Bug analyzed - how to fix it?

Martin Laabs info at martinlaabs.de
Fri Jan 4 17:40:24 UTC 2013


I'm (hopefully) done with the bug analyses of
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:

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,

More information about the freebsd-emulation mailing list