net/handshake: Add new parameter 'HANDSHAKE_A_ACCEPT_KEYRING'

Add a new netlink parameter 'HANDSHAKE_A_ACCEPT_KEYRING' to provide
the serial number of the keyring to use.

Signed-off-by: Hannes Reinecke <[e-mail]>
Reviewed-by: Chuck Lever <[e-mail]>
Acked-by: Jakub Kicinski <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Paolo Abeni <[e-mail]>

Documentation/netlink/specs/handshake.yaml

···
       -
         name: peername
         type: string
+      -
+        name: keyring
+        type: u32
   -
     name: done
     attributes:
···
             - peer-identity
             - certificate
             - peername
+            - keyring
     -
       name: done
       doc: Handler reports handshake completion

include/uapi/linux/handshake.h

···
 	HANDSHAKE_A_ACCEPT_PEER_IDENTITY,
 	HANDSHAKE_A_ACCEPT_CERTIFICATE,
 	HANDSHAKE_A_ACCEPT_PEERNAME,
+	HANDSHAKE_A_ACCEPT_KEYRING,
 
 	__HANDSHAKE_A_ACCEPT_MAX,
 	HANDSHAKE_A_ACCEPT_MAX = (__HANDSHAKE_A_ACCEPT_MAX - 1)

net/handshake/tlshd.c

···
 		if (ret < 0)
 			goto out_cancel;
 	}
+	if (treq->th_keyring) {
+		ret = nla_put_u32(msg, HANDSHAKE_A_ACCEPT_KEYRING,
+				  treq->th_keyring);
+		if (ret < 0)
+			goto out_cancel;
+	}
 
 	ret = nla_put_u32(msg, HANDSHAKE_A_ACCEPT_AUTH_MODE,
 			  treq->th_auth_mode);