tcpdump mailing list archives
Re: How does packet capture interact with
From: Aaron Turner <synfinatic () gmail com>
Date: Thu, 24 Sep 2009 13:03:50 -0700
On Thu, Sep 24, 2009 at 12:40 PM, Robert Burgess <burgess () systems cs cornell edu> wrote:
As long as the destination IP address of the packets are not of the firewall then you shouldn't need a host-based firewall to drop the packets.It still has to drop them, though---I think---because I don't want the packets forwarded on until I say so.
Assuming you do the forwarding in user space (ala tcpbridge) with libpcap then it won't be a problem. If you're doing the forwarding in the kernel, then you've got a big problem since by the time you read the packet via libpcap, chances are the kernel has already forwarded it on.
Also, I forgot to mention that on some platforms, libpcap supports only sniffing packets going a certain direction (in our out the interface). You should use that API when possible as it will improve performance a good deal.That's pcap_setdirection, yes? Thanks!
yep. -- Aaron Turner http://synfin.net/ http://tcpreplay.synfin.net/ - Pcap editing and replay tools for Unix & Windows Those who would give up essential Liberty, to purchase a little temporary Safety, deserve neither Liberty nor Safety. -- Benjamin Franklin - This is the tcpdump-workers list. Visit https://cod.sandelman.ca/ to unsubscribe.
Current thread:
- Re: How does packet capture interact with firewalls?, (continued)
- Re: How does packet capture interact with firewalls? Phil Vandry (Sep 23)
- Re: How does packet capture interact with firewalls? Robert Burgess (Sep 23)
- Re: How does packet capture interact with Robert Burgess (Sep 23)
- Re: How does packet capture interact with firewalls? Phil Vandry (Sep 23)
- Re: How does packet capture interact with firewalls? Robert Burgess (Sep 23)
- Re: How does packet capture interact with Aaron Turner (Sep 23)
- Re: How does packet capture interact with Tillmann Werner (Sep 24)
- Re: How does packet capture interact with Robert Burgess (Sep 24)
- Re: How does packet capture interact with Aaron Turner (Sep 24)
- Re: How does packet capture interact with Robert Burgess (Sep 24)
- Re: How does packet capture interact with Aaron Turner (Sep 24)
- Re: How does packet capture interact with firewalls? Robert Burgess (Sep 23)
- Re: How does packet capture interact with firewalls? Phil Vandry (Sep 23)
- Re: How does packet capture interact with Robert Burgess (Sep 24)