sctp: add SCTP_PR_SUPPORTED on sctp sockopt

According to section 4.5 of rfc7496, prsctp_enable should be per asoc.
We will add prsctp_enable to both asoc and ep, and replace the places
where it used net.sctp->prsctp_enable with asoc->prsctp_enable.

ep->prsctp_enable will be initialized with net.sctp->prsctp_enable, and
asoc->prsctp_enable will be initialized with ep->prsctp_enable. We can
also modify it's value through sockopt SCTP_PR_SUPPORTED.

Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/sctp/sm_make_chunk.c b/net/sctp/sm_make_chunk.c
index 56f364d..0e3045e 100644
--- a/net/sctp/sm_make_chunk.c
+++ b/net/sctp/sm_make_chunk.c
@@ -261,7 +261,7 @@
 	chunksize += WORD_ROUND(SCTP_SAT_LEN(num_types));
 	chunksize += sizeof(ecap_param);
 
-	if (net->sctp.prsctp_enable)
+	if (asoc->prsctp_enable)
 		chunksize += sizeof(prsctp_param);
 
 	/* ADDIP: Section 4.2.7:
@@ -355,7 +355,7 @@
 		sctp_addto_param(retval, num_ext, extensions);
 	}
 
-	if (net->sctp.prsctp_enable)
+	if (asoc->prsctp_enable)
 		sctp_addto_chunk(retval, sizeof(prsctp_param), &prsctp_param);
 
 	if (sp->adaptation_ind) {
@@ -2024,8 +2024,8 @@
 	for (i = 0; i < num_ext; i++) {
 		switch (param.ext->chunks[i]) {
 		case SCTP_CID_FWD_TSN:
-			if (net->sctp.prsctp_enable && !asoc->peer.prsctp_capable)
-				    asoc->peer.prsctp_capable = 1;
+			if (asoc->prsctp_enable && !asoc->peer.prsctp_capable)
+				asoc->peer.prsctp_capable = 1;
 			break;
 		case SCTP_CID_AUTH:
 			/* if the peer reports AUTH, assume that he
@@ -2169,7 +2169,7 @@
 		break;
 
 	case SCTP_PARAM_FWD_TSN_SUPPORT:
-		if (net->sctp.prsctp_enable)
+		if (ep->prsctp_enable)
 			break;
 		goto fallthrough;
 
@@ -2653,7 +2653,7 @@
 		break;
 
 	case SCTP_PARAM_FWD_TSN_SUPPORT:
-		if (net->sctp.prsctp_enable) {
+		if (asoc->prsctp_enable) {
 			asoc->peer.prsctp_capable = 1;
 			break;
 		}