netlink_packet_core/
header.rs

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1// SPDX-License-Identifier: MIT
2
3use netlink_packet_utils::DecodeError;
4
5use crate::buffer::NETLINK_HEADER_LEN;
6use crate::{Emitable, NetlinkBuffer, Parseable};
7
8/// A Netlink header representation. A netlink header has the following
9/// structure:
10///
11/// ```no_rust
12/// 0                8                16              24               32
13/// +----------------+----------------+----------------+----------------+
14/// |                 packet length (including header)                  |
15/// +----------------+----------------+----------------+----------------+
16/// |          message type           |              flags              |
17/// +----------------+----------------+----------------+----------------+
18/// |                           sequence number                         |
19/// +----------------+----------------+----------------+----------------+
20/// |                   port number (formerly known as PID)             |
21/// +----------------+----------------+----------------+----------------+
22/// ```
23#[derive(Debug, PartialEq, Eq, Clone, Copy, Hash, Default)]
24#[non_exhaustive]
25pub struct NetlinkHeader {
26    /// Length of the netlink packet, including the header and the payload
27    pub length: u32,
28
29    /// NetlinkMessage type. The meaning of this field depends on the netlink
30    /// protocol family in use.
31    pub message_type: u16,
32
33    /// Flags. It should be set to one of the `NLM_F_*` constants.
34    pub flags: u16,
35
36    /// Sequence number of the packet
37    pub sequence_number: u32,
38
39    /// Port number (usually set to the the process ID)
40    pub port_number: u32,
41}
42
43impl Emitable for NetlinkHeader {
44    fn buffer_len(&self) -> usize {
45        NETLINK_HEADER_LEN
46    }
47
48    fn emit(&self, buffer: &mut [u8]) {
49        let mut buffer = NetlinkBuffer::new(buffer);
50        buffer.set_message_type(self.message_type);
51        buffer.set_length(self.length);
52        buffer.set_flags(self.flags);
53        buffer.set_sequence_number(self.sequence_number);
54        buffer.set_port_number(self.port_number);
55    }
56}
57
58impl<'a, T: AsRef<[u8]> + ?Sized> Parseable<NetlinkBuffer<&'a T>> for NetlinkHeader {
59    type Error = DecodeError;
60    fn parse(buf: &NetlinkBuffer<&'a T>) -> Result<NetlinkHeader, DecodeError> {
61        Ok(NetlinkHeader {
62            length: buf.length(),
63            message_type: buf.message_type(),
64            flags: buf.flags(),
65            sequence_number: buf.sequence_number(),
66            port_number: buf.port_number(),
67        })
68    }
69}
70
71#[cfg(test)]
72mod tests {
73    use super::*;
74    use crate::constants::*;
75
76    // a packet captured with tcpdump that was sent when running `ip link show`
77    #[rustfmt::skip]
78    static IP_LINK_SHOW_PKT: [u8; 40] = [
79        0x28, 0x00, 0x00, 0x00, // length = 40
80        0x12, 0x00, // message type = 18 (RTM_GETLINK)
81        0x01, 0x03, // flags = Request + Specify Tree Root + Return All Matching
82        0x34, 0x0e, 0xf9, 0x5a, // sequence number = 1526271540
83        0x00, 0x00, 0x00, 0x00, // port id = 0
84        // payload
85        0x11, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
86        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
87        0x08, 0x00, 0x1d, 0x00, 0x01, 0x00, 0x00, 0x00];
88
89    const RTM_GETLINK: u16 = 18;
90
91    #[test]
92    fn repr_parse() {
93        let repr =
94            NetlinkHeader::parse(&NetlinkBuffer::new_checked(&IP_LINK_SHOW_PKT[..]).unwrap())
95                .unwrap();
96        assert_eq!(repr.length, 40);
97        assert_eq!(repr.message_type, RTM_GETLINK);
98        assert_eq!(repr.sequence_number, 1_526_271_540);
99        assert_eq!(repr.port_number, 0);
100        assert_eq!(repr.flags, NLM_F_ROOT | NLM_F_REQUEST | NLM_F_MATCH);
101    }
102
103    #[test]
104    fn repr_emit() {
105        let repr = NetlinkHeader {
106            length: 40,
107            message_type: RTM_GETLINK,
108            sequence_number: 1_526_271_540,
109            flags: NLM_F_ROOT | NLM_F_REQUEST | NLM_F_MATCH,
110            port_number: 0,
111        };
112        assert_eq!(repr.buffer_len(), 16);
113        let mut buf = vec![0; 16];
114        repr.emit(&mut buf[..]);
115        assert_eq!(&buf[..], &IP_LINK_SHOW_PKT[..16]);
116    }
117}
netlink_packet_core/header.rs

netlink_packet_core/
header.rs
