From: Ken Brown <kbrown@cornell.edu>
To: cygwin-developers@cygwin.com
Subject: Re: The unreliability of AF_UNIX datagram sockets
Date: Fri, 21 May 2021 17:54:37 -0400 [thread overview]
Message-ID: <fa8c4879-cd89-bcef-3296-85986dbada54@cornell.edu> (raw)
In-Reply-To: <YKa3x4Ha3iWhI9Ow@calimero.vinschen.de>
On 5/20/2021 3:25 PM, Corinna Vinschen wrote:
> On May 20 09:46, Ken Brown wrote:
>> On 4/29/2021 7:05 AM, Corinna Vinschen wrote:
>>> I think it should be possible to switch to STREAM sockets to emulate
>>> DGRAM semantics. Our advantage is that this is all local. For all
>>> practical purposes there's no chance data gets really lost. Windows has
>>> an almost indefinite send buffer.
>>>
>>> If you look at the STREAM as a kind of tunneling layer for getting DGRAM
>>> messages over the (local) line, the DGRAM content could simply be
>>> encapsulated in a tunnel packet or frame, basically the same way the
>>> new, boring AF_UNIX code does it. A DGRAM message encapsulated in a
>>> STREAM message always has a header which at least contains the length of
>>> the actual DGRAM message. So when the peer reads from the socket, it
>>> always only reads the header until it's complete. Then it knows how
>>> much payload is expected and then it reads until the payload has been
>>> received.
>>
>> I think I'd like to go ahead and try to do this DGRAM emulation in the
>> current (AF_LOCAL) code. It shouldn't be too hard, and it would solve the
>> unreliability problem while we look for a better way to handle AF_UNIX
>> sockets.
>
> Yeah, sounds like the way to go for now.
Unfortunately, I ran into a problem. Trying to emulate DGRAM sockets in STREAM
sockets breaks the DGRAM send/recv semantics. For example, WSARecvFrom won't
return the source address. I hope I'm just missing something, but I don't see a
way around this.
Ken
next prev parent reply other threads:[~2021-05-21 21:54 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-27 15:47 Ken Brown
2021-04-29 11:05 ` Corinna Vinschen
2021-04-29 11:16 ` Corinna Vinschen
2021-04-29 14:38 ` Ken Brown
2021-04-29 15:05 ` Corinna Vinschen
2021-04-29 15:18 ` Corinna Vinschen
2021-04-29 16:44 ` Ken Brown
2021-04-29 17:39 ` Corinna Vinschen
2021-05-01 21:41 ` Ken Brown
2021-05-03 10:30 ` Corinna Vinschen
2021-05-03 15:45 ` Corinna Vinschen
2021-05-03 16:56 ` Ken Brown
2021-05-03 18:40 ` Corinna Vinschen
2021-05-03 19:48 ` Ken Brown
2021-05-03 20:50 ` Ken Brown
2021-05-04 11:06 ` Corinna Vinschen
2021-05-13 14:30 ` Ken Brown
2021-05-17 10:26 ` Corinna Vinschen
2021-05-17 13:02 ` Ken Brown
2021-05-17 13:02 ` Ken Brown
2021-05-20 13:46 ` Ken Brown
2021-05-20 19:25 ` Corinna Vinschen
2021-05-21 21:54 ` Ken Brown [this message]
2021-05-22 15:49 ` Corinna Vinschen
2021-05-22 16:50 ` Ken Brown
2021-05-22 18:21 ` Ken Brown
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