[zeromq-dev] [PATCH] IPv4/IPv6 wiring for 3.0

Steven McCoy steven.mccoy at miru.hk
Tue Jul 19 17:58:32 CEST 2011

On 17 July 2011 21:22, Steven McCoy <steven.mccoy at miru.hk> wrote:

> On 17 July 2011 21:16, Steven McCoy <steven.mccoy at miru.hk> wrote:
>>    - Add two options, prefer-ipv4-stack and prefer-ipv6-addresses.
>> I might have the inverse interpretation of prefer-ipv6-addresses, Sun had
> way too many incompetent technical writers.
> *java.net.preferIPv6Addresses* (default: false)
>> If IPv6 is available on the operating system the default preference is to
>> prefer an IPv4-mapped address over an IPv6 address.
This reads as IPv4-in-IPv6 preferred to native IPv6, i.e. the preference is
with mapped addresses.

>  This is for backward compatibility reasons - for example applications that
>> depend on access to an IPv4 only service or applications that depend on the
>> %d.%d.%d.%d representation of an IP address.
This reads as do not use IPv4-in-IPv6 as the mapped address will not be
understood by the application, so the preference is for native IPv4
addressing instead of IPv6 addressing, i.e. the opposite of
the preceding statement

> This property can be set to try to change the preferences to use IPv6
>> addresses over IPv4 addresses. This allows applications to be tested and
>> deployed in environments where the application is expected to connect to
>> IPv6 services.
This discusses using IPv4-in-IPv6 mapping to test IPv6 due to the lack of
native IPv6 addresses, so the default should be to not to use mapped
addressing (which aligns with most OSs) but is a contradiction to earlier

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