2 files changed, 95 insertions, 2 deletions

diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
index c1e467e1b07d..7389804e3bb7 100644
--- a/net/sunrpc/clnt.c
+++ b/net/sunrpc/clnt.c
@@ -288,6 +288,7 @@ struct rpc_clnt *rpc_create(struct rpc_create_args *args)
                 .srcaddr = args->saddress,
                 .dstaddr = args->address,
                 .addrlen = args->addrsize,
+                .bc_xprt = args->bc_xprt,
         };
         char servername[48];
 
diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
index d9a2b815714e..bee415465754 100644
--- a/net/sunrpc/xprtsock.c
+++ b/net/sunrpc/xprtsock.c
@@ -2468,11 +2468,93 @@ static struct rpc_xprt *xs_setup_tcp(struct xprt_create *args)
         return ERR_PTR(-EINVAL);
 }
 
+/**
+ * xs_setup_bc_tcp - Set up transport to use a TCP backchannel socket
+ * @args: rpc transport creation arguments
+ *
+ */
+static struct rpc_xprt *xs_setup_bc_tcp(struct xprt_create *args)
+{
+        struct sockaddr *addr = args->dstaddr;
+        struct rpc_xprt *xprt;
+        struct sock_xprt *transport;
+        struct svc_sock *bc_sock;
+
+        if (!args->bc_xprt)
+                ERR_PTR(-EINVAL);
+
+        xprt = xs_setup_xprt(args, xprt_tcp_slot_table_entries);
+        if (IS_ERR(xprt))
+                return xprt;
+        transport = container_of(xprt, struct sock_xprt, xprt);
+
+        xprt->prot = IPPROTO_TCP;
+        xprt->tsh_size = sizeof(rpc_fraghdr) / sizeof(u32);
+        xprt->max_payload = RPC_MAX_FRAGMENT_SIZE;
+        xprt->timeout = &xs_tcp_default_timeout;
+
+        /* backchannel */
+        xprt_set_bound(xprt);
+        xprt->bind_timeout = 0;
+        xprt->connect_timeout = 0;
+        xprt->reestablish_timeout = 0;
+        xprt->idle_timeout = 0;
+
+        /*
+         * The backchannel uses the same socket connection as the
+         * forechannel
+         */
+        xprt->bc_xprt = args->bc_xprt;
+        bc_sock = container_of(args->bc_xprt, struct svc_sock, sk_xprt);
+        bc_sock->sk_bc_xprt = xprt;
+        transport->sock = bc_sock->sk_sock;
+        transport->inet = bc_sock->sk_sk;
+
+        xprt->ops = &bc_tcp_ops;
+
+        switch (addr->sa_family) {
+        case AF_INET:
+                xs_format_peer_addresses(xprt, "tcp",
+                                         RPCBIND_NETID_TCP);
+                break;
+        case AF_INET6:
+                xs_format_peer_addresses(xprt, "tcp",
+                                   RPCBIND_NETID_TCP6);
+                break;
+        default:
+                kfree(xprt);
+                return ERR_PTR(-EAFNOSUPPORT);
+        }
+
+        if (xprt_bound(xprt))
+                dprintk("RPC:       set up xprt to %s (port %s) via %s\n",
+                                xprt->address_strings[RPC_DISPLAY_ADDR],
+                                xprt->address_strings[RPC_DISPLAY_PORT],
+                                xprt->address_strings[RPC_DISPLAY_PROTO]);
+        else
+                dprintk("RPC:       set up xprt to %s (autobind) via %s\n",
+                                xprt->address_strings[RPC_DISPLAY_ADDR],
+                                xprt->address_strings[RPC_DISPLAY_PROTO]);
+
+        /*
+         * Since we don't want connections for the backchannel, we set
+         * the xprt status to connected
+         */
+        xprt_set_connected(xprt);
+
+
+        if (try_module_get(THIS_MODULE))
+                return xprt;
+        kfree(xprt->slot);
+        kfree(xprt);
+        return ERR_PTR(-EINVAL);
+}
+
 static struct xprt_class        xs_udp_transport = {
         .list           = LIST_HEAD_INIT(xs_udp_transport.list),
         .name           = "udp",
         .owner          = THIS_MODULE,
-        .ident          = IPPROTO_UDP,
+        .ident          = XPRT_TRANSPORT_UDP,
         .setup          = xs_setup_udp,
 };
 
@@ -2480,10 +2562,18 @@ static struct xprt_class	xs_tcp_transport = {
         .list           = LIST_HEAD_INIT(xs_tcp_transport.list),
         .name           = "tcp",
         .owner          = THIS_MODULE,
-        .ident          = IPPROTO_TCP,
+        .ident          = XPRT_TRANSPORT_TCP,
         .setup          = xs_setup_tcp,
 };
 
+static struct xprt_class        xs_bc_tcp_transport = {
+        .list           = LIST_HEAD_INIT(xs_bc_tcp_transport.list),
+        .name           = "tcp NFSv4.1 backchannel",
+        .owner          = THIS_MODULE,
+        .ident          = XPRT_TRANSPORT_BC_TCP,
+        .setup          = xs_setup_bc_tcp,
+};
+
 /**
  * init_socket_xprt - set up xprtsock's sysctls, register with RPC client
  *
@@ -2497,6 +2587,7 @@ int init_socket_xprt(void)
 
         xprt_register_transport(&xs_udp_transport);
         xprt_register_transport(&xs_tcp_transport);
+        xprt_register_transport(&xs_bc_tcp_transport);
 
         return 0;
 }
@@ -2516,6 +2607,7 @@ void cleanup_socket_xprt(void)
 
         xprt_unregister_transport(&xs_udp_transport);
         xprt_unregister_transport(&xs_tcp_transport);
+        xprt_unregister_transport(&xs_bc_tcp_transport);
 }
 
 static int param_set_uint_minmax(const char *val, struct kernel_param *kp,