[Python-Dev] Comments of the PEP 3151

[Charles-François Natali]

>> I assume that ESHUTDOWN is the errno in question?  (This is also already mentioned in the PEP.)
>
> Indeed, I mentioned it in the PEP, as it appears in asyncore.py.
> But I can't find it on www.opengroup.org, and no man page on my Linux
> system (except the "errno" man page) seems to mention it.

It's not POSIX, but it's defined on Linux and FreeBSD (at least):
http://lxr.free-electrons.com/source/include/asm-generic/errno.h#L81
http://fxr.watson.org/fxr/source/sys/errno.h?v=FREEBSD53#L122

> The description from errnomodule.c says "Cannot send after transport
> endpoint shutdown", but send() actually returns EPIPE, not ESHUTDOWN,
> when the socket has been shutdown:

Indeed, as required by POSIX.

But grepping through the Linux kernel source code, it seems to be used
extensively for USB devices, see
http://lxr.free-electrons.com/ident?i=ESHUTDOWN
So the "transport endpoint" doesn't necessarily refer to a socket.
It's also documented in
http://lxr.free-electrons.com/source/Documentation/usb/error-codes.txt

Finally, I found one place in the networking stack where ESHUTDOWN is
used, in the SCTP code:
http://lxr.free-electrons.com/source/net/sctp/outqueue.c#L329