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use crate::protocol::codec::Decode;
use crate::protocol::ip::IPProtocol;
use nom::bits;
use nom::error::Error;
use nom::number;
use nom::sequence;
use nom::IResult;
use std::net::Ipv4Addr;
/******************************************************************************
* Struct
******************************************************************************/
/*
* Internet Header Format
*
* 0 1 2 3
* 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* |Version| IHL |Type of Service| Total Length |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | Identification |Flags| Fragment Offset |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | Time to Live | Protocol | Header Checksum |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | Source Address |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | Destination Address |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | Options | Padding |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
*/
#[derive(Clone, Debug, PartialEq, Eq)]
pub struct IPv4Header {
pub version: u8, // 4 bit
pub ihl: u8, // 4 bit
pub tos: u8,
pub length: u16,
pub id: u16,
pub flags: u8, // 3 bit
pub frag_offset: u16, // 13 bit
pub ttl: u8,
pub protocol: IPProtocol,
pub checksum: u16,
pub source_address: Ipv4Addr,
pub dest_address: Ipv4Addr,
}
/******************************************************************************
* API
******************************************************************************/
fn flag_offset_decode(input: &[u8]) -> IResult<&[u8], (u8, u16)> {
bits::bits::<_, _, Error<_>, _, _>(sequence::pair(
bits::streaming::take(3u8),
bits::streaming::take(13u16),
))(input)
}
fn version_hlen_decode(input: &[u8]) -> IResult<&[u8], (u8, u8)> {
bits::bits::<_, _, Error<_>, _, _>(sequence::pair(
bits::streaming::take(4u8),
bits::streaming::take(4u8),
))(input)
}
fn address_v4_decode(input: &[u8]) -> IResult<&[u8], Ipv4Addr> {
let (input, ipv4) = nom::bytes::streaming::take(4u8)(input)?;
Ok((input, Ipv4Addr::from(<[u8; 4]>::try_from(ipv4).unwrap())))
}
impl Decode for IPv4Header {
type Iterm = IPv4Header;
fn decode(input: &[u8]) -> IResult<&[u8], IPv4Header> {
let (input, verihl) = version_hlen_decode(input)?;
let (input, tos) = number::streaming::be_u8(input)?;
let (input, length) = number::streaming::be_u16(input)?;
let (input, id) = number::streaming::be_u16(input)?;
let (input, flag_frag_offset) = flag_offset_decode(input)?;
let (input, ttl) = number::streaming::be_u8(input)?;
let (input, protocol) = IPProtocol::decode(input)?;
let (input, checksum) = number::streaming::be_u16(input)?;
let (input, source_address) = address_v4_decode(input)?;
let (input, dest_address) = address_v4_decode(input)?;
// TODO IPv4 Options Decode
Ok((
input,
IPv4Header {
version: verihl.0,
ihl: verihl.1 * 4, // verihl.1 * 32 / 8
tos,
length,
id,
flags: flag_frag_offset.0,
frag_offset: flag_frag_offset.1,
ttl,
protocol,
checksum,
source_address,
dest_address,
},
))
}
}
/******************************************************************************
* TEST
******************************************************************************/
#[cfg(test)]
mod tests {
use super::IPv4Header;
use crate::protocol::codec::Decode;
use crate::protocol::ip::IPProtocol;
use std::net::Ipv4Addr;
const LAST_SLICE: &'static [u8] = &[0xff];
#[test]
fn ipv4_header_decode() {
/*
* Internet Protocol Version 4, Src: 192.168.0.101, Dst: 121.14.154.93
* 0100 .... = Version: 4
* .... 0101 = Header Length: 20 bytes (5)
* Differentiated Services Field: 0x00 (DSCP: CS0, ECN: Not-ECT)
* 0000 00.. = Differentiated Services Codepoint: Default (0)
* .... ..00 = Explicit Congestion Notification: Not ECN-Capable Transport (0)
* Total Length: 70
* Identification: 0xe2db (58075)
* 000. .... = Flags: 0x0
* 0... .... = Reserved bit: Not set
* .0.. .... = Don't fragment: Not set
* ..0. .... = More fragments: Not set
* ...0 0000 0000 0000 = Fragment Offset: 0
* Time to Live: 64
* Protocol: UDP (17)
* Header Checksum: 0xc352 [correct]
* [Header checksum status: Good]
* [Calculated Checksum: 0xc352]
* Source Address: 192.168.0.101
* Destination Address: 121.14.154.93
* User Datagram Protocol, Src Port: 64820, Dst Port: 53
*/
let bytes = [
0x45, /* Version and Header length */
0x00, /* Differentiated Services Field */
0x00, 0x46, /* Total Length */
0xe2, 0xdb, /* Identification */
0x00, 0x00, /* Flags and Fragment Offset */
0x40, /* Time to Live */
0x11, /* Protocol */
0xc3, 0x52, /* Header Checksum */
0xc0, 0xa8, 0x00, 0x65, /* Source Address */
0x79, 0x0e, 0x9a, 0x5d, /* Destination Address */
0xff, /* Payload */
];
let expectation = IPv4Header {
version: 4,
ihl: 20,
tos: 0,
length: 70,
id: 0xe2db,
flags: 0x0,
frag_offset: 0,
ttl: 64,
protocol: IPProtocol::UDP,
checksum: 0xc352,
source_address: Ipv4Addr::new(192, 168, 0, 101),
dest_address: Ipv4Addr::new(121, 14, 154, 93),
};
assert_eq!(IPv4Header::decode(&bytes), Ok((LAST_SLICE, expectation)));
// example
let result = IPv4Header::decode(&bytes);
match result {
Ok((payload, header)) => {
println!("OK: {:?}, payload: {}", header, payload.len());
}
Err(e) => {
println!("ERR: {:?}", e);
}
}
// assert_eq!(1, 0);
}
}
|
