Subject: Re: CVS commit: syssrc
To: None <firstname.lastname@example.org>
From: enami tsugutomo <email@example.com>
Date: 10/08/2000 16:24:19
> >Log Message:
> >- Keep track of allhost multicast address record we joined into
> > each in_ifaddr and delete it when an address is purged.
> maybe the above commit changed the goal slightly.
> the goal of multicast kludge table (which i ported from
> sys/netinet6/in6.c) was to keep multicast group information ONLY,
> when all the interface address is gone. it was not my intention
> to avoid the removal of the last IPv4 interface address.
> could you tell me why is the change?
Hmm, I guess you're misunderstanding my change or the comment I wrote
was miss the point. I didn't change ``to avoid the removal of the
last IPv4 interface address.''
The change this comment refer is:
- Add ia_allhost to in_ifaddr.
- Remember the value in_addmulti returns in it. Note that
same in_multi may be shared.
- Call in_delmulti for it when address is deleted.
I just used the last in_ifaddr for the chain head of in_multi. And we
have to keep track of the value retrun by in_addmulti for the reason I
> >- Don't simply try to delete a multicast address record listed in the
> > ia_multiaddrs. It results a dangling pointer. Let who holds a
> > reference to it to delete it.
> this refers to in_purgemkludge(), correct? i experimented this
> with IPv6 case and IPv4 case, and don't understand why we have
> dangling pointer. i assumed that in_purgemkludge() is called
> only after we flushed all interface addresses.
It refers the both loops in the patch like this:
for (inm = LIST_FIRST(&ia->ia_multiaddrs); ....)
As I wrote in the other mail, since the struct in_multi is reference
counted, this is insufficient. Of course, the reference in
ia_multiadrs isn't counted, since the counter is for the caller who
called in_addmulti(). It is refered from a socket and now from a
in_ifaddr. The in_multi refered from a socket is used when the socket
is closed. So, we have to remove the reference when interface is
gone. Without it, we gets panic after a program who uses multicast
close a socket. And, it is done in in_pcbpurgeif().
For example, in_purgeif() and in_pcbpurgeif() are called with
So, for the in_multi refered from socket, calling in_delmulti() for it
while in in_purgeif() is wrong. And it should be unnecessary if all
references are kept. To keep all reference, I've add ia_allhosts to
There was also a bug that if an interface is removed while in_multi
was kept in kludge table, in_delmulti() will dereference the null