802.11 information elements

Many management frames include a section that amounts to a concatenation of these information elements, so that the sender can choose which information to send and the receiver can ignore the parts it doesn't understand. More...


Data Structures

struct  ieee80211_ie_header
 Generic 802.11 information element header. More...
struct  ieee80211_ie_ssid
 802.11 SSID information element More...
struct  ieee80211_ie_rates
 802.11 rates information element More...
struct  ieee80211_ie_ds_param
 802.11 Direct Spectrum parameter information element More...
struct  ieee80211_ie_country_ext_triplet
 802.11 Country information element regulatory extension triplet More...
struct  ieee80211_ie_country_band_triplet
 802.11 Country information element regulatory band triplet More...
union  ieee80211_ie_country_triplet
 802.11 Country information element regulatory triplet More...
struct  ieee80211_ie_country
 802.11 Country information element More...
struct  ieee80211_ie_request
 802.11 Request information element More...
struct  ieee80211_ie_challenge_text
 802.11 Challenge Text information element More...
struct  ieee80211_ie_power_constraint
 802.11 Power Constraint information element More...
struct  ieee80211_ie_power_capab
 802.11 Power Capability information element More...
struct  ieee80211_ie_channels_channel_band
 802.11 Channels information element channel band tuple More...
struct  ieee80211_ie_channels
 802.11 Channels information element More...
struct  ieee80211_ie_erp_info
 802.11 ERP Information information element More...
struct  ieee80211_ie_rsn
 802.11 Robust Security Network ("WPA") information element More...
struct  ieee80211_ie_vendor
 802.11 Vendor Specific information element More...
union  ieee80211_ie
 Any 802.11 information element. More...

Defines

#define IEEE80211_IE_SSID   0
 Information element ID for SSID information element.
#define IEEE80211_IE_RATES   1
 Information element ID for rates information element.
#define IEEE80211_IE_EXT_RATES   50
 Information element ID for extended rates information element.
#define IEEE80211_IE_DS_PARAM   3
 Information element ID for Direct Spectrum parameter information element.
#define IEEE80211_IE_COUNTRY   7
 Information element ID for Country information element.
#define IEEE80211_IE_REQUEST   10
 Information element ID for Request information element.
#define IEEE80211_IE_CHALLENGE_TEXT   16
 Information element ID for Challenge Text information element.
#define IEEE80211_IE_POWER_CONSTRAINT   52
 Information element ID for Power Constraint information element.
#define IEEE80211_IE_POWER_CAPAB   33
 Information element ID for Power Capability information element.
#define IEEE80211_IE_CHANNELS   36
 Information element ID for Channels information element.
#define IEEE80211_IE_ERP_INFO   42
 Information element ID for ERP Information information element.
#define IEEE80211_ERP_NONERP_PRESENT   0x01
 ERP information element: Flag set if 802.11b stations are present.
#define IEEE80211_ERP_USE_PROTECTION   0x02
 ERP information element: Flag set if CTS protection must be used.
#define IEEE80211_ERP_BARKER_LONG   0x04
 ERP information element: Flag set if long preambles must be used.
#define IEEE80211_IE_RSN   48
 Information element ID for Robust Security Network information element.
#define _MKOUI(a, b, c, t)   ( ( ( t ) << 24 ) | ( ( c ) << 16 ) | ( ( b ) << 8 ) | ( a ) )
 Make OUI plus type byte into 32-bit integer for easy comparison.
#define OUI_ORG_MASK   0x00FFFFFF
#define OUI_TYPE_MASK   0xFF000000
#define IEEE80211_RSN_OUI   _MKOUI ( 0x00, 0x0F, 0xAC, 0 )
 Organization part for OUIs in standard RSN IE.
#define IEEE80211_WPA_OUI   _MKOUI ( 0x00, 0x50, 0xF2, 0 )
 Organization part for OUIs in old WPA IE.
#define IEEE80211_WPA_OUI_VEN   _MKOUI ( 0x00, 0x50, 0xF2, 0x01 )
 Old vendor-type WPA IE OUI type + subtype.
#define IEEE80211_RSN_VERSION   1
 802.11 RSN IE: expected version number
#define IEEE80211_RSN_CTYPE_WEP40   _MKOUI ( 0, 0, 0, 0x01 )
 802.11 RSN IE: cipher type for 40-bit WEP
#define IEEE80211_RSN_CTYPE_WEP104   _MKOUI ( 0, 0, 0, 0x05 )
 802.11 RSN IE: cipher type for 104-bit WEP
#define IEEE80211_RSN_CTYPE_TKIP   _MKOUI ( 0, 0, 0, 0x02 )
 802.11 RSN IE: cipher type for TKIP ("WPA")
#define IEEE80211_RSN_CTYPE_CCMP   _MKOUI ( 0, 0, 0, 0x04 )
 802.11 RSN IE: cipher type for CCMP ("WPA2")
#define IEEE80211_RSN_CTYPE_USEGROUP   _MKOUI ( 0, 0, 0, 0x00 )
 802.11 RSN IE: cipher type for "use group"
#define IEEE80211_RSN_ATYPE_8021X   _MKOUI ( 0, 0, 0, 0x01 )
 802.11 RSN IE: auth method type for using an 802.1X server
#define IEEE80211_RSN_ATYPE_PSK   _MKOUI ( 0, 0, 0, 0x02 )
 802.11 RSN IE: auth method type for using a pre-shared key
#define IEEE80211_RSN_CAPAB_PREAUTH   0x001
 802.11 RSN IE capabilities: AP supports pre-authentication
#define IEEE80211_RSN_CAPAB_NO_PAIRWISE   0x002
 802.11 RSN IE capabilities: Node has conflict between TKIP and WEP
#define IEEE80211_RSN_CAPAB_PTKSA_REPLAY   0x00C
 802.11 RSN IE capabilities: Number of PTKSA replay counters
#define IEEE80211_RSN_CAPAB_GTKSA_REPLAY   0x030
 802.11 RSN IE capabilities: Number of GTKSA replay counters
#define IEEE80211_RSN_CAPAB_PEERKEY   0x200
 802.11 RSN IE capabilities: PeerKey Handshaking is suported
#define IEEE80211_RSN_1_CTR   0x000
 802.11 RSN IE capabilities: One replay counter
#define IEEE80211_RSN_2_CTR   0x014
 802.11 RSN IE capabilities: Two replay counters
#define IEEE80211_RSN_4_CTR   0x028
 802.11 RSN IE capabilities: Four replay counters
#define IEEE80211_RSN_16_CTR   0x03C
 802.11 RSN IE capabilities: 16 replay counters
#define IEEE80211_IE_VENDOR   221
 Information element ID for Vendor Specific information element.

