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paket header query?

Posted on 2004-04-16
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Last Modified: 2010-03-18
can it be possible to modify packet header? can i add some own header field to packet header and let it be sent by kernel?
my system is redhat linux 9 kernel 2.4.24?
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Question by:b123coder
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by:sunnycoder
ID: 10841117
Hi b123coder,

You can use raw sockets and form header in any way you like ... However note that if you form the header which does not correspond to the standards (RFC for that protocol ... see ietf.org) then recepient willnot be able to understand it and will reject it ..

http://mixter.void.ru/rawip.html

good luck
Sunnycoder
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by:sunnycoder
ID: 10841139
Hi n_uthra25,

btw, if you just wish to mangle the packet a bit without descending into the kernel, then check libipq
http://www.cs.princeton.edu/~nakao/libipq.htm

Sunnycoder
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by:owensleftfoot
ID: 10841652
http://sourceforge.net/projects/pacgen/ is a program which allows you to send customised packets.
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by:b123coder
ID: 10849285

 i want to know also:-
while reading computer networks book i came across a statement that all machines are required to receive at least 576 bytes?
what is that mean? then what is the ethernet handling 1500 bytes payload then? it means that those machines cannot transfer 1500 payloads?
Is there any room for implementing own header field in options of IP header?
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sunnycoder earned 90 total points
ID: 10856495
>all machines are required to receive at least 576 bytes?
>what is that mean?
This is protocol specific information and will vary from protocol to protocol ... ATM cells are 53 bytes and minimum valid ethernet frame is perhaps 64 bytes (if I recollect correctly)

>then what is the ethernet handling 1500 bytes payload then? it means that those machines
>cannot transfer 1500 payloads?
What you read was specific to a protocols and universally applicable to all protocols ... An ethernet frame has its own minimum and maximum size

>Is there any room for implementing own header field in options of IP header?
There is an options field in V4
http://www.freesoft.org/CIE/RFC/791/12.htm

For details of what you can and cannot do with V4 and V6 headers, I recommend that you go through the rfcs
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LVL 45

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by:sunnycoder
ID: 10856536
>What you read was specific to a protocols and universally applicable to all protocols

I meant

What you read was specific to a protocol and NOT universally applicable to all protocols
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