[10/39] wimax: Generic messaging interface between user space and driver/device

diff --git a/net/wimax/op-msg.c b/net/wimax/op-msg.c
new file mode 100644
index 0000000..cfa7929
--- /dev/null
+++ b/net/wimax/op-msg.c
@@ -0,0 +1,495 @@ 
+/*
+ * Linux WiMAX
+ * Generic messaging interface between userspace and driver/device
+ *
+ *
+ * Copyright (C) 2007-2008 Intel Corporation <linux-wimax@intel.com>
+ * Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License version
+ * 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ *
+ *
+ * This implements a direct communication channel between user space and
+ * the driver/device, by which free form messages can be sent back and
+ * forth.
+ *
+ * This is intended for device-specific features, vendor quirks, etc.
+ *
+ * By default, all devices get one default pipe ("the messaging
+ * pipe").
+ *
+ * Due to limitations in the way generic netlink is implemented (no
+ * multicast from user space clients to the kernel), the messaging
+ * pipe is the only way to send messages from user space to the
+ * driver.
+ *
+ * However, devices can create as many kernel-to-user pipes as
+ * needed.
+ *
+ * The functions wimax.h:wimax_msg_*() operate identical to
+ * wimax_pipe_msg*(), but over the default pipe.
+ *
+ * See include/net/wimax.h
+ *
+ * GENERIC NETLINK ENCODING AND CAPACITY
+ *
+ * Messages are encoded as a binary netlink attribute using nla_put()
+ * using type NLA_UNSPEC (as some versions of libnl still in
+ * deployment don't yet understand NLA_BINARY).
+ *
+ * The maximum capacity of this transport is undetermined. Sending of
+ * messages up to 4k has been tested with success. Bigger buffers
+ * beware.
+ *
+ * RECEPTION OF MESSAGES
+ *
+ * When a message is received from user space, it is passed verbatim
+ * to the driver calling wimax_dev->op_msg_from_user(). The return
+ * value from this function is passed back to user space as an ack
+ * over the generic netlink protocol.
+ *
+ * Remember these messages from user space to the kernel always
+ * operate over the default pipe.
+ *
+ * The stack doesn't do any processing or interpretation of these
+ * messages.
+ *
+ * SENDING MESSAGES
+ *
+ * Messages can be sent with wimax_[pipe_]msg().
+ *
+ * If the message delivery needs to happen on a different context to
+ * that of its creation, wimax_[pipe_]msg_alloc() can be used to get a
+ * pointer to the message that can be delivered later on with
+ * wimax_[pipe_]msg_send().
+ *
+ * ROADMAP
+ *
+ * wimax_gnl_doit_msg_from_user()    Process a message from user space
+ *   wimax_dev_get_by_genl_info()
+ *   wimax_dev->op_msg_from_user()   Delivery of message to the driver
+ *
+ * wimax_pipe_msg()                  Send a message to user space
+ *   wimax_pipe_msg_alloc()
+ *   wimax_pipe_msg_send()
+ *
+ * wimax_pipe_add()		     Create a new pipe
+ * wimax_pipe_rm()                   Remove a pipe
+ */
+#include <linux/device.h>
+#include <net/genetlink.h>
+#include <linux/netdevice.h>
+#include <linux/wimax.h>
+#include <linux/security.h>
+#include "wimax-internal.h"
+
+
+#define D_SUBMODULE op_msg
+#include "debug-levels.h"
+
+
+/**
+ * wimax_pipe_add - Create a new messaging pipe
+ *
+ * @wimax_dev: WiMAX device descriptor (properly referenced)
+ *
+ * @name: Name of the new pipe
+ *
+ * Returns: Positive pipe ID descriptor [for to wimax_pipe_msg*()].
+ *     Negative errno code on error.
+ *
+ * Description:
+ *
+ * Creates a new pipe for sending messages or notifications to user
+ * space. User space can read them by receiving from the @name generic
+ * netlink multicast group associated to @wimax_dev.
+ *
+ * We allow running this when the device is still uninitialized. Not
+ * so when the device is being torn down.
