On Wed, Nov 05, 2008 at 11:30:45AM +0100, Ferenc Wagner wrote:

Jarek Poplawski [off-list ref] writes:

quoted

On Sun, Nov 02, 2008 at 12:55:56AM +0100, Ferenc Wagner wrote:

quoted

Jarek Poplawski [off-list ref] writes:

quoted

On Wed, Oct 29, 2008 at 05:56:17PM +0100, Ferenc Wagner wrote:

quoted

Jarek Poplawski [off-list ref] writes:

quoted

quoted

quoted

Ferenc Wagner [off-list ref] writes:

quoted

I expected an IP-less bridge interface to pick up no IP
packets, but apparently this isn't the case: broadcast packets
with destination address 255.255.255.255 are reported as
martians by the 2.6.18 kernel, which I find counterintuitive (I
know 2.6.18 is rather old, but that's the one supported by Xen).

  1. Is this the expected behaviour?

with IP disabled you shouldn't have any martians!

In my case, the bridge itself (?) has no IP addresses assigned, but
an other interface (which isn't a bridge port) does have.  In other
words, the only network interface of the host is a bond interface
aggregating the two physical Ethernet interfaces; the two IP
addresses of the host are assigned to this bond0.

bond0 is also the raw interface of several .1q VLAN interfaces,
which are ports of bridges (there is one bridge for each VLAN but
the native above).  The other ports of the bridges are the virtual
interfaces of the Xen guests running on this host.  If I run ping
-b 255.255.255.255 on one such guest, that gives a "martian source
255.255.255.255" warning on the given bridge.  Even though
255.255.255.255 is the destination address of that ping packet...

And this happens on 2.6.26.6, too.

This means that even with IP enabled device ip_mkroute_input() should
be skipped. So it seems it's not about 255.255.255.255 generally, but
just about source address. You didn't give any examples of these
warnings, but I guess it's not a 0 address which is most popular with
255.255.255.255.

Indeed not, sorry.  If I ping -b 255.255.255.255 on a virtual machine
with IP 193.225.14.155, whose virtual interface is a port of br891:

martian source 255.255.255.255 from 193.225.14.155, on dev br891

Hmm, I still have doubts if this bridge is IP or not IP (iconfigs of
br891 and its components could help).

wferi@xen1:~$ sudo brctl show br891
bridge name	bridge id		STP enabled	interfaces
br891		8000.00065b8e71d5	no		vif3.0
							vif4.0
							vlan891

wferi@xen1:~$ /sbin/ifconfig br891
br891     Link encap:Ethernet  HWaddr 00:06:5b:8e:71:d5  
          inet6 addr: 2001:738:0:701:206:5bff:fe8e:71d5/64 Scope:Global
          inet6 addr: fe80::206:5bff:fe8e:71d5/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:425875 errors:0 dropped:0 overruns:0 frame:0
          TX packets:6 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:22340867 (21.3 MiB)  TX bytes:476 (476.0 B)

wferi@xen1:~$ /sbin/ifconfig vif3.0
vif3.0    Link encap:Ethernet  HWaddr fe:ff:ff:ff:ff:ff  
          inet6 addr: fe80::fcff:ffff:feff:ffff/64 Scope:Link
          UP BROADCAST RUNNING PROMISC MULTICAST  MTU:1500  Metric:1
          RX packets:759861 errors:0 dropped:0 overruns:0 frame:0
          TX packets:1123300 errors:0 dropped:3 overruns:0 carrier:0
          collisions:0 txqueuelen:32 
          RX bytes:129716290 (123.7 MiB)  TX bytes:172569213 (164.5 MiB)

wferi@xen1:~$ /sbin/ifconfig vif4.0
vif4.0    Link encap:Ethernet  HWaddr fe:ff:ff:ff:ff:ff  
          inet6 addr: fe80::fcff:ffff:feff:ffff/64 Scope:Link
          UP BROADCAST RUNNING PROMISC MULTICAST  MTU:1500  Metric:1
          RX packets:5944478 errors:0 dropped:0 overruns:0 frame:0
          TX packets:4411137 errors:0 dropped:3 overruns:0 carrier:0
          collisions:0 txqueuelen:32 
          RX bytes:969710414 (924.7 MiB)  TX bytes:465817748 (444.2 MiB)

wferi@xen1:~$ /sbin/ifconfig vlan891
vlan891   Link encap:Ethernet  HWaddr 00:06:5b:8e:71:d5  
          inet6 addr: fe80::206:5bff:fe8e:71d5/64 Scope:Link
          UP BROADCAST RUNNING MASTER MULTICAST  MTU:1500  Metric:1
          RX packets:5475880 errors:0 dropped:0 overruns:0 frame:0
          TX packets:12255410 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:558161949 (532.3 MiB)  TX bytes:1557958522 (1.4 GiB)

I hope it's not the autoconfigured IPv6 addresses...

I hope too... Anyway, I did some checking and this all seems to be a
real puzzle. As I wrote earlier (according to the comment): "with IP
disabled you shouldn't have any martians!". But it looks like deleting
all inet addresses isn't enough to have this "IP disabled" status
(maybe it's about multicasts or something... - I still have to find the
reason), but it's probably not critical for this problem.

Then I guess we can reconsider this problem like this: since this is a
bridge device without any IP address, and "we" expect treating this as
IP disabled devices, IMHO it doesn't make much sense to turn rp_filter
for such a device; log_martians can report us some other strange
address combinations, so it could be useful if there is not too much
of this.

wferi@xen1:~$ sudo cat /proc/net/vlan/vlan891 
vlan891  VID: 891	 REORDER_HDR: 1  dev->priv_flags: 1
         total frames received      5476270
          total bytes received    558194978
      Broadcast/Multicast Rcvd       258638

      total frames transmitted     12255659
       total bytes transmitted   1558098776
            total headroom inc            0
           total encap on xmit            0
Device: bond0
INGRESS priority mappings: 0:0  1:0  2:0  3:0  4:0  5:0  6:0 7:0
EGRESSS priority Mappings: 

(funny syntax on the last line...)

