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, 3 insertions, 0 deletions

diff --git a/sys/net/if_var.h b/sys/net/if_var.h
index e6a6a26..18084aa 100644
--- a/sys/net/if_var.h
+++ b/sys/net/if_var.h
@@ -731,7 +731,9 @@ struct ifindex_entry {
  * to call ifnet_byindex() instead if ifnet_byindex_ref().
  */
 struct ifnet	*ifnet_byindex(u_short idx);
+struct ifnet	*ifnet_byindex_locked(u_short idx);
 struct ifnet	*ifnet_byindex_ref(u_short idx);
+void ifnet_setbyindex(u_short idx, struct ifnet *ifp);
 
 /*
  * Given the index, ifaddr_byindex() returns the one and only
@@ -755,6 +757,7 @@ int	if_allmulti(struct ifnet *, int);
 struct	ifnet* if_alloc(u_char);
 void	if_attach(struct ifnet *);
 void	if_dead(struct ifnet *);
+void	if_grow(void);
 int	if_delmulti(struct ifnet *, struct sockaddr *);
 void	if_delmulti_ifma(struct ifmultiaddr *);
 void	if_detach(struct ifnet *);