netdev - Checksum Question about new sk

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Message-ID: <362475.96996.qm@web30508.mail.mud.yahoo.com>
Date:	Wed, 22 Jul 2009 12:42:11 -0700 (PDT)
From:	Buster Holzbauer <gnomish_barbarian@...oo.com>
To:	netdev@...r.kernel.org
Subject: Checksum Question about new sk_buffs

Hello,

I am a researcher at a university working on a new protocol based off of TCP, using the 2.6.26.5 kernel on a pair of gentoo machines. I need to send additional sk_buffs containing redundancy information as well as the sk_buffs TCP would normally send containing data. 

The redundancy sk_buffs are constructed by a function called by tcp_push (). I create these sk_buffs by calling sk_stream_alloc_skb(), then updating a few fields in the header (such as sequence number), but I'm clearly doing something wrong or missing a step. I believe this because after adding a printk to the csum_error label in tcp_rcv_established, the receiver-side logs show that these redundancy sk_buffs are triggering this label. The normal data sk_buffs, as expected, do not trigger this printk.

Does anyone have any information about the specific steps to create a new sk_buff, update header fields, and populate it with data so that the receiver processes the sk_buff correctly? 

Thanks in advance for any help you can provide,
Buster Holzbauer

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