selftests: forwarding: Add suppport to create veth interfaces

For tests using veth interfaces, the test infrastructure can create
the netdevs if they do not exist. Arguably this is a preferred approach
since the tests require p$N and p$(N+1) to be pairs.
Signed-off-by: David Ahern <dsahern@gmail.com>
Reviewed-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

tools/testing/selftests/net/forwarding/forwarding.config.sample

@@ -14,6 +14,11 @@ NETIFS[p6]=veth5
 NETIFS[p7]=veth6
 NETIFS[p8]=veth7
 
+NETIF_TYPE=veth
+
+# only virtual interfaces (veth) can be created by test infra
+#NETIF_CREATE=yes
+
 ##############################################################################
 # Defines
 

tools/testing/selftests/net/forwarding/lib.sh

@@ -76,6 +76,41 @@ done
 ##############################################################################
 # Network interfaces configuration
 
+create_netif_veth()
+{
+	local i
+
+	for i in $(eval echo {1..$NUM_NETIFS}); do
+		local j=$((i+1))
+
+		ip link show dev ${NETIFS[p$i]} &> /dev/null
+		if [[ $? -ne 0 ]]; then
+			ip link add ${NETIFS[p$i]} type veth \
+				peer name ${NETIFS[p$j]}
+			if [[ $? -ne 0 ]]; then
+				echo "Failed to create netif"
+				exit 1
+			fi
+		fi
+		i=$j
+	done
+}
+
+create_netif()
+{
+	case "$NETIF_TYPE" in
+	veth) create_netif_veth
+	      ;;
+	*) echo "Can not create interfaces of type \'$NETIF_TYPE\'"
+	   exit 1
+	   ;;
+	esac
+}
+
+if [[ "$NETIF_CREATE" = "yes" ]]; then
+	create_netif
+fi
+
 for i in $(eval echo {1..$NUM_NETIFS}); do
 	ip link show dev ${NETIFS[p$i]} &> /dev/null
 	if [[ $? -ne 0 ]]; then