STRUCT CAN_FRAME(9)

💅 struct can_frame(9) — the Kernel API Manual, but make it cute

okay bestie, welcome to struct can_frame(9) from the Kernel API Manual ✨ this is the page about the Classical CAN frame structure, aka CAN 2.0B — like, the OG CAN frame, the blueprint, the blueprint-that-ate 🫶

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✨ NAME ✨

struct can_frame — Classical CAN frame structure (aka CAN 2.0B) 💖

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🌸 SYNOPSIS 🌸

here's the whole thing, character for character, no cap:

struct can_frame {
    canid_t can_id;
    union {
      __u8 len;
      __u8 can_dlc;
    };
    __u8 __pad;
    __u8 __res0;
    __u8 len8_dlc;
    __u8 data[CAN_MAX_DLEN];
 };

like… look at her. iconic. 🎀

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🦋 Members 🦋

• can_id — the CAN ID of the frame plus the CAN_*_FLAG flags. for the full deets, go look at the canid_t definition 👑
• {unnamed_union} — it's an anonymous union, bestie. no name, all main character energy 💅
• len — CAN frame payload length in byte, 0 .. 8 ✨
• can_dlc — deprecated name for CAN frame payload length in byte, 0 .. 8. yeah she's still here, but she's deprecated, so, yk, use len 🙈
• __pad — padding 🛋️
• __res0 — reserved / padding
• len8_dlc — the optional DLC value (9 .. 15) when the payload length is 8 bytes. so like, len8_dlc contains values from 9 .. 15 when the payload length is 8 bytes but the DLC value (see ISO 11898-1) is greater then 8. ⚠️ important: the CAN_CTRLMODE_CC_LEN8_DLC flag has to be enabled in the CAN driver for this to work, fr fr.
• data — CAN frame payload (up to 8 byte) 🍓

lowkey read the len8_dlc one twice, bestie — the "greater then 8" and the "flag has to be enabled in CAN driver" bits are the whole point 🫶

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🌈 SEE ALSO 🌈

• Kernel file ./include/uapi/linux/can.h
• struct canfd_frame(9)
• struct canxl_frame(9)
• struct sockaddr_can(9)
• struct can_filter(9)

like, go read them, they're all in the same friend group 💜

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and that's the whole page, bestie! 🧚 this one lives at ./include/uapi/linux in the kernel tree, from October 2026 — and the page title is struct can_frame(9), in case you forgot already 😭 slay, go forth and parse those frames 👑💖