[sr-dev] [kamailio/kamailio] nathelper: fix_nated_sdp added ignoring RFC3605-param if omitted (#2737)

[Dmitry Wagin]

#### Pre-Submission Checklist
- [x] Commit message has the format required by CONTRIBUTING guide
- [x] Commits are split per component (core, individual modules, libs, utils, ...)
- [x] Each component has a single commit (if not, squash them into one commit)
- [x] No commits to README files for modules (changes must be done to docbook files
in doc/ subfolder, the README file is autogenerated)

#### Type Of Change
- [x] Small bug fix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds new functionality)
- [ ] Breaking change (fix or feature that would change existing functionality)

#### Checklist:
- [x] PR should be backported to stable branches
- [x] Tested changes locally
- [x] Related to issue #2459

#### Description
There's a small regression after #2497.

If SDP didn't have an "a=rtcp" header (RFC1889 behavior), Kamailio had thrown an Error `can't extract 'a=rtcp' IP from the SDP` on every INVITE. After the PR Kamailio does not flood into log.

Please take into account IPv6 address parser after the commit.

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

https://github.com/kamailio/kamailio/pull/2737

-- Commit Summary --

* nathelper: fix_nated_sdp added ignoring RFC3605-param if omitted

-- File Changes --

M src/modules/nathelper/nathelper.c (22)

-- Patch Links --

https://github.com/kamailio/kamailio/pull/2737.patch
https://github.com/kamailio/kamailio/pull/2737.diff

[Daniel-Constantin Mierla]

Thanks for contributing!

Can you elaborate more on your remark `Please take into account IPv6 address parser after the commit.`? Your fix does not take care of IPv6, or the existing code does not do it?

[Boris Korzun]

@miconda the fix takes care IPv4 (AF_INET socket type). We've tested it on IPv4, but we cannot test it on IPv6. :(

[Dmitry Wagin]

The previous version only worked with IPv4. I've fixed it, but haven't test it.

[Daniel-Constantin Mierla]

@oej - is there a chance that you can test this PR? I see you discussed #2497, maybe you have some IPv6 environment at hand.

If not and no other comments, then it can be merged soon.

[Olle E. Johansson]

Let me check if I can set up tests.