RFR: 8275640 (win) java.net.NetworkInterface issues with IPv6-only environments [v6]

[Daniel Jeliński]

On Wed, 26 Jan 2022 18:25:19 GMT, Daniel Fuchs <dfuchs at openjdk.org> wrote:

>> Daniel Jeliński has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains 12 additional commits since the last revision:
>> 
>>  - Fix invalid free
>>  - Merge remote-tracking branch 'origin' into interface-cleanup
>>  - Remove redundant initialization
>>  - Remove unused / incorrect exit code -2 from enumInterfaces
>>  - Address problems reported by clang-tidy
>>  - Restore support for IPv6-only operation
>>  - Fix memory leak
>>  - Fixup getAllInterfacesAndAddresses
>>  - Fixup getAddrsFromAdapter
>>  - Fixup enumAddresses_win
>>  - ... and 2 more: https://git.openjdk.java.net/jdk/compare/fec97562...98b40812
>
> src/java.base/windows/native/libnet/NetworkInterface_winXP.c line 253:
> 
>> 251: 
>> 252:     ret = enumInterfaces(env, netifPP);
>> 253:     if (ret < 0) {
> 
> Why did we remove handling for -2 here when `enumInterfaces` might return -2 if it does not find any IPv4 network interface? Shouldn't we keep the code that reset the exception status and set *netifPP = null here if ret == -2?

`enumInterfaces` no longer returns -2. It does not fail on IPv6 machines, and if it failed, our code wouldn't recover anyway. After a discussion with @msheppar I decided to remove -2 from the list of possible return values.

> src/java.base/windows/native/libnet/NetworkInterface_winXP.c line 271:
> 
>> 269:     ret = lookupIPAddrTable(env, &tableP);
>> 270:     if (ret == -1) {
>> 271:       free_netif(*netifPP);
> 
> *netifPP might be null here.

`free_netif` (and all other `free` functions) handle `null` input just fine.

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PR: https://git.openjdk.java.net/jdk/pull/6090