general/5852

[Jos van der Meer <jm...@aidministrator.nl>]

The following reply was made to PR mod_jserv/5852; it has been noted by GNATS.

From: Jos van der Meer <jm...@aidministrator.nl>
To: apbugs@apache.org
Cc: hhor@aidministrator.nl
Subject: general/5852
Date: Tue, 14 Mar 2000 13:56:14 +0100 (MET)

 Problem 5852 is a bug in the core part of Apache (http_protocol.c).
 The problem occurs in Solaris 2.7 and might be Solaris specific.
 The problem occurs in Apache 1.3.11 and 1.3.12. Apache 1.3.6 did
 not have the bug.
 
 Cause of the Bug: In Solaris 2.7 read() on a pipe may may return 0 even
 if there is more input to read. This is conform Solaris' "read(2)" manual page:
 
 >
 > When attempting to read from an empty pipe (or FIFO):
 >
 >  o If some process has the  pipe  open  for  writing  and
 >    O_NDELAY is set, read() returns 0.
 >
 
 As a result, Apache will partially read input -- especially when it is large.
 
 The fix is to apply the "UTS 2.1.2"-work-around in http_protocol.c
 for Solaris too. The simplest way to achieve this is to add
 NDELAY_PIPE_RETURNS_ZERO in ap_config.h for Solaris. For Apache 1.3.11 src:
 
 $ diff ap_config.h ap_config.h.ORIG
 172d171
 < #define NDELAY_PIPE_RETURNS_ZERO
 
 The work-around has been tested at AIdministrator. The problem
 was reproducable before the work-around, and not-reproducable afterwards.
 I.e. the work-around fixes the bug.
 
 It seems to us that the NDELAY_PIPE_RETURNS_ZERO-behaviour would not
 cause a serious overhead in any platform: for conservative programming,
 it might be considered to integrate the NDELAY_PIPE_RETURNS_ZERO-behaviour
 in the generic Apache code.
 
 
 
 Jos van der Meer
 AIdministrator Nederland B.V.
 Julianaplein 14B, 3817 CS Amersfoort, Tel: +31-33-4659987
 mailto:Jos.van.der.Meer@AIdministrator.nl