+ */
+struct wimax_pipe *wimax_pipe_add(struct wimax_dev *wimax_dev,
+				  const char *name)
+{
+	int result;
+	struct device *dev = wimax_dev_to_dev(wimax_dev);
+	struct wimax_pipe *pipe;
+
+	d_fnstart(3, dev, "(wimax_dev %p name %s)\n", wimax_dev, name);
+	result = -ENOMEM;
+	pipe = kzalloc(sizeof(*pipe), GFP_KERNEL);
+	if (pipe == NULL) {
+		dev_err(dev, "cannot allocate pipe '%s': %d\n",
+			name, result);
+		goto error_kzalloc;
+	}
+
+	snprintf(pipe->mcg.name, sizeof(pipe->mcg.name), name);
+	result = genl_register_mc_group(&wimax_dev->gnl_family, &pipe->mcg);
+	if (unlikely(result < 0)) {
+		dev_err(dev, "cannot register pipe '%s': %d\n",
+			name, result);
+		goto error_register_mc_group;
+	}
+	mutex_lock(&wimax_dev->mutex);
+	list_add_tail(&pipe->list_node, &wimax_dev->pipe_list);
+	mutex_unlock(&wimax_dev->mutex);
+	d_fnstart(3, dev, "(wimax_dev %p name %s) = %p\n",
+		  wimax_dev, name, pipe);
+	return pipe;
+
+error_register_mc_group:
+	kfree(pipe);
+error_kzalloc:
+	d_fnstart(3, dev, "(wimax_dev %p name %s) = %d\n",
+		  wimax_dev, name, result);
+	return ERR_PTR(result);
+}
+EXPORT_SYMBOL_GPL(wimax_pipe_add);
+
+
+/*
+ * Remove a pipe with locking (lock assumed taken)
+ *
+ * We do it like this to avoid calling the generic netlink code with
+ * the lock held -- the lockdep validator will complain in some false
+ * positive cases.
+ */
+void __wimax_pipe_rm(struct wimax_dev *wimax_dev, struct wimax_pipe *pipe)
+{
+	struct device *dev = wimax_dev_to_dev(wimax_dev);
+
+	d_fnstart(3, dev, "(wimax_dev %p pipe %p)\n", wimax_dev, pipe);
+	list_del(&pipe->list_node);
+	genl_unregister_mc_group(&wimax_dev->gnl_family, &pipe->mcg);
+	kfree(pipe);
+	d_fnend(3, dev, "(wimax_dev %p pipe %p) = void\n", wimax_dev, pipe);
+}
+
+
+/**
+ * wimax_pipe_rm - Remove a messaging pipe
+ *
+ * @wimax_dev: WiMAX device descriptor (properly referenced)
+ *
+ * @name: name of the pipe to remove
+ *
+ * Removes a messaging pipe previously created with wimax_pipe_add().
+ */
+void wimax_pipe_rm(struct wimax_dev *wimax_dev, struct wimax_pipe *pipe)
+{
+	struct device *dev = wimax_dev_to_dev(wimax_dev);
+
+	d_fnstart(3, dev, "(wimax_dev %p pipe %p)\n", wimax_dev, pipe);
+	mutex_lock(&wimax_dev->mutex);
+	list_del(&pipe->list_node);
+	mutex_unlock(&wimax_dev->mutex);
+	genl_unregister_mc_group(&wimax_dev->gnl_family, &pipe->mcg);
+	kfree(pipe);
+	d_fnend(3, dev, "(wimax_dev %p pipe %p) = void\n", wimax_dev, pipe);
+}
+EXPORT_SYMBOL_GPL(wimax_pipe_rm);
+
+
+/**
+ * wimax_pipe_msg_alloc - Create a new skb for sending a message to userspace
+ *
+ * @wimax_dev: WiMAX device descriptor
+ * @msg: pointer to the message data to send
+ * @size: size of the message to send (in bytes), including the header.
+ * @gfp_flags: flags for memory allocation.
+ *
+ * Returns: %0 if ok, negative errno code on error
+ *
+ * Description:
+ *
+ * Allocates an skb that will contain the message to send to user
+ * space over the messaging pipe and initializes it, copying the
+ * payload.
+ *
+ * Once this call is done, you can deliver it with
+ * wimax_pipe_msg_send().
+ *
+ * IMPORTANT:
+ *
+ * Don't use skb_push()/skb_pull()/skb_reserve() on the skb, as
+ * wimax_pipe_msg_send() depends on skb->data being placed at the
+ * beginning of the user message.
