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xt_ECHO: calculate UDP checksum

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This commit is contained in:
Jan Engelhardt
2011-09-25 14:20:07 +02:00
parent 30d227135b
commit 434dea2b53
2 changed files with 15 additions and 1 deletions
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14
extensions/xt_ECHO.c
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@@ -70,13 +70,25 @@ echo_tg4(struct sk_buff **poldskb, const struct xt_action_param *par)
newudp->source = oldudp->dest;
newudp->dest = oldudp->source;
newudp->len = oldudp->len;
newudp->check = 0;
data_len = htons(oldudp->len) - sizeof(*oldudp);
payload = skb_header_pointer(oldskb, par->thoff +
sizeof(*oldudp), data_len, NULL);
memcpy(skb_put(newskb, data_len), payload, data_len);
#if 0
/*
* Since no fields are modified (we just swapped things around),
* this works too in our specific echo case.
*/
newudp->check = oldudp->check;
#else
newudp->check = 0;
newudp->check = csum_tcpudp_magic(newip->saddr, newip->daddr,
ntohs(newudp->len), IPPROTO_UDP,
csum_partial(newudp, ntohs(newudp->len), 0));
#endif
/* ip_route_me_harder expects the skb's dst to be set */
skb_dst_set(newskb, dst_clone(skb_dst(oldskb)));