On Sun, 2007-02-11 at 11:04 -0800, Tom Eastep wrote:
> Alternatively, I've long suspected that rp_filter doesn't take the packet mark
> into consideration.

I would be quite surprised if rp_filter did that.

> What does "ip route get 74.111.215.93 from 72.38.184.236" give you?

# ip route get 74.111.215.93 from 72.38.184.236
74.111.215.93 from 72.38.184.236 via 72.38.184.1 dev eth1 
    cache  mtu 1500 advmss 1460 metric 10 64

> >From your 'shorewall dump':
> 
> Chain eth1_masq (1 references)
>  pkts bytes target     prot opt in     out     source
> destination
> ...
>     3   456 SNAT       all  --  *      *       66.11.173.224        0.0.0.0/0
>           policy match dir out pol none to:72.38.184.236
> 
> So the SNAT rule has been exercised at some point.

That is what I was thinking at some point too.  But I can't see how as
it's only supposed to happen on packets going out of eth1.  To test,
I've added a logging rule right before that SNAT rule:

Chain eth1_masq (1 references)
num   pkts bytes target     prot opt in     out     source               
destination         
...
7        0     0 LOG        all  --  *      *       66.11.173.224        
0.0.0.0/0           LOG flags 0 level 6 prefix `SNATting:' 
8        4   608 SNAT       all  --  *      *       66.11.173.224        
0.0.0.0/0           policy match dir out pol none to:72.38.184.236 

and when I trigger the situation though many packets were sent and many
martians logged only a single occurence of:

SNATting:IN= OUT=eth1 SRC=66.11.173.224 DST=74.111.215.93 LEN=152 TOS=0x00 
PREC=0x00 TTL=64 ID=0 DF PROTO=UDP SPT=1194 DPT=1194 LEN=132 

and that one looks pretty legit to me.

I'm really leaning towards this being a logging anomaly/strangeness
rather than actual packet manipulation.

> If any of those connections
> was your freenet6 application,

Naw, this was plain old openvpn.  I was trying to ping something on the
other end of an openvpn tunnel.

> it would explain how the ppp0 address got into
> the Martian messages.

b.

-- 
My other computer is your Microsoft Windows server.

Brian J. Murrell

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