SUNRPC: add a new svc_find_listener helper

svc_find_listener will return the transport instance pointer for the
endpoint accepting connections/peer traffic from the specified transport
class and matching sockaddr.
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

include/linux/sunrpc/svc_xprt.h

@@ -150,6 +150,8 @@ void	svc_xprt_copy_addrs(struct svc_rqst *rqstp, struct svc_xprt *xprt);
 void	svc_xprt_close(struct svc_xprt *xprt);
 int	svc_port_is_privileged(struct sockaddr *sin);
 int	svc_print_xprts(char *buf, int maxlen);
+struct svc_xprt *svc_find_listener(struct svc_serv *serv, const char *xcl_name,
+				   struct net *net, const struct sockaddr *sa);
 struct	svc_xprt *svc_find_xprt(struct svc_serv *serv, const char *xcl_name,
 			struct net *net, const sa_family_t af,
 			const unsigned short port);

net/sunrpc/svc_xprt.c

@@ -1276,6 +1276,40 @@ static struct svc_deferred_req *svc_deferred_dequeue(struct svc_xprt *xprt)
 	return dr;
 }
 
+/**
+ * svc_find_listener - find an RPC transport instance
+ * @serv: pointer to svc_serv to search
+ * @xcl_name: C string containing transport's class name
+ * @net: owner net pointer
+ * @sa: sockaddr containing address
+ *
+ * Return the transport instance pointer for the endpoint accepting
+ * connections/peer traffic from the specified transport class,
+ * and matching sockaddr.
+ */
+struct svc_xprt *svc_find_listener(struct svc_serv *serv, const char *xcl_name,
+				   struct net *net, const struct sockaddr *sa)
+{
+	struct svc_xprt *xprt;
+	struct svc_xprt *found = NULL;
+
+	spin_lock_bh(&serv->sv_lock);
+	list_for_each_entry(xprt, &serv->sv_permsocks, xpt_list) {
+		if (xprt->xpt_net != net)
+			continue;
+		if (strcmp(xprt->xpt_class->xcl_name, xcl_name))
+			continue;
+		if (!rpc_cmp_addr_port(sa, (struct sockaddr *)&xprt->xpt_local))
+			continue;
+		found = xprt;
+		svc_xprt_get(xprt);
+		break;
+	}
+	spin_unlock_bh(&serv->sv_lock);
+	return found;
+}
+EXPORT_SYMBOL_GPL(svc_find_listener);
+
 /**
  * svc_find_xprt - find an RPC transport instance
  * @serv: pointer to svc_serv to search