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, 0 deletions

diff --git a/sys/kern/kern_linker.c b/sys/kern/kern_linker.c
index 9350713..2237107 100644
--- a/sys/kern/kern_linker.c
+++ b/sys/kern/kern_linker.c
@@ -993,6 +993,12 @@ kern_kldload(struct thread *td, const char *file, int *fileid)
 		return (error);
 
 	/*
+	 * It's possible that kldloaded module will attach a new ifnet,
+	 * so vnet context must be set when this ocurs.
+	 */
+	CURVNET_SET(TD_TO_VNET(td));
+
+	/*
 	 * If file does not contain a qualified name or any dot in it
 	 * (kldname.ko, or kldname.ver.ko) treat it as an interface
 	 * name.
@@ -1019,6 +1025,7 @@ kern_kldload(struct thread *td, const char *file, int *fileid)
 		*fileid = lf->id;
 unlock:
 	KLD_UNLOCK();
+	CURVNET_RESTORE();
 	return (error);
 }
 
@@ -1056,6 +1063,7 @@ kern_kldunload(struct thread *td, int fileid, int flags)
 	if ((error = priv_check(td, PRIV_KLD_UNLOAD)) != 0)
 		return (error);
 
+	CURVNET_SET(TD_TO_VNET(td));
 	KLD_LOCK();
 	lf = linker_find_file_by_id(fileid);
 	if (lf) {
@@ -1092,6 +1100,7 @@ kern_kldunload(struct thread *td, int fileid, int flags)
 		PMC_CALL_HOOK(td, PMC_FN_KLD_UNLOAD, (void *) &pkm);
 #endif
 	KLD_UNLOCK();
+	CURVNET_RESTORE();
 	return (error);
 }