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, 8 insertions, 2 deletions

diff --git a/sys/kern/sys_socket.c b/sys/kern/sys_socket.c
index 813b1dd..61b0361 100644
--- a/sys/kern/sys_socket.c
+++ b/sys/kern/sys_socket.c
@@ -50,6 +50,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/stat.h>
 #include <sys/uio.h>
 #include <sys/ucred.h>
+#include <sys/vimage.h>
 
 #include <net/if.h>
 #include <net/route.h>
@@ -74,16 +75,19 @@ soo_read(struct file *fp, struct uio *uio, struct ucred *active_cred,
     int flags, struct thread *td)
 {
 	struct socket *so = fp->f_data;
-#ifdef MAC
 	int error;
 
+#ifdef MAC
 	SOCK_LOCK(so);
 	error = mac_socket_check_receive(active_cred, so);
 	SOCK_UNLOCK(so);
 	if (error)
 		return (error);
 #endif
-	return (soreceive(so, 0, uio, 0, 0, 0));
+	CURVNET_SET(so->so_vnet);
+	error = soreceive(so, 0, uio, 0, 0, 0);
+	CURVNET_RESTORE();
+	return (error);
 }
 
 /* ARGSUSED */
@@ -125,6 +129,7 @@ soo_ioctl(struct file *fp, u_long cmd, void *data, struct ucred *active_cred,
 	struct socket *so = fp->f_data;
 	int error = 0;
 
+	CURVNET_SET(so->so_vnet);
 	switch (cmd) {
 	case FIONBIO:
 		SOCK_LOCK(so);
@@ -205,6 +210,7 @@ soo_ioctl(struct file *fp, u_long cmd, void *data, struct ucred *active_cred,
 			    (so, cmd, data, 0, td));
 		break;
 	}
+	CURVNET_RESTORE();
 	return (error);
 }