000
+++ ppp-2.4.4/pppd/pppd.8	2010-04-22 17:08:38.000000000 +1000
@@ -121,6 +121,12 @@
 This entry is removed when the PPP connection is broken.  This option
 is privileged if the \fInodefaultroute\fR option has been specified.
 .TP
+.B defaultroute-metric
+Define the metric of the \fIdefaultroute\fR and only add it if there
+is no other default route with the same metric.  With the default
+value of -1, the route is only added if there is no default route at
+all.
+.TP
 .B disconnect \fIscript
 Execute the command specified by \fIscript\fR, by passing it to a
 shell, after