Created attachment 314189 [details]
Patch to increase the lengths of the index in sscanf

Description of problem:

With a large number of interfaces (like in a Xen environments with multiple xen bridges), the index of the interfaces can be greater than 255. In such a case, net-snmp will fails to parse /proc/net/if_inet6 if one of the index is greater than 0xFF and will generate errors.

Version-Release number of selected component (if applicable):

net-snmp-5.3.1-24.el5_2.1

How reproducible:

100% reproducible

Steps to Reproduce:

1.Set-up an system with a lot of network interfaces
2.Check if one of the interfaces in proc/net/if_inet6 has an index greater than 0xFF
3.Install and configure net-snmp
  
Actual results:

snmpd[13835]: ioctl 35123 returned -1 
last message repeated <many> times
...

Expected results:

No error message

Additional info:

The parsing is done in _load_v6() (in agent/mibgroup/ip-mib/data_access/ipaddress_linux.c) with:

        /*
         * fe800000000000000200e8fffe5b5c93 05 40 20 80 eth0
         *             A                    D  P  S  F  I
         * A: address
         * D: device number
         * P: prefix len
         * S: scope (see include/net/ipv6.h, net/ipv6/addrconf.c)
         * F: flags (see include/linux/rtnetlink.h, net/ipv6/addrconf.c)
         * I: interface
         */
        rc = sscanf(line, "%39s %02x %02x %02x %02x %8s\n",
                    addr, &if_index, &pfx_len, &scope, &flags, if_name);

So if the index is greater than 0xFF, scanf %02x will not read the entire index and break the pasing of the remaining items.