[ 032/122] ipv4: add a fib_type to fib_info

Greg Kroah-Hartman
2012-10-10T23:15:06Z

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit f4ef85bbda96324785097356336bc79cdd37db0a ]

commit d2d68ba9fe8 (ipv4: Cache input routes in fib_info nexthops.)
introduced a regression for forwarding.

This was hard to reproduce but the symptom was that packets were
delivered to local host instead of being forwarded.

David suggested to add fib_type to fib_info so that we dont
inadvertently share same fib_info for different purposes.

With help from Julian Anastasov who provided very helpful
hints, reproduced here :

<quote>
Can it be a problem related to fib_info reuse
from different routes. For example, when local IP address
is created for subnet we have:

broadcast 192.168.0.255 dev DEV proto kernel scope link src
192.168.0.1
192.168.0.0/24 dev DEV proto kernel scope link src 192.168.0.1
local 192.168.0.1 dev DEV proto kernel scope host src 192.168.0.1

The "dev DEV proto kernel scope link src 192.168.0.1" is
a reused fib_info structure where we put cached routes.
The result can be same fib_info for 192.168.0.255 and
192.168.0.0/24. RTN_BROADCAST is cached only for input
routes. Incoming broadcast to 192.168.0.255 can be cached
and can cause problems for traffic forwarded to 192.168.0.0/24.
So, this patch should solve the problem because it
separates the broadcast from unicast traffic.

And the ip_route_input_slow caching will work for
local and broadcast input routes (above routes 1 and 3) just
because they differ in scope and use different fib_info.

</quote>

Many thanks to Chris Clayton for his patience and help.

Reported-by: Chris Clayton <chris2553@googlemail.com>
Bisected-by: Chris Clayton <chris2553@googlemail.com>
Reported-by: Dave Jones <davej@redhat.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Julian Anastasov <ja@ssi.bg>
Tested-by: Chris Clayton <chris2553@googlemail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
include/net/ip_fib.h | 1 +
net/ipv4/fib_semantics.c | 2 ++
2 files changed, 3 insertions(+)

--- a/include/net/ip_fib.h
+++ b/include/net/ip_fib.h
@@ -102,6 +102,7 @@ struct fib_info {
unsigned char fib_dead;
unsigned char fib_protocol;
unsigned char fib_scope;
+ unsigned char fib_type;
__be32 fib_prefsrc;
u32 fib_priority;
u32 *fib_metrics;
--- a/net/ipv4/fib_semantics.c
+++ b/net/ipv4/fib_semantics.c
@@ -314,6 +314,7 @@ static struct fib_info *fib_find_info(co
nfi->fib_scope == fi->fib_scope &&
nfi->fib_prefsrc == fi->fib_prefsrc &&
nfi->fib_priority == fi->fib_priority &&
+ nfi->fib_type == fi->fib_type &&
memcmp(nfi->fib_metrics, fi->fib_metrics,
sizeof(u32) * RTAX_MAX) == 0 &&
((nfi->fib_flags ^ fi->fib_flags) & ~RTNH_F_DEAD) == 0 &&
@@ -833,6 +834,7 @@ struct fib_info *fib_create_info(struct
fi->fib_flags = cfg->fc_flags;
fi->fib_priority = cfg->fc_priority;
fi->fib_prefsrc = cfg->fc_prefsrc;
+ fi->fib_type = cfg->fc_type;

fi->fib_nhs = nhs;
change_nexthops(fi) {