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110 lines
3.6 KiB
Rust
110 lines
3.6 KiB
Rust
//! An array of eBPF program file descriptors used as a jump table.
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use std::{
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borrow::{Borrow, BorrowMut},
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os::fd::{AsFd as _, AsRawFd as _, RawFd},
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};
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use crate::{
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maps::{check_bounds, check_kv_size, MapData, MapError, MapKeys},
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programs::ProgramFd,
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sys::{bpf_map_delete_elem, bpf_map_update_elem, SyscallError},
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};
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/// An array of eBPF program file descriptors used as a jump table.
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///
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/// eBPF programs can jump to other programs calling `bpf_tail_call(ctx,
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/// prog_array, index)`. You can use [`ProgramArray`] to configure which
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/// programs correspond to which jump indexes.
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///
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/// # Minimum kernel version
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///
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/// The minimum kernel version required to use this feature is 4.2.
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///
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/// # Examples
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/// ```no_run
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/// # let mut bpf = aya::Ebpf::load(&[])?;
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/// use aya::maps::ProgramArray;
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/// use aya::programs::CgroupSkb;
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///
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/// let mut prog_array = ProgramArray::try_from(bpf.take_map("JUMP_TABLE").unwrap())?;
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/// let prog_0: &CgroupSkb = bpf.program("example_prog_0").unwrap().try_into()?;
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/// let prog_0_fd = prog_0.fd().unwrap();
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/// let prog_1: &CgroupSkb = bpf.program("example_prog_1").unwrap().try_into()?;
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/// let prog_1_fd = prog_1.fd().unwrap();
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/// let prog_2: &CgroupSkb = bpf.program("example_prog_2").unwrap().try_into()?;
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/// let prog_2_fd = prog_2.fd().unwrap();
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/// let flags = 0;
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///
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/// // bpf_tail_call(ctx, JUMP_TABLE, 0) will jump to prog_0
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/// prog_array.set(0, &prog_0_fd, flags);
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///
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/// // bpf_tail_call(ctx, JUMP_TABLE, 1) will jump to prog_1
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/// prog_array.set(1, &prog_1_fd, flags);
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///
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/// // bpf_tail_call(ctx, JUMP_TABLE, 2) will jump to prog_2
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/// prog_array.set(2, &prog_2_fd, flags);
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/// # Ok::<(), aya::EbpfError>(())
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/// ```
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#[doc(alias = "BPF_MAP_TYPE_PROG_ARRAY")]
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pub struct ProgramArray<T> {
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pub(crate) inner: T,
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}
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impl<T: Borrow<MapData>> ProgramArray<T> {
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pub(crate) fn new(map: T) -> Result<Self, MapError> {
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let data = map.borrow();
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check_kv_size::<u32, RawFd>(data)?;
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Ok(Self { inner: map })
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}
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/// An iterator over the indices of the array that point to a program. The iterator item type
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/// is `Result<u32, MapError>`.
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pub fn indices(&self) -> MapKeys<'_, u32> {
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MapKeys::new(self.inner.borrow())
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}
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}
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impl<T: BorrowMut<MapData>> ProgramArray<T> {
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/// Sets the target program file descriptor for the given index in the jump table.
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///
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/// When an eBPF program calls `bpf_tail_call(ctx, prog_array, index)`, control
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/// flow will jump to `program`.
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pub fn set(&mut self, index: u32, program: &ProgramFd, flags: u64) -> Result<(), MapError> {
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let data = self.inner.borrow_mut();
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check_bounds(data, index)?;
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let fd = data.fd().as_fd();
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let prog_fd = program.as_fd();
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let prog_fd = prog_fd.as_raw_fd();
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bpf_map_update_elem(fd, Some(&index), &prog_fd, flags).map_err(|(_, io_error)| {
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SyscallError {
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call: "bpf_map_update_elem",
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io_error,
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}
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})?;
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Ok(())
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}
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/// Clears the value at index in the jump table.
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///
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/// Calling `bpf_tail_call(ctx, prog_array, index)` on an index that has been cleared returns an
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/// error.
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pub fn clear_index(&mut self, index: &u32) -> Result<(), MapError> {
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let data = self.inner.borrow_mut();
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check_bounds(data, *index)?;
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let fd = data.fd().as_fd();
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bpf_map_delete_elem(fd, index)
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.map(|_| ())
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.map_err(|(_, io_error)| {
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SyscallError {
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call: "bpf_map_delete_elem",
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io_error,
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}
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.into()
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})
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}
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}
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