Reintroduce: Fix for ipv6 link local with scope

[gabekassel]

This reintroduces commit c1abc7f. Commit was reverted in #9375 and #9376 for a Google-internal compilation issue. Re-raising this commit as it fixes a critical issue for our use case, and prods Google team whether this is still an issue internally.

Please also advise if this should be back ported to any specific release branches if approved.

[ejona86]

Yes, this is still an issue. The internal issue is very ugly, and essentially means we should avoid Guava's net package. I did look to get alternative solutions here, because I still feel like there's other issues with this flow, but it was an android-specific issue which made testing to investigate details too onerous at the time.

[ejona86]

CC @temawi, @YifeiZhuang

[gabekassel]

@ejona86 would it be possible to have an overload of configureTlsExtensions() that uses a build flag to enables us to use the isInetAddress check and an overload of that method that passes false by default? Hopefully this would make the current internal code follow its original path while whoever needs this check could just enforce it.

Does the codebase have patterns for flags like that we could follow?

[ejona86]

The internal problem is a build-time error, so a boolean is not sufficient. It might be possible to inject the reference to Guava instead, but that would have its own difficulties and short-term. Easiest solutions are to avoid Guava or to catch this problem earlier before the code gets to this point (which could allow using different libraries). To avoid Guava, easiest approach may be to just catch the exception from SNIHostName.

[linux-foundation-easycla]

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[gabekassel]

@ejona86 we've gone with the approach of catching IllegalArgumentException to avoid the Guava import. Please let us know if there's anything else we should do and if this is acceptable.

[gabekassel]

@ejona86 can you PTAL at this updated PR?

[gabekassel]

@ejona86 any update?