how to know a datagram has been fragmented, from a raw socket point-of-view ?

how to know a datagram has been fragmented, from a raw socket point-of-view ?

Post by No Spa » Tue, 31 Jul 2001 01:14:58



Hi all,

I'm looking for a way to know if a received datagram on a raw socket has
been or not fragmented.

Reading the IP header given by the system is not interesting as the
datagram has been rassembled by the kernel. And the use of packet
socket, seems to imply to implementation in userspace of IP protocol.

Is there any system call that could give this information ? any option
to pass to getsockopt(2) ? Or any undocumented feature ?

Edrusb.

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1. Sending datagram in raw socket

Hello,

I work in a network 192.168.1.0.
When I send datagram (from IP 192.168.1.2)
to IP which doesn't exist in my network
(e.g. 192.168.1.111), my sniffer installed on
a computer (192.168.1.1) can see it.

But, my sniffer has to work on an embedded
device with Linux. Unfortunatelly, on this
device, my sniffer can only see datagrams
sent directly to it and broadcasts. It doesn't
catch datagrams sent to other computers.

I wrote a sender application which sends datagrams
using raw sockets. Now my sniffer on an
embedded device can catch all datagrams.
But it is not a solutions for me -- a normal
computer with my sniffer can catch datagrams
sent by all applications (not only mine using raw
sockets). I want the same for an embedded device.

Maybe an embedded device has wrong kernel
configuration or something...
What could be wrong?

Thanks in advance,
    Vicky.

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