netlink_packet_core/
header.rs

1// SPDX-License-Identifier: MIT
2
3use crate::{
4    buffer::NETLINK_HEADER_LEN, DecodeError, Emitable, NetlinkBuffer, Parseable,
5};
6
7/// A Netlink header representation. A netlink header has the following
8/// structure:
9///
10/// ```no_rust
11/// 0                8                16              24               32
12/// +----------------+----------------+----------------+----------------+
13/// |                 packet length (including header)                  |
14/// +----------------+----------------+----------------+----------------+
15/// |          message type           |              flags              |
16/// +----------------+----------------+----------------+----------------+
17/// |                           sequence number                         |
18/// +----------------+----------------+----------------+----------------+
19/// |                   port number (formerly known as PID)             |
20/// +----------------+----------------+----------------+----------------+
21/// ```
22#[derive(Debug, PartialEq, Eq, Clone, Copy, Hash, Default)]
23#[non_exhaustive]
24pub struct NetlinkHeader {
25    /// Length of the netlink packet, including the header and the payload
26    pub length: u32,
27
28    /// NetlinkMessage type. The meaning of this field depends on the netlink
29    /// protocol family in use.
30    pub message_type: u16,
31
32    /// Flags. It should be set to one of the `NLM_F_*` constants.
33    pub flags: u16,
34
35    /// Sequence number of the packet
36    pub sequence_number: u32,
37
38    /// Port number (usually set to the the process ID)
39    pub port_number: u32,
40}
41
42impl Emitable for NetlinkHeader {
43    fn buffer_len(&self) -> usize {
44        NETLINK_HEADER_LEN
45    }
46
47    fn emit(&self, buffer: &mut [u8]) {
48        let mut buffer = NetlinkBuffer::new(buffer);
49        buffer.set_message_type(self.message_type);
50        buffer.set_length(self.length);
51        buffer.set_flags(self.flags);
52        buffer.set_sequence_number(self.sequence_number);
53        buffer.set_port_number(self.port_number);
54    }
55}
56
57impl<T: AsRef<[u8]> + ?Sized> Parseable<NetlinkBuffer<&T>> for NetlinkHeader {
58    fn parse(buf: &NetlinkBuffer<&T>) -> Result<NetlinkHeader, DecodeError> {
59        Ok(NetlinkHeader {
60            length: buf.length(),
61            message_type: buf.message_type(),
62            flags: buf.flags(),
63            sequence_number: buf.sequence_number(),
64            port_number: buf.port_number(),
65        })
66    }
67}
68
69#[cfg(test)]
70mod tests {
71    use super::*;
72    use crate::constants::*;
73
74    // a packet captured with tcpdump that was sent when running `ip link show`
75    #[rustfmt::skip]
76    static IP_LINK_SHOW_PKT: [u8; 40] = [
77        0x28, 0x00, 0x00, 0x00, // length = 40
78        0x12, 0x00, // message type = 18 (RTM_GETLINK)
79        0x01, 0x03, // flags = Request + Specify Tree Root + Return All Matching
80        0x34, 0x0e, 0xf9, 0x5a, // sequence number = 1526271540
81        0x00, 0x00, 0x00, 0x00, // port id = 0
82        // payload
83        0x11, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
84        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
85        0x08, 0x00, 0x1d, 0x00, 0x01, 0x00, 0x00, 0x00];
86
87    const RTM_GETLINK: u16 = 18;
88
89    #[test]
90    fn repr_parse() {
91        let repr = NetlinkHeader::parse(
92            &NetlinkBuffer::new_checked(&IP_LINK_SHOW_PKT[..]).unwrap(),
93        )
94        .unwrap();
95        assert_eq!(repr.length, 40);
96        assert_eq!(repr.message_type, RTM_GETLINK);
97        assert_eq!(repr.sequence_number, 1_526_271_540);
98        assert_eq!(repr.port_number, 0);
99        assert_eq!(repr.flags, NLM_F_ROOT | NLM_F_REQUEST | NLM_F_MATCH);
100    }
101
102    #[test]
103    fn repr_emit() {
104        let repr = NetlinkHeader {
105            length: 40,
106            message_type: RTM_GETLINK,
107            sequence_number: 1_526_271_540,
108            flags: NLM_F_ROOT | NLM_F_REQUEST | NLM_F_MATCH,
109            port_number: 0,
110        };
111        assert_eq!(repr.buffer_len(), 16);
112        let mut buf = [0; 16];
113        repr.emit(&mut buf[..]);
114        assert_eq!(&buf[..], &IP_LINK_SHOW_PKT[..16]);
115    }
116}
netlink_packet_core/header.rs

netlink_packet_core/
header.rs
