[3.16.y-ckt stable] Patch "fib_trie: Fix /proc/net/fib_trie when CONFIG_IP_MULTIPLE_TABLES is not defined" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    fib_trie: Fix /proc/net/fib_trie when CONFIG_IP_MULTIPLE_TABLES is not defined

to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.16.y-queue

This patch is scheduled to be released in version 3.16.7-ckt8.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 7819a0d964def5ae327540f58519521fd82bb3b4 Mon Sep 17 00:00:00 2001
From: Alexander Duyck <alexander.h.duyck at redhat.com>
Date: Tue, 2 Dec 2014 10:58:21 -0800
Subject: fib_trie: Fix /proc/net/fib_trie when CONFIG_IP_MULTIPLE_TABLES is
 not defined

commit a5a519b2710be43fce3cf9ce7bd8de8db3f2a9de upstream.

In recent testing I had disabled CONFIG_IP_MULTIPLE_TABLES and as a result
when I ran "cat /proc/net/fib_trie" the main trie was displayed multiple
times.  I found that the problem line of code was in the function
fib_trie_seq_next.  Specifically the line below caused the indexes to go in
the opposite direction of our traversal:

	h = tb->tb_id & (FIB_TABLE_HASHSZ - 1);

This issue was that the RT tables are defined such that RT_TABLE_LOCAL is ID
255, while it is located at TABLE_LOCAL_INDEX of 0, and RT_TABLE_MAIN is 254
with a TABLE_MAIN_INDEX of 1.  This means that the above line will return 1
for the local table and 0 for main.  The result is that fib_trie_seq_next
will return NULL at the end of the local table, fib_trie_seq_start will
return the start of the main table, and then fib_trie_seq_next will loop on
main forever as h will always return 0.

The fix for this is to reverse the ordering of the two tables.  It has the
advantage of making it so that the tables now print in the same order
regardless of if multiple tables are enabled or not.  In order to make the
definition consistent with the multiple tables case I simply masked the to
RT_TABLE_XXX values by (FIB_TABLE_HASHSZ - 1).  This way the two table
layouts should always stay consistent.

Fixes: 93456b6 ("[IPV4]: Unify access to the routing tables")
Signed-off-by: Alexander Duyck <alexander.h.duyck at redhat.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 include/net/ip_fib.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/net/ip_fib.h b/include/net/ip_fib.h
index 9922093f575e..699c4046a8cb 100644
--- a/include/net/ip_fib.h
+++ b/include/net/ip_fib.h
@@ -200,8 +200,8 @@ void fib_free_table(struct fib_table *tb);

 #ifndef CONFIG_IP_MULTIPLE_TABLES

-#define TABLE_LOCAL_INDEX	0
-#define TABLE_MAIN_INDEX	1
+#define TABLE_LOCAL_INDEX	(RT_TABLE_LOCAL & (FIB_TABLE_HASHSZ - 1))
+#define TABLE_MAIN_INDEX	(RT_TABLE_MAIN  & (FIB_TABLE_HASHSZ - 1))

 static inline struct fib_table *fib_get_table(struct net *net, u32 id)
 {