iw_handler.h

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/*
 * This file define the new driver API for Wireless Extensions
 *
 * Version :    8   16.3.07
 *
 * Authors :    Jean Tourrilhes - HPL - <[email protected]>
 * 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.
 */
#define IW_HANDLER_VERSION  8

/*
 * 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 */
#define IW_WIRELESS_SPY
#define IW_WIRELESS_THRSPY

/* Special error message for the driver to indicate that we
 * should do a commit after return from the iw_handler */
#define EIWCOMMIT   EINPROGRESS

/* 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;

#ifdef CONFIG_WEXT_PRIV
    __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;
#endif

    /* 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 stuctures 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 */
extern 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 */
extern void wireless_send_event(struct net_device * dev,
                unsigned int        cmd,
                union iwreq_data *  wrqu,
                const char *        extra);

/* We may need a function to send a stream of events to user space.
 * More on that later... */

/* Standard handler for SIOCSIWSPY */
extern int iw_handler_set_spy(struct net_device *   dev,
                  struct iw_request_info *  info,
                  union iwreq_data *    wrqu,
                  char *            extra);
/* Standard handler for SIOCGIWSPY */
extern int iw_handler_get_spy(struct net_device *   dev,
                  struct iw_request_info *  info,
                  union iwreq_data *    wrqu,
                  char *            extra);
/* Standard handler for SIOCSIWTHRSPY */
extern int iw_handler_set_thrspy(struct net_device *    dev,
                 struct iw_request_info *info,
                 union iwreq_data * wrqu,
                 char *         extra);
/* Standard handler for SIOCGIWTHRSPY */
extern 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 */
extern 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)
{
#ifdef CONFIG_COMPAT
    if (info->flags & IW_REQUEST_FLAG_COMPAT)
        return IW_EV_COMPAT_LCP_LEN;
#endif
    return IW_EV_LCP_LEN;
}

static inline int iwe_stream_point_len(struct iw_request_info *info)
{
#ifdef CONFIG_COMPAT
    if (info->flags & IW_REQUEST_FLAG_COMPAT)
        return IW_EV_COMPAT_POINT_LEN;
#endif
    return IW_EV_POINT_LEN;
}

static inline int iwe_stream_event_len_adjust(struct iw_request_info *info,
                          int event_len)
{
#ifdef CONFIG_COMPAT
    if (info->flags & IW_REQUEST_FLAG_COMPAT) {
        event_len -= IW_EV_LCP_LEN;
        event_len += IW_EV_COMPAT_LCP_LEN;
    }
#endif

    return event_len;
}

/*------------------------------------------------------------------*/
/*
 * Wrapper to add an Wireless Event to a stream of events.
 */
static inline char *
iwe_stream_add_event(struct iw_request_info *info, char *stream, char *ends,
             struct iw_event *iwe, int event_len)
{
    int lcp_len = iwe_stream_lcp_len(info);

    event_len = iwe_stream_event_len_adjust(info, event_len);

    /* Check if it's possible */
    if(likely((stream + event_len) < ends)) {
        iwe->len = event_len;
        /* Beware of alignement issues on 64 bits */
        memcpy(stream, (char *) iwe, IW_EV_LCP_PK_LEN);
        memcpy(stream + lcp_len, &iwe->u,
               event_len - lcp_len);
        stream += event_len;
    }
    return stream;
}

/*------------------------------------------------------------------*/
/*
 * Wrapper to add an short Wireless Event containing a pointer to a
 * stream of events.
 */
static inline char *
iwe_stream_add_point(struct iw_request_info *info, char *stream, char *ends,
             struct iw_event *iwe, char *extra)
{
    int event_len = iwe_stream_point_len(info) + iwe->u.data.length;
    int point_len = iwe_stream_point_len(info);
    int lcp_len   = iwe_stream_lcp_len(info);

    /* Check if it's possible */
    if(likely((stream + event_len) < ends)) {
        iwe->len = event_len;
        memcpy(stream, (char *) iwe, IW_EV_LCP_PK_LEN);
        memcpy(stream + lcp_len,
               ((char *) &iwe->u) + IW_EV_POINT_OFF,
               IW_EV_POINT_PK_LEN - IW_EV_LCP_PK_LEN);
        memcpy(stream + point_len, extra, iwe->u.data.length);
        stream += event_len;
    }
    return stream;
}

/*------------------------------------------------------------------*/
/*
 * 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).
 */
static inline char *
iwe_stream_add_value(struct iw_request_info *info, char *event, char *value,
             char *ends, struct iw_event *iwe, int event_len)
{
    int lcp_len = iwe_stream_lcp_len(info);

    /* Don't duplicate LCP */
    event_len -= IW_EV_LCP_LEN;

    /* Check if it's possible */
    if(likely((value + event_len) < ends)) {
        /* Add new value */
        memcpy(value, &iwe->u, event_len);
        value += event_len;
        /* Patch LCP */
        iwe->len = value - event;
        memcpy(event, (char *) iwe, lcp_len);
    }
    return value;
}

#endif  /* _IW_HANDLER_H */