Strange behaviour of route command

[Giorgos Keramidas]

On 2007-09-10 14:05, Giorgos Keramidas <keramida at freebsd.org> wrote:
> On 2007-09-10 02:03, Nuno Antunes <nuno.antunes at gmail.com> wrote:
> >>> Tom Judge wrote:
> >>>> Hi,
> >>>> While making some changes to the routing table on one of our routers
> >>>> today I noticed that "route add" was showing some strange
> >>>> behaviour. When adding a route for 128/8 to the table rather than
> >>>> adding 128.0.0.0/8 it would add 0.0.0.0/8, however adding 10/9 works
> >>>> correctly.
> >>>>
> >>>> Is this a bug in route or the routing table?
> >
> > Hi,
> > Can you take a look at this patch, please?
> >
> > http://leaf.dragonflybsd.org/mailarchive/submit/2007-09/msg00000.html
>
> Fantastic, thanks for the pointer! :-)
>
> Skimming fast through the diff it seems to be ok.  It doesn't apply
> cleanly over HEAD so some merging was required to get this version
> instead:
>
> %%%
> diff -r 3624c4072e63 sbin/route/route.c
> --- a/sbin/route/route.c	Fri Sep 07 09:19:22 2007 +0000
> +++ b/sbin/route/route.c	Mon Sep 10 14:02:01 2007 +0300
> @@ -799,18 +799,19 @@ inet_makenetandmask(net, sin, bits)
>  	rtm_addrs |= RTA_NETMASK;
>  	if (net == 0)
>  		mask = addr = 0;
> [snip]
> +	else {
> +		if (net <= 0xff)
> +			addr = net << IN_CLASSA_NSHIFT;
> +		else if (net < 0xffff)
> +			addr = net << IN_CLASSB_NSHIFT;
> +		else if (net < 0xffffff)
> +			addr = net << IN_CLASSC_NSHIFT;

... which will fail for 0xffff and 0xffffff comparisons.  I apologize
for not testing all the possible address lengths before emailing the
first patch.

I should have used <= here, so an updated patch is:

%%%
diff -r 3624c4072e63 sbin/route/route.c
--- a/sbin/route/route.c	Fri Sep 07 09:19:22 2007 +0000
+++ b/sbin/route/route.c	Mon Sep 10 14:55:16 2007 +0300
@@ -799,18 +799,19 @@ inet_makenetandmask(net, sin, bits)
 	rtm_addrs |= RTA_NETMASK;
 	if (net == 0)
 		mask = addr = 0;
-	else if (net < 128) {
-		addr = net << IN_CLASSA_NSHIFT;
-		mask = IN_CLASSA_NET;
-	} else if (net < 65536) {
-		addr = net << IN_CLASSB_NSHIFT;
-		mask = IN_CLASSB_NET;
-	} else if (net < 16777216L) {
-		addr = net << IN_CLASSC_NSHIFT;
-		mask = IN_CLASSC_NET;
-	} else {
-		addr = net;
-		if ((addr & IN_CLASSA_HOST) == 0)
+	else {
+		if (net <= 0xff)
+			addr = net << IN_CLASSA_NSHIFT;
+		else if (net <= 0xffff)
+			addr = net << IN_CLASSB_NSHIFT;
+		else if (net <= 0xffffff)
+			addr = net << IN_CLASSC_NSHIFT;
+		else
+			addr = net;
+
+		if (bits)
+			mask = 0xffffffff << (32 - bits);
+		else if ((addr & IN_CLASSA_HOST) == 0)
 			mask =  IN_CLASSA_NET;
 		else if ((addr & IN_CLASSB_HOST) == 0)
 			mask =  IN_CLASSB_NET;
@@ -819,8 +820,6 @@ inet_makenetandmask(net, sin, bits)
 		else
 			mask = -1;
 	}
-	if (bits)
-		mask = 0xffffffff << (32 - bits);
 	sin->sin_addr.s_addr = htonl(addr);
 	sin = &so_mask.sin;
 	sin->sin_addr.s_addr = htonl(mask);
%%%