STRUCT INET_FRAG_QUEUE(9)

💅 struct inet_frag_queue(9) — kernel API manual, but make it make sense

okay bestie, so this page is all about struct inet_frag_queue, aka the fragment queue ✨ — literally the data structure the kernel uses when it's holding onto all the lil' pieces of a datagram until it can put them back together. think of it as the group chat where every fragment has to show up before the convo can actually be read 🫶

✨ SYNOPSIS ✨

here's the whole struct exactly as it lives, no cap, every field in order 💖

struct inet_frag_queue {
    struct rhash_head       node;
    union {
      struct frag_v4_compare_key v4;
      struct frag_v6_compare_key v6;
    } key;
    struct timer_list       timer;
    spinlock_t lock;
    refcount_t refcnt;
    struct rb_root          rb_fragments;
    struct sk_buff          *fragments_tail;
    struct sk_buff          *last_run_head;
    ktime_t stamp;
    int len;
    int meat;
    u8 tstamp_type;
    __u8 flags;
    u16 max_size;
    struct fqdir            *fqdir;
    struct rcu_head         rcu;
 };

🌸 Members 🌸

like. the whole cast. main character energy each and every one 👑

• node — the rhash node, bestie. it's how this queue sits in the hash. 💫
• key — the keys that identify this frag, lowkey its whole identity 🪪
• timer — the queue expiration timer ⏰ yes she has a deadline
• lock — the spinlock protecting this frag 🔒 do not skip the lock, fr fr
• refcnt — reference count of the queue 🧮
• rb_fragments — received fragments rb-tree root 🌳 the family tree of pieces
• fragments_tail — received fragments tail 🍑 (no seriously, the tail)
• last_run_head — the head of the last "run". see ip_fragment.c 🔍 iykyk
• stamp — timestamp of the last received fragment ⏱️
• len — total length of the original datagram 📏 the big picture
• meat — length of received fragments so far 🥩 (yes it's literally called meat, and yes i'm obsessed)
• tstamp_type — stamp has a mono delivery time (EDT) 🕰️
• flags — fragment queue flags 🚩
• max_size — maximum received fragment size 📦
• fqdir — pointer to struct fqdir 👉
• rcu — rcu head for freeing deferall 🧹 (yes, that's how it's spelled on the page, we don't gatekeep)

ngl the meat field is the icon here. it's giving "the actual payload received so far" and honestly? slay.

🦋 SEE ALSO 🦋

• ./include/net/inet_frag.h — Kernel file 🌈
• enum (anonymous)(9) — also in that header, go read it, it's right there 🎀

💜 the cute sign-off 💜

this lil' page lives in ./include/net, and the version tag on it reads October 2026 — so yes, bestie, she's from the future and she's still just a fragment queue. periodt. 🧚🌸

pages like this are why you read the header files — go put your fragments back together responsibly 💖