bgpkit-parser 0.11.1

MRT/BGP/BMP data processing library
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

use crate::models::{CommonHeader, EntryType};
use crate::ParserError;
use bytes::{Buf, BufMut, Bytes, BytesMut};
use std::io::Read;

/// MRT common header [RFC6396][header].
///
/// [header]: https://tools.ietf.org/html/rfc6396#section-4.1
///
/// A MRT record is constructed as the following:
/// ```text
///  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
/// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/// |                           Timestamp                           |
/// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/// |             Type              |            Subtype            |
/// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/// |                             Length                            |
/// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/// |                      Message... (variable)
/// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
///
/// ```
///
/// Or with extended timestamp:
/// ```text
///  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
/// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/// |                           Timestamp                           |
/// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/// |             Type              |            Subtype            |
/// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/// |                             Length                            |
/// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/// |                      Microsecond Timestamp                    |
/// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/// |                      Message... (variable)
/// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/// ```
pub fn parse_common_header<T: Read>(input: &mut T) -> Result<CommonHeader, ParserError> {
    let mut raw_bytes = [0u8; 12];
    input.read_exact(&mut raw_bytes)?;
    let mut data = BytesMut::from(&raw_bytes[..]);

    let timestamp = data.get_u32();
    let entry_type_raw = data.get_u16();
    let entry_type = EntryType::try_from(entry_type_raw)?;
    let entry_subtype = data.get_u16();
    // the length field does not include the length of the common header
    let mut length = data.get_u32();

    let microsecond_timestamp = match &entry_type {
        EntryType::BGP4MP_ET => {
            length -= 4;
            let mut raw_bytes: [u8; 4] = [0; 4];
            input.read_exact(&mut raw_bytes)?;
            Some(BytesMut::from(&raw_bytes[..]).get_u32())
        }
        _ => None,
    };

    Ok(CommonHeader {
        timestamp,
        microsecond_timestamp,
        entry_type,
        entry_subtype,
        length,
    })
}

impl CommonHeader {
    pub fn encode(&self) -> Bytes {
        let mut bytes = BytesMut::new();
        bytes.put_slice(&self.timestamp.to_be_bytes());
        bytes.put_u16(self.entry_type as u16);
        bytes.put_u16(self.entry_subtype);

        match self.microsecond_timestamp {
            None => bytes.put_u32(self.length),
            Some(microseconds) => {
                // When the microsecond timestamp is present, the length must be adjusted to account
                // for the stace used by the extra timestamp data.
                bytes.put_u32(self.length + 4);
                bytes.put_u32(microseconds);
            }
        };
        bytes.freeze()
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::models::EntryType;
    use bytes::Buf;

    /// Test that the length is not adjusted when the microsecond timestamp is not present.
    #[test]
    fn test_encode_common_header() {
        let header = CommonHeader {
            timestamp: 1,
            microsecond_timestamp: None,
            entry_type: EntryType::BGP4MP,
            entry_subtype: 4,
            length: 5,
        };

        let expected = Bytes::from_static(&[
            0, 0, 0, 1, // timestamp
            0, 16, // entry type
            0, 4, // entry subtype
            0, 0, 0, 5, // length
        ]);

        let encoded = header.encode();
        assert_eq!(encoded, expected);

        let mut reader = expected.reader();
        let parsed = parse_common_header(&mut reader).unwrap();
        assert_eq!(parsed, header);
    }

    /// Test that the length is adjusted when the microsecond timestamp is present.
    #[test]
    fn test_encode_common_header_et() {
        let header = CommonHeader {
            timestamp: 1,
            microsecond_timestamp: Some(230_000),
            entry_type: EntryType::BGP4MP_ET,
            entry_subtype: 4,
            length: 5,
        };

        let expected = Bytes::from_static(&[
            0, 0, 0, 1, // timestamp
            0, 17, // entry type
            0, 4, // entry subtype
            0, 0, 0, 9, // length
            0, 3, 130, 112, // microsecond timestamp
        ]);

        let encoded = header.encode();
        assert_eq!(encoded, expected);

        let mut reader = expected.reader();
        let parsed = parse_common_header(&mut reader).unwrap();
        assert_eq!(parsed, header);
    }
}