pdu 1.4.2

Small, fast, and correct L2/L3/L4 packet parser.
Documentation 
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
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163

/*
   Copyright (c) 2019 Alex Forster <alex@alexforster.com>

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.

   SPDX-License-Identifier: Apache-2.0
*/

use core::convert::TryInto;

use crate::{util, Error, Result};

/// Represents a GRE header and payload
#[derive(Debug, Copy, Clone)]
pub struct GrePdu<'a> {
    buffer: &'a [u8],
}

/// Contains the inner payload of a [`GrePdu`]
#[derive(Debug, Copy, Clone)]
pub enum Gre<'a> {
    Raw(&'a [u8]),
    Ethernet(super::EthernetPdu<'a>),
    Ipv4(super::Ipv4Pdu<'a>),
    Ipv6(super::Ipv6Pdu<'a>),
}

impl<'a> GrePdu<'a> {
    /// Constructs a [`GrePdu`] backed by the provided `buffer`
    pub fn new(buffer: &'a [u8]) -> Result<Self> {
        if buffer.len() < 4 {
            return Err(Error::Truncated);
        }
        if buffer[1] & 0x07 != 0 {
            // we only support rfc2784 GRE frames
            return Err(Error::Malformed);
        }
        let pdu = GrePdu { buffer };
        if buffer.len() < pdu.computed_ihl() {
            return Err(Error::Truncated);
        }
        Ok(pdu)
    }

    /// Returns a reference to the entire underlying buffer that was provided during construction
    pub fn buffer(&'a self) -> &'a [u8] {
        self.buffer
    }

    /// Consumes this object and returns a reference to the entire underlying buffer that was provided during
    /// construction
    pub fn into_buffer(self) -> &'a [u8] {
        self.buffer
    }

    /// Returns the slice of the underlying buffer that contains the header part of this PDU
    pub fn as_bytes(&'a self) -> &'a [u8] {
        self.clone().into_bytes()
    }

    /// Consumes this object and returns the slice of the underlying buffer that contains the header part of this PDU
    pub fn into_bytes(self) -> &'a [u8] {
        &self.buffer[0..self.computed_ihl()]
    }

    /// Returns an object representing the inner payload of this PDU
    pub fn inner(&'a self) -> Result<Gre<'a>> {
        self.clone().into_inner()
    }

    /// Consumes this object and returns an object representing the inner payload of this PDU
    pub fn into_inner(self) -> Result<Gre<'a>> {
        let rest = &self.buffer[self.computed_ihl()..];
        Ok(match self.ethertype() {
            super::EtherType::TEB => Gre::Ethernet(super::EthernetPdu::new(rest)?),
            super::EtherType::IPV4 => Gre::Ipv4(super::Ipv4Pdu::new(rest)?),
            super::EtherType::IPV6 => Gre::Ipv6(super::Ipv6Pdu::new(rest)?),
            _ => Gre::Raw(rest),
        })
    }

    pub fn computed_ihl(&'a self) -> usize {
        let mut ihl = 4;
        if self.has_checksum() {
            ihl += 4;
        }
        if self.has_key() {
            ihl += 4;
        }
        if self.has_sequence_number() {
            ihl += 4;
        }
        ihl
    }

    pub fn version(&'a self) -> u8 {
        self.buffer[1] & 0x07
    }

    pub fn ethertype(&'a self) -> u16 {
        u16::from_be_bytes(self.buffer[2..=3].try_into().unwrap())
    }

    pub fn has_checksum(&'a self) -> bool {
        (self.buffer[0] & 0x80) != 0
    }

    pub fn has_key(&'a self) -> bool {
        (self.buffer[0] & 0x20) != 0
    }

    pub fn has_sequence_number(&'a self) -> bool {
        (self.buffer[0] & 0x10) != 0
    }

    pub fn checksum(&'a self) -> Option<u16> {
        if self.has_checksum() {
            Some(u16::from_be_bytes(self.buffer[4..=5].try_into().unwrap()))
        } else {
            None
        }
    }

    pub fn computed_checksum(&'a self) -> Option<u16> {
        if self.has_checksum() {
            Some(util::checksum(&[&self.buffer[0..=3], &self.buffer[6..]]))
        } else {
            None
        }
    }

    pub fn key(&'a self) -> Option<u32> {
        if self.has_checksum() && self.has_key() {
            Some(u32::from_be_bytes(self.buffer[8..=11].try_into().unwrap()))
        } else if self.has_key() {
            Some(u32::from_be_bytes(self.buffer[4..=7].try_into().unwrap()))
        } else {
            None
        }
    }

    pub fn sequence_number(&'a self) -> Option<u32> {
        if self.has_sequence_number() && self.has_checksum() && self.has_key() {
            Some(u32::from_be_bytes(self.buffer[12..=15].try_into().unwrap()))
        } else if self.has_sequence_number() && (self.has_checksum() || self.has_key()) {
            Some(u32::from_be_bytes(self.buffer[8..=11].try_into().unwrap()))
        } else if self.has_sequence_number() {
            Some(u32::from_be_bytes(self.buffer[4..=7].try_into().unwrap()))
        } else {
            None
        }
    }
}