SUNRPC: add xprt switch API for printing formatted remote peer addresses

Add a new method to the transport switch API to provide a way to convert
the opaque contents of xprt->addr to a human-readable string.

Test plan:
Compile kernel with CONFIG_NFS enabled.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

include/linux/sunrpc/xprt.h

@@ -51,6 +51,14 @@ struct rpc_timeout {
 	unsigned char		to_exponential;
 };
 
+enum rpc_display_format_t {
+	RPC_DISPLAY_ADDR = 0,
+	RPC_DISPLAY_PORT,
+	RPC_DISPLAY_PROTO,
+	RPC_DISPLAY_ALL,
+	RPC_DISPLAY_MAX,
+};
+
 struct rpc_task;
 struct rpc_xprt;
 struct seq_file;
@@ -103,6 +111,7 @@ struct rpc_rqst {
 
 struct rpc_xprt_ops {
 	void		(*set_buffer_size)(struct rpc_xprt *xprt, size_t sndsize, size_t rcvsize);
+	char *		(*print_addr)(struct rpc_xprt *xprt, enum rpc_display_format_t format);
 	int		(*reserve_xprt)(struct rpc_task *task);
 	void		(*release_xprt)(struct rpc_xprt *xprt, struct rpc_task *task);
 	void		(*rpcbind)(struct rpc_task *task);
@@ -207,6 +216,8 @@ struct rpc_xprt {
 	void			(*old_data_ready)(struct sock *, int);
 	void			(*old_state_change)(struct sock *);
 	void			(*old_write_space)(struct sock *);
+
+	char *			address_strings[RPC_DISPLAY_MAX];
 };
 
 #define XPRT_LAST_FRAG		(1 << 0)

net/sunrpc/xprtsock.c

@@ -125,6 +125,47 @@ static inline void xs_pktdump(char *msg, u32 *packet, unsigned int count)
 }
 #endif
 
+static void xs_format_peer_addresses(struct rpc_xprt *xprt)
+{
+	struct sockaddr_in *addr = (struct sockaddr_in *) &xprt->addr;
+	char *buf;
+
+	buf = kzalloc(20, GFP_KERNEL);
+	if (buf) {
+		snprintf(buf, 20, "%u.%u.%u.%u",
+				NIPQUAD(addr->sin_addr.s_addr));
+	}
+	xprt->address_strings[RPC_DISPLAY_ADDR] = buf;
+
+	buf = kzalloc(8, GFP_KERNEL);
+	if (buf) {
+		snprintf(buf, 8, "%u",
+				ntohs(addr->sin_port));
+	}
+	xprt->address_strings[RPC_DISPLAY_PORT] = buf;
+
+	if (xprt->prot == IPPROTO_UDP)
+		xprt->address_strings[RPC_DISPLAY_PROTO] = "udp";
+	else
+		xprt->address_strings[RPC_DISPLAY_PROTO] = "tcp";
+
+	buf = kzalloc(48, GFP_KERNEL);
+	if (buf) {
+		snprintf(buf, 48, "addr=%u.%u.%u.%u port=%u proto=%s",
+			NIPQUAD(addr->sin_addr.s_addr),
+			ntohs(addr->sin_port),
+			xprt->prot == IPPROTO_UDP ? "udp" : "tcp");
+	}
+	xprt->address_strings[RPC_DISPLAY_ALL] = buf;
+}
+
+static void xs_free_peer_addresses(struct rpc_xprt *xprt)
+{
+	kfree(xprt->address_strings[RPC_DISPLAY_ADDR]);
+	kfree(xprt->address_strings[RPC_DISPLAY_PORT]);
+	kfree(xprt->address_strings[RPC_DISPLAY_ALL]);
+}
+
 #define XS_SENDMSG_FLAGS	(MSG_DONTWAIT | MSG_NOSIGNAL)
 
 static inline int xs_send_head(struct socket *sock, struct sockaddr *addr, int addrlen, struct xdr_buf *xdr, unsigned int base, unsigned int len)
@@ -490,6 +531,7 @@ static void xs_destroy(struct rpc_xprt *xprt)
 
 	xprt_disconnect(xprt);
 	xs_close(xprt);
+	xs_free_peer_addresses(xprt);
 	kfree(xprt->slot);
 }
 
@@ -964,6 +1006,19 @@ static unsigned short xs_get_random_port(void)
 	return rand + xprt_min_resvport;
 }
 
