[jdk8u-dev] RFR: 8339414: Fix JDK-8202369 incorrect backport for 8u

[Thomas Fitzsimmons]

There is a large `#ifdef` in JDK 8's `Inet4AddressImpl.c`:


#if defined(__GLIBC__) || (defined(__FreeBSD__) && (__FreeBSD_version >= 601104))
#define HAS_GLIBC_GETHOSTBY_R   1
#endif

#if defined(_ALLBSD_SOURCE) && !defined(HAS_GLIBC_GETHOSTBY_R)
[... 261 lines ...]
#else /* defined(_ALLBSD_SOURCE) && !defined(HAS_GLIBC_GETHOSTBY_R) */
[... ~ 244 similar lines ...]
#endif /* _ALLBSD_SOURCE */


When the fix for https://bugs.openjdk.org/browse/JDK-8201369 was backported to `8`, the second branch of the large `#ifdef` in `Inet4AddressImpl.c` was not changed at the same time, which is incorrect, since reverse lookup should only ever happen on `Solaris`, according to the description of `JDK-8201369`.

I used the `JDK 11` `unix/native/libnet/Inet4AddressImpl.c` implementation; after this change, the only difference between `11`'s `Java_java_net_Inet4AddressImpl_getLocalHostName` and the `defined(HAS_GLIBC_GETHOSTBY_R)` one will be the use of `JVM_GetHostName` in `8` versus `gethostname` in `11`.

I decided to update the `hostlen` argument to `getnameinfo` from `NI_MAXHOST` to `sizeof(hostname)` to fix https://bugs.openjdk.org/browse/JDK-8202181 for this function.  I do not have a `Solaris` machine to test on, but this matches `11`'s `getnameinfo` calls, and is correct given `hostname[NI_MAXHOST] = '\0'`.

The resulting behaviour should be the same, other than the reverse lookup only being performed on `Solaris`.

The implementations of `Java_java_net_Inet4AddressImpl_getLocalHostName` in each of the `#ifdef` branches diverge already because the fix for https://bugs.openjdk.org/browse/JDK-7112670 (https://github.com/openjdk/jdk8u-dev/commit/a62dd6282b7a0f1f3c75dad90385783b93d30e61) was only applied to the second branch.

Probably the upper `Java_java_net_Inet4AddressImpl_getLocalHostName` implementation could be made identical to the lower, but I do not want to do that, just in case `NI_MAXHOST` is preferred to `sizeof(hostname)` on `!defined(HAS_GLIBC_GETHOSTBY_R)` operating systems.

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Commit messages:
 - 8339414: Fix JDK-8202369 incorrect backport

Changes: https://git.openjdk.org/jdk8u-dev/pull/661/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk8u-dev&pr=661&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8339414
  Stats: 26 lines in 1 file changed: 9 ins; 13 del; 4 mod
  Patch: https://git.openjdk.org/jdk8u-dev/pull/661.diff
  Fetch: git fetch https://git.openjdk.org/jdk8u-dev.git pull/661/head:pull/661

PR: https://git.openjdk.org/jdk8u-dev/pull/661