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net/rds: SOL_RDS socket option to explicitly select transport

PATCH In review Sowmini Varadhan 2 participants 5 messages May 29, 2015 – Jun 1, 2015

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Networking Network drivers RDS - reliable datagram sockets
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Sowmini Varadhan

author
#0 lore raw

cover net/rds: SOL_RDS socket option to explicitly select transport

Today the underlying transport (TCP or IB) for a PF_RDS socket is implicitly selected based on the local address used to bind(2) the PF_RDS socket. This results in some non-deterministic behavior when there are un-numbered and IPoIB interfaces sharing the same IP address. It also places the constraint that the IB interface must have an IP address (and thus, IPoIB) configured on it.

The non-determinism may be avoided by providing the user-space application a socket option that allows it to explicitly select the transport prior to bind(2).

Patch 1 of this series provides the constant definitions needed by the application via <linux/rds.h>.

Patch 2 provides the setsockopt support, and Patch 3 provides the getsockopt support.

Sowmini Varadhan (3):
Declare SO_RDS_TRANSPORT and RDS_TRANS_* constants in
uapi/linux/rds.h
Add setsockopt support for SO_RDS_TRANSPORT Add setsockopt support for SO_RDS_TRANSPORT

 include/uapi/linux/rds.h |   10 ++++++++++
 net/rds/af_rds.c         |   41 +++++++++++++++++++++++++++++++++++++++++
 net/rds/bind.c           |    4 ++++
 net/rds/rds.h            |    6 +-----
 net/rds/transport.c      |   21 +++++++++++++++++++++
 5 files changed, 77 insertions(+), 5 deletions(-)
author
#1 lore raw

PATCH 1/3 net/rds: Declare SO_RDS_TRANSPORT and RDS_TRANS_* constants in uapi/linux/rds.h

User space applications that desire to explicitly select the underlying transport for a PF_RDS socket may do so by using the SO_RDS_TRANSPORT socket option at the SOL_RDS level before bind(). The integer argument provided to the socket option would be one of the RDS_TRANS_* values, e.g., RDS_TRANS_TCP. This commit exports the constant values need by such applications via <linux/rds.h>

Signed-off-by Sowmini Varadhan <[email protected]>
---
 include/uapi/linux/rds.h |   10 ++++++++++
 net/rds/rds.h            |    5 -----
 2 files changed, 10 insertions(+), 5 deletions(-)
include/uapi/linux/rds.h +10 -0
index 9195095..0f9265c 100644
@@ -38,6 +38,8 @@
 
 #define RDS_IB_ABI_VERSION		0x301
 
+#define	SOL_RDS		276
+
 /*
  * setsockopt/getsockopt for SOL_RDS
  */

@@ -48,6 +50,14 @@
 #define RDS_RECVERR			5
 #define RDS_CONG_MONITOR		6
 #define RDS_GET_MR_FOR_DEST		7
+#define SO_RDS_TRANSPORT		8
+
+/* supported values for SO_RDS_TRANSPORT */
+#define	RDS_TRANS_IB	0
+#define	RDS_TRANS_IWARP	1
+#define	RDS_TRANS_TCP	2
+#define RDS_TRANS_COUNT	3
+#define	RDS_TRANS_NONE	(~0)
 
 /*
  * Control message types for SOL_RDS.
net/rds/rds.h +0 -5
index 0d41155..76db508 100644
@@ -408,11 +408,6 @@ struct rds_notifier {
  *                 should try hard not to block.
  */
 
-#define RDS_TRANS_IB	0
-#define RDS_TRANS_IWARP	1
-#define RDS_TRANS_TCP	2
-#define RDS_TRANS_COUNT	3
-
 struct rds_transport {
 	char			t_name[TRANSNAMSIZ];
 	struct list_head	t_item;
Signature · 1 line
1.7.1
author
#2 lore raw

PATCH 2/3 net/rds: Add setsockopt support for SO_RDS_TRANSPORT

In reply to Sowmini Varadhan

An application may deterministically attach the underlying transport for a PF_RDS socket by invoking setsockopt(2) with the SO_RDS_TRANSPORT option at the SOL_RDS level. The integer argument to setsockopt must be one of the RDS_TRANS_* transport types, e.g., RDS_TRANS_TCP. The option must be specified before invoking bind(2) on the socket, and may only be used once on the socket. An attempt to set the option on a bound socket, or to invoke the option after a successful SO_RDS_TRANSPORT attachment, will return EOPNOTSUPP.

Signed-off-by Sowmini Varadhan <[email protected]>
---
 net/rds/af_rds.c    |   27 +++++++++++++++++++++++++++
 net/rds/bind.c      |    4 ++++
 net/rds/rds.h       |    1 +
 net/rds/transport.c |   21 +++++++++++++++++++++
 4 files changed, 53 insertions(+), 0 deletions(-)
net/rds/af_rds.c +27 -0
index 3d83641..0487744 100644
@@ -270,6 +270,28 @@ static int rds_cong_monitor(struct rds_sock *rs, char __user *optval,
 	return ret;
 }
 
