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|
//! A module with all the nftables expressions that can be added to [`Rule`]s to build up how
//! they match against packets.
//!
//! [`Rule`]: struct.Rule.html
use std::ffi::CStr;
use std::ffi::CString;
use std::fmt::Debug;
use std::rc::Rc;
use super::rule::Rule;
use rustables_sys::{self as sys, libc};
pub struct ExpressionWrapper {
pub(crate) expr: *const sys::nftnl_expr,
// we also need the rule here to ensure that the rule lives as long as the `expr` pointer
#[allow(dead_code)]
pub(crate) rule: Rc<Rule>,
}
impl Debug for ExpressionWrapper {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
write!(f, "{:?}", self.get_str())
}
}
impl ExpressionWrapper {
/// Retrieves a textual description of the expression.
pub fn get_str(&self) -> CString {
let mut descr_buf = vec![0i8; 4096];
unsafe {
sys::nftnl_expr_snprintf(
descr_buf.as_mut_ptr(),
(descr_buf.len() - 1) as u64,
self.expr,
sys::NFTNL_OUTPUT_DEFAULT,
0,
);
CStr::from_ptr(descr_buf.as_ptr()).to_owned()
}
}
/// Retrieves the type of expression ("log", "counter", ...).
pub fn get_kind(&self) -> Option<&CStr> {
unsafe {
let ptr = sys::nftnl_expr_get_str(self.expr, sys::NFTNL_EXPR_NAME as u16);
if !ptr.is_null() {
Some(CStr::from_ptr(ptr))
} else {
None
}
}
}
/// Attempt to decode the expression as the type T, returning None if such
/// conversion is not possible or failed.
pub fn decode_expr<T: Expression>(&self) -> Option<T> {
if let Some(kind) = self.get_kind() {
let raw_name = unsafe { CStr::from_ptr(T::get_raw_name()) };
if kind == raw_name {
return T::from_expr(self.expr);
}
}
None
}
}
/// Trait for every safe wrapper of an nftables expression.
pub trait Expression {
/// Returns the raw name used by nftables to identify the rule.
fn get_raw_name() -> *const libc::c_char;
/// Try to parse the expression from a raw nftables expression,
/// returning None if the attempted parsing failed.
fn from_expr(_expr: *const sys::nftnl_expr) -> Option<Self>
where
Self: Sized,
{
None
}
/// Allocates and returns the low level `nftnl_expr` representation of this expression.
/// The caller to this method is responsible for freeing the expression.
fn to_expr(&self, rule: &Rule) -> *mut sys::nftnl_expr;
}
/// A netfilter data register. The expressions store and read data to and from these
/// when evaluating rule statements.
#[derive(Debug, Copy, Clone, Eq, PartialEq, Hash)]
#[repr(i32)]
pub enum Register {
Verdict = libc::NFT_REG_VERDICT,
Reg1 = libc::NFT_REG_1,
Reg2 = libc::NFT_REG_2,
Reg3 = libc::NFT_REG_3,
Reg4 = libc::NFT_REG_4,
}
impl Register {
pub fn to_raw(self) -> u32 {
self as u32
}
pub fn from_raw(val: u32) -> Option<Self> {
match val as i32 {
libc::NFT_REG_VERDICT => Some(Self::Verdict),
libc::NFT_REG_1 => Some(Self::Reg1),
libc::NFT_REG_2 => Some(Self::Reg2),
libc::NFT_REG_3 => Some(Self::Reg3),
libc::NFT_REG_4 => Some(Self::Reg4),
_ => None,
}
}
}
mod bitwise;
pub use self::bitwise::*;
mod cmp;
pub use self::cmp::*;
mod counter;
pub use self::counter::*;
pub mod ct;
pub use self::ct::*;
mod immediate;
pub use self::immediate::*;
mod log;
pub use self::log::*;
mod lookup;
pub use self::lookup::*;
mod masquerade;
pub use self::masquerade::*;
mod meta;
pub use self::meta::*;
mod nat;
pub use self::nat::*;
mod payload;
pub use self::payload::*;
mod verdict;
pub use self::verdict::*;
#[macro_export(local_inner_macros)]
macro_rules! nft_expr {
(bitwise mask $mask:expr,xor $xor:expr) => {
nft_expr_bitwise!(mask $mask, xor $xor)
};
(cmp $op:tt $data:expr) => {
nft_expr_cmp!($op $data)
};
(counter) => {
$crate::expr::Counter { nb_bytes: 0, nb_packets: 0}
};
(ct $key:ident set) => {
nft_expr_ct!($key set)
};
(ct $key:ident) => {
nft_expr_ct!($key)
};
(immediate $expr:ident $value:expr) => {
nft_expr_immediate!($expr $value)
};
(log group $group:ident prefix $prefix:expr) => {
nft_expr_log!(group $group prefix $prefix)
};
(log group $group:ident) => {
nft_expr_log!(group $group)
};
(log prefix $prefix:expr) => {
nft_expr_log!(prefix $prefix)
};
(log) => {
nft_expr_log!()
};
(lookup $set:expr) => {
nft_expr_lookup!($set)
};
(masquerade) => {
$crate::expr::Masquerade
};
(meta $expr:ident set) => {
nft_expr_meta!($expr set)
};
(meta $expr:ident) => {
nft_expr_meta!($expr)
};
(payload $proto:ident $field:ident) => {
nft_expr_payload!($proto $field)
};
(verdict $verdict:ident) => {
nft_expr_verdict!($verdict)
};
(verdict $verdict:ident $chain:expr) => {
nft_expr_verdict!($verdict $chain)
};
}
|
