[ipv6] Re: [RFR]: 8222562: IPv6 only systems fail on setsockopt(IPV6_V6ONLY, 0)

[Arthur Eubanks]

On Wed, Apr 24, 2019 at 9:03 AM mark sheppard <macanaoire at hotmail.com>
wrote:

> an observation on IPv4_supported and IPV6_supported for your consideration
>
> <BIKESHED>
>
>  both, IPv4_support and IPv6_support use socket creation in the
> appropriate AF domain as a
> a verification of support, but the v6 version also checks that there is a
> set of
> address binding or ipv6 address configuration by accessing
> /proc/net/if_inet6
>
> afaik there is no equivalent /proc/net/if_inet or if_inet4, thus the ipv4
> version more
> liberal in its deliberation.
>
> as such, it is possible that for IPv4 the support is available but not yet
> configured,
> but that has no impact on availability.
> For IPv6 that the support is enabled but not yet configured and that will
> impact the
> availability evaluation.
>
> Implicit in this is the /proc/net/if_inet6 considered absolutely
> necessary ?
>
> this has at times been the cause of spurious intermittent test failures if
> my memory is correct.
>
> Another consideration is that if an application starts when IPv6 has yet
> to be configured properly,
> it will most likely lead to the application requiring a restart after the
> IPv6 to access IPv6 functionality
>
>
> </BIKESHED>
>
> regards
> Mark
>
IIUC, you're saying that the IPv6_supported() may return false when it
should return true in some cases?
That's not directly related to this change, since this change doesn't touch
IPv6_supported().
A repro of intermittent test failures or discussion about this in the past
would be good. Maybe you could file a bug or propose a patch?
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