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A first analysis should be sent before: Wed Apr 09 11:00:01 PDT 1997
>Number: 335
>Category: os-irix
>Synopsis: cgi-bin script not receiving SIGPIPE during output if client
>hits STOP
>Confidential: no
>Severity: critical
>Priority: medium
>Responsible: apache (Apache HTTP Project)
>State: open
>Class: sw-bug
>Submitter-Id: apache
>Arrival-Date: Tue Apr 8 23:50:01 1997
>Originator: [EMAIL PROTECTED]
>Organization:
apache
>Release: Apache/1.2b7
>Environment:
[EMAIL PROTECTED] RLOGIN 4 : uname -a
IRIX puck 6.3 09192338 IP32
[EMAIL PROTECTED] RLOGIN 6 : versions | grep C.Compiler.Version
I c_dev.sw.v6_c 03/05/97 C Compiler Version 6
>Description:
A cgi-bin script (See below) should receive a SIGPIPE after the user hits
STOP the moment it outputs text to the closed socket.
This doesn't seem to happen w/apache; the process remains running,
the socket stuck in CLOSE_WAIT.
It should also be updating one line per second to the browser, since
there's a flush after each print.. at my installation, I just get a
blank screen.. I don't see any of the 'Testing' messages.
#!/usr/local/bin/perl
$| = 1; # flush after every print
print "Content-type: text/html\n\n<PRE>";
while (1)
{
printf("This is a test %d\n", time);
sleep(1);
}
Usually when a cgi-bin script writes to a closed socket, it receives
a SIGPIPE. This is necessary if the script prints a steady stream of data
to the client.
When the client hits the STOP button, this closes the TCP connection,
and the cgi-bin script gets a SIGPIPE the moment it does the write(2).
This doesn't seem to happen w/apache 1.2b7.
The above does seem to work correctly in NCSA 1.5.2, both printing
one line per second, and killing the process when the user hits Stop.
>How-To-Repeat:
Put the following in your cgi-bin, and invoke it from the browser.
#!/usr/local/bin/perl
require "flush.pl";
print "Content-type: text/html\n\n<PRE>";
while (1)
{
printf("This is a test %d\n", time);
flush(STDOUT);
sleep(1);
}
I would expect to see lines of text appearing in the browser one line per
second. When I hit Stop, the process on the server should die within a
second as the result of a SIGPIPE.
What I see:
No text is printed one line per second; just the netscape star
animation running. Eventually, the netscape browser pops up a
dialog saying 'Document contains no data'.
When I hit Stop, the process is still running, and appears to
continue running even after several minutes. netstat shows the
connection in CLOSE_WAIT.
The above does seem to work correctly in NCSA 1.5.2 running on the same
platform, with the same cgi-bin script.. it prints one line per second,
and kills the process when the user hits Stop.
>Fix:
Make sure SIGPIPE is not being blocked after the fork(), or have the daemon
manually send a kill signal to the child with SIGPIPE the moment it detects
the TCP connection closes down.
Also, make sure that when the cgi-bin program does a flush, the data is forced
through to the client browser, so that realtime data can be displayed
>Audit-Trail:
>Unformatted:
