Implement reference counting for ifmultiaddr, in_multi, and in6_multi

structures. Detect when ifnet instances are detached from the network
stack and perform appropriate cleanup to prevent memory leaks.

This has been implemented in such a way as to be backwards ABI compatible.
Kernel consumers are changed to use if_delmulti_ifma(); in_delmulti()
is unable to detect interface removal by design, as it performs searches
on structures which are removed with the interface.

With this architectural change, the panics FreeBSD users have experienced
with carp and pfsync should be resolved.

Obtained from:	p4 branch bms_netdev
Reviewed by:	andre
Sponsored by:	Garance A Drosehn
Idea from:	NetBSD
MFC after:	1 month

1 files changed, 2 insertions, 2 deletions

diff --git a/sys/net/if_var.h b/sys/net/if_var.h
index 574bb72..032bcca 100644
--- a/sys/net/if_var.h
+++ b/sys/net/if_var.h
@@ -600,8 +600,6 @@ struct ifprefix {
 /*
  * Multicast address structure.  This is analogous to the ifaddr
  * structure except that it keeps track of multicast addresses.
- * Also, the reference count here is a count of requests for this
- * address, not a count of pointers to this structure.
  */
 struct ifmultiaddr {
 	TAILQ_ENTRY(ifmultiaddr) ifma_link; /* queue macro glue */
@@ -610,6 +608,7 @@ struct ifmultiaddr {
 	struct	ifnet *ifma_ifp;	/* back-pointer to interface */
 	u_int	ifma_refcount;		/* reference count */
 	void	*ifma_protospec;	/* protocol-specific state, if any */
+	struct	ifmultiaddr *ifma_llifma; /* pointer to ifma for ifma_lladdr */
 };
 
 #ifdef _KERNEL
@@ -667,6 +666,7 @@ int	if_allmulti(struct ifnet *, int);
 struct	ifnet* if_alloc(u_char);
 void	if_attach(struct ifnet *);
 int	if_delmulti(struct ifnet *, struct sockaddr *);
+void	if_delmulti_ifma(struct ifmultiaddr *);
 void	if_detach(struct ifnet *);
 void	if_purgeaddrs(struct ifnet *);
 void	if_down(struct ifnet *);