sunrpc: add dst_attr attributes to the sysfs xprt directory

Allow to query and set the destination's address of a transport.
Setting of the destination address is allowed only for TCP or RDMA
based connections.

Signed-off-by: Olga Kornievskaia <kolga@netapp.com>

net/sunrpc/sysfs.c

@@ -4,6 +4,9 @@
  */
 #include <linux/sunrpc/clnt.h>
 #include <linux/kobject.h>
+#include <linux/sunrpc/addr.h>
+#include <linux/sunrpc/xprtsock.h>
+
 #include "sysfs.h"
 
 static struct kset *rpc_sunrpc_kset;
@@ -42,6 +45,70 @@ static struct kobject *rpc_sysfs_object_alloc(const char *name,
 	return NULL;
 }
 
+static inline struct rpc_xprt *
+rpc_sysfs_xprt_kobj_get_xprt(struct kobject *kobj)
+{
+	struct rpc_sysfs_xprt_switch_xprt *x = container_of(kobj,
+		struct rpc_sysfs_xprt_switch_xprt, kobject);
+	struct rpc_xprt *xprt;
+
+	rcu_read_lock();
+	xprt = xprt_get(rcu_dereference(x->xprt));
+	rcu_read_unlock();
+	return xprt;
+}
+
+static ssize_t rpc_sysfs_xprt_dstaddr_show(struct kobject *kobj,
+					   struct kobj_attribute *attr,
+					   char *buf)
+{
+	struct rpc_xprt *xprt = rpc_sysfs_xprt_kobj_get_xprt(kobj);
+	ssize_t ret;
+
+	if (!xprt)
+		return 0;
+	if (xprt->xprt_class->ident == XPRT_TRANSPORT_LOCAL)
+		ret = sprintf(buf, "localhost");
+	else
+		ret = rpc_ntop((struct sockaddr *)&xprt->addr, buf, PAGE_SIZE);
+	buf[ret] = '\n';
+	xprt_put(xprt);
+	return ret + 1;
+}
+
+static ssize_t rpc_sysfs_xprt_dstaddr_store(struct kobject *kobj,
+					    struct kobj_attribute *attr,
+					    const char *buf, size_t count)
+{
+	struct rpc_xprt *xprt = rpc_sysfs_xprt_kobj_get_xprt(kobj);
+	struct sockaddr *saddr;
+	int port;
+
+	if (!xprt)
+		return 0;
+	if (!(xprt->xprt_class->ident == XPRT_TRANSPORT_TCP ||
+	      xprt->xprt_class->ident == XPRT_TRANSPORT_RDMA)) {
+		xprt_put(xprt);
+		return -EOPNOTSUPP;
+	}
+
+	wait_on_bit_lock(&xprt->state, XPRT_LOCKED, TASK_KILLABLE);
+	saddr = (struct sockaddr *)&xprt->addr;
+	port = rpc_get_port(saddr);
+
+	kfree(xprt->address_strings[RPC_DISPLAY_ADDR]);
+	xprt->address_strings[RPC_DISPLAY_ADDR] = kstrndup(buf, count - 1,
+							   GFP_KERNEL);
+	xprt->addrlen = rpc_pton(xprt->xprt_net, buf, count - 1, saddr,
+				 sizeof(*saddr));
+	rpc_set_port(saddr, port);
+
+	xprt->ops->connect(xprt, NULL);
+	clear_bit(XPRT_LOCKED, &xprt->state);
+	xprt_put(xprt);
+	return count;
+}
+
 int rpc_sysfs_init(void)
 {
 	rpc_sunrpc_kset = kset_create_and_add("sunrpc", NULL, kernel_kobj);
@@ -105,6 +172,14 @@ static const void *rpc_sysfs_xprt_switch_xprt_namespace(struct kobject *kobj)
 			    kobject)->net;
 }
 
+static struct kobj_attribute rpc_sysfs_xprt_dstaddr = __ATTR(dstaddr,
+	0644, rpc_sysfs_xprt_dstaddr_show, rpc_sysfs_xprt_dstaddr_store);
+
+static struct attribute *rpc_sysfs_xprt_attrs[] = {
+	&rpc_sysfs_xprt_dstaddr.attr,
+	NULL,
+};
+
 static struct kobj_type rpc_sysfs_client_type = {
 	.release = rpc_sysfs_client_release,
 	.sysfs_ops = &kobj_sysfs_ops,
@@ -119,6 +194,7 @@ static struct kobj_type rpc_sysfs_xprt_switch_type = {
 
 static struct kobj_type rpc_sysfs_xprt_switch_xprt_type = {
 	.release = rpc_sysfs_xprt_switch_xprt_release,
+	.default_attrs = rpc_sysfs_xprt_attrs,
 	.sysfs_ops = &kobj_sysfs_ops,
 	.namespace = rpc_sysfs_xprt_switch_xprt_namespace,
 };