[PATCH 3.16.y-ckt 159/183] fib_trie: Fix /proc/net/fib_trie when CONFIG_IP_MULTIPLE_TABLES is not defined

Luis Henriques luis.henriques at canonical.com
Fri Mar 6 09:57:30 UTC 2015

3.16.7-ckt8 -stable review patch.  If anyone has any objections, please let me know.


From: Alexander Duyck <alexander.h.duyck at redhat.com>

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

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