BACKPORT: xfrm/compat: Add 32=>64-bit messages translator

Provide the user-to-kernel translator under XFRM_USER_COMPAT, that
creates for 32-bit xfrm-user message a 64-bit translation.
The translation is afterwards reused by xfrm_user code just as if
userspace had sent 64-bit message.

Signed-off-by: Dmitry Safonov <dima@arista.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
(cherry picked from commit 5106f4a8acff480e244300bc5097c0ad7048c3a2)
[adelva: nlmsg_parse_deprecated -> nlmsg_parse]
Bug: 163141236
Signed-off-by: Alistair Delva <adelva@google.com>
Change-Id: If15999b86e4704b75307fbcc3d7f0c8d8bc89e7a
diff --git a/include/net/xfrm.h b/include/net/xfrm.h
index 44975df..fd4361a 100644
--- a/include/net/xfrm.h
+++ b/include/net/xfrm.h
@@ -2095,11 +2095,17 @@
 }
 
 extern const int xfrm_msg_min[XFRM_NR_MSGTYPES];
+extern const struct nla_policy xfrma_policy[XFRMA_MAX+1];
 
 struct xfrm_translator {
 	/* Allocate frag_list and put compat translation there */
 	int (*alloc_compat)(struct sk_buff *skb, const struct nlmsghdr *src);
 
+	/* Allocate nlmsg with 64-bit translaton of received 32-bit message */
+	struct nlmsghdr *(*rcv_msg_compat)(const struct nlmsghdr *nlh,
+			int maxtype, const struct nla_policy *policy,
+			struct netlink_ext_ack *extack);
+
 	struct module *owner;
 };