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aya/ebpf/aya-ebpf/src/maps/xdp/dev_map_hash.rs

143 lines
4.5 KiB
Rust

use core::{cell::UnsafeCell, mem, num::NonZeroU32};
use aya_ebpf_bindings::bindings::bpf_devmap_val;
use super::{dev_map::DevMapValue, try_redirect_map};
use crate::{
bindings::{bpf_map_def, bpf_map_type::BPF_MAP_TYPE_DEVMAP_HASH},
lookup,
maps::PinningType,
};
/// A map of network devices.
///
/// XDP programs can use this map to redirect packets to other network devices. It is similar to
/// [`DevMap`](super::DevMap), but is an hash map rather than an array. Keys do not need to be
/// contiguous nor start at zero, but there is a hashing cost to every lookup.
///
/// # Minimum kernel version
///
/// The minimum kernel version required to use this feature is 5.4.
///
/// # Examples
///
/// ```rust,no_run
/// use aya_ebpf::{bindings::xdp_action, macros::{map, xdp}, maps::DevMapHash, programs::XdpContext};
///
/// #[map]
/// static MAP: DevMapHash = DevMapHash::with_max_entries(1, 0);
///
/// #[xdp]
/// fn xdp(_ctx: XdpContext) -> u32 {
/// MAP.redirect(42, xdp_action::XDP_PASS as u64).unwrap_or(xdp_action::XDP_DROP)
/// }
/// ```
#[repr(transparent)]
pub struct DevMapHash {
def: UnsafeCell<bpf_map_def>,
}
unsafe impl Sync for DevMapHash {}
impl DevMapHash {
/// Creates a [`DevMapHash`] with a set maximum number of elements.
///
/// # Examples
///
/// ```rust,no_run
/// use aya_ebpf::{macros::map, maps::DevMapHash};
///
/// #[map]
/// static MAP: DevMapHash = DevMapHash::with_max_entries(8, 0);
/// ```
pub const fn with_max_entries(max_entries: u32, flags: u32) -> DevMapHash {
DevMapHash {
def: UnsafeCell::new(bpf_map_def {
type_: BPF_MAP_TYPE_DEVMAP_HASH,
key_size: mem::size_of::<u32>() as u32,
value_size: mem::size_of::<bpf_devmap_val>() as u32,
max_entries,
map_flags: flags,
id: 0,
pinning: PinningType::None as u32,
}),
}
}
/// Creates a [`DevMapHash`] with a set maximum number of elements that can be pinned to the BPF
/// File System (bpffs).
///
/// # Examples
///
/// ```rust,no_run
/// use aya_ebpf::{macros::map, maps::DevMapHash};
///
/// #[map]
/// static MAP: DevMapHash = DevMapHash::pinned(8, 0);
/// ```
pub const fn pinned(max_entries: u32, flags: u32) -> DevMapHash {
DevMapHash {
def: UnsafeCell::new(bpf_map_def {
type_: BPF_MAP_TYPE_DEVMAP_HASH,
key_size: mem::size_of::<u32>() as u32,
value_size: mem::size_of::<bpf_devmap_val>() as u32,
max_entries,
map_flags: flags,
id: 0,
pinning: PinningType::ByName as u32,
}),
}
}
/// Retrieves the interface index with `key` in the map.
///
/// To actually redirect a packet, see [`DevMapHash::redirect`].
///
/// # Examples
///
/// ```rust,no_run
/// use aya_ebpf::{macros::map, maps::DevMapHash};
///
/// #[map]
/// static MAP: DevMapHash = DevMapHash::with_max_entries(1, 0);
///
/// let target_if_index = MAP.get(42).unwrap().if_index;
///
/// // redirect to ifindex
/// ```
#[inline(always)]
pub fn get(&self, key: u32) -> Option<DevMapValue> {
let value = lookup(self.def.get(), &key)?;
let value: &bpf_devmap_val = unsafe { value.as_ref() };
Some(DevMapValue {
if_index: value.ifindex,
// SAFETY: map writes use fd, map reads use id.
// https://elixir.bootlin.com/linux/v6.2/source/include/uapi/linux/bpf.h#L6136
prog_id: NonZeroU32::new(unsafe { value.bpf_prog.id }),
})
}
/// Redirects the current packet on the interface at `key`.
///
/// The lower two bits of `flags` are used for the return code if the map lookup fails, which
/// can be used as the XDP program's return code if a CPU cannot be found.
///
/// # Examples
///
/// ```rust,no_run
/// use aya_ebpf::{bindings::xdp_action, macros::{map, xdp}, maps::DevMapHash, programs::XdpContext};
///
/// #[map]
/// static MAP: DevMapHash = DevMapHash::with_max_entries(8, 0);
///
/// #[xdp]
/// fn xdp(_ctx: XdpContext) -> u32 {
/// MAP.redirect(7, 0).unwrap_or(xdp_action::XDP_DROP)
/// }
/// ```
#[inline(always)]
pub fn redirect(&self, key: u32, flags: u64) -> Result<u32, u32> {
try_redirect_map(&self.def, key, flags)
}
}