STRUCT TID_AMPDU_TX(9)

👑 struct tid_ampdu_tx(9) 👑

okay bestie, welcome to the Kernel API Manual, section 9 — this is the whole entire glow-up of struct tid_ampdu_tx, aka TID aggregation info but make it transmit. she's the Tx sister, she's booked and busy, and she's about to explain herself. periodt. 💅

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✨ NAME ✨

struct tid_ampdu_tx — TID aggregation information (Tx). yes that's literally what it is, no notes, she ate. 🎀

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🦋 SYNOPSIS 🦋

struct tid_ampdu_tx {
    struct rcu_head rcu_head;
    struct timer_list session_timer;
    struct timer_list addba_resp_timer;
    struct sk_buff_head pending;
    struct sta_info *sta;
    unsigned long state;
    unsigned long last_tx;
    u16 timeout;
    u8 dialog_token;
    u8 stop_initiator;
    bool tx_stop;
    u16 buf_size;
    u16 ssn;
    u16 failed_bar_ssn;
    bool bar_pending;
    bool amsdu;
    bool ndp;
    u8 tid;
 };

look at her. seventeen fields. main character energy fr fr. every single one is listed below, so don't you dare skip ahead 👀

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🌸 MEMBERS 🌸

• rcu_head — the rcu head for freeing the structure. she's the exit plan, lowkey iconic of her.
• session_timer — checks if we keep Tx-ing on the TID, based on the timeout value. she's the vibe check that keeps the session alive. ⏰
• addba_resp_timer — timer for the peer's response to the addba request. it's giving "waiting for the group chat to text back". 😭
• pending — the pending frames queue — and heads up, use the sta's spinlock to protect it. 🔒
• sta — the station we are attached to. our plus-one. 🫶
• state — session state (see above). yes, "see above", that's what the manpage says, iykyk.
• last_tx — jiffies of the last tx activity. timestamping the last time she spoke, honestly relatable.
• timeout — session timeout value, to be filled in ADDBA requests. she's the deadline queen. 👑
• dialog_token — dialog token for the aggregation session. no cap, she's just the token.
• stop_initiator — the initiator of a session stop. who hit the brakes, exactly.
• tx_stop — TX DelBA frame when stopping. yes babe, announce your exit. 🌈
• buf_size — reorder buffer size at the receiver. not ours! theirs. keep up. 💀
• ssn — starting sequence number of the session. the origin story, literally.
• failed_bar_ssn — ssn of the last failed BAR tx attempt. the flop we don't talk about. 🙈
• bar_pending — BAR needs to be re-sent. she's got a draft that never got sent, we've all been there. 📩
• amsdu — support A-MSDU within A-MDPU. (yes, that's how the original spells it, we don't fix it, we don't touch it, we respect it. 🎀)
• ndp — this session is using NDP Block ACKs. fancy.
• tid — the TID number. the number herself.

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💖 DESCRIPTION 💖

so this structure's lifetime is managed by RCU, and any assignment to the array that holds it must hold the aggregation mutex. rules are rules bestie, no skipping. 🔒

now here's the spicy part — the TX path can access it under RCU lock-free if, and only if, the state has the flag HT_AGG_STATE_OPERATIONAL set. otherwise? the TX path must also acquire the spinlock and re-check the state. read the comments in the tx code that touches it, i'm begging. 😭

fr fr, "if and only if" is doing a LOT of heavy lifting in that sentence. don't be the person who ignores it. that's not a vibe, that's a bug.

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⭐ SEE ALSO ⭐

Kernel file ./net/mac80211/sta_info.h enum ieee80211_sta_info_flags(9), struct tid_ampdu_rx(9), struct sta_ampdu_mlme(9), struct ieee80211_fast_tx(9), struct ieee80211_fast_rx(9), struct mesh_sta(9), struct link_sta_info(9), struct ieee80211_sta_removed_link_stats(9), struct sta_info(9), __sta_info_flush(9), sta_info_flush(9)

like the whole friend group showed up. slay. 🫶💜

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that's the page babes — brought to you straight out of ./net/mac80211, dated October 2026, with love. 🧚✨ go read struct tid_ampdu_rx(9) next, she misses you. 🍓💖