netfilter: conntrack: Fix gre tunneling over ipv6

stable inclusion
from stable-5.10.29
commit b0c795f4cc53dbf7580812bad9db7cb20da8c995
bugzilla: 51789

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

[ Upstream commit 8b2030b4 ]

This fix permits gre connections to be tracked within ip6tables rules
Signed-off-by: NLudovic Senecaux <linuxludo@free.fr>
Acked-by: NFlorian Westphal <fw@strlen.de>
Signed-off-by: NPablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Acked-by: N  Weilong Chen <chenweilong@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

net/netfilter/nf_conntrack_proto_gre.c

@@ -218,9 +218,6 @@ int nf_conntrack_gre_packet(struct nf_conn *ct,
 			    enum ip_conntrack_info ctinfo,
 			    const struct nf_hook_state *state)
 {
-	if (state->pf != NFPROTO_IPV4)
-		return -NF_ACCEPT;
-
 	if (!nf_ct_is_confirmed(ct)) {
 		unsigned int *timeouts = nf_ct_timeout_lookup(ct);