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Commit 9f7c824a authored by Liping Zhang's avatar Liping Zhang Committed by Pablo Neira Ayuso
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netfilter: nf_dup4: remove redundant checksum recalculation 



IP header checksum will be recalculated at ip_local_out, so
there's no need to calculated it here, remove it. Also update
code comments to illustrate it, and delete the misleading
comments about checksum recalculation.

Signed-off-by: default avatarLiping Zhang <liping.zhang@spreadtrum.com>
Signed-off-by: default avatarPablo Neira Ayuso <pablo@netfilter.org>
parent ceee4091

net/ipv4/netfilter/nf_dup_ipv4.c

+4 −6
Original line number Diff line number Diff line
@@ -74,21 +74,19 @@ void nf_dup_ipv4(struct net *net, struct sk_buff *skb, unsigned int hooknum, 
	nf_conntrack_get(skb->nfct);

#endif

	/*

	 * If we are in PREROUTING/INPUT, the checksum must be recalculated

	 * since the length could have changed as a result of defragmentation.

	 *

	 * We also decrease the TTL to mitigate potential loops between two

	 * hosts.

	 * If we are in PREROUTING/INPUT, decrease the TTL to mitigate potential

	 * loops between two hosts.

	 *

	 * Set %IP_DF so that the original source is notified of a potentially

	 * decreased MTU on the clone route. IPv6 does this too.

	 *

	 * IP header checksum will be recalculated at ip_local_out.

	 */

	iph = ip_hdr(skb);

	iph->frag_off |= htons(IP_DF);

	if (hooknum == NF_INET_PRE_ROUTING ||

	    hooknum == NF_INET_LOCAL_IN)

		--iph->ttl;

	ip_send_check(iph);



	if (nf_dup_ipv4_route(net, skb, gw, oif)) {

		__this_cpu_write(nf_skb_duplicated, true);