802.11s mesh powersaving for linux

• Implement non-realtime powersaving features of 802.11s draft:
  • powersaving level indication;
  • traffic buffering for sleeping peers;
  • TIM/DTIM in beacons;
  • peer service period;
• Provide powersaving level control on MSTA/peer link basis;
• Provide peer link control;

Enhance current in-kernel 802.11s implementation:

• powersaving scheme proposed by 802.11s draft closely resemble AP-based scheme (traffic buffering/TIM/DTIM), so this code may be reused;
• powersaving level indication (both peer and non-peer)/mesh awake window attributes need to be added;
• wakeup for peer beacon reception may be implemented later, now it's enough to stay awake continuously and just calculate whether station would actually hear the frames that it receives;
• peer service period logic need to be added, it's a simple state machine;

Testing may be carried out with mac80211_hwsim driver.

• MSTA power mode tracking (11C.13.3);
• each peering power mode tracking (11C.13.4);
• TIM/DTIM in beacons (11C.13.5-6) – ieee80211_beacon_get_tim;
• mesh awake window (11C.13.7);
• wake-up scheduling for peer beacons (optional);
• ps-poll requests and responses (?);
• service period tracking (11C.13.10);
• frame buffering for doze peers – ieee80211_tx_h_multicast_ps_buf, ieee80211_tx_h_unicast_ps_buf;
• user interface controls – like nl80211_set_power_save;