* [LARTC] Routing fundamentals
@ 2003-03-28 5:14 Kjell Chris Flor
2003-03-28 10:59 ` Stef Coene
` (4 more replies)
0 siblings, 5 replies; 6+ messages in thread
From: Kjell Chris Flor @ 2003-03-28 5:14 UTC (permalink / raw)
To: lartc
Hi,
Tell me if I understand this right.
For a packet that is not for local host,
but comes in on one interface and goes
out on another;
Will that packet traverse PREROTING, FORWARD and POSTROUTING
on _both_ underface, or
will that packet traverse PREROTING, FORWARD and POSTROUTING
only once, where PREROTING is when a packet "is in" the incoming
physical interface, and is in FORWARD and POSTROUTING when
the packet "is in" the outgoing interfave?
regards,
Kjell
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [LARTC] Routing fundamentals
2003-03-28 5:14 [LARTC] Routing fundamentals Kjell Chris Flor
@ 2003-03-28 10:59 ` Stef Coene
2003-03-28 16:28 ` Kjell Chris Flor
` (3 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: Stef Coene @ 2003-03-28 10:59 UTC (permalink / raw)
To: lartc
On Friday 28 March 2003 06:14, Kjell Chris Flor wrote:
> Hi,
>
> Tell me if I understand this right.
>
> For a packet that is not for local host,
> but comes in on one interface and goes
> out on another;
>
> Will that packet traverse PREROTING, FORWARD and POSTROUTING
> on _both_ underface, or
>
> will that packet traverse PREROTING, FORWARD and POSTROUTING
> only once, where PREROTING is when a packet "is in" the incoming
> physical interface, and is in FORWARD and POSTROUTING when
> the packet "is in" the outgoing interfave?
Maybe this can help :
http://www.docum.org/stef.coene/qos/kptd/
Stef
--
stef.coene@docum.org
"Using Linux as bandwidth manager"
http://www.docum.org/
#lartc @ irc.oftc.net
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [LARTC] Routing fundamentals
2003-03-28 5:14 [LARTC] Routing fundamentals Kjell Chris Flor
2003-03-28 10:59 ` Stef Coene
@ 2003-03-28 16:28 ` Kjell Chris Flor
2003-03-28 16:46 ` Erik S. Johansen
` (2 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: Kjell Chris Flor @ 2003-03-28 16:28 UTC (permalink / raw)
To: lartc
> > For a packet that is not for local host,
> > but comes in on one interface and goes
> > out on another;
(1)
> > Will that packet traverse PREROTING, FORWARD and POSTROUTING
> > on _both_ underface, or
(2)
> > will that packet traverse PREROTING, FORWARD and POSTROUTING
> > only once, where PREROTING is when a packet "is in" the incoming
> > physical interface, and is in FORWARD and POSTROUTING when
> > the packet "is in" the outgoing interfave?
> >
> Maybe this can help :
> http://www.docum.org/stef.coene/qos/kptd/
No. It would help if you told me what is right.
The figure I got from before, and really don't
rule out number one.
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http://mailman.ds9a.nl/mailman/listinfo/lartc HOWTO: http://lartc.org/
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [LARTC] Routing fundamentals
2003-03-28 5:14 [LARTC] Routing fundamentals Kjell Chris Flor
2003-03-28 10:59 ` Stef Coene
2003-03-28 16:28 ` Kjell Chris Flor
@ 2003-03-28 16:46 ` Erik S. Johansen
2003-03-28 19:32 ` Martin A. Brown
2003-03-28 20:08 ` Martin A. Brown
4 siblings, 0 replies; 6+ messages in thread
From: Erik S. Johansen @ 2003-03-28 16:46 UTC (permalink / raw)
To: lartc
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1
On Friday 28 March 2003 07:14, Kjell Chris Flor wrote:
> Hi,
>
> Tell me if I understand this right.
>
> For a packet that is not for local host,
> but comes in on one interface and goes
> out on another;
>
> Will that packet traverse PREROTING, FORWARD and POSTROUTING
> on _both_ underface, or
>
> will that packet traverse PREROTING, FORWARD and POSTROUTING
> only once, where PREROTING is when a packet "is in" the incoming
> physical interface, and is in FORWARD and POSTROUTING when
> the packet "is in" the outgoing interfave?
