channel: prevent infinite loop sending to closed channel

[jaysoffian]

Both sendall and sendall_stderr call send inside a loop and use its result to advance their buffer. If the channel is closed, send returns 0 which causes both sendall methods to go into an infinite loop. Prevent this from occurring by using the open_only decorator.

I'm not sure this is the best fix since I haven't verified whether the channel can be closed after the sending begins. If so, then both sendall routines should instead raise an exception if send returns 0.

[ploxiln]

I'm unsure of this particular solution, because:

• @open_only checks for both eof_sent and eof_received. stdin and stdout are independent. These send methods should probably only check eof_sent?
• These methods call send() which calls _send(), which raises an exception if the socket is closed (another thing @open_only checks). But it does seem that _send() can just return 0 if eof_sent, maybe just that should be checked.
• Maybe the check should be inside the while loop in these send_all methods, instead of on the outside, in case the EOF occurs after starting the method?

[jaysoffian]

I'm unsure of this particular solution, because:

These are all good questions, but I was stuck with an infinite loop and this seemed like a minimally invasive fix at the time. I'll work on a more targeted fix that just avoids the infinite loop and hopefully has no other side-effects.