net: sctp: implement rfc6458, 5.3.5. SCTP_RCVINFO cmsg support

This patch implements section 5.3.5. of RFC6458, that is, support
for 'SCTP Receive Information Structure' (SCTP_RCVINFO) which is
placed into ancillary data cmsghdr structure for each recvmsg()
call.

This option can be enabled/disabled via setsockopt(2) on SOL_SCTP
level by setting an int value with 1/0 for SCTP_RECVRCVINFO in user
space applications as per RFC6458, section 8.1.29.

The sctp_rcvinfo structure is defined as per RFC as below ...

  struct sctp_rcvinfo {
    uint16_t rcv_sid;
    uint16_t rcv_ssn;
    uint16_t rcv_flags;
    <-- 2 bytes hole  -->
    uint32_t rcv_ppid;
    uint32_t rcv_tsn;
    uint32_t rcv_cumtsn;
    uint32_t rcv_context;
    sctp_assoc_t rcv_assoc_id;
  };

... and provided under cmsg_level IPPROTO_SCTP, cmsg_type
SCTP_RCVINFO, while cmsg_data[] contains struct sctp_rcvinfo.
An sctp_rcvinfo item always corresponds to the data in msg_iov.

Joint work with Daniel Borkmann.

Signed-off-by: Geir Ola Vaagland <geirola@gmail.com>
Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/sctp/structs.h

@@ -207,7 +207,9 @@ struct sctp_sock {
 	struct sctp_paddrparams paddrparam;
 	struct sctp_event_subscribe subscribe;
 	struct sctp_assocparams assocparams;
+
 	int user_frag;
+
 	__u32 autoclose;
 	__u8 nodelay;
 	__u8 disable_fragments;
@@ -215,6 +217,7 @@ struct sctp_sock {
 	__u8 frag_interleave;
 	__u32 adaptation_ind;
 	__u32 pd_point;
+	__u8 recvrcvinfo;
 
 	atomic_t pd_mode;
 	/* Receive to here while partial delivery is in effect. */

include/net/sctp/ulpevent.h

@@ -129,7 +129,10 @@ struct sctp_ulpevent *sctp_ulpevent_make_sender_dry_event(
 	const struct sctp_association *asoc, gfp_t gfp);
 
 void sctp_ulpevent_read_sndrcvinfo(const struct sctp_ulpevent *event,
-	struct msghdr *);
+				   struct msghdr *);
+void sctp_ulpevent_read_rcvinfo(const struct sctp_ulpevent *event,
+				struct msghdr *);
+
 __u16 sctp_ulpevent_get_notification_type(const struct sctp_ulpevent *event);
 
 /* Is this event type enabled? */

include/uapi/linux/sctp.h

@@ -95,6 +95,7 @@ typedef __s32 sctp_assoc_t;
 #define SCTP_GET_ASSOC_ID_LIST	29	/* Read only */
 #define SCTP_AUTO_ASCONF       30
 #define SCTP_PEER_ADDR_THLDS	31
+#define SCTP_RECVRCVINFO	32
 
 /* Internal Socket Options. Some of the sctp library functions are
  * implemented using these socket options.
@@ -110,8 +111,7 @@ typedef __s32 sctp_assoc_t;
 #define SCTP_SOCKOPT_CONNECTX3	111	/* CONNECTX requests (updated) */
 #define SCTP_GET_ASSOC_STATS	112	/* Read only */
 
-/*
+/* 5.3.1 SCTP Initiation Structure (SCTP_INIT)
- * 5.2.1 SCTP Initiation Structure (SCTP_INIT)
  *
  *   This cmsghdr structure provides information for initializing new
  *   SCTP associations with sendmsg().  The SCTP_INITMSG socket option
@@ -121,7 +121,6 @@ typedef __s32 sctp_assoc_t;
  *   cmsg_level    cmsg_type      cmsg_data[]
  *   ------------  ------------   ----------------------
  *   IPPROTO_SCTP  SCTP_INIT      struct sctp_initmsg
- *
  */
 struct sctp_initmsg {
 	__u16 sinit_num_ostreams;
@@ -130,8 +129,7 @@ struct sctp_initmsg {
 	__u16 sinit_max_init_timeo;
 };
 
