proc_create_...single_write(9)

💅 NAME 💅

proc_create_net_single_write — bestie, this is the one that creates a writable, net_ns-specific proc file. like, a proc file that knows about network namespaces and lets you write to it. iconic behaviour tbh 🫶

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✨ SYNOPSIS ✨

struct proc_dir_entry * proc_create_net_single_write (const char *name ,
umode_t mode , struct proc_dir_entry *parent , int (*show)(struct
seq_file *, void *) , proc_write_t write , void *data );

okay so this is the <9> kernel API manual, and this is the whole signature. six args. no cap, you gotta pass all of them 🎀

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🌸 ARGUMENTS 🌸

• name — the name of the file. literally what it'll be called 🏷️
• mode — the file's access mode. you know, the permissions vibe check.
• parent — the parent directory you're creating this baby in. it needs a home 💖
• show — the seqfile show method, i.e. the thing that reads the file for you.
• write — the write method, aka how you "'modify'" the file. yes the quotes are in the original, it's giving "modify" in the loose sense 😭
• data — data for retrieval by pde_data. it lives there. it waits. it gets retrieved 💅

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🦋 DESCRIPTION 🦋

so what this actually does: it creates a network-namespaced proc file inside the parent directory, with the name and mode you passed. and the special sauce? it lets you read a file that displays a single element rather than a whole series — single, not a series, that's the whole flex — and it provides for the file accepting writes that have some arbitrary effect. arbitrary. do with that what you will ✨

the show function gets called to extract the readable content via the seq_file interface. that's its whole job and it ate 🔥

the write function gets called with the data copied into a kernel space scratch buffer, and a NUL gets appended for convenience 🎁 (so thoughtful). the buffer may be modified by the write function, so go off. write should return 0 on success — that's the green flag, return the zero, periodt.

the data value is accessible from both the show and write functions by calling pde_data on the file inode. and — important, bestie, don't skip this — the network namespace must be accessed by calling seq_file_single_net on the seq_file struct 👑

⚠️ lowkey the NUL append and the mutable scratch buffer are the whole reason this function exists separately from its siblings — don't go thinking the buffer is const, it fr fr isn't 🙈

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🌈 SEE ALSO 🌈

• Kernel file ./fs/proc/proc_net.c
• proc_create_net_data_write(9) — its sibling, go say hi 💜

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and that's the page, bestie ✨ this gem came out of ./fs/proc in the October 2026 edition of the kernel API manual — go forth and create your writable net_ns proc files, you absolute main character 👑💖🎀