fix(build): fix build on FreeBSD

[rene0]

Checklist

• I have read the contribution guidelines
• reference issue for this pull request: https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=270020
• if you changed anything related to how experiments work and you need to reflect these changes in the ooni/spec repository, please link to the related ooni/spec pull request:
• if you changed code inside an experiment, make sure you bump its version number

Description

The build of ooni-probe currently fails on FreeBSD because the compiler cannot find some required symbols (C.SOCK_STREAM, C.AF_INET, C.AF_INET6 and C.AF_UNSPEC). This causes the package net/ooni-probe-cli to be unavailable.

Fix this by including sys/socket.h when building on FreeBSD.

See also these FreeBSD bug reports (the second report also applies to Go 1.21 and Go 1.22):

• 270020: net/ooni-probe-cli: update 3.21.1 → 3.22.0, fix build
• 272643: lang/go120: Build of one port fails with could not determine kind of name for C.AF_INET, etc

I took a bit of a shortcut for the fix in the first URL by omitting the #ifdef as that patch would only exist in the FreeBSD port anyway. Both URLs also discuss if this is a problem in OONI or Go itself.

[bassosimone]

Thank you for your diff!

I've taken a look at IEEE Std 1003.1, and it says that the sys/socket.h file should define SOCK_STREAM, AF_INET, etc. About netdb.h, it reads: "inclusion of the <netdb.h> header may also make visible all symbols from [...] sys/socket.h".

Because it says may, for correctness, I think this repository should always include sys/socket.h when it is not not compiling for Windows. FreeBSD seems to have very clean headers and surfaced our optimistic include policy 😄.

Regarding this:

Both URLs also discuss if this is a problem in OONI or Go itself.

This issue is definitely an issue with this codebase and not an issue with Go itself.

Cc: @DecFox