igb: Reject requests that fail to enable time stamping on both edges.

This hardware always time stamps rising and falling edges, and so this
patch validates that the request does contains both edges.

Signed-off-by: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/ethernet/intel/igb/igb_ptp.c b/drivers/net/ethernet/intel/igb/igb_ptp.c
index 3fd6071..c39e921 100644
--- a/drivers/net/ethernet/intel/igb/igb_ptp.c
+++ b/drivers/net/ethernet/intel/igb/igb_ptp.c
@@ -528,6 +528,12 @@
 					PTP_STRICT_FLAGS))
 			return -EOPNOTSUPP;
 
+		/* Reject requests failing to enable both edges. */
+		if ((rq->extts.flags & PTP_STRICT_FLAGS) &&
+		    (rq->extts.flags & PTP_ENABLE_FEATURE) &&
+		    (rq->extts.flags & PTP_EXTTS_EDGES) != PTP_EXTTS_EDGES)
+			return -EOPNOTSUPP;
+
 		if (on) {
 			pin = ptp_find_pin(igb->ptp_clock, PTP_PF_EXTTS,
 					   rq->extts.index);