+ */
+struct sk_buff *wimax_pipe_msg_alloc(struct wimax_dev *wimax_dev,
+				     const void *msg, size_t size,
+				     gfp_t gfp_flags)
+{
+	int result;
+	struct device *dev = wimax_dev->net_dev->dev.parent;
+	void *genl_msg;
+	struct sk_buff *skb;
+
+	skb = genlmsg_new(nla_total_size(size), gfp_flags);
+	if (skb == NULL)
+		return NULL;
+	genl_msg = genlmsg_put(skb, 0, 0, &wimax_dev->gnl_family,
+			       0, WIMAX_GNL_OP_MSG_TO_USER);
+	if (genl_msg == NULL) {
+		dev_err(dev, "no memory to create generic netlink message\n");
+		goto error_genlmsg_put;
+	}
+	result = nla_put(skb, WIMAX_GNL_MSG_DATA, size, msg);
+	if (result == -1) {
+		dev_err(dev, "no memory to add payload in attribute\n");
+		goto error_nla_put;
+	}
+	genlmsg_end(skb, genl_msg);
+	return skb;
+
+error_nla_put:
+error_genlmsg_put:
+	nlmsg_free(skb);
+	return ERR_PTR(-ENOMEM);
+
+}
+EXPORT_SYMBOL_GPL(wimax_pipe_msg_alloc);
+
+
+/**
+ * wimax_msg_data - Return a pointer to a message's payload
+ *
+ * @msg: Pointer to a message created with wimax_pipe_msg_alloc()
+ */
+const void *wimax_msg_data(struct sk_buff *msg)
+{
+	struct nlmsghdr *nlh = (void *) msg->head;
+	struct nlattr *nla;
+
+	nla = nlmsg_find_attr(nlh, sizeof(struct genlmsghdr),
+			      WIMAX_GNL_MSG_DATA);
+	if (nla == NULL) {
+		printk(KERN_ERR "Cannot find attribute WIMAX_GNL_MSG_DATA\n");
+		return NULL;
+	}
+	return nla_data(nla);
+}
+EXPORT_SYMBOL_GPL(wimax_msg_data);
+
+
+/**
+ * wimax_msg_len - Return a message's payload length
+ *
+ * @msg: Pointer to a message created with wimax_pipe_msg_alloc()
+ */
+ssize_t wimax_msg_len(struct sk_buff *msg)
+{
+	struct nlmsghdr *nlh = (void *) msg->head;
+	struct nlattr *nla;
+
+	nla = nlmsg_find_attr(nlh, sizeof(struct genlmsghdr),
+			      WIMAX_GNL_MSG_DATA);
+	if (nla == NULL) {
+		printk(KERN_ERR "Cannot find attribute WIMAX_GNL_MSG_DATA\n");
+		return -EINVAL;
+	}
+	return nla_len(nla);
+}
+EXPORT_SYMBOL_GPL(wimax_msg_len);
+
+
+/**
+ * wimax_pipe_msg_send - Send a pre-allocated message to user space
+ *
+ * @wimax_dev: WiMAX device descriptor
+ *
+ * @pipe: Pipe handle, as returned by wimax_pipe_add(). For sending
+ *     over the default pipe, use a pipe id of @wimax_dev->pipe_msg.
+ *
+ * @skb: &struct sk_buff returned by wimax_pipe_msg_alloc(). Note the
+ *     ownership of @skb is transferred to this function.
+ *
+ * Returns: 0 if ok, < 0 errno code on error
+ *
+ * Description:
+ *
+ * Sends a free-form message that was preallocated with
+ * wimax_pipe_msg_alloc() and filled up.
+ *
+ * Assumes that once you pass an skb to this function for sending, it
+ * owns it and will release it when done (on success).
+ *
+ * IMPORTANT:
+ *
+ * Don't use skb_push()/skb_pull()/skb_reserve() on the skb, as
+ * wimax_pipe_msg_send() depends on skb->data being placed at the
+ * beginning of the user message.
+ */
+int wimax_pipe_msg_send(struct wimax_dev *wimax_dev, struct wimax_pipe *pipe,
+			struct sk_buff *skb)
+{
+	int result;
+	struct device *dev = wimax_dev->net_dev->dev.parent;
+	void *msg = skb->data;
+	size_t size = skb->len;
+	might_sleep();
+
+	d_printf(1, dev, "CTX: wimax msg, %zu bytes\n", size);
+	d_dump(2, dev, msg, size);
+	result = genlmsg_multicast(skb, 0, pipe->mcg.id, GFP_KERNEL);
+	d_printf(1, dev, "CTX: genl multicast result %d\n", result);
+	if (result == -ESRCH)	/* Nobody connected, ignore it */
+		result = 0;	/* btw, the skb is freed already */
+	return result;
+}
+EXPORT_SYMBOL_GPL(wimax_pipe_msg_send);
+
+
+/**
+ * wimax_pipe_msg - Send a message to user space
+ *
+ * @wimax_dev: WiMAX device descriptor (properly referenced)
+ *
+ * @pipe: Pipe handle, as returned by wimax_pipe_add(). For sending
+ *     over the default pipe, use a pipe id of @wimax_dev->pipe_msg.
+ *
+ *
+ * @buf: pointer to the message to send.
+ *
+ * @size: size of the buffer pointed to by @buf (in bytes).
+ *
+ * @gfp_flags: flags for memory allocation.
+ *
+ * Returns: %0 if ok, negative errno code on error.
+ *
+ * Description:
+ *
+ * Sends a free-form message to user space on the the @pipeid pipe of
+ * device @wimax_dev.
