[RFC] skbuff: skb_mac_header_was_set is always true on >32 bit

[Stephen Hemminger <shemminger@vyatta.com>]

Looking at the crash in log_martians(), one suspect is that the check for
mac header being set is not correct.  The value of mac_header defaults to
0 on allocation, therefore skb_mac_header_was_set will always be true on
platforms using NET_SKBUFF_USES_OFFSET.

Arnaldo, is this correct?

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>

--- a/net/core/skbuff.c	2009-06-17 08:16:46.235188728 -0700
+++ b/net/core/skbuff.c	2009-06-17 08:17:25.810314332 -0700
@@ -201,6 +201,10 @@ struct sk_buff *__alloc_skb(unsigned int
 	skb->data = data;
 	skb_reset_tail_pointer(skb);
 	skb->end = skb->tail + size;
+#ifdef NET_SKBUFF_DATA_USES_OFFSET
+	skb->mac_header = ~0U;
+#endif
+
 	/* make sure we initialize shinfo sequentially */
 	shinfo = skb_shinfo(skb);
 	atomic_set(&shinfo->dataref, 1);