-/*
+/* 5.3.2 SCTP Header Information Structure (SCTP_SNDRCV)
- * 5.2.2 SCTP Header Information Structure (SCTP_SNDRCV)
  *
  *   This cmsghdr structure specifies SCTP options for sendmsg() and
  *   describes SCTP header information about a received message through
@@ -140,7 +138,6 @@ struct sctp_initmsg {
  *   cmsg_level    cmsg_type      cmsg_data[]
  *   ------------  ------------   ----------------------
  *   IPPROTO_SCTP  SCTP_SNDRCV    struct sctp_sndrcvinfo
- *
  */
 struct sctp_sndrcvinfo {
 	__u16 sinfo_stream;
@@ -170,13 +167,32 @@ struct sctp_sndinfo {
 	sctp_assoc_t snd_assoc_id;
 };
 
+/* 5.3.5 SCTP Receive Information Structure (SCTP_RCVINFO)
+ *
+ *   This cmsghdr structure describes SCTP receive information
+ *   about a received message through recvmsg().
+ *
+ *   cmsg_level    cmsg_type      cmsg_data[]
+ *   ------------  ------------   -------------------
+ *   IPPROTO_SCTP  SCTP_RCVINFO   struct sctp_rcvinfo
+ */
+struct sctp_rcvinfo {
+	__u16 rcv_sid;
+	__u16 rcv_ssn;
+	__u16 rcv_flags;
+	__u32 rcv_ppid;
+	__u32 rcv_tsn;
+	__u32 rcv_cumtsn;
+	__u32 rcv_context;
+	sctp_assoc_t rcv_assoc_id;
+};
+
 /*
  *  sinfo_flags: 16 bits (unsigned integer)
  *
  *   This field may contain any of the following flags and is composed of
  *   a bitwise OR of these values.
  */
-
 enum sctp_sinfo_flags {
 	SCTP_UNORDERED = 1,  /* Send/receive message unordered. */
 	SCTP_ADDR_OVER = 2,  /* Override the primary destination. */
@@ -199,6 +215,8 @@ typedef enum sctp_cmsg_type {
 #define SCTP_SNDRCV	SCTP_SNDRCV
 	SCTP_SNDINFO,		/* 5.3.4 SCTP Send Information Structure */
 #define SCTP_SNDINFO	SCTP_SNDINFO
+	SCTP_RCVINFO,		/* 5.3.5 SCTP Receive Information Structure */
+#define SCTP_RCVINFO	SCTP_RCVINFO
 } sctp_cmsg_t;
 
 /*

net/sctp/socket.c

@@ -2112,9 +2112,13 @@ static int sctp_recvmsg(struct kiocb *iocb, struct sock *sk,
 		sp->pf->skb_msgname(skb, msg->msg_name, addr_len);
 	}
 
+	/* Check if we allow SCTP_RCVINFO. */
+	if (sp->recvrcvinfo)
+		sctp_ulpevent_read_rcvinfo(event, msg);
 	/* Check if we allow SCTP_SNDRCVINFO. */
 	if (sp->subscribe.sctp_data_io_event)
 		sctp_ulpevent_read_sndrcvinfo(event, msg);
+
 #if 0
 	/* FIXME: we should be calling IP/IPv6 layers.  */
 	if (sk->sk_protinfo.af_inet.cmsg_flags)
@@ -3541,7 +3545,6 @@ static int sctp_setsockopt_auto_asconf(struct sock *sk, char __user *optval,
 	return 0;
 }
 
-
 /*
  * SCTP_PEER_ADDR_THLDS
  *
@@ -3592,6 +3595,22 @@ static int sctp_setsockopt_paddr_thresholds(struct sock *sk,
 	return 0;
 }
 
