[PATCH v2 5/5] sunrpc: Create a per-rpc_clnt file for managing the destination IP address

[schumaker.anna@xxxxxxxxx]

From: Anna Schumaker <Anna.Schumaker@xxxxxxxxxx>

Reading the file displays the current destination address, and writing
to it allows users to change the address.

And since we're using IP here, restrict to only creating sysfs files for
TCP and RDMA connections.

Signed-off-by: Anna Schumaker <Anna.Schumaker@xxxxxxxxxx>
---
v2: Change filename and related functions from "address" to "dstaddr"
    Combine patches for reading and writing to this file
---
 net/sunrpc/sysfs.c | 47 ++++++++++++++++++++++++++++++++++++++++++++++
 net/sunrpc/sysfs.h |  1 +
 2 files changed, 48 insertions(+)

diff --git a/net/sunrpc/sysfs.c b/net/sunrpc/sysfs.c
index 42a690f8bb52..8b01b4df64ee 100644
--- a/net/sunrpc/sysfs.c
+++ b/net/sunrpc/sysfs.c
@@ -3,6 +3,8 @@
  * Copyright (c) 2020 Anna Schumaker <Anna.Schumaker@xxxxxxxxxx>
  */
 #include <linux/sunrpc/clnt.h>
+#include <linux/sunrpc/addr.h>
+#include <linux/sunrpc/xprtsock.h>
 #include <linux/kobject.h>
 #include "sysfs.h"
 
@@ -55,6 +57,37 @@ int rpc_sysfs_init(void)
 	return 0;
 }
 
+static ssize_t rpc_netns_dstaddr_show(struct kobject *kobj,
+		struct kobj_attribute *attr, char *buf)
+{
+	struct rpc_netns_client *c = container_of(kobj,
+				struct rpc_netns_client, kobject);
+	struct rpc_clnt *clnt = c->clnt;
+	struct rpc_xprt *xprt = rcu_dereference(clnt->cl_xprt);
+
+	return rpc_ntop((struct sockaddr *)&xprt->addr, buf, PAGE_SIZE);
+}
+
+static ssize_t rpc_netns_dstaddr_store(struct kobject *kobj,
+		struct kobj_attribute *attr, const char *buf, size_t count)
+{
+	struct rpc_netns_client *c = container_of(kobj,
+				struct rpc_netns_client, kobject);
+	struct rpc_clnt *clnt = c->clnt;
+	struct rpc_xprt *xprt = rcu_dereference(clnt->cl_xprt);
+	struct sockaddr *saddr = (struct sockaddr *)&xprt->addr;
+	int port = rpc_get_port(saddr);
+
+	xprt->addrlen = rpc_pton(xprt->xprt_net, buf, count - 1, saddr, sizeof(*saddr));
+	rpc_set_port(saddr, port);
+
+	kfree(xprt->address_strings[RPC_DISPLAY_ADDR]);
+	xprt->address_strings[RPC_DISPLAY_ADDR] = kstrndup(buf, count - 1, GFP_KERNEL);
+
+	xprt->ops->connect(xprt, NULL);
+	return count;
+}
+
 static void rpc_netns_client_release(struct kobject *kobj)
 {
 	struct rpc_netns_client *c;
@@ -68,8 +101,17 @@ static const void *rpc_netns_client_namespace(struct kobject *kobj)
 	return container_of(kobj, struct rpc_netns_client, kobject)->net;
 }
 
+static struct kobj_attribute rpc_netns_client_dstaddr = __ATTR(dstaddr,
+		0644, rpc_netns_dstaddr_show, rpc_netns_dstaddr_store);
+
+static struct attribute *rpc_netns_client_attrs[] = {
+	&rpc_netns_client_dstaddr.attr,
+	NULL,
+};
+
 static struct kobj_type rpc_netns_client_type = {
 	.release = rpc_netns_client_release,
+	.default_attrs = rpc_netns_client_attrs,
 	.sysfs_ops = &kobj_sysfs_ops,
 	.namespace = rpc_netns_client_namespace,
 };
@@ -100,10 +142,15 @@ static struct rpc_netns_client *rpc_netns_client_alloc(struct kobject *parent,
 void rpc_netns_sysfs_setup(struct rpc_clnt *clnt, struct net *net)
 {
 	struct rpc_netns_client *rpc_client;
+	struct rpc_xprt *xprt = rcu_dereference(clnt->cl_xprt);
+
+	if (!(xprt->prot & (IPPROTO_TCP | XPRT_TRANSPORT_RDMA)))
+		return;
 
 	rpc_client = rpc_netns_client_alloc(rpc_client_kobj, net, clnt->cl_clid);
 	if (rpc_client) {
 		clnt->cl_sysfs = rpc_client;
+		rpc_client->clnt = clnt;
 		kobject_uevent(&rpc_client->kobject, KOBJ_ADD);
 	}
 }
diff --git a/net/sunrpc/sysfs.h b/net/sunrpc/sysfs.h
index 279a836594e7..137a12c87954 100644
--- a/net/sunrpc/sysfs.h
+++ b/net/sunrpc/sysfs.h
@@ -8,6 +8,7 @@
 struct rpc_netns_client {
 	struct kobject kobject;
 	struct net *net;
+	struct rpc_clnt *clnt;
 };
 
 extern struct kobject *rpc_client_kobj;
-- 
2.29.2