Functions

static size_t ieee80211_rsn_size (int npair, int nauth, int npmkid, int rsn_ie)
 Calculate necessary size of RSN information element.
static int ieee80211_ie_bound (union ieee80211_ie *ie, void *end)
 Check that 802.11 information element is bounded by buffer.
static union ieee80211_ie * ieee80211_next_ie (union ieee80211_ie *ie, void *end)
 Advance to next 802.11 information element.

Variables

struct ieee80211_frame packed
 An 802.11 data or management frame without QoS or WDS header fields.

Detailed Description

Many management frames include a section that amounts to a concatenation of these information elements, so that the sender can choose which information to send and the receiver can ignore the parts it doesn't understand.

Each IE contains a two-byte header, one byte ID and one byte length, followed by IE-specific data. The length does not include the two-byte header. Information elements are required to be sorted by ID, but gPXE does not require that in those it receives.

This group also includes a few inline functions to simplify common tasks in IE processing.

Define Documentation

#define IEEE80211_IE_SSID   0

Information element ID for SSID information element.

Definition at line 581 of file ieee80211.h.

Referenced by net80211_marshal_request_info(), net80211_probe_step(), and net80211_process_ie().

#define IEEE80211_IE_RATES   1

Information element ID for rates information element.

Definition at line 599 of file ieee80211.h.

Referenced by net80211_marshal_request_info(), and net80211_process_ie().

#define IEEE80211_IE_EXT_RATES   50

Information element ID for extended rates information element.

Definition at line 602 of file ieee80211.h.

Referenced by net80211_marshal_request_info(), and net80211_process_ie().

#define IEEE80211_IE_DS_PARAM   3

Information element ID for Direct Spectrum parameter information element.

Definition at line 619 of file ieee80211.h.

Referenced by net80211_process_ie().

#define IEEE80211_IE_COUNTRY   7

Information element ID for Country information element.

Definition at line 667 of file ieee80211.h.

Referenced by net80211_process_ie().

#define IEEE80211_IE_REQUEST   10

Information element ID for Request information element.

