From: DI Roman Fiedler <roman.fiedler@telbiomed.at>
To: Mail List - Netfilter <netfilter@vger.kernel.org>
Subject: What is special about loopback
Date: Thu, 17 Jan 2008 15:08:46 +0100 [thread overview]
Message-ID: <478F616E.7070903@telbiomed.at> (raw)
Hi All,
There are some statements that PREROUTING modifications are not possible
on packets transmitted via loopback. It seems that there is some kind of
"short-circuit" when sending packets from localhost to localhost, I
guess for speed advantage.
The image
http://upload.wikimedia.org/wikipedia/de/5/5f/Nfk-traversal.png states
that a packet would have to enter the kernel with ip_rcv to pass the
complete netfilter architecture again, but loopback uses netif_rx(skb)
to feedback sent packets.
Is the assumption correct, that a modified loopback module or some other
virtual network module could feed back packets in a way that the pass
the complete filtering arch or would the local routing tables make any
efforts useless (even when local routing is modified)? Has someone
already used such a thing for iptables testing? Or would two connected
tun devices (local tunnel) do the trick?
greetings, Roman
reply other threads:[~2008-01-17 14:08 UTC|newest]
Thread overview: [no followups] expand[flat|nested] mbox.gz Atom feed
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=478F616E.7070903@telbiomed.at \
--to=roman.fiedler@telbiomed.at \
--cc=netfilter@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox