nlmsg(3)

💖 nlmsg(3) — the Netlink message helper functions page, bestie 💖

okay so this is the manual page for nlmsg from the libnetfilter_log library (that's the 3 in the name — it's a library function, not a command, iykyk). it's the whole Netlink message helper situation. buckle up, there's a lot of cute little functions in here and we're gonna go through every single one. 🎀

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✨ NAME ✨

nflog_nlmsg_put_header, nflog_attr_put_cfg_mode, nflog_attr_put_cfg_cmd, nflog_nlmsg_parse, nflog_nlmsg_snprintf — Netlink message helper functions 🦋

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🌸 SYNOPSIS 🌸

#include <netinet/in.h>
#include <libnetfilter_log/libnetfilter_log.h>

struct nlmsghdr * nflog_nlmsg_put_header (char *buf, uint8_t type, uint8_t family, uint16_t gnum)
int nflog_attr_put_cfg_mode (struct nlmsghdr *nlh, uint8_t mode, uint32_t range)
int nflog_attr_put_cfg_cmd (struct nlmsghdr *nlh, uint8_t cmd)
int nflog_nlmsg_parse (const struct nlmsghdr *nlh, struct nlattr **attr)
int nflog_nlmsg_snprintf (char *buf, size_t bufsiz, const struct nlmsghdr *nlh, struct nlattr **attr, enum nflog_output_type type, uint32_t flags)

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👑 Function Documentation 👑

💅 int nflog_attr_put_cfg_cmd (struct nlmsghdr * nlh, uint8_t cmd)

nflog_attr_put_cfg_cmd — adds a command attribute to an nflog netlink message. literally just slots that command in there, no cap. ✨

Parameters

• nlh — pointer to the netlink message
• cmd — one of the enum nfulnl_msg_config_cmds

Returns

0

Definition at line 84 of file nlmsg.c.

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🎀 int nflog_attr_put_cfg_mode (struct nlmsghdr * nlh, uint8_t mode, uint32_t range)

nflog_attr_put_cfg_mode — adds a mode attribute to an nflog netlink message. the vibe-setter of attributes fr fr. 💖

Parameters

• nlh — pointer to the netlink message
• mode — copy mode: NFULNL_COPY_NONE, NFULNL_COPY_META or NFULNL_COPY_PACKET
• range — copy range

Returns

0

Definition at line 64 of file nlmsg.c.

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🦋 int nflog_nlmsg_parse (const struct nlmsghdr * nlh, struct nlattr ** attr)

nflog_nlmsg_parse — sets the nlattrs from a netlink message. it's giving "unpack the message, bestie". 🧚

Parameters

• nlh — pointer to the netlink message
• attr — pointer to an array of nlattr of size NFULA_MAX + 1

Returns

0

Definition at line 162 of file nlmsg.c.

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🌈 struct nlmsghdr * nflog_nlmsg_put_header (char * buf, uint8_t type, uint8_t family, uint16_t gnum)

nflog_nlmsg_put_header — populates a memory buffer with nflog Netlink headers. it's the header-glow-up function. ✨

Parameters

• buf — pointer to memory buffer
• type — either NFULNL_MSG_PACKET or NFULNL_MSG_CONFIG (that's the enum nfulnl_msg_types)
• family — protocol family
• gnum — group number

Initialises buf to start with a netlink header for the log subsystem followed by an nfnetlink header with the log group. iconic behaviour honestly.

Returns

pointer to the created Netlink header structure 👑

Definition at line 39 of file nlmsg.c.

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💜 int nflog_nlmsg_snprintf (char * buf, size_t bufsiz, const struct nlmsghdr * nlh, struct nlattr ** attr, enum nflog_output_type type, uint32_t flags)

nflog_nlmsg_snprintf — prints nflog nlattrs into a buffer. the main character of this whole page ngl. 💅

Parameters

• buf — buffer used to build the printable nflog
• bufsiz — size of the buffer
• nlh — pointer to netlink message (to get queue num in the future)
• attr — pointer to an array of nlattr of size NFULA_MAX + 1
• type — print message type in enum nflog_output_type
• flags — the flag that tells what to print into the buffer

This function supports the following types / flags:

type: NFLOG_OUTPUT_XML

• NFLOG_XML_PREFIX: include the string prefix
• NFLOG_XML_HW: include the hardware link layer address
• NFLOG_XML_MARK: include the packet mark
• NFLOG_XML_DEV: include the device information
• NFLOG_XML_PHYSDEV: include the physical device information
• NFLOG_XML_PAYLOAD: include the payload (in hexadecimal)
• NFLOG_XML_TIME: include the timestamp
• NFLOG_XML_ALL: include all the logging information (all flags set)

You can combine these flags with a bitwise OR. stack 'em, bestie. 🫶

Returns

-1 on failure, else same as snprintf

Errors

EOPNOTSUPP — type is unsupported (i.e. not NFLOG_OUTPUT_XML)

ok so heads up: if you pass a type that isn't NFLOG_OUTPUT_XML, you get EOPNOTSUPP and that's it, that's the whole list. no other types live here yet. 😭

See also

snprintf(3)

Definition at line 196 of file nlmsg.c.

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🌟 Author 🌟

Generated automatically by Doxygen for libnetfilter_log from the source code. (yes, a robot wrote it, and honestly? it ate. 💅)

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and that's the whole page bestie!! tysm for reading, love u, go write some netlink messages 💖

libnetfilter_log — Version 1.0.2 🌸 — mwah, that's the sign-off, periodt. 🎀✨