table of contents
IEEE8021_VAP(9) | Kernel Developer's Manual | IEEE8021_VAP(9) |
NAME¶
net80211_vap — 802.11 network layer virtual radio supportSYNOPSIS¶
#include <net80211/ieee80211_var.h> intieee80211_vap_setup(struct ieee80211com *, struct ieee80211vap *, const char name[IFNAMSIZ], int unit, int opmode, int flags, const uint8_t bssid[IEEE80211_ADDR_LEN], const uint8_t macaddr[IEEE80211_ADDR_LEN]); int
ieee80211_vap_attach(struct ieee80211vap *, ifm_change_cb_t media_change, ifm_stat_cb_t media_stat); void
ieee80211_vap_detach(struct ieee80211vap *);
DESCRIPTION¶
The net80211 software layer provides a support framework for drivers that includes a virtual radio API that is exported to users through network interfaces (aka vaps) that are cloned from the underlying device. These interfaces have an operating mode (station, adhoc, hostap, wds, monitor, etc.) that is fixed for the lifetime of the interface. Devices that can support multiple concurrent interfaces allow multiple vaps to be cloned. The virtual radio interface defined by the net80211 layer means that drivers must be structured to follow specific rules. Drivers that support only a single interface at any time must still follow these rules. The virtual radio architecture splits state between a single per-device ieee80211com structure and one or more ieee80211vap structures. Vaps are created with theSIOCIFCREATE2
request. This results in a call into the
driver's ic_vap_create method where the driver can
decide if the request should be accepted.
The vap creation process is done in three steps. First the driver allocates the
data structure with malloc(9). This data structure must have
an ieee80211vap structure at the front but is usually
extended with driver-private state. Next the vap is setup with a call to
ieee80211_vap_setup(). This request initializes
net80211 state but does not activate the interface. The
driver can then override methods setup by net80211 and setup
driver resources before finally calling
ieee80211_vap_attach() to complete the process. Both these
calls must be done without holding any driver locks as work may require the
process block/sleep.
A vap is deleted when an SIOCIFDESTROY
ioctl request is
made or when the device detaches (causing all associated vaps to automatically
be deleted). Delete requests cause the ic_vap_delete
method to be called. Drivers must quiesce the device before calling
ieee80211_vap_detach() to deactivate the vap and isolate it
from activities such as requests from user applications. The driver can then
reclaim resources held by the vap and re-enable device operation. The exact
procedure for quiesceing a device is unspecified but typically it involves
blocking interrupts and stopping transmit and receive processing.
MULTI-VAP OPERATION¶
Drivers are responsible for deciding if multiple vaps can be created and how to manage them. Whether or not multiple concurrent vaps can be supported depends on a device's capabilities. For example, multiple hostap vaps can usually be supported but many devices do not support assigning each vap a unique BSSID. If a device supports hostap operation it can usually support concurrent station mode vaps but possibly with limitations such as losing support for hardware beacon miss support. Devices that are capable of hostap operation and can send and receive 4-address frames should be able to support WDS vaps together with an ap vap. But in contrast some devices cannot support WDS vaps without at least one ap vap (this however can be finessed by forcing the ap vap to not transmit beacon frames). All devices should support the creation of any number of monitor mode vaps concurrent with other vaps but it is the responsibility of the driver to allow this. An important consequence of supporting multiple concurrent vaps is that a driver's iv_newstate method must be written to handle being called for each vap. Where necessary, drivers must track private state for all vaps and not just the one whose state is being changed (e.g. for handling beacon timers the driver may need to know if all vaps that beacon are stopped before stopping the hardware timers).SEE ALSO¶
ieee80211(9), ifnet(9), malloc(9)August 4, 2009 | Debian |