iflib: Stop interface before (un)registering VLAN

This patch is intended to solve a specific problem that iavf(4)
encounters, but what it does can be extended to solve other issues.

To summarize the iavf(4) issue, if the PF driver configures VLAN
anti-spoof, then the VF driver needs to make sure no untagged traffic is
sent if a VLAN is configured, and vice-versa. This can be an issue when
a VLAN is being registered or unregistered, e.g. when a packet may be on
the ring with a VLAN in it, but the VLANs are being unregistered. This
can cause that tagged packet to go out and cause an MDD event.

To fix this, include a new interface-dependent function that drivers can
implement named IFDI_NEEDS_RESTART(). Right now, this function is called
in iflib_vlan_unregister/register() to determine whether the interface
needs to be stopped and started when a VLAN is registered or
unregistered. The default return value of IFDI_NEEDS_RESTART() is true,
so this fixes the MDD problem that iavf(4) encounters, since the
interface rings are flushed during a stop/init.

A future change to iavf(4) will implement that function just in case the
default value changes, and to make it explicit that this interface reset
is required when a VLAN is added or removed.

Reviewed by:	gallatin@
MFC after:	1 week
Sponsored by:	Intel Corporation
Differential Revision:	https://reviews.freebsd.org/D22086

1 files changed, 12 insertions, 6 deletions

diff --git a/sys/net/iflib.c b/sys/net/iflib.c
index 41f5a97eeeae..1c8c2f6e1521 100644
--- a/sys/net/iflib.c
+++ b/sys/net/iflib.c
@@ -4308,10 +4308,13 @@ iflib_vlan_register(void *arg, if_t ifp, uint16_t vtag)
 		return;
 
 	CTX_LOCK(ctx);
+	/* Driver may need all untagged packets to be flushed */
+	if (IFDI_NEEDS_RESTART(ctx, IFLIB_RESTART_VLAN_CONFIG))
+		iflib_stop(ctx);
 	IFDI_VLAN_REGISTER(ctx, vtag);
-	/* Re-init to load the changes */
-	if (if_getcapenable(ifp) & IFCAP_VLAN_HWFILTER)
-		iflib_if_init_locked(ctx);
+	/* Re-init to load the changes, if required */
+	if (IFDI_NEEDS_RESTART(ctx, IFLIB_RESTART_VLAN_CONFIG))
+		iflib_init_locked(ctx);
 	CTX_UNLOCK(ctx);
 }
 
@@ -4327,10 +4330,13 @@ iflib_vlan_unregister(void *arg, if_t ifp, uint16_t vtag)
 		return;
 
 	CTX_LOCK(ctx);
+	/* Driver may need all tagged packets to be flushed */
+	if (IFDI_NEEDS_RESTART(ctx, IFLIB_RESTART_VLAN_CONFIG))
+		iflib_stop(ctx);
 	IFDI_VLAN_UNREGISTER(ctx, vtag);
-	/* Re-init to load the changes */
-	if (if_getcapenable(ifp) & IFCAP_VLAN_HWFILTER)
-		iflib_if_init_locked(ctx);
+	/* Re-init to load the changes, if required */
+	if (IFDI_NEEDS_RESTART(ctx, IFLIB_RESTART_VLAN_CONFIG))
+		iflib_init_locked(ctx);
 	CTX_UNLOCK(ctx);
 }