aya_ebpf/maps/xdp/
dev_map_hash.rs

1use core::{cell::UnsafeCell, mem, num::NonZeroU32, ptr::NonNull};
2
3use aya_ebpf_bindings::bindings::bpf_devmap_val;
4use aya_ebpf_cty::c_void;
5
6use super::{dev_map::DevMapValue, try_redirect_map};
7use crate::{
8    bindings::{bpf_map_def, bpf_map_type::BPF_MAP_TYPE_DEVMAP_HASH},
9    helpers::bpf_map_lookup_elem,
10    maps::PinningType,
11};
12
13/// A map of network devices.
14///
15/// XDP programs can use this map to redirect packets to other network devices. It is similar to
16/// [`DevMap`](super::DevMap), but is an hash map rather than an array. Keys do not need to be
17/// contiguous nor start at zero, but there is a hashing cost to every lookup.
18///
19/// # Minimum kernel version
20///
21/// The minimum kernel version required to use this feature is 5.4.
22///
23/// # Examples
24///
25/// ```rust,no_run
26/// use aya_ebpf::{bindings::xdp_action, macros::{map, xdp}, maps::DevMapHash, programs::XdpContext};
27///
28/// #[map]
29/// static MAP: DevMapHash = DevMapHash::with_max_entries(1, 0);
30///
31/// #[xdp]
32/// fn xdp(_ctx: XdpContext) -> u32 {
33///     MAP.redirect(42, xdp_action::XDP_PASS as u64).unwrap_or(xdp_action::XDP_DROP)
34/// }
35/// ```
36#[repr(transparent)]
37pub struct DevMapHash {
38    def: UnsafeCell<bpf_map_def>,
39}
40
41unsafe impl Sync for DevMapHash {}
42
43impl DevMapHash {
44    /// Creates a [`DevMapHash`] with a set maximum number of elements.
45    ///
46    /// # Examples
47    ///
48    /// ```rust,no_run
49    /// use aya_ebpf::{macros::map, maps::DevMapHash};
50    ///
51    /// #[map]
52    /// static MAP: DevMapHash = DevMapHash::with_max_entries(8, 0);
53    /// ```
54    pub const fn with_max_entries(max_entries: u32, flags: u32) -> DevMapHash {
55        DevMapHash {
56            def: UnsafeCell::new(bpf_map_def {
57                type_: BPF_MAP_TYPE_DEVMAP_HASH,
58                key_size: mem::size_of::<u32>() as u32,
59                value_size: mem::size_of::<bpf_devmap_val>() as u32,
60                max_entries,
61                map_flags: flags,
62                id: 0,
63                pinning: PinningType::None as u32,
64            }),
65        }
66    }
67
68    /// Creates a [`DevMapHash`] with a set maximum number of elements that can be pinned to the BPF
69    /// File System (bpffs).
70    ///
71    /// # Examples
72    ///
73    /// ```rust,no_run
74    /// use aya_ebpf::{macros::map, maps::DevMapHash};
75    ///
76    /// #[map]
77    /// static MAP: DevMapHash = DevMapHash::pinned(8, 0);
78    /// ```
79    pub const fn pinned(max_entries: u32, flags: u32) -> DevMapHash {
80        DevMapHash {
81            def: UnsafeCell::new(bpf_map_def {
82                type_: BPF_MAP_TYPE_DEVMAP_HASH,
83                key_size: mem::size_of::<u32>() as u32,
84                value_size: mem::size_of::<bpf_devmap_val>() as u32,
85                max_entries,
86                map_flags: flags,
87                id: 0,
88                pinning: PinningType::ByName as u32,
89            }),
90        }
91    }
92
93    /// Retrieves the interface index with `key` in the map.
94    ///
95    /// To actually redirect a packet, see [`DevMapHash::redirect`].
96    ///
97    /// # Examples
98    ///
99    /// ```rust,no_run
100    /// use aya_ebpf::{macros::map, maps::DevMapHash};
101    ///
102    /// #[map]
103    /// static MAP: DevMapHash = DevMapHash::with_max_entries(1, 0);
104    ///
105    /// let target_if_index = MAP.get(42).unwrap().if_index;
106    ///
107    /// // redirect to ifindex
108    /// ```
109    #[inline(always)]
110    pub fn get(&self, key: u32) -> Option<DevMapValue> {
111        unsafe {
112            let value =
113                bpf_map_lookup_elem(self.def.get() as *mut _, &key as *const _ as *const c_void);
114            NonNull::new(value as *mut bpf_devmap_val).map(|p| DevMapValue {
115                if_index: p.as_ref().ifindex,
116                // SAFETY: map writes use fd, map reads use id.
117                // https://elixir.bootlin.com/linux/v6.2/source/include/uapi/linux/bpf.h#L6136
118                prog_id: NonZeroU32::new(p.as_ref().bpf_prog.id),
119            })
120        }
121    }
122
123    /// Redirects the current packet on the interface at `key`.
124    ///
125    /// The lower two bits of `flags` are used for the return code if the map lookup fails, which
126    /// can be used as the XDP program's return code if a CPU cannot be found.
127    ///
128    /// # Examples
129    ///
130    /// ```rust,no_run
131    /// use aya_ebpf::{bindings::xdp_action, macros::{map, xdp}, maps::DevMapHash, programs::XdpContext};
132    ///
133    /// #[map]
134    /// static MAP: DevMapHash = DevMapHash::with_max_entries(8, 0);
135    ///
136    /// #[xdp]
137    /// fn xdp(_ctx: XdpContext) -> u32 {
138    ///     MAP.redirect(7, 0).unwrap_or(xdp_action::XDP_DROP)
139    /// }
140    /// ```
141    #[inline(always)]
142    pub fn redirect(&self, key: u32, flags: u64) -> Result<u32, u32> {
143        try_redirect_map(&self.def, key, flags)
144    }
145}
aya_ebpf/maps/xdp/dev_map_hash.rs

aya_ebpf/maps/xdp/
dev_map_hash.rs