Should be corrected: maybe you will send a patch? (Otherwise let me now.)

wferi@xen1:~$ /sbin/ifconfig bond0
bond0     Link encap:Ethernet  HWaddr 00:06:5b:8e:71:d5  
          inet addr:10.253.2.7  Bcast:10.253.2.255  Mask:255.255.255.0
          inet6 addr: fe80::206:5bff:fe8e:71d5/64 Scope:Link
          UP BROADCAST RUNNING PROMISC MASTER MULTICAST  MTU:1500  Metric:1
          RX packets:41596702 errors:0 dropped:16 overruns:0 frame:0
          TX packets:44983056 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:8309642 (7.9 MiB)  TX bytes:2073809325 (1.9 GiB)

wferi@xen1:~$ /sbin/ifconfig bond0:0
bond0:0   Link encap:Ethernet  HWaddr 00:06:5b:8e:71:d5  
          inet addr:10.253.2.9  Bcast:10.253.2.255  Mask:255.255.255.0
          UP BROADCAST RUNNING PROMISC MASTER MULTICAST  MTU:1500  Metric:1

These are the two IPv4 addresses of the host.

quoted

It seems there has to be some IP seen on this br891 yet, and then I
wonder if it's not a fake problem with input of the bridge surprised
by a packet with it's own IP as source (but I didn't check for this
enough). So, the question is if you can get similar warnings without
such "special", internal pings too.

No, practically I can't.  If I ping the directed broadcast address
instead (ping -c1 -b 193.225.14.255), no warnings are emitted.
"Normal" traffic doesn't elicit them either, only the undirected
broadcasts to 255.255.255.255:

Yes, but this 255.255.255.255 address is (or was) special. According
to this:
http://en.wikipedia.org/wiki/Classful_network
and especially this:
http://tools.ietf.org/html/draft-wilson-class-e-02

it could be changed soon.

wferi@xen1:~$ zfgrep "martian source" /var/log/kern* | sed 's/.*martian source //' | sort -u
10.253.2.9 from 10.253.2.9, on dev bond0
255.255.255.255 from 193.225.14.155, on dev br891
255.255.255.255 from 193.225.14.179, on dev br891
255.255.255.255 from 193.225.14.195, on dev br891
255.255.255.255 from 193.225.14.201, on dev br891
255.255.255.255 from 193.225.14.251, on dev br891

(The first entry is a corner case which only happened when the
mentioned IP was floated over to this machine after guest migration,
which changed the bridge configuration as well.)

quoted

quoted

quoted

And, if there is some network address we have a problem: AFAIK this
255.255.255.255 broadcast is special, and it shouldn't be routed to
other networks. Your host doesn't seem to recognize this network, so
it shouldn't happen on this interface. So it seems, you expect the
bridge behavior where it's 2 in 1 (bridge + IP host).

Yes, this machine is an IP host (SSH access is needed) in a private
subnet (10.253.2/24) and also bridges traffic belonging to other
subnets (like for example the above).  It is not a router, though, so
it knows nothing about the bridged subnets.  Actually, it should be
totally separated from those, that's why I was alarmed by the martian
warnings: these "limited broadcast" (255.255.255.255, not routed, as
you note) addressed packets could reach the bridge!

Wasn't this ping done within the bridge's reach?

I'm not sure what you mean.  It was done on a virtual machine, whose
virtual inteface (vif4.0) is a port of br891 (see above).

I'm not sure what you mean by "totally separated". Bridges usually
don't help to separate, and packets with proper or not proper (for some
network) addresses are forwarded.

quoted

quoted

quoted

I'm not sure there is "right" solution for this with any model, but
I can miss something - then more details are needed. Otherwise,
maybe you should simply consider turning off log_martians on these
devices.

I could, but I'm more than a little worried that I don't understand
this stuff I'm expected to manage.  That's why I brought up the issue
here.  rp_filter is already enabled on all interfaces.  Do you think
it already ensures the separation I'm after, and all that's left is to
disable log_martians?

rp_filter prevents some kind of suspicious traffic (but legal
sometimes)

Does it drop anything legal but asymmetrically routed packets?

No, I don't think so.

quoted

but not all. log_martians should tell you if it's something
serious. If you have some martians "by design" it's probably better
to get rid of them before rp_filter

By dropping the in the nat table or by ebtables?  Anyway, "martians by
design" does sound particulary sane.

I mean e.g. when you really have to treat packets with such unusual
addresses as in your pings.

quoted

and save log_martians only for really unexpected cases.

Yes, that's what I did.  And it actually showed something unexpected.

quoted

quoted

Ps: If so, then I'd suggest placing the martian warning after
rp_filter, so that it doesn't warn about packets which get dropped
anyway, if possible.  Also, flipping the addresses in the martian
warning text would reduce confusion.  As it is, it suggests (English
is a foreign language for me, mind you) that 255.255.255.255 is the
problematic "martian source", while it's just a random destination
address in fact.

I guess we turn on log_martians just to see what is dropped.

OK, so those are dropped anyway.

Yes.

quoted

I agree the syntax of this warning is confusing, but I doubt we
should change this after so many years - this could break users'
scripts checking for this.

:) It's surprising after having read stable_api_nonsense.txt...

Hmm... Could you point me to this most :) point?

Regards,
Jarek P.