Re: [9fans] adding TCP half-duplex close

[Bakul Shah <bakul@bitblocks.com>]

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If they implement close correctly, they should be able to implement close-read correctly, it being a pure subset. In theory :-)

As for SYN+data+FIN you had to have both sides properly implement rfc1644 or the T/TCP extension. This extension was deprecated at least by 2004 due to "the ease of DoS attacks that can result". Might want to take a look at a recent TCP roadmap RFC such as rfc7414!

> On Feb 5, 2017, at 7:54 AM, Charles Forsyth <charles.forsyth@gmail.com> wrote:
> 
> It's a similar story with SYN+data+FIN to provide a basic reliable datagram. You can't rely on a consistent implementation (unless it's to defeat your purpose).
> 
>> On 5 February 2017 at 15:51, Charles Forsyth <charles.forsyth@gmail.com> wrote:
>> 
>>> On 5 February 2017 at 05:23, Bakul Shah <bakul@bitblocks.com> wrote:
>>> I think shutdown(sock, SHU_RD) is mainly to let the sender generate an SIGPIPE signal in case it has sent data on a closed direction of a connection. But I think this is only for completeness. Almost always you’d use close(sock). At least I have not found a usecase when I’d want to shutdown the read-end but continue sending on write-end. 
>> 
>> Yes. That's roughly what I tried to do with my network pipe, but at least at the time, target systems differed (as they were apparently allowed) as to whether they reliably delivered data or simply flushed it, so in the end I had to add some protocol to ensure it, and didn't need the "feature".
> 

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