SUNRPC: Support for RPC over AF_LOCAL transports

TI-RPC introduces the capability of performing RPC over AF_LOCAL
sockets.  It uses this mainly for registering and unregistering
local RPC services securely with the local rpcbind, but we could
also conceivably use it as a generic upcall mechanism.

This patch provides a client-side only implementation for the moment.
We might also consider a server-side implementation to provide
AF_LOCAL access to NLM (for statd downcalls, and such like).

Autobinding is not supported on kernel AF_LOCAL transports at this
time.  Kernel ULPs must specify the pathname of the remote endpoint
when an AF_LOCAL transport is created.  rpcbind supports registering
services available via AF_LOCAL, so the kernel could handle it with
some adjustment to ->rpcbind and ->set_port.  But we don't need this
feature for doing upcalls via well-known named sockets.

This has not been tested with ULPs that move a substantial amount of
data.  Thus, I can't attest to how robust the write_space and
congestion management logic is.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

4 files changed, 403 insertions, 4 deletions

diff --git a/include/linux/sunrpc/msg_prot.h b/include/linux/sunrpc/msg_prot.h
index 77e624883393..c68a147939a6 100644
--- a/include/linux/sunrpc/msg_prot.h
+++ b/include/linux/sunrpc/msg_prot.h
@@ -145,6 +145,7 @@ typedef __be32	rpc_fraghdr;
 #define RPCBIND_NETID_TCP       "tcp"
 #define RPCBIND_NETID_UDP6      "udp6"
 #define RPCBIND_NETID_TCP6      "tcp6"
+#define RPCBIND_NETID_LOCAL     "local"
 
 /*
  * Note that RFC 1833 does not put any size restrictions on the
diff --git a/include/linux/sunrpc/xprt.h b/include/linux/sunrpc/xprt.h
index a0f998c07c65..81cce3b3ee66 100644
--- a/include/linux/sunrpc/xprt.h
+++ b/include/linux/sunrpc/xprt.h
@@ -141,7 +141,8 @@ enum xprt_transports {
         XPRT_TRANSPORT_UDP      = IPPROTO_UDP,
         XPRT_TRANSPORT_TCP      = IPPROTO_TCP,
         XPRT_TRANSPORT_BC_TCP   = IPPROTO_TCP | XPRT_TRANSPORT_BC,
-        XPRT_TRANSPORT_RDMA     = 256
+        XPRT_TRANSPORT_RDMA     = 256,
+        XPRT_TRANSPORT_LOCAL    = 257,
 };
 
 struct rpc_xprt {
diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
index 08ed49629b86..b84d7395535e 100644
--- a/net/sunrpc/clnt.c
+++ b/net/sunrpc/clnt.c
@@ -28,7 +28,9 @@
 #include <linux/slab.h>
 #include <linux/utsname.h>
 #include <linux/workqueue.h>
+#include <linux/in.h>
 #include <linux/in6.h>
+#include <linux/un.h>
 
 #include <linux/sunrpc/clnt.h>
 #include <linux/sunrpc/rpc_pipe_fs.h>
@@ -294,6 +296,8 @@ struct rpc_clnt *rpc_create(struct rpc_create_args *args)
          * up a string representation of the passed-in address.
          */
         if (args->servername == NULL) {
+                struct sockaddr_un *sun =
+                                (struct sockaddr_un *)args->address;
                 struct sockaddr_in *sin =
                                 (struct sockaddr_in *)args->address;
                 struct sockaddr_in6 *sin6 =
@@ -301,6 +305,10 @@ struct rpc_clnt *rpc_create(struct rpc_create_args *args)
 
                 servername[0] = '\0';
                 switch (args->address->sa_family) {
+                case AF_LOCAL:
+                        snprintf(servername, sizeof(servername), "%s",
+                                 sun->sun_path);
+                        break;
                 case AF_INET:
                         snprintf(servername, sizeof(servername), "%pI4",
                                  &sin->sin_addr.s_addr);
diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
index 079366974e1f..72abb7358933 100644
--- a/net/sunrpc/xprtsock.c
+++ b/net/sunrpc/xprtsock.c
@@ -19,6 +19,7 @@
  */
 
