STRUCT TID_AMPDU_RX(9)

💅 struct tid_ampdu_rx(9) 💅

okay so bestie, we're in the Kernel API Manual today and the star of the show is struct tid_ampdu_rx — literally the TID aggregation info for the Rx side. no cap, this is the whole vibe. let's get into it 🫶

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✨ NAME ✨

struct tid_ampdu_rx — TID aggregation information (Rx). that's it, that's the tweet 💖

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🌸 SYNOPSIS 🌸

struct tid_ampdu_rx {
    struct rcu_head rcu_head;
    spinlock_t reorder_lock;
    u64 reorder_buf_filtered;
    struct sta_info *sta;
    struct timer_list session_timer;
    struct timer_list reorder_timer;
    unsigned long last_rx;
    u16 head_seq_num;
    u16 stored_mpdu_num;
    u16 ssn;
    u16 buf_size;
    u16 timeout;
    u8 tid;
    u8 auto_seq:1, removed:1, started:1;
    struct {
      struct sk_buff_head buf;
      unsigned long time;
    } reorder[];
 };

look at her. she's structured. she's iconic. she's got a flexible array member at the end like a little surprise 🎀

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🦋 Members 🦋

time for the member-by-member tour, bestie — i'm gonna hold your hand through every single one:

• rcu_head — the RCU head that gets used for freeing this struct. think of it as the little "bye bye" ticket 🎟️
• reorder_lock — serializes access to the reorder buffer (peep below for the deets). one at a time, babes, one at a time 💅
• reorder_buf_filtered — a bitmap showing where there are filtered frames sitting in the reorder buffer that should be ignored when releasing frames. lowkey a "do not disturb" list ✋
• sta — the station we are attached to. your plus-one, essentially 🫶
• session_timer — checks if the peer keeps Tx-ing on the TID (by the timeout value). like a "are you still there??" text 😭
• reorder_timer — releases expired frames from the reorder buffer. she's the one cleaning up 🧹
• last_rx — jiffies of the last rx activity. the timestamp of the last time anybody said anything ⏰
• head_seq_num — head sequence number in the reordering buffer. the front of the line, main character energy 👑
• stored_mpdu_num — number of MPDUs hanging out in the reordering buffer. headcount, fr fr 🔢
• ssn — the Starting Sequence Number expected to be aggregated. the beginning of the story ✨
• buf_size — buffer size for incoming A-MPDUs. how much room we're giving 'em 📦
• timeout — reset timer value (in TUs). the clock, bestie ⏳
• tid — TID number. a little number, big responsibilities 🎀
• auto_seq — used for offloaded BA sessions to automatically pick head_seq_and and ssn. (yes, that's exactly how it's written, i'm not touching it 💀)
• removed — this session is removed (but might still have been found due to RCU). she's gone but like… not fully gone 🙈
• started — this session has started (head ssn or higher was received). we're so back 🔥
• reorder — the reorder buffer entries. the whole squad 🌈
  • reorder.buf — the struct sk_buff_head for the frames, since there could be multiple at each entry from an A-MSDU reported as individual subframes. it's giving "it's complicated" 💀
  • reorder.time — time when this entry was filled (jiffies). when did this happen? here's the receipt ⏱️

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💜 Description 💜

okay so the important lore: this structure's lifetime is managed by RCU, and assignments to the array holding it must hold the aggregation mutex. no skipping that, bestie, that's a hard rule 🚨

the reorder_lock is what protects the members of this struct — except for timeout, buf_size and dialog_token, which are constant across the lifetime of the struct (and the dialog token is only used for debugging, so, y'know, she's just there for the plot 🕵️).

lowkey reminder: those three are exempt from the lock because they never change. don't come for them, they're fine 💅

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⭐ SEE ALSO ⭐

go check out the kernel file ./net/mac80211/sta_info.h and these absolute legends:

• enum ieee80211_sta_info_flags(9)
• struct tid_ampdu_tx(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)

the whole friend group, honestly 🫂💖

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and that's the page, bestie!! 🎀 this one lives at ./net/mac80211, dated October 2026, and it's filed under struct tid_ampdu_rx(9) — mwah, go read the source, ily, bye 💜✨