+static int sctp_setsockopt_recvrcvinfo(struct sock *sk,
+				       char __user *optval,
+				       unsigned int optlen)
+{
+	int val;
+
+	if (optlen < sizeof(int))
+		return -EINVAL;
+	if (get_user(val, (int __user *) optval))
+		return -EFAULT;
+
+	sctp_sk(sk)->recvrcvinfo = (val == 0) ? 0 : 1;
+
+	return 0;
+}
+
 /* API 6.2 setsockopt(), getsockopt()
  *
  * Applications use setsockopt() and getsockopt() to set or retrieve
@@ -3743,6 +3762,9 @@ static int sctp_setsockopt(struct sock *sk, int level, int optname,
 	case SCTP_PEER_ADDR_THLDS:
 		retval = sctp_setsockopt_paddr_thresholds(sk, optval, optlen);
 		break;
+	case SCTP_RECVRCVINFO:
+		retval = sctp_setsockopt_recvrcvinfo(sk, optval, optlen);
+		break;
 	default:
 		retval = -ENOPROTOOPT;
 		break;
@@ -3989,6 +4011,8 @@ static int sctp_init_sock(struct sock *sk)
 	/* Enable Nagle algorithm by default.  */
 	sp->nodelay           = 0;
 
+	sp->recvrcvinfo = 0;
+
 	/* Enable by default. */
 	sp->v4mapped          = 1;
 
@@ -5770,6 +5794,26 @@ static int sctp_getsockopt_assoc_stats(struct sock *sk, int len,
 	return 0;
 }
 
+static int sctp_getsockopt_recvrcvinfo(struct sock *sk,	int len,
+				       char __user *optval,
+				       int __user *optlen)
+{
+	int val = 0;
+
+	if (len < sizeof(int))
+		return -EINVAL;
+
+	len = sizeof(int);
+	if (sctp_sk(sk)->recvrcvinfo)
+		val = 1;
+	if (put_user(len, optlen))
+		return -EFAULT;
+	if (copy_to_user(optval, &val, len))
+		return -EFAULT;
+
+	return 0;
+}
+
 static int sctp_getsockopt(struct sock *sk, int level, int optname,
 			   char __user *optval, int __user *optlen)
 {
@@ -5913,6 +5957,9 @@ static int sctp_getsockopt(struct sock *sk, int level, int optname,
 	case SCTP_GET_ASSOC_STATS:
 		retval = sctp_getsockopt_assoc_stats(sk, len, optval, optlen);
 		break;
+	case SCTP_RECVRCVINFO:
+		retval = sctp_getsockopt_recvrcvinfo(sk, len, optval, optlen);
+		break;
 	default:
 		retval = -ENOPROTOOPT;
 		break;

net/sctp/ulpevent.c

@@ -886,6 +886,31 @@ void sctp_ulpevent_read_sndrcvinfo(const struct sctp_ulpevent *event,
 		 sizeof(sinfo), &sinfo);
 }
 
+/* RFC6458, Section 5.3.5 SCTP Receive Information Structure
+ * (SCTP_SNDRCV)
+ */
+void sctp_ulpevent_read_rcvinfo(const struct sctp_ulpevent *event,
+				struct msghdr *msghdr)
+{
+	struct sctp_rcvinfo rinfo;
+
+	if (sctp_ulpevent_is_notification(event))
+		return;
+
+	memset(&rinfo, 0, sizeof(struct sctp_rcvinfo));
+	rinfo.rcv_sid = event->stream;
+	rinfo.rcv_ssn = event->ssn;
+	rinfo.rcv_ppid = event->ppid;
+	rinfo.rcv_flags = event->flags;
+	rinfo.rcv_tsn = event->tsn;
+	rinfo.rcv_cumtsn = event->cumtsn;
+	rinfo.rcv_assoc_id = sctp_assoc2id(event->asoc);
+	rinfo.rcv_context = event->asoc->default_rcv_context;
+
+	put_cmsg(msghdr, IPPROTO_SCTP, SCTP_RCVINFO,
+		 sizeof(rinfo), &rinfo);
+}
+
 /* Do accounting for bytes received and hold a reference to the association
  * for each skb.
  */