ftplib does not honour "timeout" parameter for active data connections

[giampaolo]

BPO	4814
Nosy	@pitrou, @vstinner, @giampaolo, @bitdancer
Files	ftplib.patch: Modified patch which invokes settimeout() before accept()

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = 'https://github.com/giampaolo'
closed_at = <Date 2010-04-19.22:30:45.390>
created_at = <Date 2009-01-03.00:52:13.680>
labels = ['type-bug', 'library']
title = 'ftplib does not honour "timeout" parameter for active data connections'
updated_at = <Date 2010-04-19.22:30:45.388>
user = 'https://github.com/giampaolo'

bugs.python.org fields:

activity = <Date 2010-04-19.22:30:45.388>
actor = 'giampaolo.rodola'
assignee = 'giampaolo.rodola'
closed = True
closed_date = <Date 2010-04-19.22:30:45.390>
closer = 'giampaolo.rodola'
components = ['Library (Lib)']
creation = <Date 2009-01-03.00:52:13.680>
creator = 'giampaolo.rodola'
dependencies = []
files = ['12643']
hgrepos = []
issue_num = 4814
keywords = ['patch']
message_count = 6.0
messages = ['78912', '79390', '79392', '97061', '97095', '103650']
nosy_count = 4.0
nosy_names = ['pitrou', 'vstinner', 'giampaolo.rodola', 'r.david.murray']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue4814'
versions = ['Python 2.6', 'Python 3.1', 'Python 2.7', 'Python 3.2']

[giampaolo]

When using the optional ftplib.FTP()'s timeout parameter which
specifies a timeout in seconds for blocking operations like the
connection attempt, it is applied on both FTP control and passive data
channel (if any).
It is not applied for active (PORT/EPRT) data connections.
The patch in attachment modifies ftplib so that when ntransfer method
is called in active mode, timeout is applied on the resulting data
connection.

[vstinner]

Your patch looks correct.

[giampaolo]

I'm sorry, I realized right now that settimeout() should be used also
*before* invoking accept(), to avoid the client to stall in case the
server does not establish any connection.
The second patch in attachment does that by using settimeout() straight
into FTP.makeport() method.

[pitrou]

This looks good, of course. Perhaps you want to add a test, if it isn't
too difficult to do so.

[giampaolo]

This time it's not easy as I see no way to distinguish whether the
timeout exception gets raised by the command or the control socket, as
makeport() method implementation deals with both:

<snippet>
host = self.sock.getsockname()[0]
if self.af == socket.AF_INET:
resp = self.sendport(host, port) # socket.timeout can be
raised here
else:
resp = self.sendeprt(host, port) # ...here
if self.timeout is not _GLOBAL_DEFAULT_TIMEOUT:
sock.settimeout(self.timeout) # or here
</snippet>

I think the best we can do is add a test which checks the timeout
applied to the data socket resulting from a PASV/PORT request.
That doesn't cover this specific bug at all but it's something which is
currently missing and that it would be nice to have.

[giampaolo]

Fixed as r80226 (2.7) and r80228 (3.2).