1.\" 2.\" Copyright (c) 2004 Bruce M. Simpson <bms@spc.org> 3.\" Copyright (c) 2004 Darron Broad <darron@kewl.org> 4.\" All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 15.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 16.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 17.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 18.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 19.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 20.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 21.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 22.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 23.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 24.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 25.\" SUCH DAMAGE. 26.\" 27.\" $FreeBSD$ 28.\" 29.Dd April 28, 2010 30.Dt IEEE80211_NODE 9 31.Os 32.Sh NAME 33.Nm ieee80211_node 34.Nd software 802.11 stack node management functions 35.Sh SYNOPSIS 36.In net80211/ieee80211_var.h 37.\" 38.Ft struct ieee80211_node * 39.Fo ieee80211_find_rxnode 40.Fa "struct ieee80211com *" 41.Fa "const struct ieee80211_frame_min *" 42.Fc 43.\" 44.Ft struct ieee80211_node * 45.Fo ieee80211_find_rxnode_withkey 46.Fa "struct ieee80211com *" 47.Fa "const struct ieee80211_frame_min *" 48.Fa "ieee80211_keyix" 49.Fc 50.\" 51.Ft struct ieee80211_node * 52.Fn ieee80211_ref_node "struct ieee80211_node *" 53.\" 54.Ft void 55.Fn ieee80211_unref_node "struct ieee80211_node *" 56.\" 57.Ft void 58.Fn ieee80211_free_node "struct ieee80211_node *" 59.\" 60.Ft void 61.Fo ieee80211_iterate_nodes 62.Fa "struct ieee80211_node_table *" 63.Fa "ieee80211_iter_func *f" 64.Fa "void *arg" 65.Fc 66.\" 67.Ft void 68.Fo ieee80211_dump_nodes 69.Fa "struct ieee80211_node_table *" 70.Fc 71.\" 72.Ft void 73.Fo ieee80211_dump_node 74.Fa "struct ieee80211_node *" 75.Fc 76.Sh DESCRIPTION 77The 78.Nm net80211 79layer that supports 802.11 device drivers maintains a database of 80peer stations called the 81.Dq node table 82in the 83.Vt ic_sta 84entry of the 85.Vt ieee80211com 86structure. 87Station mode vaps create an entry for the access point 88the station is associated to. 89AP mode vaps create entries for associated stations. 90Adhoc and mesh mode vaps create entries for neighbor stations. 91WDS mode vaps create an entry for the peer station. 92Stations for all vaps reside in the same table; each node 93entry has a 94.Vt ni_vap 95field that identifies the vap that created it. 96In some instances an entry is used by multiple vaps (e.g. for 97dynamic WDS a station associated to an ap vap may also be the peer 98of a WDS vap). 99.Pp 100Node table entries are reference counted. 101That is, there is a count of all long term references that determines 102when an entry may be reclaimed. 103References are held by every in-flight frame sent to a station to 104ensure the entry is not reclaimed while the frame is queued or otherwise 105held by a driver. 106Routines that lookup a table entry return a 107.Dq held reference 108(i.e. a pointer to a table entry with the reference count incremented). 109The 110.Fn ieee80211_ref_node 111and 112.Fn ieee80211_unref_node 113calls explicitly increment/decrement the reference count of a node, 114but are rarely used. 115Instead most callers use 116.Fn ieee80211_free_node 117to release a reference and, if the count goes to zero, reclaim the 118table entry. 119.Pp 120The station table and its entries are exposed to drivers in several ways. 121Each frame transmitted to a station includes a reference to the 122associated node in the 123.Vt m_pkthdr.rcvif 124field. 125This reference must be reclaimed by the driver when transmit processing 126is done. 127For each frame received the driver must lookup the table entry to 128use in dispatching the frame 129.Dq up the stack . 130This lookup implicitly obtains a reference to the table entry and 131the driver must reclaim the reference when frame processing is completed. 