* rp_filter
@ 2002-12-27 21:11 Stephen Frost
2002-12-28 8:46 ` rp_filter Patrick Schaaf
2002-12-28 9:17 ` rp_filter Patrick Schaaf
0 siblings, 2 replies; 10+ messages in thread
From: Stephen Frost @ 2002-12-27 21:11 UTC (permalink / raw)
To: Netfilter Developers
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Hey all,
Can we *please* move the rp_filter cruft into the firewalling code
proper? I've had yet another friend come to me asking for help after
fighting with his iptables setup for 6 hours trying to get it to work
to discover the whole problem was rp_filter getting in the way. If
rp_filter was part of the actual firewalling code where it should be
people wouldn't run into this stupid problem.
rp_filter is an obscure option that only the poor souls who ran into
it know about. I've met people who have implemented it all by hand in
iptables because they didn't know it existed, and then didn't entirely
trust it. The people who need the option (those who actually run
routers or firewalls) know they need it and will take care of having
it enabled in their firewalling code, for most people (desktop users
and whatnot) it's useless anyway because they've only got one
interface.
Stephen
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^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: rp_filter
2002-12-27 21:11 rp_filter Stephen Frost
@ 2002-12-28 8:46 ` Patrick Schaaf
2002-12-29 17:28 ` rp_filter Stephen Frost
2002-12-28 9:17 ` rp_filter Patrick Schaaf
1 sibling, 1 reply; 10+ messages in thread
From: Patrick Schaaf @ 2002-12-28 8:46 UTC (permalink / raw)
To: Netfilter Developers
Stephen,
> Can we *please* move the rp_filter cruft into the firewalling code
> proper?
If that's not a joke, please take your cruisade to the linux-net mailing
list. It is not up to netfilter / iptables developers to even think
about removal of base network stack features, in my opinion. Convince
Dave Miller and Alexey Kusnetsov (speling probably wrong, sorry).
I'll refrain from speaking against the idea itself, here.
best regards
Patrick
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: rp_filter
2002-12-27 21:11 rp_filter Stephen Frost
2002-12-28 8:46 ` rp_filter Patrick Schaaf
@ 2002-12-28 9:17 ` Patrick Schaaf
2003-01-08 12:38 ` rp_filter Roberto Nibali
1 sibling, 1 reply; 10+ messages in thread
From: Patrick Schaaf @ 2002-12-28 9:17 UTC (permalink / raw)
To: Netfilter Developers
Stephen & all,
> Can we *please* move the rp_filter cruft into the firewalling code
> proper?
Upon thinking a bit more about your request, there is one thing
that annoys me about rp_filter, and where iptables may eventually
help: there was (and probably is) the idea of a DROP table, where
you can LOG packets coming from all kinds of drop sites within
the network stack. It would be great if I had a way to LOG packets
rejected by rp_filter. IMHO the big problem to the unwary end-user,
is the _invisibility_ of the drops caused by rp_filter.
A simple net_ratelimit()ed printk() in the appropriate place, would
already help a lot. If you walk your request over to linux-net, maybe
you could make that your fallback position :-)
best regards
Patrick
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: rp_filter
2002-12-28 8:46 ` rp_filter Patrick Schaaf
@ 2002-12-29 17:28 ` Stephen Frost
0 siblings, 0 replies; 10+ messages in thread
From: Stephen Frost @ 2002-12-29 17:28 UTC (permalink / raw)
To: Patrick Schaaf; +Cc: Netfilter Developers
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* Patrick Schaaf (bof@bof.de) wrote:
> Stephen,
>
> > Can we *please* move the rp_filter cruft into the firewalling code
> > proper?
>
> If that's not a joke, please take your cruisade to the linux-net mailing
> list. It is not up to netfilter / iptables developers to even think
> about removal of base network stack features, in my opinion. Convince
> Dave Miller and Alexey Kusnetsov (speling probably wrong, sorry).
>
> I'll refrain from speaking against the idea itself, here.
If we had the functionality in netfilter to do what rp_filter does now I
think it'd make for a much better case to get rid of it as it exists.
For that I think we'd need a match target that checked source IP and
incoming interface and compared it against the routing table. Not
something I'd expect to be very difficult...