 #include <linux/types.h>
+#include <linux/string.h>
 #include <linux/slab.h>
 #include <linux/module.h>
 #include <linux/capability.h>
@@ -28,6 +29,7 @@
 #include <linux/in.h>
 #include <linux/net.h>
 #include <linux/mm.h>
+#include <linux/un.h>
 #include <linux/udp.h>
 #include <linux/tcp.h>
 #include <linux/sunrpc/clnt.h>
@@ -45,6 +47,9 @@
 #include <net/tcp.h>
 
 #include "sunrpc.h"
+
+static void xs_close(struct rpc_xprt *xprt);
+
 /*
  * xprtsock tunables
  */
@@ -261,6 +266,11 @@ static inline struct sockaddr *xs_addr(struct rpc_xprt *xprt)
         return (struct sockaddr *) &xprt->addr;
 }
 
+static inline struct sockaddr_un *xs_addr_un(struct rpc_xprt *xprt)
+{
+        return (struct sockaddr_un *) &xprt->addr;
+}
+
 static inline struct sockaddr_in *xs_addr_in(struct rpc_xprt *xprt)
 {
         return (struct sockaddr_in *) &xprt->addr;
@@ -276,23 +286,34 @@ static void xs_format_common_peer_addresses(struct rpc_xprt *xprt)
         struct sockaddr *sap = xs_addr(xprt);
         struct sockaddr_in6 *sin6;
         struct sockaddr_in *sin;
+        struct sockaddr_un *sun;
         char buf[128];
 
-        (void)rpc_ntop(sap, buf, sizeof(buf));
-        xprt->address_strings[RPC_DISPLAY_ADDR] = kstrdup(buf, GFP_KERNEL);
-
         switch (sap->sa_family) {
+        case AF_LOCAL:
+                sun = xs_addr_un(xprt);
+                strlcpy(buf, sun->sun_path, sizeof(buf));
+                xprt->address_strings[RPC_DISPLAY_ADDR] =
+                                                kstrdup(buf, GFP_KERNEL);
+                break;
         case AF_INET:
+                (void)rpc_ntop(sap, buf, sizeof(buf));
+                xprt->address_strings[RPC_DISPLAY_ADDR] =
+                                                kstrdup(buf, GFP_KERNEL);
                 sin = xs_addr_in(xprt);
                 snprintf(buf, sizeof(buf), "%08x", ntohl(sin->sin_addr.s_addr));
                 break;
         case AF_INET6:
+                (void)rpc_ntop(sap, buf, sizeof(buf));
+                xprt->address_strings[RPC_DISPLAY_ADDR] =
+                                                kstrdup(buf, GFP_KERNEL);
                 sin6 = xs_addr_in6(xprt);
                 snprintf(buf, sizeof(buf), "%pi6", &sin6->sin6_addr);
                 break;
         default:
                 BUG();
         }
+
         xprt->address_strings[RPC_DISPLAY_HEX_ADDR] = kstrdup(buf, GFP_KERNEL);
 }
 
@@ -506,6 +527,60 @@ static inline void xs_encode_stream_record_marker(struct xdr_buf *buf)
 }
 
