[erlang-questions] low level packet access from erlang

[Garry Hodgson]

On 07/07/2013 09:37 AM, Michael Santos wrote:

 > There were a few bugs: TCP options were left out of the
 > record to binary conversion and the length of the payload
 > was left out of the checksum.

after i posted i made my own version that included the opts
and the wireshark errors went away, so i figured it was that.
didn't know about the payload length issue, though, so mine
might still have that problem. i wonder if that could be causing
it to still not work despite (hopefully) well formed packets.

 > Also, use pkt:makesum/1 to calculate the checksum.
 > This should work: TestSum = pkt:makesum( [ IPv4, Tcp, TcpPayload ] ),

yes, i was using that at first, then switched to call my own
versions. i'll retrofit once i turn latest version into rpm form.

 > You may still see some checksum mismatches if your
 > system uses TCP checksum offloading.

oh, goodie. more things to trip over.

thanks a lot for your help.

-- 
Garry Hodgson
AT&T Chief Security Office (CSO)

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