Strange behaviour of route command

[Giorgos Keramidas]

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;
-	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);
%%%

With this version, I can successfully add *and* delete a route for 128/8
on my laptop and route -nv monitor reports:

# got message of size 132 on Mon Sep 10 14:03:56 2007
# RTM_ADD: Add Route: len 132, pid: 2698, seq 1, errno 0,
# flags:<UP,GATEWAY,DONE,STATIC>
# locks:  inits: 
# sockaddrs: <DST,GATEWAY,NETMASK>
#  128.0.0.0 127.0.0.1 (0) 0 ff
# 
# got message of size 132 on Mon Sep 10 14:03:57 2007
# RTM_DELETE: Delete Route: len 132, pid: 2702, seq 1, errno 0,
# flags:<GATEWAY,DONE,STATIC>
# locks:  inits: 
# sockaddrs: <DST,GATEWAY,NETMASK>
#  128.0.0.0 127.0.0.1 (255) ffff ff