sctp: add asoc intl_enable negotiation during 4 shakehands

asoc intl_enable will be set when local sp strm_interleave is set
and there's I-DATA chunk in init and init_ack extensions, as said
in section 2.2.1 of RFC8260.

asoc intl_enable indicates all data will be sent as I-DATA chunks.
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

@@ -102,6 +102,9 @@ enum sctp_cid {
 	/* AUTH Extension Section 4.1 */
 	SCTP_CID_AUTH			= 0x0F,
 
+	/* sctp ndata 5.1. I-DATA */
+	SCTP_CID_I_DATA			= 0x40,
+
 	/* PR-SCTP Sec 3.2 */
 	SCTP_CID_FWD_TSN		= 0xC0,
 

net/sctp/sm_make_chunk.c

@@ -228,7 +228,7 @@ struct sctp_chunk *sctp_make_init(const struct sctp_association *asoc,
 	struct sctp_inithdr init;
 	union sctp_params addrs;
 	struct sctp_sock *sp;
-	__u8 extensions[4];
+	__u8 extensions[5];
 	size_t chunksize;
 	__be16 types[2];
 	int num_ext = 0;
@@ -278,6 +278,11 @@ struct sctp_chunk *sctp_make_init(const struct sctp_association *asoc,
 	if (sp->adaptation_ind)
 		chunksize += sizeof(aiparam);
 
+	if (sp->strm_interleave) {
+		extensions[num_ext] = SCTP_CID_I_DATA;
+		num_ext += 1;
+	}
+
 	chunksize += vparam_len;
 
 	/* Account for AUTH related parameters */
@@ -392,7 +397,7 @@ struct sctp_chunk *sctp_make_init_ack(const struct sctp_association *asoc,
 	struct sctp_inithdr initack;
 	union sctp_params addrs;
 	struct sctp_sock *sp;
-	__u8 extensions[4];
+	__u8 extensions[5];
 	size_t chunksize;
 	int num_ext = 0;
 	int cookie_len;
@@ -442,6 +447,11 @@ struct sctp_chunk *sctp_make_init_ack(const struct sctp_association *asoc,
 	if (sp->adaptation_ind)
 		chunksize += sizeof(aiparam);
 
+	if (asoc->intl_enable) {
+		extensions[num_ext] = SCTP_CID_I_DATA;
+		num_ext += 1;
+	}
+
 	if (asoc->peer.auth_capable) {
 		auth_random = (struct sctp_paramhdr *)asoc->c.auth_random;
 		chunksize += ntohs(auth_random->length);
@@ -2032,6 +2042,10 @@ static void sctp_process_ext_param(struct sctp_association *asoc,
 			if (net->sctp.addip_enable)
 				asoc->peer.asconf_capable = 1;
 			break;
+		case SCTP_CID_I_DATA:
+			if (sctp_sk(asoc->base.sk)->strm_interleave)
+				asoc->intl_enable = 1;
+			break;
 		default:
 			break;
 		}