STRUCT AF_ALG_CTX(9)

💅 struct af_alg_ctx(9) 💅

okay so bestie, welcome to the kernel API manual — this one's a kernel API page about a little struct called af_alg_ctx, and honestly? it's giving backstage-pass energy. it's the definition of the crypto context. that's it, that's the whole vibe. 🎀

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✨ NAME ✨

struct af_alg_ctx — literally just the definition of the crypto context, no cap 💖

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✨ SYNOPSIS ✨

okay here's the actual shape of it, copy it exactly bestie, don't freestyle:

struct af_alg_ctx {
    struct list_head tsgl_list;
    void *iv;
    void *state;
    size_t aead_assoclen;
    struct crypto_wait wait;
    size_t used;
    atomic_t rcvused;
    bool more:1, merge:1, enc:1, write:1, init:1;
    unsigned int len;
    unsigned int inflight;
 };

look at those bitfields. more:1, merge:1, enc:1, write:1, init:1 — five whole booleans living in one byte, she's thriving on efficiency 🧚✨

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🌸 Members 🌸

• tsgl_list — the link to TX SGL. that's her whole job, she holds the link 🔗
• iv — the IV for the cipher operation. yes, the IV. iconic 💜
• state — existing state, for when you're continuing an operation (picking up right where you left off, main character energy) 🦋
• aead_assoclen — length of the AAD for AEAD cipher operations 🎀
• wait — for waiting for completion of async crypto ops. she waits. gracefully. patiently. 🫶
• used — TX bytes sent to kernel. and why do we care? because this variable is used to make sure user space cannot cause the kernel to allocate too much memory in a sendmsg operation. protective queen behavior honestly 👑
• rcvused — total RX bytes to be filled by kernel. and again, this variable is used to make sure user space cannot cause the kernel to allocate too much memory in a recvmsg operation. same energy, receiving side 💅
• more — more data to be expected from user space? (yes/no, that's the question) 🙈
• merge — shall new data from user space be merged into the existing SG? 👀
• enc — the cryptographic operation to be performed when recvmsg is invoked 🌈
• write — true if we are in the middle of a write ⭐
• init — true if metadata has been sent ✅
• len — length of memory allocated for this data structure 📏
• inflight — non-zero when requests are in flight. for debugging only, bestie — don't go building your whole personality on it 💀

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💖 Description 💖

so what does she do? the crypto context tracks the input data during the lifetime of an AF_ALG socket. that's the whole gig. she's there the entire time, keeping receipts on the input data, from start to finish. obsessed with her consistency fr fr 🍓

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🔥 SEE ALSO 🔥

go read these next, iykyk:

• Kernel file ./include/crypto/if_alg.h
• struct af_alg_async_req(9)
• af_alg_sndbuf(9)
• af_alg_writable(9)
• af_alg_rcvbuf(9)
• af_alg_readable(9)

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ok that's the whole page!! no notes, she ate 💅

and that's a wrap bestie 🎀 this one lives in ./include/crypto, and it's dated October 2026 — so yeah, very demure, very forward-looking. mwah 😭💖