netdev - Re: TCP using IPv4-mapped IPv6 address as source

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Date:   Wed, 11 Jan 2017 12:34:04 -0500
From:   "Jonathan T. Leighton" <jtleight@...l.edu>
To:     Eric Dumazet <eric.dumazet@...il.com>
Cc:     netdev@...r.kernel.org, edumazet@...gle.com,
        Yuchung Cheng <ycheng@...gle.com>,
        Neal Cardwell <ncardwell@...gle.com>
Subject: Re: TCP using IPv4-mapped IPv6 address as source

On 1/11/17 11:20 AM, Eric Dumazet wrote:
> On Thu, 2017-01-05 at 16:25 -0500, Jonathan T. Leighton wrote:
>> I've observed TCP using an IPv4-mapped IPv6 address as the source
>> address, which I believe contradicts
>> https://tools.ietf.org/html/rfc6890#page-14 (BCP 153). This occurs when
>> an IPv6 TCP socket, bound to a local IPv4-mapped IPv6 address, attempts
>> to connect to a remote IPv6 address. Presumable connect() should return
>> EAFNOSUPPORT in this case. Please advise me if this is not to
>> appropriate list to report this.
> Hi Jonathan
>
> I believe your concern makes sense.
> Do you have a patch to address this issue ?

Thanks for responding Eric. I have limited experience with kernel 
patches. Nevertheless, unless there's someone with the experience and 
time to jump on this, I'm interested in taking a crack at it. I think 
the issue certainly warrants attention: instead of returning immediately 
with EAFNOSUPPPORT, connect() retransmits its SYN 6 times, ultimately 
returning ETIMEDOUT after 127 sec (1+2+4+...+64).

> Thanks
>
>