[PATCH] Fix "ip rule delete table 256"

[PATCH] Fix "ip rule delete table 256"

[Andreas Henriksson]

When trying to delete a table >= 256 using iproute2 the local table
will be deleted.
The table id is specified as a netlink attribute when it needs more then
8 bits and iproute2 then sets the table field to RT_TABLE_UNSPEC (0).
Preconditions to matching the table id in the rule delete code
doesn't seem to take the "table id in netlink attribute" into condition
so the frh_get_table helper function never gets to do its job when
matching against current rule.
Use the helper function twice instead of peaking at the table value directly.

Originally reported at: http://bugs.debian.org/724783

Reported-by: Nicolas HICHER <nhicher@avencall.com>
Signed-off-by: Andreas Henriksson <andreas@fatal.se>
---
 net/core/fib_rules.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

An alternative would be to say RT_TABLE_UNSPEC is incorrect value
to use for the rule->table when using the netlink attribute and
change iproute2 instead....
... but RT_TABLE_UNSPEC sounds quite suitable, so why not
change the kernel to be more forgiving.

diff --git a/net/core/fib_rules.c b/net/core/fib_rules.c
index 2e65413..f409e0b 100644
--- a/net/core/fib_rules.c
+++ b/net/core/fib_rules.c
@@ -460,7 +460,8 @@ static int fib_nl_delrule(struct sk_buff *skb, struct nlmsghdr* nlh)
 		if (frh->action && (frh->action != rule->action))
 			continue;
 
-		if (frh->table && (frh_get_table(frh, tb) != rule->table))
+		if (frh_get_table(frh, tb) &&
+		    (frh_get_table(frh, tb) != rule->table))
 			continue;
 
 		if (tb[FRA_PRIORITY] &&
-- 
1.8.4.2

Re: [PATCH] Fix "ip rule delete table 256"

[David Miller]

From: Andreas Henriksson <andreas@fatal.se>
Date: Thu, 7 Nov 2013 18:26:38 +0100

> When trying to delete a table >= 256 using iproute2 the local table
> will be deleted.
> The table id is specified as a netlink attribute when it needs more then
> 8 bits and iproute2 then sets the table field to RT_TABLE_UNSPEC (0).
> Preconditions to matching the table id in the rule delete code
> doesn't seem to take the "table id in netlink attribute" into condition
> so the frh_get_table helper function never gets to do its job when
> matching against current rule.
> Use the helper function twice instead of peaking at the table value directly.
> 
> Originally reported at: http://bugs.debian.org/724783
> 
> Reported-by: Nicolas HICHER <nhicher@avencall.com>
> Signed-off-by: Andreas Henriksson <andreas@fatal.se>

Good catch, applied and queued up for -stable, thanks!