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use super::*;
/// Decoded packet headers (data link layer and higher).
/// You can use PacketHeaders::from_ethernet_slice or PacketHeader::from_ip_slice
/// to decode and get this struct as a result.
#[derive(Clone, Debug, Eq, PartialEq)]
pub struct PacketHeaders<'a> {
pub link: Option<Ethernet2Header>,
pub vlan: Option<VlanHeader>,
pub ip: Option<IpHeader>,
pub transport: Option<TransportHeader>,
/// Rest of the packet that could not be decoded as a header (usually the payload).
pub payload: &'a [u8]
}
impl<'a> PacketHeaders<'a> {
/// Tries to decode as much as possible of a packet.
pub fn from_ethernet_slice(packet: &[u8]) -> Result<PacketHeaders, ReadError> {
let (ethernet, mut rest) = Ethernet2Header::from_slice(packet)?;
let mut ether_type = ethernet.ether_type;
let mut result = PacketHeaders{
link: Some(ethernet),
vlan: None,
ip: None,
transport: None,
payload: &[]
};
//parse vlan header(s)
use crate::EtherType::*;
const VLAN_TAGGED_FRAME: u16 = VlanTaggedFrame as u16;
const PROVIDER_BRIDGING: u16 = ProviderBridging as u16;
const VLAN_DOUBLE_TAGGED_FRAME: u16 = VlanDoubleTaggedFrame as u16;
result.vlan = match ether_type {
VLAN_TAGGED_FRAME | PROVIDER_BRIDGING | VLAN_DOUBLE_TAGGED_FRAME => {
use crate::VlanHeader::*;
let (outer, outer_rest) = SingleVlanHeader::from_slice(rest)?;
//set the rest & ether_type for the following operations
rest = outer_rest;
ether_type = outer.ether_type;
//parse second vlan header if present
match ether_type {
//second vlan tagging header
VLAN_TAGGED_FRAME | PROVIDER_BRIDGING | VLAN_DOUBLE_TAGGED_FRAME => {
let (inner, inner_rest) = SingleVlanHeader::from_slice(rest)?;
//set the rest & ether_type for the following operations
rest = inner_rest;
ether_type = inner.ether_type;
Some(Double(DoubleVlanHeader{
outer,
inner
}))
},
//no second vlan header detected -> single vlan header
_ => Some(Single(outer))
}
},
//no vlan header
_ => None
};
//parse ip (if present)
const IPV4: u16 = Ipv4 as u16;
const IPV6: u16 = Ipv6 as u16;
match ether_type {
IPV4 => {
let (ip, ip_rest) = Ipv4Header::from_slice(rest)?;
let (ip_ext, ip_protocol, ip_ext_rest) = Ipv4Extensions::from_slice(ip.protocol, ip_rest)?;
//set the ip result & rest
rest = ip_ext_rest;
result.ip = Some(IpHeader::Version4(ip, ip_ext));
//parse the transport layer
let (transport, transport_rest) = read_transport(ip_protocol, rest)?;
//assign to the output
rest = transport_rest;
result.transport = transport;
},
IPV6 => {
let (ip, ip_rest) = Ipv6Header::from_slice(rest)?;
let (ip_ext, next_header, ip_ext_rest) = Ipv6Extensions::from_slice(ip.next_header, ip_rest)?;
//set the ip result & rest
rest = ip_ext_rest;
result.ip = Some(IpHeader::Version6(ip, ip_ext));
//parse the transport layer
let (transport, transport_rest) = read_transport(next_header, rest)?;
rest = transport_rest;
result.transport = transport;
},
_ => {}
}
//finally update the rest slice based on the cursor position
result.payload = rest;
Ok(result)
}
/// Tries to decode an ip packet and its transport headers.
/// Assumes the given slice starts with the first byte of the IP header
/// # Example
/// ```
/// # use etherparse::*;
/// // build a UDP packet
/// let payload = [0u8;18];
/// let builder = PacketBuilder::
/// ipv4([192,168,1,1], //source ip
/// [192,168,1,2], //desitionation ip
/// 20) //time to life
/// .udp(21, //source port
/// 1234); //desitnation port
///
/// // serialize the packet
/// let packet = {
/// let mut packet = Vec::<u8>::with_capacity(
/// builder.size(payload.len()));
/// builder.write(&mut packet, &payload).unwrap();
/// packet
/// };
/// # // should be 64 bytes long (including the ethernet FCS/CRC32) but since
/// # // this is not provided at the moment we're gonna be fine with 46
/// # assert_eq!(packet.len(), 46);
///
/// // parse the ip packet from a slice
/// let p = PacketHeaders::from_ip_slice(&packet)
/// .expect("Failed to decode the packet");
/// # assert_eq!(p.payload, payload);
/// ```
pub fn from_ip_slice(packet: &[u8]) -> Result<PacketHeaders, ReadError> {
let mut result = PacketHeaders {
link: None,
vlan: None,
ip: None,
transport: None,
payload: &[],
};
let (transport_proto, rest) = {
let (ip, transport_proto, rest) = IpHeader::from_slice(packet)?;
// update output
result.ip = Some(ip);
(transport_proto, rest)
};
// try to parse the transport header
let (transport, rest) = read_transport(transport_proto, rest)?;
// update output
result.transport = transport;
result.payload = rest;
Ok(result)
}
}
/// helper function to process transport headers
fn read_transport(
protocol: u8,
rest: &[u8],
) -> Result<(Option<TransportHeader>, &[u8]), ReadError> {
use crate::ip_number::*;
match protocol {
UDP => Ok(UdpHeader::from_slice(rest)
.map(|value| (Some(TransportHeader::Udp(value.0)), value.1))?),
TCP => Ok(TcpHeader::from_slice(rest)
.map(|value| (Some(TransportHeader::Tcp(value.0)), value.1))?),
_ => Ok((None, rest)),
}
}