132Otherwise drivers frequently inspect the contents of the 133.Vt iv_bss 134node when handling state machine changes as important information 135is maintained in the data structure. 136.Pp 137The node table is opaque to drivers. 138Entries may be looked up using one of the pre-defined API's or the 139.Fn ieee80211_iterate_nodes 140call may be used to iterate through all entries to do per-node 141processing or implement some non-standard search mechanism. 142Note that 143.Fn ieee80211_iterate_nodes 144is single-threaded per-device 145and the effort processing involved is fairly 146substantial so it should be used carefully. 147.Pp 148Two routines are provided to print the contents of nodes to the console 149for debugging: 150.Fn ieee80211_dump_node 151displays the contents of a single node while 152.Fn ieee80211_dump_nodes 153displays the contents of the specified node table. 154Nodes may also be displayed using 155.Xr ddb 4 156with the 157.Dq show node 158directive and the station node table can be displayed with 159.Dq show statab . 160.Sh DRIVER PRIVATE STATE 161Node data structures may be extended by the driver to include 162driver-private state. 163This is done by overriding the 164.Vt ic_node_alloc 165method used to allocate a node table entry. 166The driver method must allocate a structure that is an extension 167of the 168.Vt ieee80211_node 169structure. 170For example the 171.Xr iwi 4 172driver defines a private node structure as: 173.Bd -literal -offset indent 174struct iwi_node { 175 struct ieee80211_node in_node; 176 int in_station; 177}; 178.Ed 179.Pp 180and then provides a private allocation routine that does this: 181.Bd -literal -offset indent 182static struct ieee80211_node * 183iwi_node_alloc(struct ieee80211vap *vap, 184 const uint8_t mac[IEEE80211_ADDR_LEN]) 185{ 186 struct iwi_node *in; 187 188 in = malloc(sizeof (struct iwi_node), M_80211_NODE, 189 M_NOWAIT | M_ZERO); 190 if (in == NULL) 191 return NULL; 192 in->in_station = -1; 193 return &in->in_node; 194} 195.Ed 196.Pp 197Note that when reclaiming a node allocated by the driver the 198.Dq parent method 199must be called to ensure 200.Nm net80211 201state is reclaimed; for example: 202.Bd -literal -offset indent 203static void 204iwi_node_free(struct ieee80211_node *ni) 205{ 206 struct ieee80211com *ic = ni->ni_ic; 207 struct iwi_softc *sc = ic->ic_ifp->if_softc; 208 struct iwi_node *in = (struct iwi_node *)ni; 209 210 if (in->in_station != -1) 211 free_unr(sc->sc_unr, in->in_station); 212 sc->sc_node_free(ni); /* invoke net80211 free handler */ 213} 214.Ed 215.Pp 216Beware that care must be taken to avoid holding references that 217might cause nodes from being reclaimed. 218.Nm net80211 219will reclaim a node when the last reference is reclaimed in 220its data structures. 221However if a driver holds additional references then 222.Nm net80211 223will not recognize this and table entries will not be reclaimed. 224Such references should not be needed if the driver overrides the 225.Vt ic_node_cleanup 226and/or 227.Vt ic_node_free 228methods. 229.Sh KEY TABLE SUPPORT 230Node table lookups are typically done using a hash of the stations' 231mac address. 232When receiving frames this is sufficient to find the node table entry 233for the transmitter. 234But some devices also identify the sending station in the device 235state received with each frame and this data can be used to optimize 236lookups on receive using a companion table called the 237.Dq keytab . 238This table records a separate node table reference that can be fetched 239without any locking using the table index. 240This logic is handled with the 241.Fn ieee80211_find_rxnode_withkey 242call: if a keytab entry is found using the specified index then it is 243returned directly; otherwise a normal lookup is done and the keytab 244entry is written using the specified index. 245If the specified index is 246.Dv IEEE80211_KEYIX_NONE 247then a normal lookup is done without a table update. 248.Sh SEE ALSO 249.Xr ddb 9 , 250.Xr ieee80211 9 , 251.Xr ieee80211_proto 9 252