sctp: allow users to set ep ecn flag by sockopt

SCTP_ECN_SUPPORTED sockopt will be added to allow users to change
ep ecn flag, and it's similar with other feature flags.

Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/uapi/linux/sctp.h

@@ -136,6 +136,7 @@ typedef __s32 sctp_assoc_t;
 #define SCTP_EVENT	127
 #define SCTP_ASCONF_SUPPORTED	128
 #define SCTP_AUTH_SUPPORTED	129
+#define SCTP_ECN_SUPPORTED	130
 
 /* PR-SCTP policies */
 #define SCTP_PR_SCTP_NONE	0x0000

net/sctp/socket.c

@@ -4560,6 +4560,34 @@ static int sctp_setsockopt_auth_supported(struct sock *sk,
 	return retval;
 }
 
+static int sctp_setsockopt_ecn_supported(struct sock *sk,
+					 char __user *optval,
+					 unsigned int optlen)
+{
+	struct sctp_assoc_value params;
+	struct sctp_association *asoc;
+	int retval = -EINVAL;
+
+	if (optlen != sizeof(params))
+		goto out;
+
+	if (copy_from_user(&params, optval, optlen)) {
+		retval = -EFAULT;
+		goto out;
+	}
+
+	asoc = sctp_id2assoc(sk, params.assoc_id);
+	if (!asoc && params.assoc_id != SCTP_FUTURE_ASSOC &&
+	    sctp_style(sk, UDP))
+		goto out;
+
+	sctp_sk(sk)->ep->ecn_enable = !!params.assoc_value;
+	retval = 0;
+
+out:
+	return retval;
+}
+
 /* API 6.2 setsockopt(), getsockopt()
  *
  * Applications use setsockopt() and getsockopt() to set or retrieve
@@ -4766,6 +4794,9 @@ static int sctp_setsockopt(struct sock *sk, int level, int optname,
 	case SCTP_AUTH_SUPPORTED:
 		retval = sctp_setsockopt_auth_supported(sk, optval, optlen);
 		break;
+	case SCTP_ECN_SUPPORTED:
+		retval = sctp_setsockopt_ecn_supported(sk, optval, optlen);
+		break;
 	default:
 		retval = -ENOPROTOOPT;
 		break;
@@ -7828,6 +7859,45 @@ static int sctp_getsockopt_auth_supported(struct sock *sk, int len,
 	return retval;
 }
 
+static int sctp_getsockopt_ecn_supported(struct sock *sk, int len,
+					 char __user *optval,
+					 int __user *optlen)
+{
+	struct sctp_assoc_value params;
+	struct sctp_association *asoc;
+	int retval = -EFAULT;
+
+	if (len < sizeof(params)) {
+		retval = -EINVAL;
+		goto out;
+	}
+
+	len = sizeof(params);
+	if (copy_from_user(&params, optval, len))
+		goto out;
+
+	asoc = sctp_id2assoc(sk, params.assoc_id);
+	if (!asoc && params.assoc_id != SCTP_FUTURE_ASSOC &&
+	    sctp_style(sk, UDP)) {
+		retval = -EINVAL;
+		goto out;
+	}
+
+	params.assoc_value = asoc ? asoc->peer.ecn_capable
+				  : sctp_sk(sk)->ep->ecn_enable;
+
+	if (put_user(len, optlen))
+		goto out;
+
+	if (copy_to_user(optval, &params, len))
+		goto out;
+
+	retval = 0;
+
+out:
+	return retval;
+}
+
 static int sctp_getsockopt(struct sock *sk, int level, int optname,
 			   char __user *optval, int __user *optlen)
 {
@@ -8037,6 +8107,9 @@ static int sctp_getsockopt(struct sock *sk, int level, int optname,
 		retval = sctp_getsockopt_auth_supported(sk, len, optval,
 							optlen);
 		break;
+	case SCTP_ECN_SUPPORTED:
+		retval = sctp_getsockopt_ecn_supported(sk, len, optval, optlen);
+		break;
 	default:
 		retval = -ENOPROTOOPT;
 		break;