On Mon, Jun 25, 2018 at 04:31:26PM +0900, David Miller wrote:

From: Xin Long <lucien.xin@gmail.com>
Date: Mon, 25 Jun 2018 10:14:35 +0800

quoted

 struct sctp_paddrparams {

@@ -773,6 +775,8 @@ struct sctp_paddrparams {
 	__u32			spp_pathmtu;
 	__u32			spp_sackdelay;
 	__u32			spp_flags;
+	__u32			spp_ipv6_flowlabel;
+	__u8			spp_dscp;
 } __attribute__((packed, aligned(4)));

I don't think you can change the size of this structure like this.

This check in sctp_setsockopt_peer_addr_params():

	if (optlen != sizeof(struct sctp_paddrparams))
		return -EINVAL;

is going to trigger in old kernels when executing programs
built against the new struct definition.

I think thats also the reason its a packed aligned attribute, it can't be
changed, or older kernels won't be able to fill it out properly.
Neil