[Freeswitch-users] NAT traversal questions - (long)...
David Ponzone
david.ponzone at ipeva.fr
Sun Aug 29 15:06:36 PDT 2010
Dave,
I misread your mail the first time and did not see you sent traces.
I think there are some interesting things in those.
For the packet coming from your HT-287 without the static port NAT:
Via: SIP/2.0/UDP 10.8.11.149:5062;branch=z9hG4bKda48f838c8689e41
-> rport is missing
For the packet coming from the one behind a DD-WRT:
rport is missing too, but the source port in the Via matches the
source port of the packet, so it works, the same way it works with
your pfSense if you add the static port NAT.
But why FS manages to guess it's behind NAT eludes me, but the NAT
detecting algo in FS is clearly complex.
For the packet coming from the HT-503:
I think you made a mistake. You said at the beginning of your mail
that it is behind DD-WRT, but before the trace, you say "one more
packet coming from Comcast/SMC".
Anyway, this one is interesting.
rport is there, so HT-503 is rport-capable (but HT-287 is not).
I would check if a configuration or a firmware upgrade could enable
rport on the HT-287.
Also, you wonder if modern routers have some automatic static NAT.
Actually, no, but what they do quite often is to not change the source
port of the packet if this port is available on the external interface.
For instance, if your device sends a packet from port 5060, and this
port is free on the external side of the router, it will preserve 5060.
Then if a second device sends a packet from port 5060, as it is
already used, it will use a random port.
You end up having a pseudo static NAT behaviour for the first device
on your network.
I saw that on business routers from Draytek, Funkwerk and others.
So perhaps your ipcop was doing that ?
Wild guess: if you add a second phone with the same source port 5060
behind a DD-WRT router, I am pretty sure you will have issues with its
registration.
About your question "is FreeSWITCH not tagging the device as behind
nat because it is on the same subnet as pfSense ?".
That's quite possible.
I think there are places in FS conf where you define what is local. I
think it's the special keyword localnet.auto.
But I really think the end of all isues is rport.
If rport is not available on your device, you can still force rport on
FS side:
<param name="NDLB-force-rport" value="true"/>
David Ponzone Direction Technique
email: david.ponzone at ipeva.fr
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Le 29/08/2010 à 09:01, Dave Redmore a écrit :
> Hello All,
>
> I ran into an issue today that has burned up most of my day
> troubleshooting. I have resolved the problem, but would really like
> to understand what caused it, or some of the internal Freeswitch
> plumbing that is at play so that I can learn something from all of
> this time I have invested.
>
> I have a Freeswitch server running that acts as a proxy to an
> account with an ITSP for doing T38 faxing. The Freeswitch server
> has a public IP address - there are four "users" who register simple
> FXS ATAs to my server and it then proxies to the ITSP using the
> "proxy_media" functionality. It has been working very well for the
> last 6 months or so. I have never had to deal with any NAT
> traversal issues - I just point the ATA to the IP to register and
> everything is great.
>
> Here is what the four users "looked" like -
>
> User1 : Grandstream HT-287 -> DD-WRT Router (NAT) -> Internet ->
> Freeswitch Proxy
> User2 : Grandstream HT-503 -> DD-WRT Router (NAT) -> Internet ->
> Freeswitch Proxy
> User3 : Grandstream HT-502 -> Comcast/SMC Router (NAT) -> Internet -
> > Freeswitch Proxy
> User4 : Grandstream HT-287 -> IPCOP 1.4.11 (NAT) -> Comcast Gateway
> -> Freeswitch Proxy
>
> (User4 is my office, so the IPCOP firewall and the Freeswitch Proxy
> sit on the same Comcast Gateway)
>
> As I said, this all worked perfectly without any need to "fiddle"
> with anything on any firewalls - worked right out of the box.
>
> So, today I changed out my IPCOP firewall for a pfsense firewall -
> and my HT-287 would no longer register.
>
> After much head-scratching, packet captures, etc. I found that I
> needed to set up a Static Port NAT for the port the HT-287 was using
> (5062) in order to get this to work.
>
> So, I see WHAT is happening, but I really want to know WHY it is
> happening.
