Review for fix to Bug 7078386

[Brandon Passanisi]

Hello net-dev.  I was wondering if somebody could review the proposed 
fix for the following bug:

    Bug URL: http://monaco.sfbay.sun.com/detail.jsf?cr=7078386
    Webrev : http://cr.openjdk.java.net/~michaelm/7078386/webrev.1/


The bug is caused by an incorrect format string used in the fscanf call 
within enumIPv6Interfaces of 
jdk/src/solaris/native/java/net/NetworkInterface.c, which specifies a 
two-digit hex number for the network interface index value.  It has been 
shown that network interface index values can be more than 255, thus 
requiring the need to obtain more than two digits.  I eventually 
searched through the following linux kernel source file:

    linux-source-2.6.32/net/ipv6/addrconf.c

... and it appears the interface index value is being written and an 
integer within the function inet6_fill_ifinfo in the following block of 
code starting on line 3785:

         if (dev->ifindex != dev->iflink)
             NLA_PUT_U32(skb, IFLA_LINK, dev->iflink);

iflink is defined in linux-source-2.6.32/include/linux/netdevice.h as an 
int on line 742:

         /* Interface index. Unique device identifier    */
         int            ifindex;
         int            iflink;

Because of this and because an integer is 32 bits, it appears that 
updating the format string to use %08x for the interface index value 
seems most correct.

I have tested out this fix successfully in the following ways:

    1. I ran the IBM-supplied test programs tapadd and Scope to create
    over 255 address in order to test an interface index value of at
    least three digits.  (These programs will be added to the bug report
    if not present at this time.)  The tapadd program is a C test
    requiring root access that uses tun/tap to create over 255
    interfaces.  Scope is a java program that does a
    NetworkInterface.getByName() on a known interface with an index over
    255.

    2. I modified the Scope program to additionally test all created
    interfaces, not just one interface with an index value over 255. 
    (The original Scope test program just checks a single interface.) 
    This is important to show there aren't regressions.

    3. I created another test program using a script to run 'ip'
    commands to create over 255 interfaces.  This script runs in a loop
    using the commands "sudo ip tunnel add..." and "sudo ip -6 addr
    add..." to add the interfaces.  Then, I used the Scope program to
    verify the created interfaces.

I wasn't able to create a script that would create a really huge amount 
of interfaces because using numbers like 65536 or higher in my script 
caused my Ubuntu linux to hang.  So, I'm not quite sure how to truly 
test large interface index values like 65536 or more.

Thanks.
-- 
Oracle <http://www.oracle.com>
Brandon Passanisi | Principle Member of Technical Staff

Green Oracle <http://www.oracle.com/commitment> Oracle is committed to 
developing practices and products that help protect the environment
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