itojun@itojun.org said:
> 	Linux IPv6 implementation is ancient and uses RFC2133 API, which
> lacks sin6_scope_id.

Hmm - the sin6_scope_id member is present in unpatched 2.4 kernels, it was
missing in 2.2. This doesn't mean of course that it is actually supported,
but software just referencing it should compile, and the resulting code
shound't work worse than before, right?
The ntp4.2 release notes state:
> If the Basic Socket Interface Extensions for IPv6 (RFC-2553) is detected,
> support for the IPv6 address family is generated
and since scope_id is part of rfc2553, ntp should not try to compile in
IPv6 support if scope_id is not present.
As you see, I'm trying to avoid to introduce unnecessary #ifdefs...
Do you think this argument is good enough, so I can suggest my present
patches to the ntp people?

> 	how does it get the list of interface addresses?  getifaddrs?
> 	SIOCGIFCONF?

It has code for both sysctl(NET_RT_IFLIST) and ioctl(SIOCGIFCONF),
sysctl is preferred.

> anyways, we need to translate KAME-mangled address into
> 	normal one (with sin6_scope_id filled) on getifaddrs/SIOCGIFCONF.

Well, you have seen my patches...

> 	yes, we could change SIOCGIFCONF to do the dirty work in the kernel,
> 	however, (1) we would have INET6-specific code in sys/net/route.c
> 	and/or rtsock.c which is ugly

agreed, such stuff should be in protocol specific functions, but having
it in many userland applications is not much better...
A clean userland interface would be good to have.

> i'm not sure if such API change
> 	will be safe after long-time deployment of the mangled API

I see that there is no short-term solution, but a viable plan could be to
introduce a macro for address exporting, something like

#define __KAME_EXPORT_IP6_ADDRESS(a) do {\
	if (IN6_IS_ADDR_{,MC_}LINKLOCAL(a) &&\
	    (a->sin6_addr[{2,3}] != 0)) {\
		a->sin6_scope_id = ...;\
		a->sin6_addr[{2,3}] = 0;\
	}\
} while(0);

and get it into all affected code.
Then the kernel could be changed later and the code would still work.

Just an idea...

best regards
Matthias