 /**
+ * xs_local_send_request - write an RPC request to an AF_LOCAL socket
+ * @task: RPC task that manages the state of an RPC request
+ *
+ * Return values:
+ *        0:    The request has been sent
+ *   EAGAIN:    The socket was blocked, please call again later to
+ *              complete the request
+ * ENOTCONN:    Caller needs to invoke connect logic then call again
+ *    other:    Some other error occured, the request was not sent
+ */
+static int xs_local_send_request(struct rpc_task *task)
+{
+        struct rpc_rqst *req = task->tk_rqstp;
+        struct rpc_xprt *xprt = req->rq_xprt;
+        struct sock_xprt *transport =
+                                container_of(xprt, struct sock_xprt, xprt);
+        struct xdr_buf *xdr = &req->rq_snd_buf;
+        int status;
+
+        xs_encode_stream_record_marker(&req->rq_snd_buf);
+
+        xs_pktdump("packet data:",
+                        req->rq_svec->iov_base, req->rq_svec->iov_len);
+
+        status = xs_sendpages(transport->sock, NULL, 0,
+                                                xdr, req->rq_bytes_sent);
+        dprintk("RPC:       %s(%u) = %d\n",
+                        __func__, xdr->len - req->rq_bytes_sent, status);
+        if (likely(status >= 0)) {
+                req->rq_bytes_sent += status;
+                req->rq_xmit_bytes_sent += status;
+                if (likely(req->rq_bytes_sent >= req->rq_slen)) {
+                        req->rq_bytes_sent = 0;
+                        return 0;
+                }
+                status = -EAGAIN;
+        }
+
+        switch (status) {
+        case -EAGAIN:
+                status = xs_nospace(task);
+                break;
+        default:
+                dprintk("RPC:       sendmsg returned unrecognized error %d\n",
+                        -status);
+        case -EPIPE:
+                xs_close(xprt);
+                status = -ENOTCONN;
+        }
+
+        return status;
+}
+
+/**
  * xs_udp_send_request - write an RPC request to a UDP socket
  * @task: address of RPC task that manages the state of an RPC request
  *
@@ -788,6 +863,88 @@ static inline struct rpc_xprt *xprt_from_sock(struct sock *sk)
         return (struct rpc_xprt *) sk->sk_user_data;
 }
 
+static int xs_local_copy_to_xdr(struct xdr_buf *xdr, struct sk_buff *skb)
+{
+        struct xdr_skb_reader desc = {
+                .skb            = skb,
+                .offset         = sizeof(rpc_fraghdr),
+                .count          = skb->len - sizeof(rpc_fraghdr),
+        };
+
+        if (xdr_partial_copy_from_skb(xdr, 0, &desc, xdr_skb_read_bits) < 0)
+                return -1;
+        if (desc.count)
+                return -1;
+        return 0;
+}
+
+/**
+ * xs_local_data_ready - "data ready" callback for AF_LOCAL sockets
+ * @sk: socket with data to read
+ * @len: how much data to read
+ *
+ * Currently this assumes we can read the whole reply in a single gulp.
+ */
+static void xs_local_data_ready(struct sock *sk, int len)
+{
+        struct rpc_task *task;
+        struct rpc_xprt *xprt;
+        struct rpc_rqst *rovr;
+        struct sk_buff *skb;
+        int err, repsize, copied;
+        u32 _xid;
+        __be32 *xp;
+
+        read_lock_bh(&sk->sk_callback_lock);
+        dprintk("RPC:       %s...\n", __func__);
+        xprt = xprt_from_sock(sk);
+        if (xprt == NULL)
+                goto out;
+
+        skb = skb_recv_datagram(sk, 0, 1, &err);
+        if (skb == NULL)
+                goto out;
+
+        if (xprt->shutdown)
+                goto dropit;
+
+        repsize = skb->len - sizeof(rpc_fraghdr);
+        if (repsize < 4) {
+                dprintk("RPC:       impossible RPC reply size %d\n", repsize);
+                goto dropit;
+        }
+
+        /* Copy the XID from the skb... */
+        xp = skb_header_pointer(skb, sizeof(rpc_fraghdr), sizeof(_xid), &_xid);
+        if (xp == NULL)
+                goto dropit;
+
+        /* Look up and lock the request corresponding to the given XID */
+        spin_lock(&xprt->transport_lock);
+        rovr = xprt_lookup_rqst(xprt, *xp);
+        if (!rovr)
+                goto out_unlock;
+        task = rovr->rq_task;
+
+        copied = rovr->rq_private_buf.buflen;
+        if (copied > repsize)
+                copied = repsize;
+
+        if (xs_local_copy_to_xdr(&rovr->rq_private_buf, skb)) {
+                dprintk("RPC:       sk_buff copy failed\n");
+                goto out_unlock;
+        }
+
+        xprt_complete_rqst(task, copied);
+
+ out_unlock:
+        spin_unlock(&xprt->transport_lock);
+ dropit:
+        skb_free_datagram(sk, skb);
+ out:
+        read_unlock_bh(&sk->sk_callback_lock);
+}
+
 /**
  * xs_udp_data_ready - "data ready" callback for UDP sockets
  * @sk: socket with data to read
@@ -1573,11 +1730,31 @@ static int xs_bind(struct sock_xprt *transport, struct socket *sock)
         return err;
 }
 
