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, 2 insertions, 2 deletions

diff --git a/sys/net/bpf.c b/sys/net/bpf.c
index 5a28e69..d8ed7c2 100644
--- a/sys/net/bpf.c
+++ b/sys/net/bpf.c
@@ -873,11 +873,10 @@ bpfwrite(struct cdev *dev, struct uio *uio, int ioflag)
 	m->m_len -= hlen;
 	m->m_data += hlen;	/* XXX */
 
+	CURVNET_SET(ifp->if_vnet);
 #ifdef MAC
 	BPFD_LOCK(d);
-	CURVNET_SET(ifp->if_vnet);
 	mac_bpfdesc_create_mbuf(d, m);
-	CURVNET_RESTORE();
 	if (mc != NULL)
 		mac_bpfdesc_create_mbuf(d, mc);
 	BPFD_UNLOCK(d);
@@ -893,6 +892,7 @@ bpfwrite(struct cdev *dev, struct uio *uio, int ioflag)
 		else
 			m_freem(mc);
 	}
+	CURVNET_RESTORE();
 
 	return (error);
 }