Definition at line 682 of file ieee80211.h.

#define IEEE80211_IE_CHALLENGE_TEXT   16

Information element ID for Challenge Text information element.

Definition at line 697 of file ieee80211.h.

#define IEEE80211_IE_POWER_CONSTRAINT   52

Information element ID for Power Constraint information element.

Definition at line 712 of file ieee80211.h.

#define IEEE80211_IE_POWER_CAPAB   33

Information element ID for Power Capability information element.

Definition at line 729 of file ieee80211.h.

#define IEEE80211_IE_CHANNELS   36

Information element ID for Channels information element.

Definition at line 753 of file ieee80211.h.

#define IEEE80211_IE_ERP_INFO   42

Information element ID for ERP Information information element.

Definition at line 767 of file ieee80211.h.

Referenced by net80211_process_ie().

#define IEEE80211_ERP_NONERP_PRESENT   0x01

ERP information element: Flag set if 802.11b stations are present.

Definition at line 770 of file ieee80211.h.

#define IEEE80211_ERP_USE_PROTECTION   0x02

ERP information element: Flag set if CTS protection must be used.

Definition at line 773 of file ieee80211.h.

Referenced by net80211_process_ie().

#define IEEE80211_ERP_BARKER_LONG   0x04

ERP information element: Flag set if long preambles must be used.

Definition at line 776 of file ieee80211.h.

Referenced by net80211_process_ie().

#define IEEE80211_IE_RSN   48

Information element ID for Robust Security Network information element.

Definition at line 833 of file ieee80211.h.

Referenced by net80211_marshal_request_info(), sec80211_find_rsn(), and wpa_make_rsn_ie().

#define _MKOUI ( a,
b,
c,
t   )     ( ( ( t ) << 24 ) | ( ( c ) << 16 ) | ( ( b ) << 8 ) | ( a ) )

Make OUI plus type byte into 32-bit integer for easy comparison.

Definition at line 855 of file ieee80211.h.

#define OUI_ORG_MASK   0x00FFFFFF

Definition at line 857 of file ieee80211.h.

#define OUI_TYPE_MASK   0xFF000000

Definition at line 858 of file ieee80211.h.

Referenced by sec80211_rsn_get_net80211_crypt().

#define IEEE80211_RSN_OUI   _MKOUI ( 0x00, 0x0F, 0xAC, 0 )

Organization part for OUIs in standard RSN IE.

Definition at line 862 of file ieee80211.h.

Referenced by rsn_get_desc().

#define IEEE80211_WPA_OUI   _MKOUI ( 0x00, 0x50, 0xF2, 0 )

Organization part for OUIs in old WPA IE.

Definition at line 865 of file ieee80211.h.

Referenced by rsn_get_desc().

#define IEEE80211_WPA_OUI_VEN   _MKOUI ( 0x00, 0x50, 0xF2, 0x01 )

Old vendor-type WPA IE OUI type + subtype.

Definition at line 868 of file ieee80211.h.

Referenced by sec80211_find_rsn(), and wpa_make_rsn_ie().

#define IEEE80211_RSN_VERSION   1

802.11 RSN IE: expected version number

Definition at line 872 of file ieee80211.h.

Referenced by sec80211_find_rsn(), and wpa_make_rsn_ie().

#define IEEE80211_RSN_CTYPE_WEP40   _MKOUI ( 0, 0, 0, 0x01 )

802.11 RSN IE: cipher type for 40-bit WEP

Definition at line 875 of file ieee80211.h.

#define IEEE80211_RSN_CTYPE_WEP104   _MKOUI ( 0, 0, 0, 0x05 )

802.11 RSN IE: cipher type for 104-bit WEP

Definition at line 878 of file ieee80211.h.

#define IEEE80211_RSN_CTYPE_TKIP   _MKOUI ( 0, 0, 0, 0x02 )

802.11 RSN IE: cipher type for TKIP ("WPA")

Definition at line 881 of file ieee80211.h.

#define IEEE80211_RSN_CTYPE_CCMP   _MKOUI ( 0, 0, 0, 0x04 )

802.11 RSN IE: cipher type for CCMP ("WPA2")

Definition at line 884 of file ieee80211.h.

#define IEEE80211_RSN_CTYPE_USEGROUP   _MKOUI ( 0, 0, 0, 0x00 )

802.11 RSN IE: cipher type for "use group"

This can only appear as a pairwise cipher, and means unicast frames should be encrypted in the same way as broadcast/multicast frames.

