cnstr_shdsc_chachapoly(9)

📦 version 7.3.1, in nixpkgs unstable

💅 cnstr_shdsc_chachapoly — kernel API manual, bestie edition 🎀

okay so real talk, this is a 9 section page from the Kernel API Manual, and the star of the show is cnstr_shdsc_chachapoly. It builds you a shared descriptor for Chacha20 + Poly1305 generic AEAD (that's rfc7539, iykyk) and for IPsec ESP (that's rfc7634, a.k.a. rfc7539esp). Non-protocol, bestie. It's giving "I just make the descriptor, you take it from here." ✨

🌸 NAME 🌸

cnstr_shdsc_chachapoly — the Chacha20 + Poly1305 generic AEAD (rfc7539) and IPsec ESP (rfc7634, a.k.a. rfc7539esp) shared descriptor builder (non-protocol). literally her whole job 💖

✨ SYNOPSIS ✨

void cnstr_shdsc_chachapoly (u32 * const desc , struct alginfo *cdata ,
struct alginfo *adata , unsigned int ivsize , unsigned int icvsize ,
const bool encap , const bool is_qi );

no return value, she just goes off and does the thing 🫶

🦋 ARGUMENTS 🦋

  • desc — pointer to the buffer you're using for descriptor construction. this is where the magic gets written, so pls have it ready 💅
  • cdata — pointer to the block cipher transform definitions. valid algorithm values are OP_ALG_ALGSEL_CHACHA20 ANDed with OP_ALG_AAI_AEAD. that's the combo, no substitutions 🎀
  • adata — pointer to the authentication transform definitions. valid algorithm values are OP_ALG_ALGSEL_POLY1305 ANDed with OP_ALG_AAI_AEAD. same deal, ANDed and iconic ⭐
  • ivsize — initialization vector size 👑
  • icvsize — integrity check value (ICV) size, and yes it can be truncated or full, your call 💀
  • encap — true if encapsulation, false if decapsulation. pick a lane bestie 🌈
  • is_qi — true when called from caam/qi 🌸

🔥 SEE ALSO 🔥

kernel file ./drivers/crypto/caam/caamalg_desc.c — like, go read her, she's the source fr fr

and the whole friend group, no cap:

heads up bestie: the algorithm values are strict. OP_ALG_ALGSEL_CHACHA20 ANDed with OP_ALG_AAI_AEAD for cdata, and OP_ALG_ALGSEL_POLY1305 ANDed with OP_ALG_AAI_AEAD for adata. don't freestyle, she will not slay 🙈

and that's the whole page, mwah 💋 this icon lives in ./drivers/crypto/caam and this particular printing is the October 2026 edition of cnstr_shdsc_chachapoly(9). go build some descriptors, bestie, you got this 🧚💜

📦 where this page comes from