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, 9 insertions, 1 deletions

diff --git a/sys/netinet6/nd6.c b/sys/netinet6/nd6.c
index e387a7f..a74ee7d 100644
--- a/sys/netinet6/nd6.c
+++ b/sys/netinet6/nd6.c
@@ -489,6 +489,14 @@ nd6_llinfo_timer(void *arg)
 	if ((ifp = ((ln->lle_tbl != NULL) ? ln->lle_tbl->llt_ifp : NULL)) == NULL)
 		panic("ln ifp == NULL");
 
+/*
+ * XXX XXX XXX XXX XXX
+ *
+ * Why the ^%(@)*&%^) is this #define MIN() needed for CURVNET_SET()?!?
+ * And #define MIN() is in sys/param.h already, which is #included first
+ * here?!?
+ */
+#define       MIN(a,b) (((a)<(b))?(a):(b))
 	CURVNET_SET(ifp->if_vnet);
 	INIT_VNET_INET6(curvnet);
 
@@ -592,7 +600,7 @@ done:
 void
 nd6_timer(void *arg)
 {
-	CURVNET_SET_QUIET((struct vnet *) arg);
+	CURVNET_SET((struct vnet *) arg);
 	INIT_VNET_INET6(curvnet);
 	int s;
 	struct nd_defrouter *dr;