pf-nat with userland ppp source address issue

[Max Laier]

On Wednesday 24 May 2006 21:32, Gergely CZUCZY wrote:
> i've met a very strange issue with NATting.
>
> i've noticed that only every second outgoing SSH connections succeed, and
> this was a bit strange. i've started a few, and tcp dumped them, applied
> a filter for S/SA tcp flags, and i've got the following result:
>
> No.     Time        Source                Destination           Protocol
> Info 31 4.513136    213.178.116.238       195.56.55.204         TCP     
> 53480 > ssh [SYN] Seq=0 Len=0 MSS=1460 WS=1 TSV=2969214 TSER=0 32 6.542201 
>   213.178.109.103       195.56.55.204         TCP      56051 > ssh [SYN]
> Seq=0 Len=0 MSS=1460 WS=1 TSV=2971243 TSER=0 73 8.293252    213.178.116.238
>       195.56.55.204         TCP      61535 > ssh [SYN] Seq=0 Len=0 MSS=1460
> WS=1 TSV=2972994 TSER=0 74 9.834288    213.178.109.103       195.56.55.204 
>        TCP      59672 > ssh [SYN] Seq=0 Len=0 MSS=1460 WS=1 TSV=2974535
> TSER=0 115 11.384353   213.178.116.238       195.56.55.204         TCP     
> 60708 > ssh [SYN] Seq=0 Len=0 MSS=1460 WS=1 TSV=2976085 TSER=0
>
> take a look at the source address
> now i've checked the interface configuration:
>
> # ifconfig tun0
> tun0: flags=8051<UP,POINTOPOINT,RUNNING,MULTICAST> mtu 1492
>         inet 213.178.109.103 --> 195.70.32.11 netmask 0xffffffff
>         Opened by PID 208
>
> for my information i looked them up:
> 238.116.178.213.in-addr.arpa domain name pointer
> caracas-4334.adsl.interware.hu. 103.109.178.213.in-addr.arpa domain name
> pointer caracas-2407.adsl.interware.hu.
>
> so it appears that's just an other user-IP from my ISP's ADSL-pool.
>
> now the ppp.log looked like really interesting, here comes the point:
> --- chop with axe here ---
> May 24 18:08:02 beeblebrox ppp[208]: tun0: IPCP:  IPADDR[6] changing
> address: 213.178.116.238  --> 213. 178.109.103
> --- chop with axe here ---
> as you can see, one source IP is the old one i had before, and the other on
> is that i'm using currently. i've tried to re-read pf.conf with pfctl -f,
> but that didn't helped, nor -d/-e (disabling and then enabling it).
>
> this solved it:
> # pfctl -d
> # pfctl -F nat
> # pfctl -F state
> # pfctl -F Sources
> # pfctl -f /etc/pf.conf
> # pfctl -e
>
> i'm using userland ppp service, as it seems from the tun0 interface.
>
> is this issue alread known, and is it really a bug, or i'm doing something
> wrong? the pf.conf is availabe from here. this is my home gateway, it's
> also a testbox, some kind of playground.
>
> uname -a:
> FreeBSD beeblebrox.harmless.lan 6.1-STABLE FreeBSD 6.1-STABLE #0: Fri May
> 19 14:25:03 CEST 2006    
> root at beeblebrox.harmless.lan:/usr/obj/usr/src/sys/BEEBLEBROX  i386
>
> pf.conf:
> http://phoemix.harmless.hu/pf.beeblebrox.conf

Try using:

(tun0:0) in "to", "from" and "->" statements.  The ":0" after the interface 
name will make sure that we don't use alias addresses on the interface.  In 
fact this is a bug in ppp, but it was decided that it was non-trivial to fix 
it.  I don't remember all the details, but

http://www.freebsd.org/cgi/query-pr.cgi?pr=69954

was the PR back then.

btw, you seem to be missing "()" around $if_ppp in the ftp-proxy rule.

-- 
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\ /  Max Laier                          | ICQ #67774661
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