openvpn plugin: Fix parsing empty fields

[rpv-tomsk]

Closes: #3424

Changelog: openvpn plugin: Fix parsing empty fields

I have some another improvements too, but I'm not interested in publishing them due to lack of fast response from "trusted maintainers" and I'm not trusted enough to merge my own changes myself.

[NikolayTsvetkov]

Hi Pavel, Thank you for the contribution !
I'm sure the community and all the users would be thankful profiting from the further improvements you can provide to the plugin.
Merging your own PR has never been a good practice in any project, as code review doesn't only check the code quality, but in most cases leads to better ideas and improvements.
Looking forward seeing the new features here or in a separate PR.

Cheers !

[rpv-tomsk]

as code review doesn't only check the code quality,

Code review in this project does nothing:
Examples:
#3381 - merged non-working implementation.
#1339 - (merged recently) - implementation effectively replaced by a const value
#2910 - (merged recently) - implemenation violates codestyle

... also I have another examples of review quality.

I do not believe that someone really checks the code. They simply push "approve"+"merge" buttons, and I able to do that myself, w/o third-party help.

Practice shows me - nobody interested in merging PRs, to which person has no relation.

[rpv-tomsk]

... but in most cases leads to better ideas and improvements.

In most cases it leads to worthless waiting.

There was examples of 6+ months waiting. It takes so much time to review?
No, it simply just shows the attitude towards the developers, like the other endless problems of CI and clang-format infrastructure.

[faxm0dem]

Hi Pavel, what's your rationale behind also changing the version detection?

[rpv-tomsk]

Hi Pavel, what's your rationale behind also changing the version detection?

Versions 2 and 3 differs only by delimiter.
We need to detect delimiter to use it in parser.

[faxm0dem]

according to manpage, strsep also supports a string as separator:

   that  is  delimited  by one of the bytes in the string delim.
   This token is terminated by overwriting the delimiter 

[rpv-tomsk]

This implementation not uses strsep.

[faxm0dem]

oh sorry, I misread.
oki doki, makes sense.
I'll test your patch ritght away, thanks

[faxm0dem]

successfully tested on Centos7