Definition at line 891 of file ieee80211.h.

#define IEEE80211_RSN_ATYPE_8021X   _MKOUI ( 0, 0, 0, 0x01 )

802.11 RSN IE: auth method type for using an 802.1X server

Definition at line 894 of file ieee80211.h.

#define IEEE80211_RSN_ATYPE_PSK   _MKOUI ( 0, 0, 0, 0x02 )

802.11 RSN IE: auth method type for using a pre-shared key

Definition at line 897 of file ieee80211.h.

#define IEEE80211_RSN_CAPAB_PREAUTH   0x001

802.11 RSN IE capabilities: AP supports pre-authentication

Definition at line 900 of file ieee80211.h.

#define IEEE80211_RSN_CAPAB_NO_PAIRWISE   0x002

802.11 RSN IE capabilities: Node has conflict between TKIP and WEP

This is a legacy issue; APs always set it to 0, and gPXE sets it to 0.

Definition at line 907 of file ieee80211.h.

#define IEEE80211_RSN_CAPAB_PTKSA_REPLAY   0x00C

802.11 RSN IE capabilities: Number of PTKSA replay counters

A value of 0 means one replay counter, 1 means two, 2 means four, and 3 means sixteen.

Definition at line 914 of file ieee80211.h.

#define IEEE80211_RSN_CAPAB_GTKSA_REPLAY   0x030

802.11 RSN IE capabilities: Number of GTKSA replay counters

A value of 0 means one replay counter, 1 means two, 2 means four, and 3 means sixteen.

Definition at line 921 of file ieee80211.h.

#define IEEE80211_RSN_CAPAB_PEERKEY   0x200

802.11 RSN IE capabilities: PeerKey Handshaking is suported

Definition at line 924 of file ieee80211.h.

#define IEEE80211_RSN_1_CTR   0x000

802.11 RSN IE capabilities: One replay counter

This should be AND'ed with IEEE80211_RSN_CAPAB_PTKSA_REPLAY or IEEE80211_RSN_CAPAB_GTKSA_REPLAY (or both) to produce a value which can be OR'ed into the capabilities field.

Definition at line 933 of file ieee80211.h.

#define IEEE80211_RSN_2_CTR   0x014

802.11 RSN IE capabilities: Two replay counters

Definition at line 936 of file ieee80211.h.

#define IEEE80211_RSN_4_CTR   0x028

802.11 RSN IE capabilities: Four replay counters

Definition at line 939 of file ieee80211.h.

#define IEEE80211_RSN_16_CTR   0x03C

802.11 RSN IE capabilities: 16 replay counters

Definition at line 942 of file ieee80211.h.

#define IEEE80211_IE_VENDOR   221

Information element ID for Vendor Specific information element.

Definition at line 959 of file ieee80211.h.

Referenced by net80211_marshal_request_info(), sec80211_find_rsn(), wpa_handle_1_of_4(), wpa_make_rsn_ie(), and wpa_maybe_install_gtk().

Function Documentation

static size_t ieee80211_rsn_size ( int  npair,
int  nauth,
int  npmkid,
int  rsn_ie 
) [inline, static]

Calculate necessary size of RSN information element.

Parameters:
npair Number of pairwise ciphers supported
nauth Number of authentication types supported
npmkid Number of PMKIDs to include
is_rsn If TRUE, calculate RSN IE size; if FALSE, calculate WPA IE size
Return values:
size Necessary size of IE, including header bytes

Definition at line 843 of file ieee80211.h.

Referenced by wpa_make_rsn_ie().

00844                                                        {
00845         return 16 + 4 * ( npair + nauth ) + 16 * npmkid - 4 * ! rsn_ie;
00846 }

static int ieee80211_ie_bound ( union ieee80211_ie *  ie,
void *  end 
) [inline, static]

Check that 802.11 information element is bounded by buffer.

Parameters:
ie Information element
end End of buffer in which information element is stored
Return values:
ok TRUE if the IE is completely contained within the buffer

Definition at line 1011 of file ieee80211.h.

References len.

Referenced by ieee80211_next_ie(), net80211_probe_step(), net80211_process_ie(), sec80211_find_rsn(), wpa_handle_1_of_4(), and wpa_maybe_install_gtk().

