Errors on android

[Kofituo]

Hi there,
I'm trying out this crate on an android device but I'm facing this error

log_panics: thread '<unnamed>' panicked at 'Error happened Permission denied (os error 13)': src/lib.rs:78

This is the code surrounding line 78

fn get_mac_through_arp(interface: NetworkInterface, target_ip: Ipv4Addr) -> MacAddr {
    let source_ip = interface
        .ips
        .iter()
        .find(|ip| ip.is_ipv4())
        .map(|ip| match ip.ip() {
            IpAddr::V4(ip) => ip,
            _ => unreachable!(),
        })
        .unwrap();

    let (mut sender, mut receiver) = match pnet::datalink::channel(&interface, Default::default()) {
        Ok(Channel::Ethernet(tx, rx)) => (tx, rx),
        Ok(_) => panic!("Unknown channel type"),
        Err(e) => panic!("Error happened {}", e), // line 78
    };

    let mut ethernet_buffer = [0u8; 42];
    let mut ethernet_packet = MutableEthernetPacket::new(&mut ethernet_buffer).unwrap();

    ethernet_packet.set_destination(MacAddr::broadcast());
    ethernet_packet.set_source(interface.mac.unwrap());
    ethernet_packet.set_ethertype(EtherTypes::Arp);

    let mut arp_buffer = [0u8; 28];
    let mut arp_packet = MutableArpPacket::new(&mut arp_buffer).unwrap();

    arp_packet.set_hardware_type(ArpHardwareTypes::Ethernet);
    arp_packet.set_protocol_type(EtherTypes::Ipv4);
    arp_packet.set_hw_addr_len(6);
    arp_packet.set_proto_addr_len(4);
    arp_packet.set_operation(ArpOperations::Request);
    arp_packet.set_sender_hw_addr(interface.mac.unwrap());
    arp_packet.set_sender_proto_addr(source_ip);
    arp_packet.set_target_hw_addr(MacAddr::zero());
    arp_packet.set_target_proto_addr(target_ip);

    ethernet_packet.set_payload(arp_packet.packet_mut());

    sender
        .send_to(ethernet_packet.packet(), None)
        .unwrap()
        .unwrap();

    println!("Sent ARP request");

    loop {
        let buf = receiver.next().unwrap();
        let arp = ArpPacket::new(&buf[MutableEthernetPacket::minimum_packet_size()..]).unwrap();
        if arp.get_sender_proto_addr() == target_ip
            && arp.get_target_hw_addr() == interface.mac.unwrap()
        {
            println!("Received reply");
            return arp.get_sender_hw_addr();
        }
    }
    // unreachable
}

The code is from the examples folder (arp_packet.rs)

[Kofituo]

On further debugging, the error originates here:
linux.rs lines 101-109

let (typ, proto) = match config.channel_type {
        super::ChannelType::Layer2 => (libc::SOCK_RAW, eth_p_all),
        super::ChannelType::Layer3(proto) => (libc::SOCK_DGRAM, proto),
    };
    let socket = unsafe { libc::socket(libc::AF_PACKET, typ, proto.to_be() as i32) };
    if socket == -1 {
        return Err(io::Error::last_os_error()); // here
    }

[Martichou]

Afaik, you can't create a socket with eth_p_all if you're non-root. Solution would be to give your app root access or to switch to using a VPN-like API from Android to do that (but that's outside the scope of this project).

[Kofituo]

@Martichou Is there an alternative this library can use to it works on all android?

[Martichou]

The goal of this (I suppose you use datalink), is to get all packets. And afaik there's not other way (at least, not without root permission).

Raw sockets provide unrestricted access to the underlying protocols, which can be a security risks if misused. So the vast majority of OSes restrict it to superuser.