HARDWARE CRYPTO ACCELERATION(9)

📦 version 7.3.1, in nixpkgs unstable

✨ Hardware crypto acceleration ✨

okay so this is the Hardware crypto acceleration(9) page from the Kernel API Manual, and bestie it is giving hardware crypto realness. mac80211 is capable of taking advantage of many hardware acceleration designs for encryption and decryption operations. iconic behavior, honestly 💅

The set_key callback in the struct ieee80211_ops for a given device is called to enable hardware acceleration of encryption and decryption. The callback takes a sta parameter that will be NULL for default keys or keys used for transmission only, or point to the station information for the peer for individual keys. Multiple transmission keys with the same key index may be used when VLANs are configured for an access point. periodt.

When transmitting, the TX control data will use the hw_key_idx selected by the driver by modifying the struct ieee80211_key_conf pointed to by the key parameter to the set_key function.

The set_key call for the SET_KEY command should return 0 if the key is now in use, -EOPNOTSUPP or -ENOSPC if it couldn't be added; if you return 0 then hw_key_idx must be assigned to the hardware key index. You are free to use the full u8 range. slay.

okay but real talk: note that in the case that the IEEE80211_HW_SW_CRYPTO_CONTROL flag is set, mac80211 will not automatically fall back to software crypto if enabling hardware crypto failed. The set_key call may also return the value 1 to permit this specific key/algorithm to be done in software. 💖

When the cmd is DISABLE_KEY then it must succeed. no exceptions, bestie.

Note that it is permissible to not decrypt a frame even if a key for it has been uploaded to hardware. The stack will not make any decision based on whether a key has been uploaded or not but rather based on the receive flags.

The struct ieee80211_key_conf structure pointed to by the key parameter is guaranteed to be valid until another call to set_key removes it, but it can only be used as a cookie to differentiate keys. it's literally just a little key cookie 🍪

In TKIP some HW need to be provided a phase 1 key, for RX decryption acceleration (i.e. iwlwifi). Those drivers should provide update_tkip_key handler. The update_tkip_key call updates the driver with the new phase 1 key. This happens every time the iv16 wraps around (every 65536 packets). The set_key call will happen only once for each key (unless the AP did rekeying); it will not include a valid phase 1 key. The valid phase 1 key is provided by update_tkip_key only. The trigger that makes mac80211 call this handler is software decryption with wrap around of iv16. 💫

The set_default_unicast_key call updates the default WEP key index configured to the hardware for WEP encryption type. This is required for devices that support offload of data packets (e.g. ARP responses). 🫶

Mac80211 drivers should set the NL80211_EXT_FEATURE_CAN_REPLACE_PTK0 flag when they are able to replace in-use PTK keys according to the following requirements:

  1. They do not hand over frames decrypted with the old key to mac80211

🌈 SEE ALSO 🌈

okay bestie, this is the mac80211 extended universe and it is not playing around 😭 every single related-page reference from the original is below, same order, zero skips. Consider this your “go read the lore” starter pack — and yes, it’s giving a lot of pages. 💅

and that’s the whole see-also cinematic universe, bestie 🫶 footer tea: source ./include/net, date October 2026, page Hardware cry...acceleration(9) — and the Kernel file up top was ./include/net/mac80211.h. now go hydrate and maybe read one (1) linked page. 💖

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