+/*
+ * We don't support autobind on AF_LOCAL sockets
+ */
+static void xs_local_rpcbind(struct rpc_task *task)
+{
+        xprt_set_bound(task->tk_xprt);
+}
+
+static void xs_local_set_port(struct rpc_xprt *xprt, unsigned short port)
+{
+}
 
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 static struct lock_class_key xs_key[2];
 static struct lock_class_key xs_slock_key[2];
 
+static inline void xs_reclassify_socketu(struct socket *sock)
+{
+        struct sock *sk = sock->sk;
+
+        BUG_ON(sock_owned_by_user(sk));
+        sock_lock_init_class_and_name(sk, "slock-AF_LOCAL-RPC",
+                &xs_slock_key[1], "sk_lock-AF_LOCAL-RPC", &xs_key[1]);
+}
+
 static inline void xs_reclassify_socket4(struct socket *sock)
 {
         struct sock *sk = sock->sk;
@@ -1599,6 +1776,9 @@ static inline void xs_reclassify_socket6(struct socket *sock)
 static inline void xs_reclassify_socket(int family, struct socket *sock)
 {
         switch (family) {
+        case AF_LOCAL:
+                xs_reclassify_socketu(sock);
+                break;
         case AF_INET:
                 xs_reclassify_socket4(sock);
                 break;
@@ -1608,6 +1788,10 @@ static inline void xs_reclassify_socket(int family, struct socket *sock)
         }
 }
 #else
+static inline void xs_reclassify_socketu(struct socket *sock)
+{
+}
+
 static inline void xs_reclassify_socket4(struct socket *sock)
 {
 }
@@ -1646,6 +1830,94 @@ out:
         return ERR_PTR(err);
 }
 
+static int xs_local_finish_connecting(struct rpc_xprt *xprt,
+                                      struct socket *sock)
+{
+        struct sock_xprt *transport = container_of(xprt, struct sock_xprt,
+                                                                        xprt);
+
+        if (!transport->inet) {
+                struct sock *sk = sock->sk;
+
+                write_lock_bh(&sk->sk_callback_lock);
+
+                xs_save_old_callbacks(transport, sk);
+
+                sk->sk_user_data = xprt;
+                sk->sk_data_ready = xs_local_data_ready;
+                sk->sk_write_space = xs_udp_write_space;
+                sk->sk_error_report = xs_error_report;
+                sk->sk_allocation = GFP_ATOMIC;
+
+                xprt_clear_connected(xprt);
+
+                /* Reset to new socket */
+                transport->sock = sock;
+                transport->inet = sk;
+
+                write_unlock_bh(&sk->sk_callback_lock);
+        }
+
+        /* Tell the socket layer to start connecting... */
+        xprt->stat.connect_count++;
+        xprt->stat.connect_start = jiffies;
+        return kernel_connect(sock, xs_addr(xprt), xprt->addrlen, 0);
+}
+
+/**
+ * xs_local_setup_socket - create AF_LOCAL socket, connect to a local endpoint
+ * @xprt: RPC transport to connect
+ * @transport: socket transport to connect
+ * @create_sock: function to create a socket of the correct type
+ *
+ * Invoked by a work queue tasklet.
+ */
+static void xs_local_setup_socket(struct work_struct *work)
+{
+        struct sock_xprt *transport =
+                container_of(work, struct sock_xprt, connect_worker.work);
+        struct rpc_xprt *xprt = &transport->xprt;
+        struct socket *sock;
+        int status = -EIO;
+
+        if (xprt->shutdown)
+                goto out;
+
+        clear_bit(XPRT_CONNECTION_ABORT, &xprt->state);
+        status = __sock_create(xprt->xprt_net, AF_LOCAL,
+                                        SOCK_STREAM, 0, &sock, 1);
+        if (status < 0) {
+                dprintk("RPC:       can't create AF_LOCAL "
+                        "transport socket (%d).\n", -status);
+                goto out;
+        }
+        xs_reclassify_socketu(sock);
+
+        dprintk("RPC:       worker connecting xprt %p via AF_LOCAL to %s\n",
+                        xprt, xprt->address_strings[RPC_DISPLAY_ADDR]);
+
+        status = xs_local_finish_connecting(xprt, sock);
+        switch (status) {
+        case 0:
+                dprintk("RPC:       xprt %p connected to %s\n",
+                                xprt, xprt->address_strings[RPC_DISPLAY_ADDR]);
+                xprt_set_connected(xprt);
+                break;
+        case -ENOENT:
+                dprintk("RPC:       xprt %p: socket %s does not exist\n",
+                                xprt, xprt->address_strings[RPC_DISPLAY_ADDR]);
+                break;
+        default:
+                printk(KERN_ERR "%s: unhandled error (%d) connecting to %s\n",
+                                __func__, -status,
+                                xprt->address_strings[RPC_DISPLAY_ADDR]);
+        }
+
+out:
+        xprt_clear_connecting(xprt);
+        xprt_wake_pending_tasks(xprt, status);
+}
+
 static void xs_udp_finish_connecting(struct rpc_xprt *xprt, struct socket *sock)
 {
         struct sock_xprt *transport = container_of(xprt, struct sock_xprt, xprt);
@@ -1930,6 +2202,32 @@ static void xs_connect(struct rpc_task *task)
 }
 
