[sr-dev] [kamailio/kamailio] tm: prevent t_suspend memory leak (#2763)

[Julien Chavanton]

When suspending while already in t_continue when processing a reply / suspending twice in a reply.

Thanks to @giavac https://github.com/kamailio/kamailio/pull/2721 we can now suspend more then once in a reply route.

This is working well, however a memory leak was detected.

This modification is proposing a solution that will prevent calling `sip_msg_cloner` over an already twice over the same pointer, creating the memory leak.


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I assume this is a non "breaking change" since it can only trigger in a very the specific case that was not supported anyway.
Conditions when this alternate behavior can trigger:
1- must be in t_suspend
2- must be in a reply `if (msg->first_line.type == SIP_REPLY) {`
3- must have an already cloned `if (t->uac[branch].reply) {`

An alternate solution would be to free everything in the cloned message and recreate it.


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load test done that included connections, failures and timeouts while suspending multiple times.

```
6(31) INFO: tm [t_suspend.c:126]: t_suspend(): [>>>SUSPEND<<<] cloning message !
53(78) INFO: tm [t_suspend.c:136]: t_suspend(): [>>>SUSPEND<<<] message already cloned, re-using !
```

```
Total 100000 INVITE calls sent in 1710825 ms at rate of 58/sec
Total 100000 connection responses received in 1714999 ms at rate of 58/sec:
>> Detailed connection responses received:
- 200 connection responses: 24924 (OK)
- 404 connection responses: 25145 (Not Found)
- 408 connection responses: 24912 (Request Timeout)
- 500 connection responses: 25019 (Internal Server Error)
>> Detailed disconnection responses received:
- 200 disconnection responses: 24924 (OK)
------
TOTAL responses: 24924 (rate=14/sec)
```


#### Description
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You can view, comment on, or merge this pull request online at:

https://github.com/kamailio/kamailio/pull/2763

-- Commit Summary --

* tm: prevent t_suspend memory leak

-- File Changes --

M src/modules/tm/t_suspend.c (21)

-- Patch Links --

https://github.com/kamailio/kamailio/pull/2763.patch
https://github.com/kamailio/kamailio/pull/2763.diff

[Julien Chavanton]

@jchavanton pushed 1 commit.

e5259053c0c30f1ad511a8d2d11550048f95f0ec tm: prevent t_suspend memory leak

[Julien Chavanton]

@jchavanton pushed 1 commit.

ed12500804ccdbf4f9428e1fc8c1fcfe58217f6e tm: prevent t_suspend memory leak

[Daniel-Constantin Mierla]

I am fine to merge it.

[Julien Chavanton]

Merged #2763 into master.