[PATCH] ipt_TOS fix.

[Rusty Russell]

Linus, please apply v2.4.0.

ipt_TOS checksum calculations were completely broken, causing bad csum
packets.  Whoever implemented it didn't understand the code it was
copied from.

This fixes the problem (tested in userspace against all TOS changes).

Rusty.
--
Premature optmztion is rt of all evl. --DK

diff -urN -I \$.*\$ -X /tmp/kerndiff.ZtZl97 --minimal linux-2.4.0-official/net/ipv4/netfilter/ipt_TOS.c working-2.4.0/net/ipv4/netfilter/ipt_TOS.c
--- linux-2.4.0-official/net/ipv4/netfilter/ipt_TOS.c	Fri Apr 28 08:43:15 2000
+++ working-2.4.0/net/ipv4/netfilter/ipt_TOS.c	Mon Jan 29 18:40:37 2001
@@ -19,11 +19,11 @@
 	const struct ipt_tos_target_info *tosinfo = targinfo;
 
 	if ((iph->tos & IPTOS_TOS_MASK) != tosinfo->tos) {
-		u_int8_t diffs[2];
+		u_int16_t diffs[2];
 
-		diffs[0] = iph->tos;
+		diffs[0] = htons(iph->tos) ^ 0xFFFF;
 		iph->tos = (iph->tos & IPTOS_PREC_MASK) | tosinfo->tos;
-		diffs[1] = iph->tos;
+		diffs[1] = htons(iph->tos);
 		iph->check = csum_fold(csum_partial((char *)diffs,
 		                                    sizeof(diffs),
 		                                    iph->check^0xFFFF));