IPQ_SET_VERDICT(3)

💅 IPQ_SET_VERDICT — the "okay bestie, here's my ruling" page 💅

So this is a page from the Linux Programmer's Manual (section 3, for the library girlies), and it's all about <pink>ipq_set_verdict</pink> — the function that lets you pass judgment on a packet. Iconic behavior honestly. 👑

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✨ NAME ✨

ipq_set_verdict — issue a verdict (and optionally a glow-up modified packet) back to the kernel 💌

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🌸 SYNOPSIS 🌸

#include <linux/netfilter.h>
#include <libipq.h>

int ipq_set_verdict(const struct ipq_handle *h, ipq_id_t id, unsigned int verdict, size_t data_len, unsigned char *buf);

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🦋 DESCRIPTION 🦋

Okay so picture this: you already grabbed a packet with ipq_read, right? Now ipq_set_verdict is the function where you announce your decision about what should happen to it — like the packet's fate is literally in your hands, main character energy fr. And if you want, you can also hand back a modified version of the payload data. Glow-up delivered. ✨

Let me break down the parameters because every single one matters, no skipping:

• h — the context handle 🫶 and here's the thing: it must have previously been returned successfully from a call to ipq_create_handle. No handle, no vibes, no verdict.
• id — the packet identifier, which you got via ipq_get_packet. It's how the kernel knows which packet you're judging. iykyk.
• verdict — the big one, the actual ruling 💅 and it must be one of these three:
  • NF_ACCEPT — accept the packet and continue traversal within the kernel 🟢 (she's approved, let her through)
  • NF_DROP — drop the packet 💀 (blocked, deleted, not today)
  • NF_QUEUE — requeue the packet 🔁 (back in line she goes)
• 🚨 NF_STOLEN and NF_REPEAT are kernel-internal constants and should not be used from userspace — like, their exact side effects have not been investigated, so don't be brave. 🙈
• data_len — the length of the data pointed to by buf, aka the optional replacement payload data 📦
• buf — the pointer to that optional replacement payload data.

🎀 Pro tip straight from the page: if you're simply setting a verdict without modifying the payload data, use zero for data_len and NULL for buf. Easy.

And one more thing bestie, listen: the application is responsible for recalculating any packet checksums when modifying packets. That's on you. Not the kernel. You. 🫵 Do not forget, I'm begging.

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💖 RETURN VALUE 💖

• On failure, -1 is returned 😭
• On success, a non-zero positive value is returned 🎉 slay

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🌈 ERRORS 🌈

On error, a descriptive error message will be available via the ipq_errstr function. She literally tells you what went wrong. Communication queen. 💅

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💀 BUGS 💀

None known. Flawless. Periodt. 👑

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🌟 AUTHOR 🌟

James Morris <jmorris@intercode.com.au> — thank you king 🫶

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🎀 COPYRIGHT 🎀

Copyright (c) 2000-2001 Netfilter Core Team.

Distributed under the GNU General Public License. 📜

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🔥 SEE ALSO 🔥

• iptables(8)
• libipq(3)

Go read them, they're giving lore. ✨

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Okay that's the whole page, mwah 💋 — and just so we're fully cited, this came from Linux iptables 1.2, dated 16 October 2001, in the good old Linux Programmer's Manual. Vintage but still serving. 🎀✨