RFR: JDK-8313804: JDWP support for -Djava.net.preferIPv6Addresses=system [v4]

[Alex Menkov]

On Tue, 19 Sep 2023 15:41:23 GMT, Liam Miller-Cushon <cushon at openjdk.org> wrote:

>> Please consider this fix for [JDK-8313804](https://bugs.openjdk.org/browse/JDK-8313804), which adds support to JDWP for `-Djava.net.preferIPv6Addresses=system`. Previously it only handled `-Djava.net.preferIPv6Addresses=true` and `-Djava.net.preferIPv6Addresses=false`.
>
> Liam Miller-Cushon has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Fix pre-existing typo

1st pass in attach (line 970) is also not needed, can be something like

    -    /* 1st pass - preferredAddressFamily (by default IPv4), 2nd pass - the rest */
    +    // 1st pass - preferredAddressFamily (by default IPv4), 2nd pass - the rest;
    +    // if java.net.preferIPv6Addresses == "system", only 2nd pass is needed
    +  pass = preferredAddressFamily != AF_UNSPEC ? 0 : 1;
    -    for (pass = 0; pass < 2 && socketFD < 0; pass++) {
    +    for (; pass < 2 && socketFD < 0; pass++) {
            for (ai = addrInfo; ai != NULL; ai = ai->ai_next) {

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PR Comment: https://git.openjdk.org/jdk/pull/15796#issuecomment-1726672963