PF issue (rule match but rule fails)

Tue Feb 28 14:43:25 UTC 2012

Hi  Damien, PF folks
yes 
checking the pflog is  important. I am not entirely sure but please correct were 
I go off path.

I send SMTP traffic from client here is pflog:

# tcpdump -nei pflog0 host 10.156.81.10 and port 25 
tcpdump: listening on pflog0, link-type PFLOG
09:37:14.901238 rule 12/(match) pass in on bge0: 10.156.81.10.55718 > 
172.19.4.41.25: S 3029008357:3029008357(0) win 64240 <mss 
1260,nop,nop,nop,nop,nop,nop,nop,nop,[|tcp]> (DF) [tos 0xb8]
09:37:14.901276 rule 12/(match) pass out on vlan579: 10.156.81.10.55718 > 
172.19.4.41.25: S 3597046675:3597046675(0) win 64240 <mss 
1260,nop,nop,nop,nop,nop,nop,nop,nop,[|tcp]> [tos 0xb8]
09:37:35.901429 rule 12/(match) pass in on bge0: 10.156.81.10.55718 > 
172.19.4.41.25: S 3029008357:3029008357(0) win 64240 <mss 
1260,nop,nop,nop,nop,nop,nop,nop,nop,[|tcp]> (DF) [tos 0xb8]
09:37:35.901471 rule 12/(match) pass out on vlan579: 10.156.81.10.55718 > 
172.19.4.41.25: S 3619107731:3619107731(0) win 64240 <mss 
1260,nop,nop,nop,nop,nop,nop,nop,nop,[|tcp]> [tos 0xb8]

Now I am not sure what indicated this rules is used. From below

@11 pass in quick inet proto tcp from 172.19.4.75 to 172.19.5.1 port = ssh flags 
any modulate state label "RULE -1 -- ACCEPT "
  [ Evaluations: 0         Packets: 0         Bytes: 0           States: 0     ]
  [ Inserted: uid 0 pid 1901 State Creations: 0     ]
@12 pass log quick inet proto tcp from <tbl.r0.s:22> to <tbl.r0.d:4> port = smtp 
flags any modulate state label "RULE 0 -- ACCEPT "
  [ Evaluations: 111973184  Packets: 12400     Bytes: 893938      States: 6     
]

you have packets, byes and states. Is it the state I must see incrementing? I 
have doen this several times and I see the state incrementing.

@11 pass in quick inet proto tcp from 172.19.4.75 to 172.19.5.1 port = ssh flags 
any modulate state label "RULE -1 -- ACCEPT "
  [ Evaluations: 0         Packets: 0         Bytes: 0           States: 0     ]
  [ Inserted: uid 0 pid 1901 State Creations: 0     ]
@12 pass log quick inet proto tcp from <tbl.r0.s:22> to <tbl.r0.d:4> port = smtp 
flags any modulate state label "RULE 0 -- ACCEPT "
  [ Evaluations: 111650386  Packets: 12362     Bytes: 891246      States: 24    
]

I do see states changing on this rule @12.

What is the modulate state, I was looking in the book of PF didn't see it as 
modulate, what setting or how to change that?

Lastly, how to disable scrub in tcp reassembly. I am not sure.

I will look into these though

Regards

----- Original Message ----
From: Damien Fleuriot <ml at my.gd>
To: freebsd-pf at freebsd.org
Sent: Tue, February 28, 2012 3:06:55 AM
Subject: Re: PF issue (rule match but rule fails)

On 2/28/12 2:27 AM, csbender wrote:
> Hi Folks,
> it is great to join you.
> I am pretty new to the world of PF so please excuse some ignorance at least for 
>
> now. 
> 
> 
> 
> I have a PF running freebsd 8.2. 
> 
> Here is my issue...
> 
> I have SMTP rule allowing traffic in and out for certain networks.
> Some SMTP traffic fails, eventhough I see rule match, I have no idea why.
> 
> Evidence...Here is am sending email from a network which comes across the FW.
> Here is the tcpdump.
> 
> 
> # tcpdump -ni bge0 host 10.156.81.10 and port 25    
> tcpdump: listening on bge0, link-type EN10MB
> 14:26:50.220591 10.156.81.10.60809 > 172.19.4.41.25: S 3154136673:3154136673(0) 
>
> win 64240 <mss 
> 1260,nop,nop,nop,nop,nop,nop,nop,nop,nop,nop,nop,nop,nop,nop,nop,nop> (DF) [tos 
>
> 0xb8]
> 14:26:50.244314 10.156.81.10.60809 > 172.19.4.41.25:R 3154136674:3154136735(61) 
>
> ack 1245040067 win 0 (DF) [tos 0xb8]
> 14:27:11.233494 10.156.81.10.60809 > 172.19.4.41.25: S 3154136673:3154136673(0) 
>
> win 64240 <mss 
> 1260,nop,nop,nop,nop,nop,nop,nop,nop,nop,nop,nop,nop,nop,nop,nop,nop> (DF) [tos 
>
> 0xb8]
> 14:27:11.245057 10.156.81.10.60809 > 172.19.4.41.25:R 0:61(61) ack 1 win 0 (DF) 
>
> [tos 0xb8]
>>From the above it is easy to see traffic isn't passing. 
> 
> Below is the rule that this traffic should be matching.
> 
> pass log quick inet proto tcp from <tbl.r0.d> to any port = smtp flags any 
> modulate state label "RULE 1 -- ACCEPT "
> 
> First question ...what command can I run to verify that the rule above is 
> pertaining to the traffic above?
> Secondly....what else could be squashing this SMTP traffic. It all works well 
> when pfctl is -d.
> 

First, check the logs from PF itself, not just a tcpdump from the
interface, and check what rule number matches:

tcpdump -nei pflog0

Then, obviously, display your pf rules and check what rule matched the
traffic, using its number: pfctl -vvsr

Second, get rid of "modulate state" and use "keep state" instead.

Third, if that doesn't fix your problem, disable tcp reassembly in your
"scrub" rules.

We had similar problems with scrubbing + TCP reassembly enabled over a
year ago on 8.x

_______________________________________________
freebsd-pf at freebsd.org mailing list
http://lists.freebsd.org/mailman/listinfo/freebsd-pf
To unsubscribe, send any mail to "freebsd-pf-unsubscribe at freebsd.org"