net: lwtunnel: Add extack to encap attr validation

Pass extack down to lwtunnel_valid_encap_type and
lwtunnel_valid_encap_type_attr. Add messages for unknown
or unsupported encap types.

Signed-off-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c
index 715b796..4e678fa 100644
--- a/net/ipv4/fib_frontend.c
+++ b/net/ipv4/fib_frontend.c
@@ -685,7 +685,8 @@ static int rtm_to_fib_config(struct net *net, struct sk_buff *skb,
 			break;
 		case RTA_MULTIPATH:
 			err = lwtunnel_valid_encap_type_attr(nla_data(attr),
-							     nla_len(attr));
+							     nla_len(attr),
+							     extack);
 			if (err < 0)
 				goto errout;
 			cfg->fc_mp = nla_data(attr);
@@ -702,7 +703,8 @@ static int rtm_to_fib_config(struct net *net, struct sk_buff *skb,
 			break;
 		case RTA_ENCAP_TYPE:
 			cfg->fc_encap_type = nla_get_u16(attr);
-			err = lwtunnel_valid_encap_type(cfg->fc_encap_type);
+			err = lwtunnel_valid_encap_type(cfg->fc_encap_type,
+							extack);
 			if (err < 0)
 				goto errout;
 			break;