Snort mailing list archives
Re: simple question on packet sizes
From: Martin Roesch <roesch () sourcefire com>
Date: Mon, 28 May 2001 00:43:25 -0400
"James R. Hendrick" wrote:
Hi, When looking at the output of snort, there are several (basic) fields that I need some help understanding: IpLen
IP header length from the p->iph->ip_hlen field of the IP header. This is normally set to "5" (indicated in the decode as 20-bytes) except when IP options are present.
TcpLen
Value of the p->tcph->th_off field, indicates the length of TCP headers. This is normally "5" (20-bytes in the output again) except when TCP options are available.
DgmLen
This is the datagram length from the p->iph->ip_len field, it indicates the length of the packet (including the IP header).
Len
UDP length from the UDP header decode, length of the payload + UDP header. -Marty
I am trying to determine the number of bytes in packets (of various types, mostly TCP) that make up "payload" vs. "header" for various services and must simply be missing something obvious (need more coffffeeeeee). The part that confuses me is that I see DgmLen in TCP packets as well as UDP and TcpLen in UDP packets as well as TCP. Can someone help me understand which fields I will see for which protocols and what they represent?
That's not right, you shouldn't be seeing TcpLen in UDP packets, the printout code is mutually exclusive so this is (should be) impossible. Can you show me an example? -Marty
Thanks! Jim _______________________________________________ Snort-users mailing list Snort-users () lists sourceforge net Go to this URL to change user options or unsubscribe: http://lists.sourceforge.net/lists/listinfo/snort-users Snort-users list archive: http://www.geocrawler.com/redir-sf.php3?list=snort-users
-- Martin Roesch roesch () sourcefire com http://www.sourcefire.com - http://www.snort.org _______________________________________________ Snort-users mailing list Snort-users () lists sourceforge net Go to this URL to change user options or unsubscribe: http://lists.sourceforge.net/lists/listinfo/snort-users Snort-users list archive: http://www.geocrawler.com/redir-sf.php3?list=snort-users
Current thread:
- simple question on packet sizes James R. Hendrick (May 08)
- Re: simple question on packet sizes Martin Roesch (May 27)