kern/174933

[Eitan Adler]

The following reply was made to PR kern/174933; it has been noted by GNATS.

From: Eitan Adler <lists at eitanadler.com>
To: bug-followup <bug-followup at freebsd.org>
Cc:  
Subject: Re: kern/174933
Date: Fri, 4 Jan 2013 13:04:31 -0500

 ---------- Forwarded message ----------
 From: Martin Laabs <info at martinlaabs.de>
 Date: 4 January 2013 12:40
 Subject: Bug analyzed - how to fix it?
 To: freebsd-emulation at freebsd.org
 
 
 Hi,
 
 I'm (hopefully) done with the bug analyses of
 "http://www.freebsd.org/cgi/query-pr.cgi?pr=174933".
 The bug in one sentences: if_nameindex (resided in the libc) fails if
 called out of a linux binary.
 
 The cause is that the if_nameindex calls a function named __opensock that
 return a socket. This socket is used to call an ioctl(SIOCGIFCONF ...).
 This ioctl call is actually implemented in the linuxulator. Unfortunately
 the __opensock function tries to create the following socket:
 
 socket(PF_NETLINK, SOCK_RAW, 0)
 in decimal: socket(16,3,0)
 
 This type of socket type however is not supported by the linuxulator and
 IMHO in freebsd at all. However - maybe it just has another name in FreeBSD.
 
 So - for me there seem to be two solutions:
 
 1. Write a dirty patch that returns a PF_INET instead of the PF_NETLINK
 socket if called with the arguments above. This should be OK since I assume
 that SIOCGIFCONF ioctl works also fine with PF_INET sockets. (I'll test
 this to verify whether this is true)
 This however would be somewhat dirty since PF_NETLINK sockets are not
 really supported and if another application tries to open a real PF_NETLINK
 socket it will get a false positive result.
 
 2. Patch the glibc to not create a PF_NETLINK socket in __opensock but
 create a PF_INET socket instead. The problem is that I do not know about
 the side effects since the __opensock function is used elsewhere in the
 libc also. The second drawback is that this would lead to a customized libc
 for the linuxulator. As far as I know the current libc(s) are just bare
 copies out of linux systems. So this solution would also increase
 maintenance effort.
 
 Do you have an other idea how to fix the problem?
 
 Thank you,
  Martin
 
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 -- 
 Eitan Adler