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PacketSniffer Problems

Hi.

I'm currently trying to make a tool that checks how much bandwith each user on a Network is using.

Tried to use FPiette's PacketSniffer but for some reason it always freezes the computers after a while... and the packet32.dll used by it is also used by the SubSeven Trojan so my AV software always start complaining...

So i found another PacketSniffer one that doesnt crash... the only problem is that i cant seem to get the source/destionation address from the packets... not sure what to do =(

It's located at:
http://home1.stofanet.dk/nitezhifter/files/Delphi%20Pcap.zip

it's actually a Delphi conversion of the WinPcap Library.

so what i need is some help on how to actually get the source/destination ip addresses...

regards,
John

karouri

As far as I know, the winpcap captures the whole packet, so you can read the source and destination IP addresses from within the packets. Notice that the packet capture does not contain the Ethernet preamble, neither the CRC at the end. Any data you can get from a packet assuming it is an IP packet can be got from the headers:
Ethernet frame header: http://wks.uts.ohio-state.edu/sysadm_course/html/sysadm-326.html
IP packet header: http://www.freesoft.org/CIE/Course/Section3/7.htm
All in all, the source IP address is the four bytes starting at byte 26 (assuming a zero based array) in network byte order, which is different from x86 machine order. So the source IP is
Eth[29]:Eth[28]:Eth[27]:Eth[26]
The next four bytes are the destination IP address, like
Eth[33]:Eth[32]:Eth[31]:Eth[30]
assuming the array holding the packet is defined as
Eth:array[0..1513] of byte

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SenDog

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karouri

Correction for my previous comment:
... in network byte order, which is different from x86 machine order. So the source IP is
Eth[26]:Eth[27]:Eth[28]:Eth[29]
The next four bytes are the destination IP address, like
Eth[30]:Eth[31]:Eth[32]:Eth[33]

The order I gave last time is reversed..

Arachnid

ASKER

ahhh... finally!
the owns project was exactly what i needed... in a way...
just went through the sourcefiles and found out how to get the ip addresses.
thanx SenDog...

sorry karouri but to me SenDogs answer was a more "complete" one...

Regards,
John

Arachnid

ASKER

karouri

actually it is fine for me too, as I needed such a work on linux, and I found it now for free

SenDog

Glad I could help!

Cheers,
SenDog