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Subject: [PATCH][RFC] packets received from cipe device are exactly 5 bytes to big
From: Lennert Buytenhek <buytenh,AT,gnu,DOT,org>
Date: Fri, 2 Nov 2001 00:41:47 +0100

Hi,

See subject.  Packets received from a CIPE protocol 4 device (i.e. ethernet
device) are exactly 5 bytes too big at the hardware level.  I suspect this
has something to do with the 'pad up to 3 mod 8 and prepend 5 bytes' thing
that the protocol documentation that I've briefly glanced over describes,
but I'm not really sure.  I'm using the attached patch for now, but it
isn't exactly clean.

This patch _finally_ makes it possible for me to ping with 5k packets over
a bridged CIPE tunnel (with the MTU forced up to the ethernet MTU, see
separate email) by the way, so I'm really wondering whether anyone
has ever put this into production use succesfully.  But that's a wholly
different matter.

Anyway, enlightened ideas about where the problem really lies are
appreciated.  I think I'll go to bed now.

cheers,
Lennert

--- cipe-1.5.2/cipe/sock.c.orig Thu Nov  1 23:25:13 2001
+++ cipe-1.5.2/cipe/sock.c      Thu Nov  1 23:25:18 2001
@@ -346,7 +346,7 @@
 
     dprintk(DEB_INP, (KERN_DEBUG "TW_DATA data=%p len=" FLEN "length=%d\n",
                       n->data, n->len, length));
-    skb_trim(n, length);
+    skb_trim(n, length - 5);
     checkpeer(c, rsaddr, rsport);
     /* adjust pointers */
 #ifdef VER_ETH





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