Re: [LARTC] Forwarded traffic bypassing filter

[Amit Gandhi <subscribeamit@yahoo.com>]

I found out the culprit piece of code in the u32 filter classifier. Some
foundation first. I am using 2.4.18 kernel on MPC855T the powerpc
version. 

Now the following code snippet from 'cls_u32.c'

static int u32_classify(struct sk_buff *skb, struct tcf_proto *tp,
struct tcf_result *res)
{
   struct {
      struct tc_u_knode *knode;
      u8      *ptr;
   } stack[TC_U32_MAXDEPTH];

   struct tc_u_hnode *ht = (struct tc_u_hnode*)tp->root;
   u8 *ptr = skb->nh.raw;
   struct tc_u_knode *n;
   int sdepth = 0;
   int off2 = 0;
   int sel = 0;
   int i;

/********* CULPRIT CODE *******/
#if !defined(__i386__) && !defined(__mc68000__)
   if ( (unsigned long)ptr & 3 )
      return -1;
#endif
/********* CULPRIT CODE *******/

......
.........

The above code checks for word alignment of a packet on PowerPC
platforms and it somehow fails for forwarded packets then packets
generated by the local host. Now, I checked newer versions of kernel &
it seems that this piece of code has been removed from them. 

So, this issue is closed.

Thanks,
+Amit

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