From c8d6591752e96c550cb98b781326d72d8eedcc79 Mon Sep 17 00:00:00 2001 From: "Steinar H. Gunderson" Date: Wed, 3 Sep 2014 06:48:37 -0700 Subject: mac80211: support DTPC IE (from Cisco Client eXtensions) Linux already supports 802.11h, where the access point can tell the client to reduce its transmission power. However, 802.11h is only defined for 5 GHz, where the need for this is much smaller than on 2.4 GHz. Cisco has their own solution, called DTPC (Dynamic Transmit Power Control). Cisco APs on a controller sometimes but not always send 802.11h; they always send DTPC, even on 2.4 GHz. This patch adds support for parsing and honoring the DTPC IE in addition to the 802.11h element (they do not always contain the same limits, so both must be honored); the format is not documented, but very simple. Tested (on top of wireless.git and on 3.16.1) against a Cisco Aironet 1142 joined to a Cisco 2504 WLC, by setting various transmit power levels for the given access points and observing the results. The Wireshark 802.11 dissector agrees with the interpretation of the element, except for negative numbers, which seem to never happen anyway. Signed-off-by: Steinar H. Gunderson Signed-off-by: Johannes Berg --- net/mac80211/util.c | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+) (limited to 'net/mac80211/util.c') diff --git a/net/mac80211/util.c b/net/mac80211/util.c index b444f27a788e..3c61060a4d2b 100644 --- a/net/mac80211/util.c +++ b/net/mac80211/util.c @@ -1015,6 +1015,31 @@ u32 ieee802_11_parse_elems_crc(const u8 *start, size_t len, bool action, } elems->pwr_constr_elem = pos; break; + case WLAN_EID_CISCO_VENDOR_SPECIFIC: + /* Lots of different options exist, but we only care + * about the Dynamic Transmit Power Control element. + * First check for the Cisco OUI, then for the DTPC + * tag (0x00). + */ + if (elen < 4) { + elem_parse_failed = true; + break; + } + + if (pos[0] != 0x00 || pos[1] != 0x40 || + pos[2] != 0x96 || pos[3] != 0x00) + break; + + if (elen != 6) { + elem_parse_failed = true; + break; + } + + if (calc_crc) + crc = crc32_be(crc, pos - 2, elen + 2); + + elems->cisco_dtpc_elem = pos; + break; case WLAN_EID_TIMEOUT_INTERVAL: if (elen >= sizeof(struct ieee80211_timeout_interval_ie)) elems->timeout_int = (void *)pos; -- cgit v1.2.1