target/linux/generic/patches-3.18/080-00-fib_trie-Fix-proc-net-fib_trie-when-CONFIG_IP_MULTIP.patch

   1 From: Alexander Duyck <alexander.h.duyck@redhat.com>
   2 Date: Tue, 2 Dec 2014 10:58:21 -0800
   3 Subject: [PATCH] fib_trie: Fix /proc/net/fib_trie when
   4  CONFIG_IP_MULTIPLE_TABLES is not defined
   5
   6 In recent testing I had disabled CONFIG_IP_MULTIPLE_TABLES and as a result
   7 when I ran "cat /proc/net/fib_trie" the main trie was displayed multiple
   8 times.  I found that the problem line of code was in the function
   9 fib_trie_seq_next.  Specifically the line below caused the indexes to go in
  10 the opposite direction of our traversal:
  11
  12         h = tb->tb_id & (FIB_TABLE_HASHSZ - 1);
  13
  14 This issue was that the RT tables are defined such that RT_TABLE_LOCAL is ID
  15 255, while it is located at TABLE_LOCAL_INDEX of 0, and RT_TABLE_MAIN is 254
  16 with a TABLE_MAIN_INDEX of 1.  This means that the above line will return 1
  17 for the local table and 0 for main.  The result is that fib_trie_seq_next
  18 will return NULL at the end of the local table, fib_trie_seq_start will
  19 return the start of the main table, and then fib_trie_seq_next will loop on
  20 main forever as h will always return 0.
  21
  22 The fix for this is to reverse the ordering of the two tables.  It has the
  23 advantage of making it so that the tables now print in the same order
  24 regardless of if multiple tables are enabled or not.  In order to make the
  25 definition consistent with the multiple tables case I simply masked the to
  26 RT_TABLE_XXX values by (FIB_TABLE_HASHSZ - 1).  This way the two table
  27 layouts should always stay consistent.
  28
  29 Fixes: 93456b6 ("[IPV4]: Unify access to the routing tables")
  30 Signed-off-by: Alexander Duyck <alexander.h.duyck@redhat.com>
  31 Signed-off-by: David S. Miller <davem@davemloft.net>
  32 ---
  33
  34 --- a/include/net/ip_fib.h
  35 +++ b/include/net/ip_fib.h
  36 @@ -201,8 +201,8 @@ void fib_free_table(struct fib_table *tb
  37
  38  #ifndef CONFIG_IP_MULTIPLE_TABLES
  39
  40 -#define TABLE_LOCAL_INDEX      0
  41 -#define TABLE_MAIN_INDEX       1
  42 +#define TABLE_LOCAL_INDEX      (RT_TABLE_LOCAL & (FIB_TABLE_HASHSZ - 1))
  43 +#define TABLE_MAIN_INDEX       (RT_TABLE_MAIN  & (FIB_TABLE_HASHSZ - 1))
  44
  45  static inline struct fib_table *fib_get_table(struct net *net, u32 id)
  46  {