[PATCH] Re: ioctl: SIOCADDMULTI (howto?)

[Bruce M. Simpson]

Jouke Witteveen wrote:
>
> So my apologies for suggesting it doesn't work at all; it seems that
> the application I'm trying to get to work (wpa_supplicant for wired
> interfaces) just doesn't _send_ its packets the right way.
That's a big relief! I added an item to the Wiki for someone to write a 
regression test.
>
> Things aren't perfect though. In if.c the if_findmulti function is
> broken (always returns NULL). I presume just comparing the
> *LLADDR((sockaddr *)sa) data on both sockets is a better check, though
> my knowledge on these things is limited.
I think I see a possible problem, though the code looks as though it is 
behaving as expected.
I am looking at RELENG_6 if.c. I think sa_equal() may be to blame.

sa_equal() performs a binary comparison on all of sa_data up to sa_len. 
Looking at struct sockaddr_dl, this might not be the right thing at all 
in that situation... though I need another pair of eyes to look. Can 
anyone shed light on this? An AF_INET and AF_INET6 address can be 
completely specified and compared with sa_equal(). An AF_LINK address 
looks as though sa_equal() may return irrational results.
>
> As for netstat, I do not really know what is keeping it from showing
> the Multicast addresses. Again: my knowledge on this matter is
> limited. All I can think of is that getifmaddrs is forgetting
> something (perhaps the lack of a group membership). Maybe you can take
> a look at it (I believe you wrote it).

I wrote the libc getifmaddrs() function and integrated it into netstat 
-g; Harti Brandt wrote the NET_RT_IFMALIST support. getifmaddrs() 
*should* return sockaddr_dl as well as sockaddr_in and all the others.

netstat skips over AF_LINK addresses. Try this patch to reveal them. It 
doesn't seem to show the IPv4 link layer memberships underneath, which 
is interesting...
>
> As I am still learning how best to contribute to a project as big as
> FreeBSD and I do not think I am skilled enough yet in C I refrain from
> writing a patch. I am eager to see one though, be it only out of
> curiosity to know what would be considered a proper fix.
Give it a try anyway!  I like to think we have strong healthy egos round 
here.

Regards,
BMS

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