>
> Here are the gory details:
>
> The sofia status of the profile looks like this - when the I have
> the Static Port NAT in place (details changed for security):
>
> _______________________________________________________________
> Call-ID: 0e551b3c694a793c at 192.168.1.137
> User: 8885554525 at 173.11.22.111
> Contact: "user" <sip:8885554525 at 192.168.1.137;fs_nat=yes;fs_path=sip%3A8885554525%40173.22.22.55%3A5060
> >
> Agent: Grandstream HT287 1.1.0.45 DevId 000b821203c5
> Status: Registered(UDP-NAT)(unknown) EXP(2010-08-29 01:17:03)
> Host: 173-11-22-111-illinois.hfc.comcastbusiness.net
> IP: 173.22.22.55
> Port: 5060
> Auth-User: 8885554525
> Auth-Realm: 173.11.22.111
> MWI-Account: 8885554525 at 173.11.22.111
>
> Call-ID: 1716488819-5062-1 at 192.168.7.150
> User: 8885554544 at 173.11.22.111
> Contact: "user" <sip:8885554544 at 192.168.7.150:5062;user=phone;fs_nat=yes
> ; fs_path=sip%3A8885554544%4098.255.0.11%3A5062%3Buser%3Dphone>
> Agent: Grandstream HT-502 V1.1B 1.0.1.63
> Status: Registered(UDP-NAT)(unknown) EXP(2010-08-29 01:48:35)
> Host: 173-11-22-111-illinois.hfc.comcastbusiness.net
> IP: 98.255.0.11
> Port: 5062
> Auth-User: 8885554544
> Auth-Realm: 173.11.22.111
> MWI-Account: 8885554544 at 173.11.22.111
>
> Call-ID: 090ee80e1a0ec9ed at 10.8.11.149
> User: 8885554549 at 173.11.22.111
> Contact: "user" <sip:8885554549 at 10.8.11.149:5062>
> Agent: Grandstream HT287 1.1.0.45 DevId 000b82127390
> Status: Registered(UDP)(unknown) EXP(2010-08-29 02:00:42)
> Host: 173-11-22-111-illinois.hfc.comcastbusiness.net
> IP: 173.11.22.99
> Port: 5062
> Auth-User: 8885554549
> Auth-Realm: 173.11.22.111
> MWI-Account: 8885554549 at 173.11.22.111
>
> Call-ID: 1035241259-5060-1 at 10.1.10.150
> User: 8885554547 at 173.11.22.111
> Contact: "user" <sip:8885554547 at 10.1.10.150:5060;user=phone;fs_nat=yes;fs
> _path=sip%3A8885554547%4098.222.55.100%3A5060%3Buser%3Dphone>
> Agent: Grandstream HT-503 V1.1B 1.0.1.63
> Status: Registered(UDP-NAT)(unknown) EXP(2010-08-29 00:15:09)
> Host: 173-11-22-111-illinois.hfc.comcastbusiness.net
> IP: 98.222.55.100
> Port: 5060
> Auth-User: 8885554547
> Auth-Realm: 173.11.22.111
> MWI-Account: 8885554547 at 173.11.22.111
> ___________________________________________________________
>
> The "User4" account is in red. The "Contact" field is substantially
> different and the "Status" indicates "Registered (UDP)", rather than
> "Registered (UDP-NAT)" as the others.
>
> When I do a packet capture on the external NIC interface (eth0) - I
> see the following when the HT-287 tries to register and the Static
> Port NAT is NOT in place:
>
> ___________________________________________________________________
> Internet Protocol, Src: 173.11.22.99 (173.11.22.99), Dst:
> 173.11.22.111 (173.11.22.111)
> User Datagram Protocol, Src Port: 11521 (11521), Dst Port: 5090 (5090)
> Session Initiation Protocol
> Request-Line: REGISTER sip:173.11.22.111:5090 SIP/2.0
> Method: REGISTER
> Request-URI: sip:173.11.22.111:5090
> Request-URI Host Part: 173.11.22.111
> Request-URI Host Port: 5090
> Message Header
> Via: SIP/2.0/UDP
> 10.8.11.149:5062;branch=z9hG4bKda48f838c8689e41
> Transport: UDP
> Sent-by Address: 10.8.11.149
> Sent-by port: 5062
> Branch: z9hG4bKda48f838c8689e41
> From: <sip:8885554549 at 173.11.22.111:5090>;tag=c8a0d452edc5ac4b
> SIP from address: sip:8885554549 at 173.11.22.111:5090
> SIP tag: c8a0d452edc5ac4b
> To: <sip:8885554549 at 173.11.22.111:5090>
> Contact: <sip:88855564549 at 10.8.11.149:5062>
> Contact Binding: <sip:8885554549 at 10.8.11.149:5062>
> Supported: replaces, timer
> Call-ID: aa77d777bae71be6 at 10.8.11.149
> CSeq: 100 REGISTER
> Sequence Number: 100
> Method: REGISTER
> Expires: 3600
> User-Agent: Grandstream HT287 1.1.0.45 DevId 000b82127390
> Max-Forwards: 70
> Allow:
> INVITE,ACK,CANCEL,BYE,NOTIFY,REFER,OPTIONS,INFO,SUBSCRIBE,UPDATE
> Content-Length: 0
> _______________________________________________________________
>
> When Freeswitch replies back with a "401 Unauthorized" - asking for
> further Auth - it replies back to port 5062 - so the packet never
> comes back (pfsense is looking for a packet back on port 11521 in
> this case).
