kern/111515: [patch] in6_setscope() sets scope flags wrong

Thomas Karcher thkarcher at
Thu Apr 12 15:10:08 UTC 2007

>Number:         111515
>Category:       kern
>Synopsis:       [patch] in6_setscope() sets scope flags wrong
>Confidential:   no
>Severity:       serious
>Priority:       low
>Responsible:    freebsd-bugs
>State:          open
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Thu Apr 12 15:10:07 GMT 2007
>Originator:     Thomas Karcher
>Release:        RELENG_6_2_0_RELEASE
In netinet6/scope6.c is a function called "in6_setscope()" which sets the appropriate scope flag for an IPv6 (in my case multicast) address.

I think line 475 is not correct, it looks like this:

474         if (IN6_IS_SCOPE_LINKLOCAL(in6) || IN6_IS_ADDR_MC_INTFACELOCAL(in6))
475                 in6->s6_addr16[1] = htons(zoneid & 0xffff);

The scope is usually just 8 bits after the 1111 1111 (FF) start of a multicast address. E. g. if I want to sent a multicast over a local link, the address should start with FF02 - the 2 is for link-local scope.

Unfortunately, the code above sets 16 bits in the second 16-bit-part of the address, so it starts with FF00:0002 which is simply wrong.

I didn't check other parts of the file for the same error.


To my extent, it should be as follows:

474         if (IN6_IS_SCOPE_LINKLOCAL(in6) || IN6_IS_ADDR_MC_INTFACELOCAL(in6))
475                 in6->s6_addr8[1] = htons(zoneid & 0xff);


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