I'll see about bringing it up on the linux-net list if this seems like a
reasonable thing to add to netfilter. I certainly agree about one of
the problems with rp_filter being that it's not noisy about things it
drops (by default at least, I think there may be an option to turn on
logging of it). It would seem reasonable to me to have the parts of the
kernel that drop packets following some administrative rule be under the
firewalling framework instead of elsewhere throughout the kernel.
Stephen
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^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: rp_filter
2002-12-28 9:17 ` rp_filter Patrick Schaaf
@ 2003-01-08 12:38 ` Roberto Nibali
0 siblings, 0 replies; 10+ messages in thread
From: Roberto Nibali @ 2003-01-08 12:38 UTC (permalink / raw)
To: Patrick Schaaf; +Cc: Netfilter Developers
>> Can we *please* move the rp_filter cruft into the firewalling code
>> proper?
I agree with Patrick on that it is not an intelligent idea to touch core network
stuff in the netfilter code. Especially I seem to see more and more routing
related POM patches for netfilter while I wonder what issues people really have
with the current routing code which is where rp_filter belongs to?
> Upon thinking a bit more about your request, there is one thing
> that annoys me about rp_filter, and where iptables may eventually
> help: there was (and probably is) the idea of a DROP table, where
> you can LOG packets coming from all kinds of drop sites within
> the network stack. It would be great if I had a way to LOG packets
I've once started it but due to the network core's diversity in handling such
cases I've stopped doing it. You get everything from silent drop via kfree over
skb_free over return EINVAL over goto drop and so on ...
> rejected by rp_filter. IMHO the big problem to the unwary end-user,
> is the _invisibility_ of the drops caused by rp_filter.
That is a general nuisance and setting verbose_route_log and log_martians
already helps a bit but most of the FIB related errors don't get logged. I know
what you're talking about, I've even once started to debug tcpdump because of a
badly set rp_filter value while doing asymmetric routing in a load balanced
environment. It sucks rocks!!
> A simple net_ratelimit()ed printk() in the appropriate place, would
> already help a lot. If you walk your request over to linux-net, maybe
> you could make that your fallback position :-)
netdev or linux-net might be the best place to discuss it, yes. As a start you
could patch ../linux/net/ipv4/fib_frontend.c:fib_validate_source(). Check for
the rpf variable and follow it's invariants.
I don't agree with putting a net_ratelimit() on every network related place for
logging. I took them out in my kernels because I rather have a system that can
filter less packets but log the most packets than having a packet filter that
can filter a lot but where syslogd doesn't get enough computing time anymore to
read the printk ringbuffer.
Best regards,
Roberto Nibali, ratz
--
echo '[q]sa[ln0=aln256%Pln256/snlbx]sb3135071790101768542287578439snlbxq' | dc
^ permalink raw reply [flat|nested] 10+ messages in thread
* rp_filter
@ 2018-07-13 15:23 Leroy Tennison
2018-07-13 16:23 ` rp_filter Grant Taylor
` (3 more replies)
0 siblings, 4 replies; 10+ messages in thread
From: Leroy Tennison @ 2018-07-13 15:23 UTC (permalink / raw)
To: lartc
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^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: rp_filter
2018-07-13 15:23 rp_filter Leroy Tennison
@ 2018-07-13 16:23 ` Grant Taylor
2018-07-13 16:26 ` rp_filter Jay Vosburgh
` (2 subsequent siblings)
3 siblings, 0 replies; 10+ messages in thread
From: Grant Taylor @ 2018-07-13 16:23 UTC (permalink / raw)
To: lartc
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On 07/13/2018 09:23 AM, Leroy Tennison wrote:
> Is there a definitive way to tell that rp_filter is dropping traffic (in
> this case echo request) other than disabling it and seeing the expected
> traffic (echo reply)? I tried an iptables packet trace but I either did
> it wrong or it showed nothing. The only indications I have right now are:
Check dmesg. That's the most reliable place I've seen for logs about
(so called) "martian" packets.
> No firewall rules blocking traffic but no replies either.
It seems like reverse path filtering operates at a lower layer before
IPTables.
> The problem is subnet-specific (only occurs on a directly-connected
> subnet).
Odd.
