From: an7 <an3h0ny@yahoo.fr>
To: davem@redhat.com
Cc: netdev@oss.sgi.com
Subject: tcp checksumming
Date: Tue, 4 Nov 2003 14:36:15 +0100 (CET) [thread overview]
Message-ID: <20031104133615.86082.qmail@web11102.mail.yahoo.com> (raw)
Hello,
In tcp_rcv_established(), when you are in fast path,
you use checksum and copy (the first function in the
chain is tcp_copy_to_iovec) to finally delivering data
to the user.
I browse datagram.c,checksum.h,skbuff.c,tcp_input.c
and only sees (mainly by following function calls in
datagram.c) checksum calculation, by a lot of calls to
csum_fold() and csum_partial(), and copy to iovec, but
i have never seen the checksum _verification_.
I learn that skb->csum is (when you have not CHECKSUM
UNECESSARY defined in the case of a device computing
the checksum by itself) the checksum on running
data.But it is used in all functions,and get replaced
by a function result. I don't see where it is used as
a comparison
My question is pretty simple : where in the code, is
the tcp checksum verified (compared to the computed
one). My first impression was that it was done in the
*copy_and_csum* functions, but i only see checksum
computation.
That is to say, it is like a side effect of keeping
data in a buffer with a bad checksum.(maybe it is
removed after ? i don't think so)
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next reply other threads:[~2003-11-04 13:36 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-11-04 13:36 an7 [this message]
-- strict thread matches above, loose matches on Subject: below --
2003-11-04 13:32 tcp checksumming an7
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