>
> If I put the Static Port NAT in place - all is well, because the
> "Source" port shows as "5062" - the rest of the packet looks pretty
> much the same.
>
> Now, here is a packet coming from one of the other Users - this one
> comes through a DD-WRT router - here we see that the Source Port is
> 5060 :
>
> _________________________________________________________________
> Internet Protocol, Src: 173.22.22.55 (173.22.22.55), Dst:
> 173.11.22.111 (173.11.22.111)
> User Datagram Protocol, Src Port: sip (5060), Dst Port: 5090 (5090)
> Session Initiation Protocol
> Request-Line: REGISTER sip:173.11.22.111:5090 SIP/2.0
> Method: REGISTER
> Request-URI: sip:173.11.22.111:5090
> [Resent Packet: False]
> Message Header
> Via: SIP/2.0/UDP 192.168.1.137;branch=z9hG4bK665bc67a1c64292b
> Transport: UDP
> Sent-by Address: 192.168.1.137
> Branch: z9hG4bK665bc67a1c64292b
> From: "fax" <sip:
> 8885554525 at 173.11.22.111:5090>;tag=8dc68b35111c4261
> To: <sip:8156564525 at 173.15.28.101:5090>
> Contact: <sip:8885554525 at 192.168.1.137>
> Contact Binding: <sip:8885554525 at 192.168.1.137>
> Call-ID: 0e551b3c694a793c at 192.168.1.137
> CSeq: 503 REGISTER
> Sequence Number: 503
> Method: REGISTER
> Expires: 3600
> User-Agent: Grandstream HT287 1.1.0.45 DevId 000b821203c5
> Max-Forwards: 70
> Allow:
> INVITE,ACK,CANCEL,BYE,NOTIFY,REFER,OPTIONS,INFO,SUBSCRIBE,UPDATE
> Content-Length: 0
> ______________________________________________________________________
>
> Here is one more packet coming from a Comcast/SMC Router - again,
> the source port is correct:
>
> ______________________________________________________________________
> Internet Protocol, Src: 98.244.55.100 (98.244.55.100), Dst:
> 173.11.22.111 (173.11.22.111)
> User Datagram Protocol, Src Port: sip (5060), Dst Port: 5090 (5090)
> Session Initiation Protocol
> Request-Line: REGISTER sip:173.11.22.111:5090 SIP/2.0
> Message Header
> Via: SIP/2.0/UDP 10.1.10.150:5060;branch=z9hG4bK58981045;rport
> Transport: UDP
> Sent-by Address: 10.1.10.150
> Sent-by port: 5060
> Branch: z9hG4bK58981045
> RPort: rport
> From: <sip:
> 8885554547 at 173.11.22.111:5090;user=phone>;tag=138706651
> To: <sip:8885554547 at 173.11.22.111:5090;user=phone>
> Call-ID: 1035241259-5060-1 at 10.1.10.150
> CSeq: 79875 REGISTER
> Sequence Number: 79875
> Method: REGISTER
> Contact: <sip:8885554547 at 10.1.10.150:5060;user=phone>;reg-
> id=1;+sip.instance="<urn:uuid:00000000-0000-1000-8000-000B821F9A84>"
> Contact Binding: <sip:8885554547 at 10.1.10.150:5060;user=phone
> >;reg-id=1;+sip.instance="<urn:uuid:00000000-0000-1000-8000-000B821F9A84
> >"
> Max-Forwards: 70
> User-Agent: Grandstream HT-503 V1.1B 1.0.1.63
> Supported: path
> Expires: 300
> Allow: INVITE, ACK, OPTIONS, CANCEL, BYE, SUBSCRIBE, NOTIFY,
> INFO, REFER, UPDATE
> Content-Length: 0
> ___________________________________________________________
>
> So, here are my questions:
>
> - Why is the Sofia Status so much different for the registration
> coming through the pfSense firewall. It looks like it doesn't get
> tagged as being NAT'd and the "Contact" info is much less.
>
> - Do most modern routers automatically Static Port NAT any SIP
> traffic? Both DD-WRT and SMC routers appear to be doing this - and
> not just on a simple Port bases (UDP 5060 only), because one of
> these examples is on 5062. Are these "SIP aware" firewalls that are
> doing this automatically, as the IPCOP did before?
>
> - Is the extra "Contact" data in the last packet example different
> because it is a different UA (HT-503 rather than an HT-287)
>
> - Is Freeswitch not flagging the registration from my office (User4)
> as being NAT'd because it is coming in on the same subnet as the
> interface Freeswitch received the packet on (Freeswitch is at
> 173.11.22.111 and pfsense is at 173.11.22.99)?
>
> Sorry for this terribly long posting - I'm just very curious to
> understand what is going on here, now that I have collected all this
> information.
>
> Thanks,
>
> Dave
>
>
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