+ *
+ * NOTES:
+ *
+ * Once the @skb is given to this function, who will own it and will
+ * release it when done (unless it returns error).
+ */
+int wimax_pipe_msg(struct wimax_dev *wimax_dev, struct wimax_pipe *pipe,
+		   const void *buf, size_t size, gfp_t gfp_flags)
+{
+	int result = -ENOMEM;
+	struct sk_buff *skb;
+
+	skb = wimax_pipe_msg_alloc(wimax_dev, buf, size, gfp_flags);
+	if (skb == NULL)
+		goto error_msg_new;
+	result = wimax_pipe_msg_send(wimax_dev, pipe, skb);
+error_msg_new:
+	return result;
+}
+EXPORT_SYMBOL_GPL(wimax_pipe_msg);
+
+
+static
+struct nla_policy wimax_gnl_msg_policy[WIMAX_GNL_ATTR_MAX + 1] = {
+	[WIMAX_GNL_MSG_DATA] = {
+		.type = NLA_UNSPEC,	/* libnl doesn't grok BINARY yet */
+	},
+};
+
+
+/*
+ * Relays a message from user space to the driver
+ *
+ * The skb is passed to the driver-specific function with the netlink
+ * and generic netlink headers already stripped.
+ *
+ * This call will block while handling/relaying the message.
+ */
+static
+int wimax_gnl_doit_msg_from_user(struct sk_buff *skb, struct genl_info *info)
+{
+	int result;
+	struct wimax_dev *wimax_dev;
+	struct device *dev;
+	struct nlmsghdr *nlh;
+	struct nlattr *tb[WIMAX_GNL_ATTR_MAX+1];
+	void *msg_buf;
+	size_t msg_len;
+
+	might_sleep();
+	d_fnstart(3, NULL, "(skb %p info %p)\n", skb, info);
+	result = -EPERM;
+	if (security_netlink_recv(skb, CAP_NET_ADMIN))
+		goto error_perm;
+	result = -ENODEV;
+	wimax_dev = wimax_dev_get_by_genl_info(info);
+	if (wimax_dev == NULL)
+		goto error_no_wimax_dev;
+	dev = wimax_dev_to_dev(wimax_dev);
+
+	nlh = (void *) skb->data;
+
+	/* Parse the message to extract arguments */
+	result = nlmsg_parse(nlh, sizeof(struct genlmsghdr),
+			     tb, ARRAY_SIZE(tb),
+			     wimax_gnl_msg_policy);
+	if (result < 0) {
+		dev_err(dev, "WIMAX_GNL_MSG_FROM_USER: "
+			"can't parse message: %d\n", result);
+		goto error_parse;
+	}
+	result = -EINVAL;
+	if (tb[WIMAX_GNL_MSG_DATA] == NULL) {
+		dev_err(dev, "WIMAX_GNL_MSG_FROM_USER: can't find MSG_DATA "
+			"attribute\n");
+		goto error_no_pid;
+	}
+	msg_buf = nla_data(tb[WIMAX_GNL_MSG_DATA]);
+	msg_len = nla_len(tb[WIMAX_GNL_MSG_DATA]);
+
+	mutex_lock(&wimax_dev->mutex);
+	result = wimax_dev_is_ready(wimax_dev);
+	if (result < 0)
+		goto error_not_ready;
+	result = -ENOSYS;
+	if (wimax_dev->op_msg_from_user == NULL)
+		goto error_noop;
+
+	d_printf(1, dev,
+		 "CRX: nlmsghdr len %u type %u flags 0x%04x seq 0x%x pid %u\n",
+		 nlh->nlmsg_len, nlh->nlmsg_type, nlh->nlmsg_flags,
+		 nlh->nlmsg_seq, nlh->nlmsg_pid);
+	d_printf(1, dev, "CRX: wimax message %zu bytes\n", msg_len);
+	d_dump(2, dev, msg_buf, msg_len);
+
+	result = wimax_dev->op_msg_from_user(wimax_dev, msg_buf, msg_len, info);
+error_noop:
+error_not_ready:
+	mutex_unlock(&wimax_dev->mutex);
+error_no_pid:
+error_parse:
+	dev_put(wimax_dev->net_dev);
+error_no_wimax_dev:
+error_perm:
+	d_fnend(3, NULL, "(skb %p info %p) = %d\n", skb, info, result);
+	return result;
+}
+
+
+/*
+ * Generic Netlink glue
+ */
+
+struct genl_ops wimax_gnl_msg_from_user = {
+	.cmd = WIMAX_GNL_OP_MSG_FROM_USER,
+	.flags = 0,
+	.policy = wimax_gnl_msg_policy,
+	.doit = wimax_gnl_doit_msg_from_user,
+	.dumpit = NULL,
+};
+