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/* SPDX-License-Identifier: GPL-2.0 */
* This file define the new driver API for Wireless Extensions
* Version : 8 16.3.07
* Authors : Jean Tourrilhes - HPL - <>
* Copyright (c) 2001-2007 Jean Tourrilhes, All Rights Reserved.
#ifndef _IW_HANDLER_H
#define _IW_HANDLER_H
/************************** DOCUMENTATION **************************/
* Initial driver API (1996 -> onward) :
* -----------------------------------
* The initial API just sends the IOCTL request received from user space
* to the driver (via the driver ioctl handler). The driver has to
* handle all the rest...
* The initial API also defines a specific handler in struct net_device
* to handle wireless statistics.
* The initial APIs served us well and has proven a reasonably good design.
* However, there is a few shortcommings :
* o No events, everything is a request to the driver.
* o Large ioctl function in driver with gigantic switch statement
* (i.e. spaghetti code).
* o Driver has to mess up with copy_to/from_user, and in many cases
* does it unproperly. Common mistakes are :
* * buffer overflows (no checks or off by one checks)
* * call copy_to/from_user with irq disabled
* o The user space interface is tied to ioctl because of the use
* copy_to/from_user.
* New driver API (2002 -> onward) :
* -------------------------------
* The new driver API is just a bunch of standard functions (handlers),
* each handling a specific Wireless Extension. The driver just export
* the list of handler it supports, and those will be called apropriately.
* I tried to keep the main advantage of the previous API (simplicity,
* efficiency and light weight), and also I provide a good dose of backward
* compatibility (most structures are the same, driver can use both API
* simultaneously, ...).
* Hopefully, I've also addressed the shortcomming of the initial API.
* The advantage of the new API are :
* o Handling of Extensions in driver broken in small contained functions
* o Tighter checks of ioctl before calling the driver
* o Flexible commit strategy (at least, the start of it)
* o Backward compatibility (can be mixed with old API)
* o Driver doesn't have to worry about memory and user-space issues
* The last point is important for the following reasons :
* o You are now able to call the new driver API from any API you
* want (including from within other parts of the kernel).
* o Common mistakes are avoided (buffer overflow, user space copy
* with irq disabled and so on).
* The Drawback of the new API are :
* o bloat (especially kernel)
* o need to migrate existing drivers to new API
* My initial testing shows that the new API adds around 3kB to the kernel
* and save between 0 and 5kB from a typical driver.
* Also, as all structures and data types are unchanged, the migration is
* quite straightforward (but tedious).
* ---
* The new driver API is defined below in this file. User space should
* not be aware of what's happening down there...
* A new kernel wrapper is in charge of validating the IOCTLs and calling
* the appropriate driver handler. This is implemented in :
* # net/core/wireless.c
* The driver export the list of handlers in :
* # include/linux/netdevice.h (one place)
* The new driver API is available for WIRELESS_EXT >= 13.
* Good luck with migration to the new API ;-)
/* ---------------------- THE IMPLEMENTATION ---------------------- */
* Some of the choice I've made are pretty controversials. Defining an
* API is very much weighting compromises. This goes into some of the
* details and the thinking behind the implementation.
* Implementation goals :
* --------------------
* The implementation goals were as follow :
* o Obvious : you should not need a PhD to understand what's happening,
* the benefit is easier maintenance.
* o Flexible : it should accommodate a wide variety of driver
* implementations and be as flexible as the old API.
* o Lean : it should be efficient memory wise to minimise the impact
* on kernel footprint.
* o Transparent to user space : the large number of user space
* applications that use Wireless Extensions should not need
* any modifications.
* Array of functions versus Struct of functions
* ---------------------------------------------
* 1) Having an array of functions allow the kernel code to access the
* handler in a single lookup, which is much more efficient (think hash
* table here).
* 2) The only drawback is that driver writer may put their handler in
* the wrong slot. This is trivial to test (I set the frequency, the
* bitrate changes). Once the handler is in the proper slot, it will be
* there forever, because the array is only extended at the end.
* 3) Backward/forward compatibility : adding new handler just require
* extending the array, so you can put newer driver in older kernel
* without having to patch the kernel code (and vice versa).
* All handler are of the same generic type
* ----------------------------------------
* That's a feature !!!
* 1) Having a generic handler allow to have generic code, which is more
* efficient. If each of the handler was individually typed I would need
* to add a big switch in the kernel (== more bloat). This solution is
* more scalable, adding new Wireless Extensions doesn't add new code.
* 2) You can use the same handler in different slots of the array. For
* hardware, it may be more efficient or logical to handle multiple
* Wireless Extensions with a single function, and the API allow you to
* do that. (An example would be a single record on the card to control
* both bitrate and frequency, the handler would read the old record,
* modify it according to info->cmd and rewrite it).
* Functions prototype uses union iwreq_data
* -----------------------------------------
* Some would have preferred functions defined this way :
* static int mydriver_ioctl_setrate(struct net_device *dev,
* long rate, int auto)
* 1) The kernel code doesn't "validate" the content of iwreq_data, and
* can't do it (different hardware may have different notion of what a
* valid frequency is), so we don't pretend that we do it.
* 2) The above form is not extendable. If I want to add a flag (for
* example to distinguish setting max rate and basic rate), I would
* break the prototype. Using iwreq_data is more flexible.
* 3) Also, the above form is not generic (see above).
* 4) I don't expect driver developper using the wrong field of the
* union (Doh !), so static typechecking doesn't add much value.
* 5) Lastly, you can skip the union by doing :
* static int mydriver_ioctl_setrate(struct net_device *dev,
* struct iw_request_info *info,
* struct iw_param *rrq,
* char *extra)
* And then adding the handler in the array like this :
* (iw_handler) mydriver_ioctl_setrate, // SIOCSIWRATE
* Using functions and not a registry
* ----------------------------------
* Another implementation option would have been for every instance to
* define a registry (a struct containing all the Wireless Extensions)
* and only have a function to commit the registry to the hardware.
* 1) This approach can be emulated by the current code, but not
* vice versa.
* 2) Some drivers don't keep any configuration in the driver, for them
* adding such a registry would be a significant bloat.
* 3) The code to translate from Wireless Extension to native format is
* needed anyway, so it would not reduce significantely the amount of code.
* 4) The current approach only selectively translate Wireless Extensions
* to native format and only selectively set, whereas the registry approach
* would require to translate all WE and set all parameters for any single
* change.
* 5) For many Wireless Extensions, the GET operation return the current
* dynamic value, not the value that was set.
* This header is <net/iw_handler.h>
* ---------------------------------
* 1) This header is kernel space only and should not be exported to
* user space. Headers in "include/linux/" are exported, headers in
* "include/net/" are not.
* Mixed 32/64 bit issues
* ----------------------
* The Wireless Extensions are designed to be 64 bit clean, by using only
* datatypes with explicit storage size.
* There are some issues related to kernel and user space using different
* memory model, and in particular 64bit kernel with 32bit user space.
* The problem is related to struct iw_point, that contains a pointer
* that *may* need to be translated.
* This is quite messy. The new API doesn't solve this problem (it can't),
* but is a step in the right direction :
* 1) Meta data about each ioctl is easily available, so we know what type
* of translation is needed.
* 2) The move of data between kernel and user space is only done in a single
* place in the kernel, so adding specific hooks in there is possible.
* 3) In the long term, it allows to move away from using ioctl as the
* user space API.
* So many comments and so few code
* --------------------------------
* That's a feature. Comments won't bloat the resulting kernel binary.
/***************************** INCLUDES *****************************/
#include <linux/wireless.h> /* IOCTL user space API */
#include <linux/if_ether.h>
/***************************** VERSION *****************************/
* This constant is used to know which version of the driver API is
* available. Hopefully, this will be pretty stable and no changes
* will be needed...
* I just plan to increment with each new version.
* Changes :
* V2 to V3
* --------
* - Move event definition in <linux/wireless.h>
* - Add Wireless Event support :
* o wireless_send_event() prototype
* o iwe_stream_add_event/point() inline functions
* V3 to V4
* --------
* - Reshuffle IW_HEADER_TYPE_XXX to map IW_PRIV_TYPE_XXX changes
* V4 to V5
* --------
* - Add new spy support : struct iw_spy_data & prototypes
* V5 to V6
* --------
* - Change the way we get to spy_data method for added safety
* - Remove spy #ifdef, they are always on -> cleaner code
* - Add IW_DESCR_FLAG_NOMAX flag for very large requests
* - Start migrating get_wireless_stats to struct iw_handler_def
* V6 to V7
* --------
* - Add struct ieee80211_device pointer in struct iw_public_data
* - Remove (struct iw_point *)->pointer from events and streams
* - Remove spy_offset from struct iw_handler_def
* - Add "check" version of event macros for ieee802.11 stack
* V7 to V8
* ----------
* - Prevent leaking of kernel space in stream on 64 bits.
/**************************** CONSTANTS ****************************/
/* Enhanced spy support available */
/* Special error message for the driver to indicate that we
* should do a commit after return from the iw_handler */
/* Flags available in struct iw_request_info */
#define IW_REQUEST_FLAG_COMPAT 0x0001 /* Compat ioctl call */
/* Type of headers we know about (basically union iwreq_data) */
#define IW_HEADER_TYPE_NULL 0 /* Not available */
#define IW_HEADER_TYPE_CHAR 2 /* char [IFNAMSIZ] */
#define IW_HEADER_TYPE_UINT 4 /* __u32 */
#define IW_HEADER_TYPE_FREQ 5 /* struct iw_freq */
#define IW_HEADER_TYPE_ADDR 6 /* struct sockaddr */
#define IW_HEADER_TYPE_POINT 8 /* struct iw_point */
#define IW_HEADER_TYPE_PARAM 9 /* struct iw_param */
#define IW_HEADER_TYPE_QUAL 10 /* struct iw_quality */
/* Handling flags */
/* Most are not implemented. I just use them as a reminder of some
* cool features we might need one day ;-) */
#define IW_DESCR_FLAG_NONE 0x0000 /* Obvious */
/* Wrapper level flags */
#define IW_DESCR_FLAG_DUMP 0x0001 /* Not part of the dump command */
#define IW_DESCR_FLAG_EVENT 0x0002 /* Generate an event on SET */
#define IW_DESCR_FLAG_RESTRICT 0x0004 /* GET : request is ROOT only */
/* SET : Omit payload from generated iwevent */
#define IW_DESCR_FLAG_NOMAX 0x0008 /* GET : no limit on request size */
/* Driver level flags */
#define IW_DESCR_FLAG_WAIT 0x0100 /* Wait for driver event */
/****************************** TYPES ******************************/
/* ----------------------- WIRELESS HANDLER ----------------------- */
* A wireless handler is just a standard function, that looks like the
* ioctl handler.
* We also define there how a handler list look like... As the Wireless
* Extension space is quite dense, we use a simple array, which is faster
* (that's the perfect hash table ;-).
* Meta data about the request passed to the iw_handler.
* Most handlers can safely ignore what's in there.
* The 'cmd' field might come handy if you want to use the same handler
* for multiple command...
* This struct is also my long term insurance. I can add new fields here
* without breaking the prototype of iw_handler...
struct iw_request_info {
__u16 cmd; /* Wireless Extension command */
__u16 flags; /* More to come ;-) */
struct net_device;
* This is how a function handling a Wireless Extension should look
* like (both get and set, standard and private).
typedef int (*iw_handler)(struct net_device *dev, struct iw_request_info *info,
union iwreq_data *wrqu, char *extra);
* This define all the handler that the driver export.
* As you need only one per driver type, please use a static const
* shared by all driver instances... Same for the members...
* This will be linked from net_device in <linux/netdevice.h>
struct iw_handler_def {
/* Array of handlers for standard ioctls
* We will call dev->wireless_handlers->standard[ioctl - SIOCIWFIRST]
const iw_handler * standard;
/* Number of handlers defined (more precisely, index of the
* last defined handler + 1) */
__u16 num_standard;
__u16 num_private;
/* Number of private arg description */
__u16 num_private_args;
/* Array of handlers for private ioctls
* Will call dev->wireless_handlers->private[ioctl - SIOCIWFIRSTPRIV]
const iw_handler * private;
/* Arguments of private handler. This one is just a list, so you
* can put it in any order you want and should not leave holes...
* We will automatically export that to user space... */
const struct iw_priv_args * private_args;
/* New location of get_wireless_stats, to de-bloat struct net_device.
* The old pointer in struct net_device will be gradually phased
* out, and drivers are encouraged to use this one... */
struct iw_statistics* (*get_wireless_stats)(struct net_device *dev);
/* ---------------------- IOCTL DESCRIPTION ---------------------- */
* One of the main goal of the new interface is to deal entirely with
* user space/kernel space memory move.
* For that, we need to know :
* o if iwreq is a pointer or contain the full data
* o what is the size of the data to copy
* For private IOCTLs, we use the same rules as used by iwpriv and
* defined in struct iw_priv_args.
* For standard IOCTLs, things are quite different and we need to
* use the structures below. Actually, this struct is also more
* efficient, but that's another story...
* Describe how a standard IOCTL looks like.
struct iw_ioctl_description {
__u8 header_type; /* NULL, iw_point or other */
__u8 token_type; /* Future */
__u16 token_size; /* Granularity of payload */
__u16 min_tokens; /* Min acceptable token number */
__u16 max_tokens; /* Max acceptable token number */
__u32 flags; /* Special handling of the request */
/* Need to think of short header translation table. Later. */
/* --------------------- ENHANCED SPY SUPPORT --------------------- */
* In the old days, the driver was handling spy support all by itself.
* Now, the driver can delegate this task to Wireless Extensions.
* It needs to include this struct in its private part and use the
* standard spy iw_handler.
