linux-kernel - Re: Error in SEND(2) man page ?

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Message-ID: <4B1DC2B6.5080004@gmail.com>
Date:	Mon, 07 Dec 2009 21:06:30 -0600
From:	Robert Hancock <hancockrwd@...il.com>
To:	"Jacques, Hugo" <Hugo.Jacques@...int.com>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: Error in SEND(2) man page ?

On 12/07/2009 12:43 PM, Jacques, Hugo wrote:
>
> Hi,
>
> I think I found a discrepancy between the man page of send()and the actual implementation.
>
> Man page mentions that:
>
> "[...] When the message does not fit into the send buffer of the socket, send() normally blocks, unless the socket has been placed in non-blocking I/O mode. In non-blocking mode it would fail with the error EAGAIN or EWOULDBLOCK in this case.  [...]"
>
> This tells me that if doing a send() on a tcp non-blocking socket whose send buffer is full, the call should return with -1 and errno=EAGAIN.
>
> But running a trivial test app (code below), send() will indicate (return value) that is sent some but not all of the data buffer when the socket's send buffer is full.
>
> Am I missing anything?
> Is the man page or the code wrong?

I think the man page would be right for a datagram (ex: UDP) socket, but 
not for a stream (ex: TCP) socket, as a stream socket has no real 
concept of "messages".
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