site_archiver@lists.apple.com Delivered-To: darwin-kernel@lists.apple.com Maximum Segment Size. -R Le 1 févr. 2010 à 22:49, Godfrey van der Linden a écrit :
On 2010-02-02, at 4:32 PM, Michael Smith wrote:
On Feb 1, 2010, at 6:40 PM, Godfrey van der Linden wrote:
I'm trying something a bit different for performance testing and have tripped over a problem that I just haven't been able to solve. Maybe you netheads out there can enlighten me.
I have a pair of threads each of which have independent AF_UNIX, SOCK_DGRAM sockets.
The client knows the servers AF_UNIX address and connect()s the client socket to the server before sending the first message.
The server on recvfrom()ing the first message then connect()s the server's socket to the received client's address. Then falls into a simple mirror loop, that is send a reply, block in recv().
After a few messages the client, closes its socket.
Q> Shouldn't the server's blocked recv() call be aborted with an ECONNRESET error, when the client's socket is closed?
No. ECONNRESET is the tunnel for the TCP RST behaviour. There is no analog for datagram sockets.
Yeah, I came to that realisation, I saw the error returned once during my testing and it never turned up again after moving the code around a bit.
Pity, what I'd really love is if we had an implementation of SOCK_SEQPACKET, in the UNIX and INETx protocol families.
I know that this is an unusual usage of DGRAM sockets, but I eventually need some sort of control on the packet size when it goes through my instrumented network driver.
Why not just advertise an appropriate MSS and let the network stack handle the rest for you?
Sounds interesting, I'm not really a network programmer so all of my knowledge is just what you can glean from Stevens. What is MSS?
My research problem:
I wish to build an energy consumption model of a heavily instrumented IOEthernetController subclass.
To determine the per-byte and per-packet energy cost of sending and receiving packets, I'll need to finely control the frame sizes as they go on the bus to calibration the energy model. I don't think there is any sensible way of controlling the TCP/IP frame on a per packet basis, hence the UDP/IP decision. I'd really, really love a connection oriented per packet socket but there doesn't seem to be such an option.
= Mike
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