From owner-freebsd-hackers  Thu Sep 20 19:50:30 2001
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From: Les Biffle <les@safety.net>
Message-Id: <200109210250.f8L2oO615274@ns3.safety.net>
Subject: Re: sendto not sending what I asked...
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To: davep@afterswish.com
Date: Thu, 20 Sep 2001 21:50:23 -0500 (CDT)
Cc: Alfred Perlstein <bright@mu.org>, hackers@FreeBSD.ORG
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> 	pkt.ipbit.ip_sum=in_cksum((unsigned short*)(void*)&pkt,20);
> 	pkt.tcpbit.th_sum=tcpsum(&pkt.ipbit);

You need to do the TCP checksum first.  It changes the payload (the TCP 
checksum).  The IP checksum includes all data, so must be done after the
payload changes are done.

-Les

-- 
Les Biffle            
(480) 585-4099    les@safety.net  http://www.les.safety.net/
Network Safety Corp., 5831 E. Dynamite Blvd.,  Cave Creek, AZ 85331

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