[PATCH] RPC: allow RPC client's port range to be adjustable

Select an RPC client source port between 650 and 1023 instead of between
1 and 800. The old range conflicts with a number of network services.
Provide sysctls to allow admins to select a different port range.

Note that this doesn't affect user-level RPC library behavior, which
still uses 1 to 800.

Based on a suggestion by Olaf Kirch <[e-mail]>.

Test-plan:
Repeated mount and unmount. Destructive testing. Idle timeouts.

Signed-off-by: Chuck Lever <[e-mail]>
Signed-off-by: Trond Myklebust <[e-mail]>

include/linux/sunrpc/debug.h

···
 	CTL_NLMDEBUG,
 	CTL_SLOTTABLE_UDP,
 	CTL_SLOTTABLE_TCP,
+	CTL_MIN_RESVPORT,
+	CTL_MAX_RESVPORT,
 };
 
 #endif /* _LINUX_SUNRPC_DEBUG_H_ */

include/linux/sunrpc/xprt.h

···
 #define RPC_REPHDRSIZE		4
 
 /*
+ * Parameters for choosing a free port
+ */
+extern unsigned int xprt_min_resvport;
+extern unsigned int xprt_max_resvport;
+
+#define RPC_MIN_RESVPORT	(1U)
+#define RPC_MAX_RESVPORT	(65535U)
+#define RPC_DEF_MIN_RESVPORT	(650U)
+#define RPC_DEF_MAX_RESVPORT	(1023U)
+
+/*
  * This describes a timeout strategy
  */
 struct rpc_timeout {
···
 	unsigned int		to_retries;		/* max # of retries */
 	unsigned char		to_exponential;
 };
+
+struct rpc_task;
+struct rpc_xprt;
 
 /*
  * This describes a complete RPC request
···
 };
 #define rq_svec			rq_snd_buf.head
 #define rq_slen			rq_snd_buf.len
-
-struct rpc_task;
-struct rpc_xprt;
 
 struct rpc_xprt_ops {
 	void		(*set_buffer_size)(struct rpc_xprt *xprt);

net/sunrpc/sysctl.c

···
 
 unsigned int xprt_udp_slot_table_entries = RPC_DEF_SLOT_TABLE;
 unsigned int xprt_tcp_slot_table_entries = RPC_DEF_SLOT_TABLE;
+unsigned int xprt_min_resvport = RPC_DEF_MIN_RESVPORT;
+EXPORT_SYMBOL(xprt_min_resvport);
+unsigned int xprt_max_resvport = RPC_DEF_MAX_RESVPORT;
+EXPORT_SYMBOL(xprt_max_resvport);
+
 
 static unsigned int min_slot_table_size = RPC_MIN_SLOT_TABLE;
 static unsigned int max_slot_table_size = RPC_MAX_SLOT_TABLE;
+static unsigned int xprt_min_resvport_limit = RPC_MIN_RESVPORT;
+static unsigned int xprt_max_resvport_limit = RPC_MAX_RESVPORT;
 
 static ctl_table debug_table[] = {
 	{
···
 		.strategy	= &sysctl_intvec,
 		.extra1		= &min_slot_table_size,
 		.extra2		= &max_slot_table_size
+	},
+	{
+		.ctl_name	= CTL_MIN_RESVPORT,
+		.procname	= "min_resvport",
+		.data		= &xprt_min_resvport,
+		.maxlen		= sizeof(unsigned int),
+		.mode		= 0644,
+		.proc_handler	= &proc_dointvec_minmax,
+		.strategy	= &sysctl_intvec,
+		.extra1		= &xprt_min_resvport_limit,
+		.extra2		= &xprt_max_resvport_limit
+	},
+	{
+		.ctl_name	= CTL_MAX_RESVPORT,
+		.procname	= "max_resvport",
+		.data		= &xprt_max_resvport,
+		.maxlen		= sizeof(unsigned int),
+		.mode		= 0644,
+		.proc_handler	= &proc_dointvec_minmax,
+		.strategy	= &sysctl_intvec,
+		.extra1		= &xprt_min_resvport_limit,
+		.extra2		= &xprt_max_resvport_limit
 	},
 	{ .ctl_name = 0 }
 };

net/sunrpc/xprtsock.c

···
 #include <net/tcp.h>
 
 /*
- * Maximum port number to use when requesting a reserved port.
- */
-#define XS_MAX_RESVPORT		(800U)
-
-/*
  * How many times to try sending a request on a socket before waiting
  * for the socket buffer to clear.
  */
···
 	struct sockaddr_in myaddr = {
 		.sin_family = AF_INET,
 	};
-	int err, port;
+	int err;
+	unsigned short port = xprt->port;
 
-	/* Were we already bound to a given port? Try to reuse it */
-	port = xprt->port;
 	do {
 		myaddr.sin_port = htons(port);
 		err = sock->ops->bind(sock, (struct sockaddr *) &myaddr,
···
 					port);
 			return 0;
 		}
-		if (--port == 0)
-			port = XS_MAX_RESVPORT;
+		if (port <= xprt_min_resvport)
+			port = xprt_max_resvport;
+		else
+			port--;
 	} while (err == -EADDRINUSE && port != xprt->port);
 
 	dprintk("RPC:      can't bind to reserved port (%d).\n", -err);
···
 	.destroy		= xs_destroy,
 };
 
-extern unsigned int xprt_udp_slot_table_entries;
-extern unsigned int xprt_tcp_slot_table_entries;
-
 /**
  * xs_setup_udp - Set up transport to use a UDP socket
  * @xprt: transport to set up
···
 	memset(xprt->slot, 0, slot_table_size);
 
 	xprt->prot = IPPROTO_UDP;
-	xprt->port = XS_MAX_RESVPORT;
+	xprt->port = xprt_max_resvport;
 	xprt->tsh_size = 0;
 	xprt->resvport = capable(CAP_NET_BIND_SERVICE) ? 1 : 0;
 	/* XXX: header size can vary due to auth type, IPv6, etc. */
···
 	memset(xprt->slot, 0, slot_table_size);
 
 	xprt->prot = IPPROTO_TCP;
-	xprt->port = XS_MAX_RESVPORT;
+	xprt->port = xprt_max_resvport;
 	xprt->tsh_size = sizeof(rpc_fraghdr) / sizeof(u32);
 	xprt->resvport = capable(CAP_NET_BIND_SERVICE) ? 1 : 0;
 	xprt->max_payload = RPC_MAX_FRAGMENT_SIZE;