ip6_gre: Reduce log level in ip6gre_err() to debug

Currently error log messages in ip6gre_err are printed at 'warn'
level. This is different to most other tunnel types which don't
print any messages. These log messages don't provide any information
that couldn't be deduced with networking tools. Also it can be annoying
to have one end of the tunnel go down and have the logs fill with
pointless messages such as "Path to destination invalid or inactive!".

This patch reduces the log level of these messages to 'dbg' level to
bring the visible behaviour into line with other tunnel types.

Signed-off-by: Matt Bennett <matt.bennett@alliedtelesis.co.nz>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/ip6_gre.c

@@ -404,13 +404,13 @@ static void ip6gre_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
 		struct ipv6_tlv_tnl_enc_lim *tel;
 		__u32 mtu;
 	case ICMPV6_DEST_UNREACH:
-		net_warn_ratelimited("%s: Path to destination invalid or inactive!\n",
-				     t->parms.name);
+		net_dbg_ratelimited("%s: Path to destination invalid or inactive!\n",
+				    t->parms.name);
 		break;
 	case ICMPV6_TIME_EXCEED:
 		if (code == ICMPV6_EXC_HOPLIMIT) {
-			net_warn_ratelimited("%s: Too small hop limit or routing loop in tunnel!\n",
-					     t->parms.name);
+			net_dbg_ratelimited("%s: Too small hop limit or routing loop in tunnel!\n",
+					    t->parms.name);
 		}
 		break;
 	case ICMPV6_PARAMPROB:
@@ -421,12 +421,12 @@ static void ip6gre_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
 		if (teli && teli == be32_to_cpu(info) - 2) {
 			tel = (struct ipv6_tlv_tnl_enc_lim *) &skb->data[teli];
 			if (tel->encap_limit == 0) {
-				net_warn_ratelimited("%s: Too small encapsulation limit or routing loop in tunnel!\n",
-						     t->parms.name);
+				net_dbg_ratelimited("%s: Too small encapsulation limit or routing loop in tunnel!\n",
+						    t->parms.name);
 			}
 		} else {
-			net_warn_ratelimited("%s: Recipient unable to parse tunneled packet!\n",
-					     t->parms.name);
+			net_dbg_ratelimited("%s: Recipient unable to parse tunneled packet!\n",
+					    t->parms.name);
 		}
 		break;
 	case ICMPV6_PKT_TOOBIG: