[OpenSIPS-Users] Wrong TCP socket being used on TLS registrations

[rvg at rvgeerligs.nl]

Hi Ray,

I am interested the solution or comments you receive. I have a similar problem. I have no voice or oneway voice on one of the clients. But I could work around it as I am using softphones on iphones as client. My work around was to turn wifi off on one of the clients, so this client gets the public IP of the phone subscription. But I still have this problem is both clients are in the same NAT.

Regards,

Ronald



September 2, 2023 at 2:17 AM, "Ray Jackson" <ray at hero.co.nz> wrote:


> 
> Hi all,
> 
>  
> 
> I'm facing a weird issue which I think is related to broken TCP socket reuse logic where the wrong client is receiving incoming calls due to the wrong socket being used for the incoming INVITE. 
> 
>  
> 
> The scenario is when I have 2 clients registering using TLS behind NAT at the same Public IPv4 address and both clients are using the same private port number.  So client 1 registers and the Via and contact header looks like: 
> 
>  
> 
> **Via: ** SIP/2.0/TLS 192.168.42.162:5062;**branch=**z9hG4bK1409895926;rport;alias**Contact: ** <sip:201 at 192.168.42.162:5062;**transport=**tls>;**reg-id=**2;+sip.instance="<urn:uuid:00000000-0000-1000-8000-C074AD928AC4> urn:uuid:00000000-0000-1000-8000-C074AD928AC4 "
> 
>  
> 
> Client 2 registers from behind the same Public IPv4 address and the Via and contact header looks like:
> 
>  
> 
> **Via: ** SIP/2.0/TLS 192.168.42.186:5062;**branch=**z9hG4bK-aff1f3b3**Contact: ** <sip:202 at 192.168.42.186:5062;**transport=**tls>;expire**s=**300
> 
>  
> 
> The location table shows Client 1 received field of 103.212.1.2:5062 and Client 103.212.1.2:23456 
> 
>  
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> When a call comes in for Client 1 the location lookup seems to return the correct 'received' address and port (e.g. 103.212.1.2:5062) and all the logs indicate that this is where the SIP INVITE *should* be going to (in the $du field).  However when you check the SIP traffic it selects Client 2's socket and the traffic goes to port 23456 instead of 5062.
> 
>  
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> I think this is related somehow to the TCP port reuse logic inside Opensips.  My suspicion is that Opensips is looking at the Contact or Via port number (which is the same for both client 1 and 2) and then somehow mapping this to the wrong TCP received socket.
> 
>  
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> Does anybody have any suggestions here?  Should I be fixing the NAT in the Contact header (using fix_nated_contact).  I read somewhere that you shouldn't rewrite the Contact header to avoid problems with sending a different Contact URI to the client on calls.  Or is this issue more related to the Via header and the TCP port reuse logic looking at this port instead of the actual received port when choosing the outgoing socket?
> 
>  
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> FYI: I am using both force_rport() and fix_nated_register() for incoming registrations from these clients and matching_mode of 0 in usrloc.  However, I am not using fix_nated_contact() for registrations.
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> Thanks,
> 
>  
> 
> Ray
>
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