01012 {
01013         void *iep = ie;
01014         return ( iep + 2 <= end && iep + 2 + ie->len <= end );
01015 }

static union ieee80211_ie* ieee80211_next_ie ( union ieee80211_ie *  ie,
void *  end 
) [static, write]

Advance to next 802.11 information element.

Parameters:
ie Current information element pointer
end Pointer to first byte not in information element space
Return values:
next Pointer to next information element, or NULL if no more
When processing received IEs, end should be set to the I/O buffer tail pointer; when marshalling IEs for sending, end should be NULL.

Definition at line 1027 of file ieee80211.h.

References ieee80211_ie_bound(), len, and NULL.

Referenced by net80211_marshal_request_info(), net80211_probe_step(), net80211_process_ie(), sec80211_find_rsn(), wpa_handle_1_of_4(), and wpa_maybe_install_gtk().

01029 {
01030         void *next_ie_byte = ( void * ) ie + ie->len + 2;
01031         union ieee80211_ie *next_ie = next_ie_byte;
01032 
01033         if ( ! end )
01034                 return next_ie;
01035 
01036         if ( ieee80211_ie_bound ( next_ie, end ) )
01037                 return next_ie;
01038 
01039         return NULL;
01040 }

Variable Documentation

struct ieee80211_auth packed

An 802.11 data or management frame without QoS or WDS header fields.

Authentication frame data.

Probe request frame data.

Reassociation request frame data.

Association or reassociation response frame data.

Association request frame data.

Disassociation or deauthentication frame data.

Beacon or probe response frame data.

802.11 Vendor Specific information element

802.11 Robust Security Network ("WPA") information element

802.11 ERP Information information element

802.11 Channels information element

802.11 Channels information element channel band tuple

802.11 Power Capability information element

802.11 Power Constraint information element

802.11 Challenge Text information element

802.11 Request information element

802.11 Country information element

802.11 Country information element regulatory band triplet

802.11 Country information element regulatory extension triplet

802.11 Direct Spectrum parameter information element

802.11 rates information element

802.11 SSID information element

Generic 802.11 information element header.

10-byte CTS or ACK frame format, with abbreviated header

16-byte RTS frame format, with abbreviated header

The 802.2 LLC/SNAP header sent before actual data in a data frame.

This header is not acknowledged in the 802.11 standard at all; it is treated just like data for MAC-layer purposes, including fragmentation and encryption. It is actually two headers concatenated: a three-byte 802.2 LLC header indicating Subnetwork Accesss Protocol (SNAP) in both source and destination Service Access Point (SAP) fields, and a five-byte SNAP header indicating a zero OUI and two-byte Ethernet protocol type field.

Thus, an eight-byte header in which six of the bytes are redundant. Lovely, isn't it?

The first 8 rates go in an IE of type RATES (1), and any more rates go in one of type EXT_RATES (50). Each rate is a byte with the low 7 bits equal to the rate in units of 500 kbps, and the high bit set if and only if the rate is "basic" (must be supported by all connected stations).

This just contains the channel number. It has the fancy name because IEEE 802.11 also defines a frequency-hopping PHY that changes channels at regular intervals following a predetermined pattern; in practice nobody uses the FH PHY.

This contains some data about RF regulations.

This contains a list of information element types we would like to be included in probe response frames.

This is used in authentication frames under Shared Key authentication.

This is used to specify an additional power limitation on top of the Country requirements.

This is used in association request frames to indicate the extremes of our TX power abilities. It is required only if we indicate support for spectrum management.

This is used in association frames to indicate the channels we can use. It is required only if we indicate support for spectrum management.

This is used to communicate some PHY-level flags.

Showing once again a striking clarity of design, the IEEE folks put dynamically-sized data in the middle of this structure. As such, the below structure definition only works for IEs we create ourselves, which always have one pairwise cipher and one AKM; received IEs should be parsed piecemeal.

Also inspired was IEEE's choice of 16-bit fields to count the number of 4-byte elements in a structure with a maximum length of 255 bytes.

Many fields reference a cipher or authentication-type ID; this is a three-byte OUI followed by one byte identifying the cipher with respect to that OUI. For all standard ciphers the OUI is 00:0F:AC, except in old-style WPA IEs encapsulated in vendor-specific IEs, where it's 00:50:F2.

One often sees the RSN IE masquerading as vendor-specific on devices that were produced prior to 802.11i (the WPA amendment) being finalized.

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