 /**
+ * xs_local_print_stats - display AF_LOCAL socket-specifc stats
+ * @xprt: rpc_xprt struct containing statistics
+ * @seq: output file
+ *
+ */
+static void xs_local_print_stats(struct rpc_xprt *xprt, struct seq_file *seq)
+{
+        long idle_time = 0;
+
+        if (xprt_connected(xprt))
+                idle_time = (long)(jiffies - xprt->last_used) / HZ;
+
+        seq_printf(seq, "\txprt:\tlocal %lu %lu %lu %ld %lu %lu %lu "
+                        "%llu %llu\n",
+                        xprt->stat.bind_count,
+                        xprt->stat.connect_count,
+                        xprt->stat.connect_time,
+                        idle_time,
+                        xprt->stat.sends,
+                        xprt->stat.recvs,
+                        xprt->stat.bad_xids,
+                        xprt->stat.req_u,
+                        xprt->stat.bklog_u);
+}
+
+/**
  * xs_udp_print_stats - display UDP socket-specifc stats
  * @xprt: rpc_xprt struct containing statistics
  * @seq: output file
@@ -2099,6 +2397,21 @@ static void bc_destroy(struct rpc_xprt *xprt)
 {
 }
 
+static struct rpc_xprt_ops xs_local_ops = {
+        .reserve_xprt           = xprt_reserve_xprt,
+        .release_xprt           = xs_tcp_release_xprt,
+        .rpcbind                = xs_local_rpcbind,
+        .set_port               = xs_local_set_port,
+        .connect                = xs_connect,
+        .buf_alloc              = rpc_malloc,
+        .buf_free               = rpc_free,
+        .send_request           = xs_local_send_request,
+        .set_retrans_timeout    = xprt_set_retrans_timeout_def,
+        .close                  = xs_close,
+        .destroy                = xs_destroy,
+        .print_stats            = xs_local_print_stats,
+};
+
 static struct rpc_xprt_ops xs_udp_ops = {
         .set_buffer_size        = xs_udp_set_buffer_size,
         .reserve_xprt           = xprt_reserve_xprt_cong,
@@ -2160,6 +2473,8 @@ static int xs_init_anyaddr(const int family, struct sockaddr *sap)
         };
 
         switch (family) {
+        case AF_LOCAL:
+                break;
         case AF_INET:
                 memcpy(sap, &sin, sizeof(sin));
                 break;
@@ -2207,6 +2522,70 @@ static struct rpc_xprt *xs_setup_xprt(struct xprt_create *args,
         return xprt;
 }
 
