STRUCT NLMSGHDR(9)

✨ struct nlmsghdr(9) ✨

okay bestie, welcome to the Kernel API Manual entry for struct nlmsghdr 💖 this is a group-chat-level explainer, but every single fact is staying put, no cap.

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🌸 NAME 🌸

struct nlmsghdr — the fixed-format metadata header of Netlink messages 👑

like, it's the little name tag every Netlink message wears to the party. fixed format. always the same shape. iconic behavior honestly.

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🦋 SYNOPSIS 🦋

struct nlmsghdr {
    __u32 nlmsg_len;
    __u16 nlmsg_type;
    __u16 nlmsg_flags;
    __u32 nlmsg_seq;
    __u32 nlmsg_pid;
 };

that's it. that's the whole struct. five fields, zero drama ✨ (well, the fields themselves have drama, keep reading).

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🎀 Members 🎀

💅 the fields, one by one

• nlmsg_len — length of the message including the header 🫶 yes, including. the header counts itself. main character energy.
• nlmsg_type — the message content type 💌 like, what kind of message is this even.
• nlmsg_flags — additional flags 🚩 the extra little stickers on top.
• nlmsg_seq — sequence number 🔢 so you can keep track of things, bestie.
• nlmsg_pid — sending process port ID 🏷️ who sent it. the return address of the netlink world.

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🌈 SEE ALSO 🌈

• Kernel file ./include/uapi/linux/netlink.h
• enum nlmsgerr_attrs(9)
• enum netlink_attribute_type(9)
• enum netlink_policy_type_attr(9)

go read those too, iykyk 💜 they're literally right there in the same header file, no excuses.

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🧚 the cute sign-off 🧚

that's the whole page, bestie 💖 this one lives in ./include/uapi/linux and it's dated October 2026 — so like, future-coded but make it kernel ⭐ mwah, slay, periodt 🎀🌷✨