I believe this ASCII to be correct, but I'm not certain so a verification from
someone would be appreciated.
-------- -------------------
| Device | | Local application |
---|---- -----|-------------
| |
V |
| |
___|_______________ ___|_______________
/ \ / \
| Connection Tracking | | Connection Tracking |
| | | | | |
| mangle/PREROUTING | | mangle/OUTPUT |
| | | | | |
| nat/PREROUTING | | nat/OUTPUT |
| | | | |
| | | filter/OUTPUT |
\___ _______________/ \___ _______________/
| |
| |
| V
| |
| ----|----
V | Routing |
| ----|----
| |
| V
| ______________ |
---|----- / \ |
| Routing |--->-----| filter/FORWARD |---
---|----- \______________/ |
| |
V V
| |
___|_________________ ________|__________
/ \ / \
| filter/INPUT | | nat/POSTROUTING |
| | | | | |
| Connection Tracking | | Connection Tracking |
\___ _________________/ \________ __________/
| |
| |
V V
| |
| |
----|--------------- --------
| Local application | | Device |
-------------------- --------
- --Erik
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [LARTC] Routing fundamentals
2003-03-28 5:14 [LARTC] Routing fundamentals Kjell Chris Flor
` (2 preceding siblings ...)
2003-03-28 16:46 ` Erik S. Johansen
@ 2003-03-28 19:32 ` Martin A. Brown
2003-03-28 20:08 ` Martin A. Brown
4 siblings, 0 replies; 6+ messages in thread
From: Martin A. Brown @ 2003-03-28 19:32 UTC (permalink / raw)
To: lartc
Kjell,
Let me try a slightly different tack.....one of the fundamental
differences between ipchains and iptables is identified and explored in
varying depths here:
http://www.netfilter.org/documentation/HOWTO//packet-filtering-HOWTO-10.html
http://www.linuxvirtualserver.org/Joseph.Mack/HOWTO/LVS-HOWTO.netfilter_hooks.html
[ Apparently, I wrote a similar statement about ipchains vs. iptables in
July of last year...the beauty of a bad memory is that I can learn
things anew by re-reading things I once knew! ]
http://lists.insecure.org/lists/firewall-wizards/2002/Jul/0228.html
In ipchains, each incoming packet hit input, forward and output chains,
which only filtered packets (OK, OK, and masqueraded).
In iptables, every incoming packet traverses the PREROUTING chains in the
conntrack (implicit), mangle and nat tables. In the PREROUTING chains,
you have access to --in-interface (-i) $RECEIVE_IF. In the PREROUTING
chain, an output interface makes no sense, because we have no idea about
where the packet is going!
Now that the PREROUTING chain has been passed, we'll route! After
routing, (and assuming the packet is bound for a non-local destination),
the packet will enter the FORWARD chain. Now, we know both --in-interface
$RECEIVE_IF and --out-interface (-o) $TRANSMIT_IF, so both options can be
used.
POSTROUTING is just about the last thing before the packet is handed off
to the much misunderstood traffic control system. And in this
chain, you'll see nalogous behaviour...the --in-interface option is not
available.
Does that answer your question?
-Martin
: > > For a packet that is not for local host,
: > > but comes in on one interface and goes
: > > out on another;
: (1)
: > > Will that packet traverse PREROTING, FORWARD and POSTROUTING
: > > on _both_ underface, or
: (2)
: > > will that packet traverse PREROTING, FORWARD and POSTROUTING
: > > only once, where PREROTING is when a packet "is in" the incoming
: > > physical interface, and is in FORWARD and POSTROUTING when
: > > the packet "is in" the outgoing interfave?
: > >
: > Maybe this can help :
: > http://www.docum.org/stef.coene/qos/kptd/
:
: No. It would help if you told me what is right.
: The figure I got from before, and really don't
: rule out number one.
