[SR-Users] TLS in-dialog set_forward_no_connect()and upstream TLS LCR gateway

[Daniel-Constantin Mierla]

On 15.09.19 03:34, Anthony Joseph Messina wrote:
> I'm going to keep testing against the issue I originally reported, and 
> probably wait until after 5.3 is released.  My issue may also be related to a 
> combination of TCPOPS keepalive not keeping the proper connection open for
>
> UAC -> Kamailio/LCR -> TLS Gateway
>
> The connection that's kept open to the TLS Gateway is the original forward of 
> the INVITE
>
> <Kamailio IP>:<ephemeral port> -> <TLS Gateway>:<Port 5061>
>
> The subsequent in-dialog connections (such as BYE from the UAC to the TLS 
> Gateway) don't use the original TLS connection so they are prevented from re-
> connecting to the TLS Gateway.
>
> Again, I have to do more testing to clear up the root issue on my end.
>
> Also, for a more compact config, would the following achieve the same thing...
>
>
> route[NATMANAGE] {
> #!ifdef WITH_NAT
>         if(is_request()) {
>                 if(has_totag()) {
>                         if(check_route_param("nat=yes")) {
>                                 setbflag(FLB_NATB);
> ### Add the command here....
> 			 set_forward_no_connect();
>                         }
>                 }
>         }
>
> ...


You have to differentiate between calls with one side behind nat and the
other one on a pubic IP that is like a server/gateway and can accept new
connections, even for requests within dialog.

My initial change to the default config file was done in the perspective
that the respective configuration is routing between local users, where
is not common for a user device to register, then close the connection,
because it was using a ephemeral port anyhow.

Cheers,
Daniel


>
>
> On Wednesday, September 11, 2019 1:21:34 AM CDT Daniel-Constantin Mierla 
> wrote:
>> It no longer looks like an issue related to  set_reply_no_connect() or
>> set_forward_no_connect() added by the commit you referenced. Those were
>> added to prevent attempting to connect to devices behind the nat (in
>> that case the device has to maintain the connection, otherwise nobody
>> can connect back to it) as well as prevent someone in the wild sending a
>> request then closing the connection, without waiting for the reply,
>> which is typically routed back to via, commonly with an ephemeral port.
>>
>> The follow up commit I did it in master recently is no longer setting
>> the flag for requests within dialog, but I understand you have
>> connection problems for requests within dialog, am I right?
>>
>> Cheers,
>> Daniel
>>
>> On 10.09.19 01:08, Anthony Joseph Messina wrote:
>>> I still ran into some trouble when one side was NAT'd.
>>>
>>> Am I correct in thinking that it would be undesirable to maintain a
>>> TCP/TLS
>>> connection to an upstream TLS gateway that is using the well-known port
>>> 5061?
>>>
>>> I was thinking this may be a case for TCP_REUSEPORT and force_send_socket,
>>> but that seems a little complex seeing as I can just let Kamailio
>>> reconnect (when necessary) rather than preventing the outbound TLS from
>>> connecting when it would otherwise succeed.
>>>
>>> I'll try and work through more detailed configuration scenarios.  -A
>>>
>>> On Monday, September 9, 2019 2:12:07 AM CDT Daniel-Constantin Mierla 
> wrote:
>>>> Hello,
>>>>
>>>> I relaxed that condition to not connect on forwarding only for initial
>>>> requests going though nat. Can you test with latest master and see how
>>>> is going for your use case?
>>>>
>>>> Cheers,
>>>> Daniel
>>>>
>>>> On 09.09.19 02:00, Anthony Joseph Messina wrote:
>>>>> In preparation for the 5.3 release, I've been testing the following
>>>>> configuration change for TCP/TLS connections:
>>>>>
>>>>> https://github.com/kamailio/kamailio/commit/
>>>>> 8bba208fe6ae7ccb4c92362b8c33f1530b9f56da
>>>>>
>>>>> route[REQINIT] {
>>>>>
>>>>> # no connect for sending replies
>>>>> set_reply_no_connect();
>>>>> if(has_totag()) {
>>>>>
>>>>> # no connect for requests within dialog
>>>>> set_forward_no_connect();
>>>>>
>>>>> }
>>>>>
>>>>> This change creates issues when a UAC TLS INVITE routes to an upstream
>>>>> gateway using TLS to port 5061 (via the LCR module).  Kamailio sends the
>>>>> initial outbound TLS connection from a local ephemeral port.  The TCPOPS
>>>>> tcp_keepalive_enable function issues keepalives from the local ephemeral
>>>>> port to the gateway port 5061:
>>>>>
>>>>> https://kamailio.org/docs/modules/stable/modules/
>>>>> tcpops#tcpops.f.tcp_keepalive_enable
>>>>>
>>>>> Even so, the TLS connection eventually times out, after which in-dialog
>>>>> requests from the UAC are no longer able to reach the upstream gateway.
>>>>>
>>>>> ERROR: tm [../../core/forward.h:293]: msg_send_buffer(): tcp_send failed
>>>>> WARNING: tm [t_fwd.c:1570]: t_send_branch(): sending request on branch 0
>>>>> failed
>>>>> ERROR: sl [sl_funcs.c:372]: sl_reply_error(): stateless error reply
>>>>> used:
>>>>> Unfortunately error on sending to next hop occurred (477/SL)
>>>>>
>>>>> I figure I must be doing something wrong with my TCPOPS here.  Is a TLS
>>>>> connection to an upstream gateway supposed to be maintained throughout
>>>>> the
>>>>> duration of a call?
>>>>>
>>>>> _______________________________________________
>>>>> Kamailio (SER) - Users Mailing List
>>>>> sr-users at lists.kamailio.org
>>>>> https://lists.kamailio.org/cgi-bin/mailman/listinfo/sr-users

-- 
Daniel-Constantin Mierla -- www.asipto.com
www.twitter.com/miconda -- www.linkedin.com/in/miconda
Kamailio Advanced Training, Oct 21-23, 2019, Berlin, Germany -- https://asipto.com/u/kat

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