+static int rds_set_transport(struct rds_sock *rs, char __user *optval,
+			     int optlen)
+{
+	int t_type;
+
+	if (rs->rs_transport)
+		return -EOPNOTSUPP; /* previously attached to transport */
+
+	if (optlen != sizeof(int))
+		return -EINVAL;
+
+	if (copy_from_user(&t_type, (int __user *)optval, sizeof(t_type)))
+		return -EFAULT;
+
+	if (t_type < 0 || t_type >= RDS_TRANS_COUNT)
+		return -EINVAL;
+
+	rs->rs_transport = rds_trans_get(t_type);
+
+	return rs->rs_transport ? 0 : -ENOPROTOOPT;
+}
+
 static int rds_setsockopt(struct socket *sock, int level, int optname,
 			  char __user *optval, unsigned int optlen)
 {

@@ -300,6 +322,11 @@ static int rds_setsockopt(struct socket *sock, int level, int optname,
 	case RDS_CONG_MONITOR:
 		ret = rds_cong_monitor(rs, optval, optlen);
 		break;
+	case SO_RDS_TRANSPORT:
+		lock_sock(sock->sk);
+		ret = rds_set_transport(rs, optval, optlen);
+		release_sock(sock->sk);
+		break;
 	default:
 		ret = -ENOPROTOOPT;
 	}
net/rds/bind.c +4 -0
index a2e6562..4ebd29c 100644
@@ -181,6 +181,10 @@ int rds_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len)
 	if (ret)
 		goto out;
 
+	if (rs->rs_transport) { /* previously bound */
+		ret = 0;
+		goto out;
+	}
 	trans = rds_trans_get_preferred(sin->sin_addr.s_addr);
 	if (!trans) {
 		ret = -EADDRNOTAVAIL;
net/rds/rds.h +1 -0
index 76db508..a33fb4a 100644
@@ -798,6 +798,7 @@ struct rds_transport *rds_trans_get_preferred(__be32 addr);
 void rds_trans_put(struct rds_transport *trans);
 unsigned int rds_trans_stats_info_copy(struct rds_info_iterator *iter,
 				       unsigned int avail);
+struct rds_transport *rds_trans_get(int t_type);
 int rds_trans_init(void);
 void rds_trans_exit(void);
net/rds/transport.c +21 -0
index 7f2ac4f..8b4a6cd 100644
@@ -101,6 +101,27 @@ struct rds_transport *rds_trans_get_preferred(__be32 addr)
 	return ret;
 }
 
+struct rds_transport *rds_trans_get(int t_type)
+{
+	struct rds_transport *ret = NULL;
+	struct rds_transport *trans;
+	unsigned int i;
+
+	down_read(&rds_trans_sem);
+	for (i = 0; i < RDS_TRANS_COUNT; i++) {
+		trans = transports[i];
+
+		if (trans && trans->t_type == t_type &&
+		    (!trans->t_owner || try_module_get(trans->t_owner))) {
+			ret = trans;
+			break;
+		}
+	}
+	up_read(&rds_trans_sem);
+
+	return ret;
+}
+
 /*
  * This returns the number of stats entries in the snapshot and only
  * copies them using the iter if there is enough space for them.  The
Signature · 1 line
1.7.1
author
#3 lore raw

PATCH 3/3 net/rds Add getsockopt support for SO_RDS_TRANSPORT

In reply to Sowmini Varadhan

The currently attached transport for a PF_RDS socket may be obtained from user space by invoking getsockopt(2) using the SO_RDS_TRANSPORT option at the SOL_RDS level. The integer optval returned will be one of the RDS_TRANS_* constants defined in linux/rds.h.

Signed-off-by Sowmini Varadhan <[email protected]>
---
 net/rds/af_rds.c |   14 ++++++++++++++
 1 files changed, 14 insertions(+), 0 deletions(-)
net/rds/af_rds.c +14 -0
index 0487744..2ad9032 100644
@@ -339,6 +339,7 @@ static int rds_getsockopt(struct socket *sock, int level, int optname,
 {
 	struct rds_sock *rs = rds_sk_to_rs(sock->sk);
 	int ret = -ENOPROTOOPT, len;
+	int trans;
 
 	if (level != SOL_RDS)
 		goto out;

@@ -364,6 +365,19 @@ static int rds_getsockopt(struct socket *sock, int level, int optname,
 		else
 			ret = 0;
 		break;
+	case SO_RDS_TRANSPORT:
+		if (len < sizeof(int)) {
+			ret = -EINVAL;
+			break;
+		}
+		trans = (rs->rs_transport ? rs->rs_transport->t_type :
+			 RDS_TRANS_NONE); /* unbound */
+		if (put_user(trans, (int __user *)optval) ||
+		    put_user(sizeof(int), optlen))
+			ret = -EFAULT;
+		else
+			ret = 0;
+		break;
 	default:
 		break;
 	}
Signature · 1 line
1.7.1
maintainer
#4 lore raw
In reply to Sowmini Varadhan

From: Sowmini Varadhan <[email protected]>
Date: Fri, 29 May 2015 17:28:06 -0400

Quoted 11 lines

Today the underlying transport (TCP or IB) for a PF_RDS socket is implicitly selected based on the local address used to bind(2) the PF_RDS socket. This results in some non-deterministic behavior when there are un-numbered and IPoIB interfaces sharing the same IP address. It also places the constraint that the IB interface must have an IP address (and thus, IPoIB) configured on it.

The non-determinism may be avoided by providing the user-space application a socket option that allows it to explicitly select the transport prior to bind(2).

Quoted 5 lines

Patch 1 of this series provides the constant definitions needed by the application via <linux/rds.h>.

Patch 2 provides the setsockopt support, and Patch 3 provides the getsockopt support.

Seems reasonable, series applied to net-next, thanks.