From owner-freebsd-net  Fri Oct 22 11: 3:59 1999
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From: Archie Cobbs <archie@whistle.com>
Message-Id: <199910221803.LAA67886@bubba.whistle.com>
Subject: Re: SIOCGIFCONF (or qmail?) problem?
In-Reply-To: <19991021193216.D86089@over.ru> from Alex Povolotsky at "Oct 21, 1999 07:32:16 pm"
To: tarkhil@over.ru (Alex Povolotsky)
Date: Fri, 22 Oct 1999 11:03:42 -0700 (PDT)
Cc: freebsd-stable@FreeBSD.ORG, freebsd-net@FreeBSD.ORG
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Alex Povolotsky writes:
> I've just found, that bringing up ppp0 on a computer with one more network
> interface causes qmail-1.03 to crash.
> 
> Investigating further, I've found that one of qmail's internal variables
> gets overwriten when calling ioctl SIOCGIFCONF with pointer to ifconf
> structure as argument (ipme.c, line 57 in qmail).
> 
> I still have not found if qmail gives wrong address to ioctl or if ioctl use
> more memory than requested. The fail seems to occur after iterating through
> ds0 interface.
> 
> By the way, what is ds0, how it should be configured, and where is it
> described? What does it do?
> 
> Does anyone else runs FreeBSD 3.3-RELEASE with qmail and dial-in access? 

This may or may not be the problem, but there is a common bug in
programs that use SIOCGIFCONF. The proper way to compute the byte
increment to the next entry is:

     ifp = (struct ifreq *) ((char *) &ifp->ifr_addr
      + MAX(ifp->ifr_addr.sa_len, sizeof(ifp->ifr_addr))))

The WRONG way to do it is:

     ifp = (struct ifreq *)
      ((char *) &ifp->ifr_addr + ifp->ifr_addr.sa_len))

This bug usually only gets triggered when there are discard,
tunnel, etc. interfaces which have no link information.

You might plow through the qmail sources and check.

-Archie

___________________________________________________________________________
Archie Cobbs   *   Whistle Communications, Inc.  *   http://www.whistle.com


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