1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130

use libc::{setsockopt, SOL_SOCKET};
use std::{
    io, mem,
    os::unix::prelude::{AsRawFd, RawFd},
};
use thiserror::Error;

use crate::{
    generated::{bpf_prog_type::BPF_PROG_TYPE_SOCKET_FILTER, SO_ATTACH_BPF, SO_DETACH_BPF},
    programs::{load_program, Link, LinkRef, ProgramData, ProgramError},
};

/// The type returned when attaching a [`SocketFilter`] fails.
#[derive(Debug, Error)]
pub enum SocketFilterError {
    /// Setting the `SO_ATTACH_BPF` socket option failed.
    #[error("setsockopt SO_ATTACH_BPF failed")]
    SoAttachBpfError {
        #[source]
        io_error: io::Error,
    },
}

/// A program used to inspect and filter incoming packets on a socket.
///
/// [`SocketFilter`] programs are attached on sockets and can be used to inspect
/// and filter incoming packets.
///
/// # Minimum kernel version
///
/// The minimum kernel version required to use this feature is 4.0.
///
/// # Examples
///
/// ```no_run
/// # #[derive(Debug, thiserror::Error)]
/// # enum Error {
/// #     #[error(transparent)]
/// #     IO(#[from] std::io::Error),
/// #     #[error(transparent)]
/// #     Map(#[from] aya::maps::MapError),
/// #     #[error(transparent)]
/// #     Program(#[from] aya::programs::ProgramError),
/// #     #[error(transparent)]
/// #     Bpf(#[from] aya::BpfError)
/// # }
/// # let mut bpf = aya::Bpf::load(&[])?;
/// use std::convert::TryInto;
/// use std::net::TcpStream;
/// use std::os::unix::io::AsRawFd;
/// use aya::programs::SocketFilter;
///
/// let mut client = TcpStream::connect("127.0.0.1:1234")?;
/// let prog: &mut SocketFilter = bpf.program_mut("filter_packets")?.try_into()?;
/// prog.load()?;
/// prog.attach(client.as_raw_fd())?;
/// # Ok::<(), Error>(())
/// ```
#[derive(Debug)]
#[doc(alias = "BPF_PROG_TYPE_SOCKET_FILTER")]
pub struct SocketFilter {
    pub(crate) data: ProgramData,
}

impl SocketFilter {
    /// Loads the program inside the kernel.
    ///
    /// See also [`Program::load`](crate::programs::Program::load).
    pub fn load(&mut self) -> Result<(), ProgramError> {
        load_program(BPF_PROG_TYPE_SOCKET_FILTER, &mut self.data)
    }

    /// Attaches the filter on the given socket.
    pub fn attach<T: AsRawFd>(&mut self, socket: T) -> Result<LinkRef, ProgramError> {
        let prog_fd = self.data.fd_or_err()?;
        let socket = socket.as_raw_fd();

        let ret = unsafe {
            setsockopt(
                socket,
                SOL_SOCKET,
                SO_ATTACH_BPF as i32,
                &prog_fd as *const _ as *const _,
                mem::size_of::<RawFd>() as u32,
            )
        };
        if ret < 0 {
            return Err(SocketFilterError::SoAttachBpfError {
                io_error: io::Error::last_os_error(),
            }
            .into());
        }

        Ok(self.data.link(SocketFilterLink {
            socket,
            prog_fd: Some(prog_fd),
        }))
    }
}

#[derive(Debug)]
struct SocketFilterLink {
    socket: RawFd,
    prog_fd: Option<RawFd>,
}

impl Link for SocketFilterLink {
    fn detach(&mut self) -> Result<(), ProgramError> {
        if let Some(fd) = self.prog_fd.take() {
            unsafe {
                setsockopt(
                    self.socket,
                    SOL_SOCKET,
                    SO_DETACH_BPF as i32,
                    &fd as *const _ as *const _,
                    mem::size_of::<RawFd>() as u32,
                );
            }
            Ok(())
        } else {
            Err(ProgramError::AlreadyDetached)
        }
    }
}

impl Drop for SocketFilterLink {
    fn drop(&mut self) {
        let _ = self.detach();
    }
}