Change the curvnet variable from a global const struct vnet *,

previously always pointing to the default vnet context, to a
dynamically changing thread-local one.  The currvnet context
should be set on entry to networking code via CURVNET_SET() macros,
and reverted to previous state via CURVNET_RESTORE().  Recursions
on curvnet are permitted, though strongly discuouraged.

This change should have no functional impact on nooptions VIMAGE
kernel builds, where CURVNET_* macros expand to whitespace.

The curthread->td_vnet (aka curvnet) variable's purpose is to be an
indicator of the vnet context in which the current network-related
operation takes place, in case we cannot deduce the current vnet
context from any other source, such as by looking at mbuf's
m->m_pkthdr.rcvif->if_vnet, sockets's so->so_vnet etc.  Moreover, so
far curvnet has turned out to be an invaluable consistency checking
aid: it helps to catch cases when sockets, ifnets or any other
vnet-aware structures may have leaked from one vnet to another.

The exact placement of the CURVNET_SET() / CURVNET_RESTORE() macros
was a result of an empirical iterative process, whith an aim to
reduce recursions on CURVNET_SET() to a minimum, while still reducing
the scope of CURVNET_SET() to networking only operations - the
alternative would be calling CURVNET_SET() on each system call entry.
In general, curvnet has to be set in three typicall cases: when
processing socket-related requests from userspace or from within the
kernel; when processing inbound traffic flowing from device drivers
to upper layers of the networking stack, and when executing
timer-driven networking functions.

This change also introduces a DDB subcommand to show the list of all
vnet instances.

Approved by:	julian (mentor)

1 files changed, 4 insertions, 3 deletions

diff --git a/sys/netinet/igmp.c b/sys/netinet/igmp.c
index 2bbd10d..3fb3711 100644
--- a/sys/netinet/igmp.c
+++ b/sys/netinet/igmp.c
@@ -1117,6 +1117,9 @@ igmp_input_v3_group_query(struct in_multi *inm, struct igmp_ifinfo *igi,
 
 	nsrc = ntohs(igmpv3->igmp_numsrc);
 
+	if (!IS_DEFAULT_VNET(curvnet))
+		return (retval);
+
 	/*
 	 * Deal with group-specific queries upfront.
 	 * If any group query is already pending, purge any recorded
@@ -3372,7 +3375,7 @@ igmp_intr(struct mbuf *m)
 	 * indexes to guard against interface detach, they are
 	 * unique to each VIMAGE and must be retrieved.
 	 */
-	CURVNET_SET(m->m_pkthdr.header);
+	CURVNET_SET((struct vnet *)(m->m_pkthdr.header));
 	INIT_VNET_NET(curvnet);
 	INIT_VNET_INET(curvnet);
 	ifindex = igmp_restore_context(m);
@@ -3654,9 +3657,7 @@ igmp_modevent(module_t mod, int type, void *unused __unused)
 	break;
     case MOD_UNLOAD:
 #ifndef VIMAGE_GLOBALS
-#ifdef NOTYET
 	vnet_mod_deregister(&vnet_igmp_modinfo);
-#endif
 #else
 	vnet_igmp_idetach(NULL);
 #endif