Re: important query on tcpdump header files and source codes

["Ignacio, Domingo Jr Ostria - igndo001" <DomingoJr.Ignacio () postgrads unisa edu au>]

Hi Guy and the rest of the gang,

Thank you very much for the info , it is most helpful. Haven't seen the
same syntax errors of bad header length, etc again!
Just a bit of clarification:

1. Since srtt(smoothed round trip time has already been defined in
tcp.h, line 255, and formula details and definition on tcp_input.c
source code, I added a new variable th_srtt, reflect this changes to
tcp_input.c options side of the source code  and equate this two so that
srtt=th_srtt, by this I can get a th_srtt estimate. The question now is
on how to output this new variable, th_srtt, into the packet header
option using tcpdump. Do I have to modify tcpdump source code and header
file ( i.e. print_tcp.c and tcp.h) to output the th_srtt option or just
use tcpdump as is? ( Note: Tried to do some modifications on tcpdump's
print_tcp.c and tcp.h, defined #define TCPOPT_TH_SRTT and TCPOLEN with
their length and kind as per RFC 793 guidelines, compile and run it and
cannot see the option , thus the question)

Or 2. When the tcpdump do the packet capture, is it looking/utilizing
the kernel variables within the protocol stacks or it is operating
independently from the kernel?( Sorry about this question guys, just
need probably to read more on tcpdump packet capturing thru libpcap:))

Help would be appreciated. Thanks.

Cheers,
dom 


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