ipv4(3)

📦
version 1.0.5 · 5 versions
, in ubuntu noble, ubuntu questing

💖 ipv4 — IPv4 helper functions 💖

okay bestie, welcome to ipv4(3) from the Library Functions Manual ✨ this is the lil squad of helper functions that deal with your IPv4 headers when you're messing around with libnetfilter_queue. she's short, she's sweet, she's giving "i know exactly what i'm doing" energy 🎀

🌸 SYNOPSIS 🌸

🦋 Modules

Internal IP functions

🦋 Functions

struct iphdr * nfq_ip_get_hdr (struct pkt_buff *pktb)
int nfq_ip_set_transport_header (struct pkt_buff *pktb, struct iphdr
    *iph)
int nfq_ip_mangle (struct pkt_buff *pktb, unsigned int dataoff, unsigned
    int match_offset, unsigned int match_len, const char *rep_buffer,
    unsigned int rep_len)
int nfq_ip_snprintf (char *buf, size_t size, const struct iphdr *iph)

✨ Detailed Description ✨

no cap, this is where the real tea lives 👑 scroll down for the actual function docs, they're all here, nothing skipped, we're doing this properly fr fr 💅

💜 Function Documentation 💜

🫶 struct iphdr * nfq_ip_get_hdr (struct pkt_buff * pktb)

nfq_ip_get_hdr — get the IPv4 header 🌈

Parameters

  • pktb — Pointer to user-space network packet buffer

Returns

a validated pointer to the IPv4 header, or NULL if the IP is malformed or it's not version 4 😭

lowkey most programs will not need to call this function. a possible use is to figure out what the layer 4 protocol is 🧚 the validation here is that the buffer is big enough for the declared lengths in the header, i.e. it's an extra check for packet truncation.

Definition at line 40 of file ipv4.c.

🔥 int nfq_ip_mangle (struct pkt_buff * pktb, unsigned int dataoff, unsigned int match_offset, unsigned int match_len, const char * rep_buffer, unsigned int rep_len)

nfq_ip_mangle — mangle IPv4 packet buffer 💅

Parameters

  • pktb — Pointer to user-space network packet buffer
  • dataoff — Offset to layer 4 header, or zero to mangle IP header
  • match_offset — Offset to content that you want to mangle
  • match_len — Length of the existing content you want to mangle
  • rep_buffer — Pointer to data you want to use to replace current content
  • rep_len — Length of data you want to use to replace current content

Returns

1 for success and 0 for failure. see pktb_mangle() for the failure case 👀

Note

this function updates the IPv4 length if necessary and recalculates the IPv4 checksum. so yeah, she's doing the math for you, iconic behavior fr 🧮✨

Definition at line 127 of file ipv4.c.

🎀 int nfq_ip_set_transport_header (struct pkt_buff * pktb, struct iphdr * iph)

nfq_ip_set_transport_header — set the transport_header field in pktb 🦋

Parameters

  • pktb — Pointer to user-space network packet buffer
  • iph — Pointer to the IPv4 header

Returns

0 on success or -1 if a minimal validation check fails 😬

Note

most programs should call nfq_ip_set_transport_header as soon as possible, because most layer 4 helper functions assume the transport_header field is valid. like, they assume it. don't leave them hanging bestie 🫶

Definition at line 73 of file ipv4.c.

⭐ int nfq_ip_snprintf (char * buf, size_t size, const struct iphdr * iph)

nfq_pkt_snprintf_ip — print IPv4 header into buffer in iptables LOG format 📝

Parameters

  • buf — Pointer to buffer that will be used to print the header
  • size — Size of the buffer (or remaining room in it)
  • iph — Pointer to a valid IPv4 header

Returns

same as snprintf 💫

See also

snprintf(3)

Definition at line 153 of file ipv4.c.

👑 Author 👑

Generated automatically by Doxygen for libnetfilter_queue from the source code. (yes bestie, a robot wrote this one, and honestly? she ate 🤖💖)

and that's the whole page, no crumbs left, we kept every detail, every param, every return value, every line number 🍓

libnetfilter_queue · Version 1.0.5 · ipv4(3) — mwah, go forth and mangle responsibly, ily 💜✨🦋

📦 where this page comes from