[LARTC] bug fixed: equal cost multipath shows first hop as dead

From: bert hubert <ahu@ds9a.nl>
To: lartc@vger.kernel.org
Subject: [LARTC] bug fixed: equal cost multipath shows first hop as dead
Date: Thu, 20 Dec 2001 13:58:59 +0000	[thread overview]
Message-ID: <marc-lartc-100885677229167@msgid-missing> (raw)

This had been bugging me for a while:

  # ip ro add dev eth0 default nexthop via 10.0.0.1 dev eth0 nexthop via
    10.0.0.202 dev eth0
  # ip ro ls
  10.0.0.0/8 dev eth0  proto kernel  scope link  src 10.0.0.11
  default
> 	nexthop via 10.0.0.1  dev eth0 weight 1 dead
  	nexthop via 10.0.0.202  dev eth0 weight 1

Some people did not see this bug, other people did. Note how the first
nexthop is 'dead', even though it isn't.

It turns out that this is due to a bug in 'ip' which only occurs with some
versions of gcc, amongst which gcc-2.95.

I posted a detailed bugreport, and our great friend Julian Anastasov replied
within minutes with this patch:

--- iproute2/ip/iproute.c.orig	Mon Aug  6 03:31:52 2001
+++ iproute2/ip/iproute.c	Thu Dec 20 13:14:06 2001
@@ -620,6 +620,8 @@
 		}
 		rtnh->rtnh_len = sizeof(*rtnh);
 		rtnh->rtnh_ifindex = 0;
+		rtnh->rtnh_flags = 0;
+		rtnh->rtnh_hops = 0;
 		rta->rta_len += rtnh->rtnh_len;
 		parse_one_nh(rta, rtnh, &argc, &argv);
 		rtnh = RTNH_NEXT(rtnh);

And then 'nexthop' works as it should. Note that this does not mean that it
does roundrobin over your nexthops. The routecache prevents this. If anybody
is a 'nexthop' expert, please help me write a section on it.

Regards,

bert

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