Bugs item #1755388, was opened at 2007-07-17 07:07
Message generated for change (Comment added) made by gagenellina
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Category: Extension Modules
Group: Python 2.5
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: STINNER Victor (haypo)
Assigned to: Nobody/Anonymous (nobody)
Summary: Problem with socket.gethostbyaddr() and KeyboardInterrupt
Initial Comment:
Hi,
I wrote a small function to translate an IP to a hostname (eg. 212.27.33.225 =>
"linuxfr.org").
---------------------------------------------
from socket import gethostbyaddr, herror as socket_host_error
def ip2name(addr):
try:
if addr in ip2name.cache:
return ip2name.cache[addr]
name = gethostbyaddr(addr)[0]
except (socket_host_error, KeyboardInterrupt, ValueError):
name = addr
ip2name.cache[addr] = name
return name
ip2name.cache = {}
---------------------------------------------
Problem: sometimes gethostbyaddr() takes 5 seconds to answer "unknown host" so
I hit CTRL+c to interrupt hit. But the "try/except" block doesn't catch the
interruption. I found a workaround: use double try/except (try: gethostbyaddr()
except KeyboardInterrupt: raise).
Last version of my function
---------------------------------------------
def ip2name(addr):
if not ip2name.resolve:
return addr
try:
if addr in ip2name.cache:
return ip2name.cache[addr]
# FIXME: Workaround Python bug
# Need double try/except to catch the bug
try:
name = gethostbyaddr(addr)[0]
except KeyboardInterrupt:
raise
except (socket_host_error, ValueError):
name = addr
except (socket_host_error, KeyboardInterrupt, ValueError):
ip2name.resolve = False
name = addr
ip2name.cache[addr] = name
return name
ip2name.cache = {}
ip2name.resolve = True
---------------------------------------------
I'm using Python 2.5.1 on Ubuntu Feisty (Linux kernel 2.6.20).
To reproduce my error, try "10.0.0.1" or "192.168.0.1" (or any other IP).
----------------------------------------------------------------------
Comment By: Gabriel Genellina (gagenellina)
Date: 2007-07-19 18:37
Message:
Logged In: YES
user_id=479790
Originator: NO
I can reproduce the bug on Windows XP SP2, a simpler program is attached.
First run, I did not press Ctrl-C:
c:\temp>python bug1.py
enter test, gethostbyname('e.p.l.w.d.com')
Yo can press Ctrl-C
inner try
<type 'type'> <class 'socket.gaierror'> False
outer try
<type 'type'> <class 'socket.gaierror'> False
exit test
The inner try/except catches the exception as expected.
Second run, I *did* press Ctrl-C:
c:\temp>python bug1.py
enter test, gethostbyname('s.g.s.w.s.com')
Yo can press Ctrl-C
outer try
<type 'type'> <type 'exceptions.KeyboardInterrupt'> True
exit test
The inner try/except didn't catch the exception, and it propagates to the
outer one. I don't understand why; even if the gethostbyname call is
blocking, and Ctrl-C is not detected until it returns, there IS an
exception raised (either KeyboardInterrupt or socket.gaierror) in the inner
block that should be handled by the inner except clause.
----------------------------------------------------------------------
You can respond by visiting:
https://sourceforge.net/tracker/?func=detail&atid=105470&aid=1755388&group_id=5470
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