2 .\" Copyright (c) 2004 Bruce M. Simpson <bms@spc.org>
3 .\" Copyright (c) 2004 Darron Broad <darron@kewl.org>
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27 .\" $FreeBSD: src/share/man/man9/ieee80211_node.9,v 1.7 2010/03/29 17:39:38 trasz Exp $
34 .Nd software 802.11 stack node management functions
38 .In netproto/802_11/ieee80211_var.h
40 .Ft struct ieee80211_node *
41 .Fo ieee80211_find_rxnode
42 .Fa "struct ieee80211com *"
43 .Fa "const struct ieee80211_frame_min *"
46 .Ft struct ieee80211_node *
47 .Fo ieee80211_find_rxnode_withkey
48 .Fa "struct ieee80211com *"
49 .Fa "const struct ieee80211_frame_min *"
53 .Ft struct ieee80211_node *
54 .Fn ieee80211_ref_node "struct ieee80211_node *"
57 .Fn ieee80211_unref_node "struct ieee80211_node *"
60 .Fn ieee80211_free_node "struct ieee80211_node *"
63 .Fo ieee80211_iterate_nodes
64 .Fa "struct ieee80211_node_table *"
65 .Fa "ieee80211_iter_func *f"
70 .Fo ieee80211_dump_nodes
71 .Fa "struct ieee80211_node_table *"
75 .Fo ieee80211_dump_node
76 .Fa "struct ieee80211_node *"
81 layer that supports 802.11 device drivers maintains a database of
82 peer stations called the
89 Station mode vaps create an entry for the access point
90 the station is associated to.
91 AP mode vaps create entries for associated stations.
92 Adhoc and mesh mode vaps create entries for neighbor stations.
93 WDS mode vaps create an entry for the peer station.
94 Stations for all vaps reside in the same table; each node
97 field that identifies the vap that created it.
98 In some instances an entry is used by multiple vaps (e.g. for
99 dynamic WDS a station associated to an ap vap may also be the peer
102 Node table entries are reference counted.
103 That is, there is a count of all long term references that determines
104 when an entry may be reclaimed.
105 References are held by every in-flight frame sent to a station to
106 insure the entry is not reclaimed while the frame is queued or otherwise
108 Routines that lookup a table entry return a
110 (i.e. a pointer to a table entry with the reference count incremented).
112 .Fn ieee80211_ref_node
114 .Fn ieee80211_unref_node
115 calls explicitly increment/decrement the reference count of a node,
117 Instead most callers use
118 .Fn ieee80211_free_node
119 to release a reference and, if the count goes to zero, reclaim the
122 The station table and its entries are exposed to drivers in several ways.
123 Each frame transmitted to a station includes a reference to the
124 associated node in the
127 This reference must be reclaimed by the driver when transmit processing
129 For each frame received the driver must lookup the table entry to
130 use in dispatching the frame
132 This lookup implicitly obtains a reference to the table entry and
133 the driver must reclaim the reference when frame processing is completed.
134 Otherwise drivers frequently inspect the contents of the
136 node when handling state machine changes as important information
137 is maintained in the data structure.
139 The node table is opaque to drivers.
140 Entries may be looked up using one of the pre-defined API's or the
141 .Fn ieee80211_iterate_nodes
142 call may be used to iterate through all entries to do per-node
143 processing or implement some non-standard search mechanism.
145 .Fn ieee80211_iterate_nodes
146 is single-threaded per-device
147 and the effort processing involved is fairly
148 substantial so it should be used carefully.
150 Two routines are provided to print the contents of nodes to the console
152 .Fn ieee80211_dump_node
153 displays the contents of a single node while
154 .Fn ieee80211_dump_nodes
155 displays the contents of the specified node table.
156 Nodes may also be displayed using
160 directive and the station node table can be displayed with
162 .Sh DRIVER PRIVATE STATE
163 Node data structures may be extended by the driver to include
164 driver-private state.
165 This is done by overriding the
167 method used to allocate a node table entry.
168 The driver method must allocate a structure that is an extension
174 driver defines a private node structure as:
175 .Bd -literal -offset indent
177 struct ieee80211_node in_node;
182 and then provides a private allocation routine that does this:
183 .Bd -literal -offset indent
184 static struct ieee80211_node *
185 iwi_node_alloc(struct ieee80211vap *vap,
186 const uint8_t mac[IEEE80211_ADDR_LEN])
190 in = malloc(sizeof (struct iwi_node), M_80211_NODE,
199 Note that when reclaiming a node allocated by the driver the
201 must be called to ensure
203 state is reclaimed; for example:
204 .Bd -literal -offset indent
206 iwi_node_free(struct ieee80211_node *ni)
208 struct ieee80211com *ic = ni->ni_ic;
209 struct iwi_softc *sc = ic->ic_ifp->if_softc;
210 struct iwi_node *in = (struct iwi_node *)ni;
212 if (in->in_station != -1)
213 free_unr(sc->sc_unr, in->in_station);
214 sc->sc_node_free(ni); /* invoke net80211 free handler */
218 Beware that care must be taken to avoid holding references that
219 might cause nodes from being reclaimed.
221 will reclaim a node when the last reference is reclaimed in
223 However if a driver holds additional references then
225 will not recognize this and table entries will not be reclaimed.
226 Such references should not be needed if the driver overrides the
231 .Sh KEY TABLE SUPPORT
232 Node table lookups are typically done using a hash of the stations'
234 When receiving frames this is sufficient to find the node table entry
236 But some devices also identify the sending station in the device
237 state received with each frame and this data can be used to optimize
238 lookups on receive using a companion table called the
240 This table records a separate node table reference that can be fetched
241 without any locking using the table index.
242 This logic is handled with the
243 .Fn ieee80211_find_rxnode_withkey
244 call: if a keytab entry is found using the specified index then it is
245 returned directly; otherwise a normal lookup is done and the keytab
246 entry is written using the specified index.
247 If the specified index is
248 .Dv IEEE80211_KEYIX_NONE
249 then a normal lookup is done without a table update.
253 .Xr ieee80211_proto 9