SIOCGIFCONF under Linux on Itanium in 32 bit compatibility mode

[Shaun <delius () progsoc uts edu au>]

Hi All,

When running 32 bit code on the Itanium under Linux the kernel goes to
some effort to try to mask the fact that the kernel is 32 bit and provide
binary compatibility. Unfortunately, the compatibility layer frequently
fails to adequately hide all of the details and one of these problems
effects libpcap.

In this case, the sys32_ioctl routine handles the SIOCGIFCONF ioctl and
handles converting the input 32 bit ifconf struct into a 64 bit one then
converts each of the 64 bit ifreq structures that are returned from the
real ioctl handler back into 32 bit versions. Unfortunately it doesn't
properly convert the ifc_len from the sum of the 64 bit ifreqs to the sum
of the 32 bit reqs. Thus the ifc_len is incorrectly larger than expected.

This bites libpcap because when it attempts to read off the end of the
real end of the interfaces it finds an interface with an empty name and
fails to retrieve the flags for the interface, terminating the interface
finding procedure. The fix I commited to our internal licpcap is to
'break' out of the loop if we find an interface with a null name, does
anyone object to this approach for the mainline? If not I'll send over a
patch.

Cheers,
Shaun
-
This is the TCPDUMP workers list. It is archived at
http://www.tcpdump.org/lists/workers/index.html
To unsubscribe use mailto:tcpdump-workers-request () tcpdump org?body=unsubscribe