sctp: sctp_diag should dump sctp socket type

Now we cannot distinguish that one sk is a udp or sctp style when
we use ss to dump sctp_info. it's necessary to dump it as well.

For sctp_diag, ss support is not officially available, thus there
are no official users of this yet, so we can add this field in the
middle of sctp_info without breaking user API.

v1->v2:
  - move 'sctpi_s_type' field to the end of struct sctp_info, so
    that it won't cause incompatibility with applications already
    built.
  - add __reserved3 in sctp_info to make sure sctp_info is 8-byte
    alignment.
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/sctp.h

@@ -765,6 +765,8 @@ struct sctp_info {
 	__u8	sctpi_s_disable_fragments;
 	__u8	sctpi_s_v4mapped;
 	__u8	sctpi_s_frag_interleave;
+	__u32	sctpi_s_type;
+	__u32	__reserved3;
 };
 
 struct sctp_infox {

net/sctp/socket.c

@@ -4220,6 +4220,7 @@ int sctp_get_sctp_info(struct sock *sk, struct sctp_association *asoc,
 		info->sctpi_s_disable_fragments = sp->disable_fragments;
 		info->sctpi_s_v4mapped = sp->v4mapped;
 		info->sctpi_s_frag_interleave = sp->frag_interleave;
+		info->sctpi_s_type = sp->type;
 
 		return 0;
 	}