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• byteorder
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• cpu
• crypto.aead
• crypto.comp
• crypto.rng
• crypto.shash
• crypto.skcipher
• data
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• fib
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• linux
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• lunatik.runner
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• net
• netfilter
• notifier
• probe
• rcu
• signal
• socket
• socket.inet
• socket.raw
• socket.unix
• syscall
• syscall.table
• thread
• xdp
• xtable

Topics

• README

Module linux

Various Linux kernel facilities.

This library includes functions for random number generation, task scheduling, time retrieval, kernel symbol lookup, network interface information, access to kernel constants like file modes, task states, and error numbers.

Functions

difftime (t2, t1)	Calculates the difference between two timestamps.
errname (err)	Returns the symbolic name of a kernel error number.
ifaddr (The)	Gets the HW address for the network interface index.
ifindex (interface_name)	Gets the interface index for a network device name.
lookup (symbol_name)	Looks up a kernel symbol by name.
random ([m[, n]])	Generates pseudo-random integers.
schedule ([timeout[, state]])	Puts the current task to sleep.
time ()	Gets the current real time.
tracing ([enable])	Controls kernel tracing.

Tables

task	Table of task state constants.

Functions

difftime (t2, t1)

Calculates the difference between two timestamps.

Parameters:

• t2 integer The later timestamp (e.g., from linux.time()).
• t1 integer The earlier timestamp (e.g., from linux.time()).

Returns:

integer The difference t2 - t1 in nanoseconds.

errname (err)

Returns the symbolic name of a kernel error number. For example, it converts 2 to "ENOENT".

Parameters:

• err integer The error number (e.g., 2).

Returns:

string The symbolic name of the error (e.g., "ENOENT"). Returns "unknown" (or the error number as a string) if the name cannot be resolved.

Usage:

local name = linux.errname(2)
print("Error name:", name) -- "ENOENT"

ifaddr (The)

Gets the HW address for the network interface index.

Parameters:

• The integer interface index number.

Returns:

string The interface HW address.

Raises:

Error if the device is not found.

Usage:

local addr = linux.ifaddr(index)
print(string.byte(addr,1,6))

ifindex (interface_name)

Gets the interface index for a network device name.

Parameters:

• interface_name string The name of the network interface (e.g., "eth0").

Returns:

integer The interface index.

Raises:

Error if the device is not found.

Usage:

local index = linux.ifindex("lo")
print("Index of lo:", index)

lookup (symbol_name)

Looks up a kernel symbol by name. Uses kallsyms_lookup_name (potentially via kprobes) to find the address of a kernel symbol.

Parameters:

• symbol_name string The name of the kernel symbol to look up.

Returns:

lightuserdata The address of the symbol if found, otherwise nil (represented as a NULL lightuserdata).

Usage:

local addr = linux.lookup("jiffies")
if addr then print("Address of jiffies:", addr) end

random ([m[, n]])

Generates pseudo-random integers. Mimics the behavior of Lua's math.random but uses kernel's random number generation facilities (get_random_u32 or get_random_u64).

Parameters:

• m integer Lower bound of the range. If only one argument n is provided, m defaults to 1. (optional)
• n integer Upper bound of the range. (optional)

Returns:

integer A pseudo-random integer. - If called without arguments, returns an integer with all bits pseudo-random. - If called with one integer n, returns a pseudo-random integer in the range [1, n]. - If called with two integers m and n, returns a pseudo-random integer in the range [m, n].

Raises:

Error if m > n or if the interval is too large.

Usage:

local r1 = linux.random()       -- Full range random integer
local r2 = linux.random(100)    -- Random integer between 1 and 100
local r3 = linux.random(50, 60) -- Random integer between 50 and 60

schedule ([timeout[, state]])

Puts the current task to sleep. Sets the current task's state and schedules it out until a timeout occurs or it is woken up.

Parameters:

• timeout integer Duration in milliseconds to sleep. Defaults to MAX_SCHEDULE_TIMEOUT (effectively indefinite sleep until woken). (optional)
• state integer The task state to set before sleeping. See linux.task for possible values. Defaults to linux.task.INTERRUPTIBLE. (optional)

Returns:

integer The remaining time in milliseconds if the sleep was interrupted before the full timeout, or 0 if the full timeout elapsed.

Raises:

Error if an invalid task state is provided.

See also:

linux.task

Usage:

linux.schedule(1000) -- Sleep for 1 second (interruptible)
linux.schedule(500, linux.task.UNINTERRUPTIBLE) -- Sleep for 0.5 seconds (uninterruptible)

time ()

Gets the current real time.

Returns:

integer The current time in nanoseconds since the epoch (from ktime_get_real_ns).

tracing ([enable])

Controls kernel tracing. Turns kernel tracing on or off via tracing_on() and tracing_off().

Parameters:

• enable boolean If true, turns tracing on. If false, turns tracing off. If omitted, does not change the state. (optional)

Returns:

boolean The current state of kernel tracing (true if on, false if off) after any change.

Usage:

local was_tracing = linux.tracing(true) -- Enable tracing
if was_tracing then print("Tracing is now on") end
local current_state = linux.tracing()   -- Get current state
linux.tracing(false)                    -- Disable tracing

Tables

task

Table of task state constants. Exports task state flags from <linux/sched.h>. These are used with linux.schedule().

Fields:

• INTERRUPTIBLE integer Task is waiting for a signal or a resource (sleeping), can be interrupted.
• UNINTERRUPTIBLE integer Task is waiting (sleeping), cannot be interrupted by signals (except fatal ones if KILLABLE is also implied by context).
• KILLABLE integer Task is waiting (sleeping) like UNINTERRUPTIBLE, but can be interrupted by fatal signals.
• IDLE integer Task is idle, similar to UNINTERRUPTIBLE but avoids loadavg accounting.

See also:

linux.schedule