[1/3] Make guest-agent buildable on FreeBSD

[yagehu]

Expected changes to Linux behavior: None

This commit, when paired with corresponding dependency patches, makes guest-agent buildable on FreeBSD. The plan is to incrementally fix guest-agent's behavior on FreeBSD.

The list of required dependency patches:

• Support FreeBSD build google/go-sev-guest#189
• Support FreeBSD build google/go-tdx-guest#101
• Support FreeBSD tarm/serial#134

[ChaitanyaKulkarni28]

Thanks for the FreeBSD port! I notice significant duplication between the new _freebsd.go files and the existing Linux implementations. To improve maintainability and avoid logic drift, we should consider refactoring the common code into shared files.

Like for the agentcrypto package:

We can create a new file, mtls_mds_unix.go, with the build directive //go:build linux || freebsd

The identical constants (rootCACertFileName, clientCredsFileName) and helper functions (writeRootCACert, writeClientCredentials, getCAStoreUpdater, certificateDirFromUpdater) can be moved there.

This would leave mtls_mds_linux.go and mtls_mds_freebsd.go to only define their platform-specific defaultCredsDir and certUpdaters maps.

The command and sshtrustedca packages could be handled similarly and ensure that core logic is maintained in a single place.

What do you think? Was this duplication to avoid any impact on Linux/Windows implementations?

[yagehu]

Thanks for the FreeBSD port! I notice significant duplication between the new _freebsd.go files and the existing Linux implementations. To improve maintainability and avoid logic drift, we should consider refactoring the common code into shared files.

Like for the agentcrypto package:

We can create a new file, mtls_mds_unix.go, with the build directive //go:build linux || freebsd

The identical constants (rootCACertFileName, clientCredsFileName) and helper functions (writeRootCACert, writeClientCredentials, getCAStoreUpdater, certificateDirFromUpdater) can be moved there.

This would leave mtls_mds_linux.go and mtls_mds_freebsd.go to only define their platform-specific defaultCredsDir and certUpdaters maps.

The command and sshtrustedca packages could be handled similarly and ensure that core logic is maintained in a single place.

What do you think? Was this duplication to avoid any impact on Linux/Windows implementations?

Done. The original intent was to minimize disruption to the existing Linux code.

[SaswatPadhi]

Thanks for the PR, @yagehu, and thanks for taking a look @ChaitanyaKulkarni28. I look at the changes and they LGTM -- mostly path tweaks for FreeBSD.

I think we could merge this, unless @ChaitanyaKulkarni28 has any remaining concerns (I'll leave it up to him for final approval).

[google-oss-prow]

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