+/**
+ * xs_print_peer_address - format an IPv4 address for printing
+ * @xprt: generic transport
+ * @format: flags field indicating which parts of the address to render
+ */
+static char *xs_print_peer_address(struct rpc_xprt *xprt, enum rpc_display_format_t format)
+{
+	if (xprt->address_strings[format] != NULL)
+		return xprt->address_strings[format];
+	else
+		return "unprintable";
+}
+
 /**
  * xs_set_port - reset the port number in the remote endpoint address
  * @xprt: generic transport
@@ -1019,8 +1074,6 @@ static void xs_udp_connect_worker(void *args)
 	if (xprt->shutdown || !xprt_bound(xprt))
 		goto out;
 
-	dprintk("RPC:      xs_udp_connect_worker for xprt %p\n", xprt);
-
 	/* Start by resetting any existing state */
 	xs_close(xprt);
 
@@ -1034,6 +1087,9 @@ static void xs_udp_connect_worker(void *args)
 		goto out;
 	}
 
+	dprintk("RPC:      worker connecting xprt %p to address: %s\n",
+			xprt, xs_print_peer_address(xprt, RPC_DISPLAY_ALL));
+
 	if (!xprt->inet) {
 		struct sock *sk = sock->sk;
 
@@ -1102,8 +1158,6 @@ static void xs_tcp_connect_worker(void *args)
 	if (xprt->shutdown || !xprt_bound(xprt))
 		goto out;
 
-	dprintk("RPC:      xs_tcp_connect_worker for xprt %p\n", xprt);
-
 	if (!xprt->sock) {
 		/* start from scratch */
 		if ((err = sock_create_kern(PF_INET, SOCK_STREAM, IPPROTO_TCP, &sock)) < 0) {
@@ -1119,6 +1173,9 @@ static void xs_tcp_connect_worker(void *args)
 		/* "close" the socket, preserving the local port */
 		xs_tcp_reuse_connection(xprt);
 
+	dprintk("RPC:      worker connecting xprt %p to address: %s\n",
+			xprt, xs_print_peer_address(xprt, RPC_DISPLAY_ALL));
+
 	if (!xprt->inet) {
 		struct sock *sk = sock->sk;
 
@@ -1260,6 +1317,7 @@ static void xs_tcp_print_stats(struct rpc_xprt *xprt, struct seq_file *seq)
 
 static struct rpc_xprt_ops xs_udp_ops = {
 	.set_buffer_size	= xs_udp_set_buffer_size,
+	.print_addr		= xs_print_peer_address,
 	.reserve_xprt		= xprt_reserve_xprt_cong,
 	.release_xprt		= xprt_release_xprt_cong,
 	.rpcbind		= rpc_getport,
@@ -1277,6 +1335,7 @@ static struct rpc_xprt_ops xs_udp_ops = {
 };
 
 static struct rpc_xprt_ops xs_tcp_ops = {
+	.print_addr		= xs_print_peer_address,
 	.reserve_xprt		= xprt_reserve_xprt,
 	.release_xprt		= xs_tcp_release_xprt,
 	.rpcbind		= rpc_getport,
@@ -1301,8 +1360,6 @@ int xs_setup_udp(struct rpc_xprt *xprt, struct rpc_timeout *to)
 {
 	size_t slot_table_size;
 
-	dprintk("RPC:      setting up udp-ipv4 transport...\n");
-
 	xprt->max_reqs = xprt_udp_slot_table_entries;
 	slot_table_size = xprt->max_reqs * sizeof(xprt->slot[0]);
 	xprt->slot = kzalloc(slot_table_size, GFP_KERNEL);
@@ -1332,6 +1389,10 @@ int xs_setup_udp(struct rpc_xprt *xprt, struct rpc_timeout *to)
 	else
 		xprt_set_timeout(&xprt->timeout, 5, 5 * HZ);
 
+	xs_format_peer_addresses(xprt);
+	dprintk("RPC:      set up transport to address %s\n",
+			xs_print_peer_address(xprt, RPC_DISPLAY_ALL));
+
 	return 0;
 }
 
@@ -1345,8 +1406,6 @@ int xs_setup_tcp(struct rpc_xprt *xprt, struct rpc_timeout *to)
 {
 	size_t slot_table_size;
 
-	dprintk("RPC:      setting up tcp-ipv4 transport...\n");
-
 	xprt->max_reqs = xprt_tcp_slot_table_entries;
 	slot_table_size = xprt->max_reqs * sizeof(xprt->slot[0]);
 	xprt->slot = kzalloc(slot_table_size, GFP_KERNEL);
@@ -1375,5 +1434,9 @@ int xs_setup_tcp(struct rpc_xprt *xprt, struct rpc_timeout *to)
 	else
 		xprt_set_timeout(&xprt->timeout, 2, 60 * HZ);
 
+	xs_format_peer_addresses(xprt);
+	dprintk("RPC:      set up transport to address %s\n",
+			xs_print_peer_address(xprt, RPC_DISPLAY_ALL));
+
 	return 0;
 }