--
Grant. . . .
unix || die
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^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: rp_filter
2018-07-13 15:23 rp_filter Leroy Tennison
2018-07-13 16:23 ` rp_filter Grant Taylor
@ 2018-07-13 16:26 ` Jay Vosburgh
2018-07-13 18:03 ` rp_filter Leroy Tennison
2018-09-04 10:11 ` rp_filter Anton Danilov
3 siblings, 0 replies; 10+ messages in thread
From: Jay Vosburgh @ 2018-07-13 16:26 UTC (permalink / raw)
To: lartc
Grant Taylor <gtaylor@tnetconsulting.net> wrote:
>On 07/13/2018 09:23 AM, Leroy Tennison wrote:
>> Is there a definitive way to tell that rp_filter is dropping traffic (in
>> this case echo request) other than disabling it and seeing the expected
>> traffic (echo reply)? I tried an iptables packet trace but I either did
>> it wrong or it showed nothing. The only indications I have right now
>> are:
>
>Check dmesg. That's the most reliable place I've seen for logs about (so
>called) "martian" packets.
I believe they're also counted in the "in_martian_src" column of
/proc/net/stat/rt_cache.
-J
>> No firewall rules blocking traffic but no replies either.
>
>It seems like reverse path filtering operates at a lower layer before
>IPTables.
>
>> The problem is subnet-specific (only occurs on a directly-connected
>> subnet).
>
>Odd.
>
>
>
>--
>Grant. . . .
>unix || die
---
-Jay Vosburgh, jay.vosburgh@canonical.com
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: rp_filter
2018-07-13 15:23 rp_filter Leroy Tennison
2018-07-13 16:23 ` rp_filter Grant Taylor
2018-07-13 16:26 ` rp_filter Jay Vosburgh
@ 2018-07-13 18:03 ` Leroy Tennison
2018-09-04 10:11 ` rp_filter Anton Danilov
3 siblings, 0 replies; 10+ messages in thread
From: Leroy Tennison @ 2018-07-13 18:03 UTC (permalink / raw)
To: lartc
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^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: rp_filter
2018-07-13 15:23 rp_filter Leroy Tennison
` (2 preceding siblings ...)
2018-07-13 18:03 ` rp_filter Leroy Tennison
@ 2018-09-04 10:11 ` Anton Danilov
3 siblings, 0 replies; 10+ messages in thread
From: Anton Danilov @ 2018-09-04 10:11 UTC (permalink / raw)
To: lartc
Hello.
This is the slowpoke post.
To check the rp filter you can use the ip route get command:
ip route get <ds-tip> from <src-ip> iif <input-interface>
In the recent kernels you will see either valid route or 'invalid
cross-device link' error. In the older kernels you won't see a valid
route if the rp_filter prevents forwarding.
Also, use command 'nstat -z TcpExtIPReversePathFilter' to check the rp
filtered packet drops counter.
Notice, the max value from conf/{all,interface}/rp_filter is used when
doing source validation on the {interface}.
On Fri, 13 Jul 2018 at 18:42, Leroy Tennison <leroy@datavoiceint.com> wrote:
>
> Is there a definitive way to tell that rp_filter is dropping traffic (in this case echo request) other than disabling it and seeing the expected traffic (echo reply)? I tried an iptables packet trace but I either did it wrong or it showed nothing. The only indications I have right now are:
>
> No firewall rules blocking traffic but no replies either.
> The problem is subnet-specific (only occurs on a directly-connected subnet).
>
> Early
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> Leroy Tennison
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> E: leroy@datavoiceint.com
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--
Anton.
^ permalink raw reply [flat|nested] 10+ messages in thread
end of thread, other threads:[~2018-09-04 10:11 UTC | newest]
Thread overview: 10+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2002-12-27 21:11 rp_filter Stephen Frost
2002-12-28 8:46 ` rp_filter Patrick Schaaf
2002-12-29 17:28 ` rp_filter Stephen Frost
2002-12-28 9:17 ` rp_filter Patrick Schaaf
2003-01-08 12:38 ` rp_filter Roberto Nibali
-- strict thread matches above, loose matches on Subject: below --
2018-07-13 15:23 rp_filter Leroy Tennison
2018-07-13 16:23 ` rp_filter Grant Taylor
2018-07-13 16:26 ` rp_filter Jay Vosburgh
2018-07-13 18:03 ` rp_filter Leroy Tennison
2018-09-04 10:11 ` rp_filter Anton Danilov
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