libpcap

[Bruce M Simpson]

On Sun, Aug 03, 2003 at 12:13:43PM -0700, Andrew Konstantinov wrote:
> 1) Is there any way how I can specify in the filter description that it should match only incoming packets on some interface? inbound/outbound keywords work only for 'slip' (according to tcpdump man page). I could do that with 'not src host' and then put the local hostname after that, but is there a more general solution, without the need for local hostname or ip address?

You need to call pcap_open_live() with the appropriate device argument,
if you wish to monitor individual interfaces.

Unfortunately the pcap interface doesn't support a means of passing the
interface name to a callback handler function. So you'd have to rewrite
pcap_loop() to call pcap_dispatch() for individual pcap_t's for each
interface you pay specific attention to.

Most pcap apps I've written that do anything elaborate require me to
override pcap_loop() anyway. Perhaps there's a good candidate for extending
the interface so that this sort of thing can be more easily done.

> 2) I can't figure out how to setup a filter so it could match several ports at once. For example, I want the filter to only match 21-25 and 113 ports for incoming traffic. How do I do that? Right know I can see only two solutions. I could simply sniff all the traffic, and then filter out the interesting ports by myself, or I could setup several filters each of which would be responsible for a specific port. But both solutions seem to be inefficient. Is there a better way to accomplish this?

This is on PHK's kernel hacker TODO list! Patches gratefully accepted...

http://people.freebsd.org/~phk/TODO/

BMS