[PATCH] net: Optimize flush calculation in inet_gro_receive()

[Helge Deller <deller@kernel.org>]

For the calculation of the flush variable, use the get_unaligned_xxx() helpers
to access only relevant bits of the IP header.

Note: Since I don't know the network details, I'm not sure if "& ~IP_DF"
(& ~0x4000) is correct, or if "& IP_OFFSET" (& 0x1FFF) should be used instead
(which I believe would be more correct). Instead of possibly breaking things I
left it as is, but maybe some expert can check?

Signed-off-by: Helge Deller <deller@gmx.de>

diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index c7731e300a44..58cad2687c2c 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -1479,7 +1479,7 @@ struct sk_buff *inet_gro_receive(struct list_head *head, struct sk_buff *skb)
 	struct sk_buff *p;
 	unsigned int hlen;
 	unsigned int off;
-	int flush = 1;
+	u16 flush = 1;
 	int proto;
 
 	off = skb_gro_offset(skb);
@@ -1504,7 +1504,8 @@ struct sk_buff *inet_gro_receive(struct list_head *head, struct sk_buff *skb)
 		goto out;
 
 	NAPI_GRO_CB(skb)->proto = proto;
-	flush = (u16)((ntohl(*(__be32 *)iph) ^ skb_gro_len(skb)) | (ntohl(*(__be32 *)&iph->id) & ~IP_DF));
+	flush = (get_unaligned_be16(&iph->tot_len) ^ skb_gro_len(skb)) |
+	        (get_unaligned_be16(&iph->frag_off) & ~IP_DF);
 
 	list_for_each_entry(p, head, list) {
 		struct iphdr *iph2;