* Instance specific spy data, i.e. addresses spied and quality for them.
struct iw_spy_data {
/* --- Standard spy support --- */
int spy_number;
u_char spy_address[IW_MAX_SPY][ETH_ALEN];
struct iw_quality spy_stat[IW_MAX_SPY];
/* --- Enhanced spy support (event) */
struct iw_quality spy_thr_low; /* Low threshold */
struct iw_quality spy_thr_high; /* High threshold */
u_char spy_thr_under[IW_MAX_SPY];
/* --------------------- DEVICE WIRELESS DATA --------------------- */
* This is all the wireless data specific to a device instance that
* is managed by the core of Wireless Extensions or the 802.11 layer.
* We only keep pointer to those structures, so that a driver is free
* to share them between instances.
* This structure should be initialised before registering the device.
* Access to this data follow the same rules as any other struct net_device
* data (i.e. valid as long as struct net_device exist, same locking rules).
/* Forward declaration */
struct libipw_device;
/* The struct */
struct iw_public_data {
/* Driver enhanced spy support */
struct iw_spy_data * spy_data;
/* Legacy structure managed by the ipw2x00-specific IEEE 802.11 layer */
struct libipw_device * libipw;
/**************************** PROTOTYPES ****************************/
* Functions part of the Wireless Extensions (defined in net/core/wireless.c).
* Those may be called only within the kernel.
/* First : function strictly used inside the kernel */
/* Handle /proc/net/wireless, called in net/code/dev.c */
int dev_get_wireless_info(char *buffer, char **start, off_t offset, int length);
/* Second : functions that may be called by driver modules */
/* Send a single event to user space */
void wireless_send_event(struct net_device *dev, unsigned int cmd,
union iwreq_data *wrqu, const char *extra);
/* flush all previous wext events - if work is done from netdev notifiers */
void wireless_nlevent_flush(void);
static inline void wireless_nlevent_flush(void) {}
/* We may need a function to send a stream of events to user space.
* More on that later... */
/* Standard handler for SIOCSIWSPY */
int iw_handler_set_spy(struct net_device *dev, struct iw_request_info *info,
union iwreq_data *wrqu, char *extra);
/* Standard handler for SIOCGIWSPY */
int iw_handler_get_spy(struct net_device *dev, struct iw_request_info *info,
union iwreq_data *wrqu, char *extra);
/* Standard handler for SIOCSIWTHRSPY */
int iw_handler_set_thrspy(struct net_device *dev, struct iw_request_info *info,
union iwreq_data *wrqu, char *extra);
/* Standard handler for SIOCGIWTHRSPY */
int iw_handler_get_thrspy(struct net_device *dev, struct iw_request_info *info,
union iwreq_data *wrqu, char *extra);
/* Driver call to update spy records */
void wireless_spy_update(struct net_device *dev, unsigned char *address,
struct iw_quality *wstats);
/************************* INLINE FUNTIONS *************************/
* Function that are so simple that it's more efficient inlining them
static inline int iwe_stream_lcp_len(struct iw_request_info *info)
if (info->flags & IW_REQUEST_FLAG_COMPAT)
return IW_EV_LCP_LEN;
static inline int iwe_stream_point_len(struct iw_request_info *info)
if (info->flags & IW_REQUEST_FLAG_COMPAT)
static inline int iwe_stream_event_len_adjust(struct iw_request_info *info,
int event_len)
if (info->flags & IW_REQUEST_FLAG_COMPAT) {
event_len -= IW_EV_LCP_LEN;
event_len += IW_EV_COMPAT_LCP_LEN;
return event_len;
* Wrapper to add an Wireless Event to a stream of events.
char *iwe_stream_add_event(struct iw_request_info *info, char *stream,
char *ends, struct iw_event *iwe, int event_len);
static inline char *
iwe_stream_add_event_check(struct iw_request_info *info, char *stream,
char *ends, struct iw_event *iwe, int event_len)
char *res = iwe_stream_add_event(info, stream, ends, iwe, event_len);
if (res == stream)
return ERR_PTR(-E2BIG);
return res;
* Wrapper to add an short Wireless Event containing a pointer to a
* stream of events.
char *iwe_stream_add_point(struct iw_request_info *info, char *stream,
char *ends, struct iw_event *iwe, char *extra);
static inline char *
iwe_stream_add_point_check(struct iw_request_info *info, char *stream,
char *ends, struct iw_event *iwe, char *extra)
char *res = iwe_stream_add_point(info, stream, ends, iwe, extra);
if (res == stream)
return ERR_PTR(-E2BIG);
return res;
* Wrapper to add a value to a Wireless Event in a stream of events.
* Be careful, this one is tricky to use properly :
* At the first run, you need to have (value = event + IW_EV_LCP_LEN).
char *iwe_stream_add_value(struct iw_request_info *info, char *event,
char *value, char *ends, struct iw_event *iwe,
int event_len);
#endif /* _IW_HANDLER_H */