Crate network_types

source ·
Expand description

Rust structs representing network protocol headers (on Layer 2, 3 and 4).

The crate is no_std, which makes it a great fit for eBPF programs written with Aya.

Examples

An example of an XDP program logging information about addresses and ports for incoming packets:

use core::mem;

use aya_bpf::{bindings::xdp_action, macros::xdp, programs::XdpContext};
use aya_log_ebpf::info;

use network_types::{
    eth::{EthHdr, EtherType},
    ip::{Ipv4Hdr, IpProto},
    tcp::TcpHdr,
    udp::UdpHdr,
};

#[xdp]
pub fn xdp_firewall(ctx: XdpContext) -> u32 {
    match try_xdp_firewall(ctx) {
        Ok(ret) => ret,
        Err(_) => xdp_action::XDP_PASS,
    }
}

#[inline(always)]
unsafe fn ptr_at<T>(ctx: &XdpContext, offset: usize) -> Result<*const T, ()> {
    let start = ctx.data();
    let end = ctx.data_end();
    let len = mem::size_of::<T>();

    if start + offset + len > end {
        return Err(());
    }

    Ok((start + offset) as *const T)
}

fn try_xdp_firewall(ctx: XdpContext) -> Result<u32, ()> {
    let ethhdr: *const EthHdr = unsafe { ptr_at(&ctx, 0)? };
    match unsafe { *ethhdr }.ether_type {
        EtherType::Ipv4 => {}
        _ => return Ok(xdp_action::XDP_PASS),
    }

    let ipv4hdr: *const Ipv4Hdr = unsafe { ptr_at(&ctx, EthHdr::LEN)? };
    let source_addr = u32::from_be(unsafe { *ipv4hdr }.src_addr);

    let source_port = match unsafe { *ipv4hdr }.proto {
        IpProto::Tcp => {
            let tcphdr: *const TcpHdr =
                unsafe { ptr_at(&ctx, EthHdr::LEN + Ipv4Hdr::LEN) }?;
            u16::from_be(unsafe { *tcphdr }.source)
        }
        IpProto::Udp => {
            let udphdr: *const UdpHdr =
                unsafe { ptr_at(&ctx, EthHdr::LEN + Ipv4Hdr::LEN) }?;
            u16::from_be(unsafe { *udphdr }.source)
        }
        _ => return Err(()),
    };

    info!(&ctx, "SRC IP: {}, SRC PORT: {}", source_addr, source_port);

    Ok(xdp_action::XDP_PASS)
}

Naming conventions

When naming stucts and fields, we are trying to stick to the following principles:

  • Use CamelCase, even for names which normally would be all uppercase (e.g. Icmp instead of ICMP). This is the convention used by the std::net module.
  • Where field names (specified by RFCs or other standards) contain spaces, replace them with _. In general, use snake_case for field names.
  • Shorten the following verbose names:
    • source -> src
    • destination -> dst
    • address -> addr

Feature flags

Serde support can be enabled through the serde feature flag. It is intended to be used with binary serialization libraries like bincode that leverage Serde’s infrastructure.

Note that no_std support is lost when enabling Serde.

Modules