Hi,

I've been testing ospfd over gif and gre tunnels, and since changing mQy
ipsec setup, I've noticed a weird problem possibly related to pf.

In a nutshell, with a pf.conf file containing only the word "pass", when
pf is enabled, my router can't forward DNS replies from the gre/ipsec
tunnel to the originating interface, yet it works fine after pfctl -d.

With tcpdump, I can see that the dns reply is encapulated in the enc0
interface, with or without pf enabled. However, if I sniff the
originating interface, I don't see the reply when pf is enabled.

The setup up is shown at http://www.cl-is.com/ospf-test-setup.gif. I am
trying to nslookup www.google.com from 10.80.1.10

Here's some tcpdump output from the router enc0 i/f at 10.80.1.2 showing
the encapsulated reply in the ipsec/gre tunnel:

(authentic,confidential): SPI 0xf4002231: 192.168.100.3 >
62.xxx.xxx.123: gre 192.168.100.3 > 172.21.5.2: [] 10.80.1.10.41081 >
212.23.3.1.53:  28993+[|domain] (ttl 63, id 56742, len 60) (ttl 64, id
42337, len 84) (ttl 64, id 36445, len 104, bad cksum 0!)
(authentic,confidential): SPI 0xe0be3b36: 62.xxx.xxx.123 >
192.168.100.3: gre 172.21.5.2 > 192.168.100.3: [] 212.23.3.1.53 >
10.80.1.10.41081:  28993[|domain] (DF) (ttl 56, id 0, len 240) (DF) (ttl
64, id 39961, len 264) (DF) (ttl 53, id 62493, len 284)

Here's the request and reply at the 10.80.1.2 interface when pf is
disabed:

10.80.1.10.44820 > 212.23.8.1.53:  [udp sum ok] 57645+ A?
www.google.com. (32) (ttl 64, id 42326, len 60)
212.23.8.1.53 > 10.80.1.10.44820:  57645 3/0/0 www.google.com. CNAME
www.l.google.com., www.l.google.com.[|domain] (DF) (ttl 55, id 0, len
112)

With pf enabled, the enc0 traffic has the dns reply; it just doesn't
show up in the 10.80.1.2 interface and so the client never receives it.

Anyone got a clue what could be wrong? I am using -current.

PS. I have just found out that I can fix my problem by using "set skip on
gre0" before the "pass" rule, but I'd have thought that "pass" alone
would be enough. Is that expected behaviour?

Cheers,
Stephen Marley

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