Following patch made against 2.6.24-rc7
It warns if IP stack gets frame with IP header not aligned on dword.
Idea is this will help to identify mis-behaving drivers that do not
enforce this alignment.
-----------------------------
commit d9ff4a47ca7bd902947eb22ed3b01682dce2752f
Author: Vladimir Kondratiev <vladimir.kondratiev@xxxxxxxxx>
Date: Mon Jan 14 10:08:09 2008 +0200
[NET] warn on non-aligned IP header
IP stack silently assumes that IP header is aligned on dword.
While IP stack may be modified to overcome this requirement, it will
impose performance penalty. Better off to force drivers to properly align
data in received frame.
This patch warns once, hoping that frame will be handled properly any way.
Drop frame in this case would be unappropriate - this will break some
wireless drivers.
diff --git a/net/ipv4/ip_input.c b/net/ipv4/ip_input.c
index 168c871..88c8369 100644
--- a/net/ipv4/ip_input.c
+++ b/net/ipv4/ip_input.c
@@ -400,7 +400,23 @@ int ip_rcv(struct sk_buff *skb, struct net_device
*dev, struct packet_type *pt,
goto inhdr_error;
iph = ip_hdr(skb);
-
+ /**
+ * IP stack silently assumes that IP header aligned on dword.
+ * If it is not:
+ * 1. extra time for non-aligned access will be paid for every
+ * architecture;
+ * 2. various things will mis-behave on hardware that do not
+ * support non-aligned access.
+ * Driver code should be fixed.
+ */
+ if (unlikely((u32)iph % 4)) {
+ static int __warned;
+ if (unlikely(!__warned)) {
+ __warned = 1;
+ dev_warn(&orig_dev->dev,"Non aligned IP header from [%s]\n",
+ orig_dev->name);
+ }
+ }
/*
* RFC1122: 3.1.2.2 MUST silently discard any IP frame that
fails the checksum.
*
-
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