netfilter: conntrack: do not print icmpv6 as unknown via /proc

stable inclusion
from linux-4.19.189
commit cb87700ccb0d4cbfc430d42bcf07029a63943d3a

--------------------------------

commit fbea3180 upstream.

/proc/net/nf_conntrack shows icmpv6 as unknown.

Fixes: 09ec82f5 ("netfilter: conntrack: remove protocol name from l4proto struct")
Signed-off-by: NPablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

net/netfilter/nf_conntrack_standalone.c

@@ -262,6 +262,7 @@ static const char* l4proto_name(u16 proto)
 	case IPPROTO_GRE: return "gre";
 	case IPPROTO_SCTP: return "sctp";
 	case IPPROTO_UDPLITE: return "udplite";
+	case IPPROTO_ICMPV6: return "icmpv6";
 	}
 
 	return "unknown";