:
:
: _______________________________________________
: LARTC mailing list / LARTC@mailman.ds9a.nl
: http://mailman.ds9a.nl/mailman/listinfo/lartc HOWTO: http://lartc.org/
:
--
Martin A. Brown --- SecurePipe, Inc. --- mabrown@securepipe.com
_______________________________________________
LARTC mailing list / LARTC@mailman.ds9a.nl
http://mailman.ds9a.nl/mailman/listinfo/lartc HOWTO: http://lartc.org/
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [LARTC] Routing fundamentals
2003-03-28 5:14 [LARTC] Routing fundamentals Kjell Chris Flor
` (3 preceding siblings ...)
2003-03-28 19:32 ` Martin A. Brown
@ 2003-03-28 20:08 ` Martin A. Brown
4 siblings, 0 replies; 6+ messages in thread
From: Martin A. Brown @ 2003-03-28 20:08 UTC (permalink / raw)
To: lartc
Aigh!
Upon re-reading, I must add that the linuxvirtualserver.org link is not
appropriate in this answer. Sorry for my confusion--please ignore the
Joseph.Mack LVS-HOWTO link for the purposes of this answer.
Apologies,
-Martin
: Kjell,
:
: Let me try a slightly different tack.....one of the fundamental
: differences between ipchains and iptables is identified and explored in
: varying depths here:
:
: http://www.netfilter.org/documentation/HOWTO//packet-filtering-HOWTO-10.html
: http://www.linuxvirtualserver.org/Joseph.Mack/HOWTO/LVS-HOWTO.netfilter_hooks.html
:
: [ Apparently, I wrote a similar statement about ipchains vs. iptables in
: July of last year...the beauty of a bad memory is that I can learn
: things anew by re-reading things I once knew! ]
:
: http://lists.insecure.org/lists/firewall-wizards/2002/Jul/0228.html
:
: In ipchains, each incoming packet hit input, forward and output chains,
: which only filtered packets (OK, OK, and masqueraded).
:
: In iptables, every incoming packet traverses the PREROUTING chains in the
: conntrack (implicit), mangle and nat tables. In the PREROUTING chains,
: you have access to --in-interface (-i) $RECEIVE_IF. In the PREROUTING
: chain, an output interface makes no sense, because we have no idea about
: where the packet is going!
:
: Now that the PREROUTING chain has been passed, we'll route! After
: routing, (and assuming the packet is bound for a non-local destination),
: the packet will enter the FORWARD chain. Now, we know both --in-interface
: $RECEIVE_IF and --out-interface (-o) $TRANSMIT_IF, so both options can be
: used.
:
: POSTROUTING is just about the last thing before the packet is handed off
: to the much misunderstood traffic control system. And in this
: chain, you'll see nalogous behaviour...the --in-interface option is not
: available.
:
: Does that answer your question?
:
: -Martin
:
: : > > For a packet that is not for local host,
: : > > but comes in on one interface and goes
: : > > out on another;
: : (1)
: : > > Will that packet traverse PREROTING, FORWARD and POSTROUTING
: : > > on _both_ underface, or
: : (2)
: : > > will that packet traverse PREROTING, FORWARD and POSTROUTING
: : > > only once, where PREROTING is when a packet "is in" the incoming
: : > > physical interface, and is in FORWARD and POSTROUTING when
: : > > the packet "is in" the outgoing interfave?
: : > >
: : > Maybe this can help :
: : > http://www.docum.org/stef.coene/qos/kptd/
: :
: : No. It would help if you told me what is right.
: : The figure I got from before, and really don't
: : rule out number one.
: :
: :
: : _______________________________________________
: : LARTC mailing list / LARTC@mailman.ds9a.nl
: : http://mailman.ds9a.nl/mailman/listinfo/lartc HOWTO: http://lartc.org/
: :
:
:
--
Martin A. Brown --- SecurePipe, Inc. --- mabrown@securepipe.com
_______________________________________________
LARTC mailing list / LARTC@mailman.ds9a.nl
http://mailman.ds9a.nl/mailman/listinfo/lartc HOWTO: http://lartc.org/
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2003-03-28 5:14 [LARTC] Routing fundamentals Kjell Chris Flor
2003-03-28 10:59 ` Stef Coene
2003-03-28 16:28 ` Kjell Chris Flor
2003-03-28 16:46 ` Erik S. Johansen
2003-03-28 19:32 ` Martin A. Brown
2003-03-28 20:08 ` Martin A. Brown
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