+static const struct rpc_timeout xs_local_default_timeout = {
+        .to_initval = 10 * HZ,
+        .to_maxval = 10 * HZ,
+        .to_retries = 2,
+};
+
+/**
+ * xs_setup_local - Set up transport to use an AF_LOCAL socket
+ * @args: rpc transport creation arguments
+ *
+ * AF_LOCAL is a "tpi_cots_ord" transport, just like TCP
+ */
+static struct rpc_xprt *xs_setup_local(struct xprt_create *args)
+{
+        struct sockaddr_un *sun = (struct sockaddr_un *)args->dstaddr;
+        struct sock_xprt *transport;
+        struct rpc_xprt *xprt;
+        struct rpc_xprt *ret;
+
+        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 = 0;
+        xprt->tsh_size = sizeof(rpc_fraghdr) / sizeof(u32);
+        xprt->max_payload = RPC_MAX_FRAGMENT_SIZE;
+
+        xprt->bind_timeout = XS_BIND_TO;
+        xprt->reestablish_timeout = XS_TCP_INIT_REEST_TO;
+        xprt->idle_timeout = XS_IDLE_DISC_TO;
+
+        xprt->ops = &xs_local_ops;
+        xprt->timeout = &xs_local_default_timeout;
+
+        switch (sun->sun_family) {
+        case AF_LOCAL:
+                if (sun->sun_path[0] != '/') {
+                        dprintk("RPC:       bad AF_LOCAL address: %s\n",
+                                        sun->sun_path);
+                        ret = ERR_PTR(-EINVAL);
+                        goto out_err;
+                }
+                xprt_set_bound(xprt);
+                INIT_DELAYED_WORK(&transport->connect_worker,
+                                        xs_local_setup_socket);
+                xs_format_peer_addresses(xprt, "local", RPCBIND_NETID_LOCAL);
+                break;
+        default:
+                ret = ERR_PTR(-EAFNOSUPPORT);
+                goto out_err;
+        }
+
+        dprintk("RPC:       set up xprt to %s via AF_LOCAL\n",
+                        xprt->address_strings[RPC_DISPLAY_ADDR]);
+
+        if (try_module_get(THIS_MODULE))
+                return xprt;
+        ret = ERR_PTR(-EINVAL);
+out_err:
+        xprt_free(xprt);
+        return ret;
+}
+
 static const struct rpc_timeout xs_udp_default_timeout = {
         .to_initval = 5 * HZ,
         .to_maxval = 30 * HZ,
@@ -2448,6 +2827,14 @@ out_err:
         return ret;
 }
 
+static struct xprt_class        xs_local_transport = {
+        .list           = LIST_HEAD_INIT(xs_local_transport.list),
+        .name           = "named UNIX socket",
+        .owner          = THIS_MODULE,
+        .ident          = XPRT_TRANSPORT_LOCAL,
+        .setup          = xs_setup_local,
+};
+
 static struct xprt_class        xs_udp_transport = {
         .list           = LIST_HEAD_INIT(xs_udp_transport.list),
         .name           = "udp",
@@ -2483,6 +2870,7 @@ int init_socket_xprt(void)
                 sunrpc_table_header = register_sysctl_table(sunrpc_table);
 #endif
 
+        xprt_register_transport(&xs_local_transport);
         xprt_register_transport(&xs_udp_transport);
         xprt_register_transport(&xs_tcp_transport);
         xprt_register_transport(&xs_bc_tcp_transport);
@@ -2503,6 +2891,7 @@ void cleanup_socket_xprt(void)
         }
 #endif
 
+        xprt_unregister_transport(&xs_local_transport);
         xprt_unregister_transport(&xs_udp_transport);
         xprt_unregister_transport(&xs_tcp_transport);
         xprt_unregister_transport(&xs_bc_tcp_transport);