tiny_ping/packet/
icmp.rs

1use crate::error::Error;
2use std::io::Write;
3
4pub const HEADER_SIZE: usize = 8;
5
6pub struct IcmpV4;
7pub struct IcmpV6;
8
9pub trait Proto {
10    const ECHO_REQUEST_TYPE: u8;
11    const ECHO_REQUEST_CODE: u8;
12    const ECHO_REPLY_TYPE: u8;
13    const ECHO_REPLY_CODE: u8;
14}
15
16impl Proto for IcmpV4 {
17    const ECHO_REQUEST_TYPE: u8 = 8;
18    const ECHO_REQUEST_CODE: u8 = 0;
19    const ECHO_REPLY_TYPE: u8 = 0;
20    const ECHO_REPLY_CODE: u8 = 0;
21}
22
23impl Proto for IcmpV6 {
24    const ECHO_REQUEST_TYPE: u8 = 128;
25    const ECHO_REQUEST_CODE: u8 = 0;
26    const ECHO_REPLY_TYPE: u8 = 129;
27    const ECHO_REPLY_CODE: u8 = 0;
28}
29
30pub struct EchoRequest {
31    pub ident: u16,
32    pub seq_cnt: u16,
33}
34
35impl EchoRequest {
36    pub fn encode<P: Proto>(&self, buffer: &mut [u8], payload: &[u8]) -> Result<Vec<u8>, Error> {
37        if buffer.len() < HEADER_SIZE + payload.len() {
38            return Err(Error::InvalidSize);
39        }
40
41        buffer[0] = P::ECHO_REQUEST_TYPE;
42        buffer[1] = P::ECHO_REQUEST_CODE;
43        buffer[2] = 0;
44        buffer[3] = 0;
45
46        buffer[4] = (self.ident >> 8) as u8;
47        buffer[5] = self.ident as u8;
48        buffer[6] = (self.seq_cnt >> 8) as u8;
49        buffer[7] = self.seq_cnt as u8;
50
51        if (&mut buffer[HEADER_SIZE..HEADER_SIZE + payload.len()])
52            .write_all(payload)
53            .is_err()
54        {
55            return Err(Error::InvalidSize);
56        }
57
58        write_checksum(&mut buffer[..HEADER_SIZE + payload.len()]);
59        Ok(buffer.to_vec())
60    }
61}
62
63pub struct EchoReply<'a> {
64    pub ident: u16,
65    pub seq_cnt: u16,
66    pub payload: &'a [u8],
67}
68
69impl<'a> EchoReply<'a> {
70    pub fn decode<P: Proto>(buffer: &'a [u8]) -> Result<Self, Error> {
71        if buffer.as_ref().len() < HEADER_SIZE {
72            return Err(Error::InvalidSize);
73        }
74
75        let type_ = buffer[0];
76        let code = buffer[1];
77        if type_ != P::ECHO_REPLY_TYPE || code != P::ECHO_REPLY_CODE {
78            return Err(Error::InvalidPacket);
79        }
80
81        let ident = (u16::from(buffer[4]) << 8) + u16::from(buffer[5]);
82        let seq_cnt = (u16::from(buffer[6]) << 8) + u16::from(buffer[7]);
83
84        let payload = &buffer[HEADER_SIZE..];
85
86        Ok(EchoReply {
87            ident,
88            seq_cnt,
89            payload,
90        })
91    }
92}
93
94fn write_checksum(buffer: &mut [u8]) {
95    let mut sum = 0u32;
96    for word in buffer.chunks(2) {
97        let mut part = u16::from(word[0]) << 8;
98        if word.len() > 1 {
99            part += u16::from(word[1]);
100        }
101        sum = sum.wrapping_add(u32::from(part));
102    }
103
104    while (sum >> 16) > 0 {
105        sum = (sum & 0xffff) + (sum >> 16);
106    }
107
108    let sum = !sum as u16;
109
110    buffer[2] = (sum >> 8) as u8;
111    buffer[3] = (sum & 0xff) as u8;
112}
113
114#[cfg(test)]
115mod tests {
116    use super::*;
117
118    #[test]
119    fn encodes_echo_request_with_valid_checksum() {
120        let request = EchoRequest {
121            ident: 0x1234,
122            seq_cnt: 7,
123        };
124        let payload = [1, 2, 3, 4];
125        let mut buffer = [0; HEADER_SIZE + 4];
126
127        let encoded = request.encode::<IcmpV4>(&mut buffer, &payload).unwrap();
128
129        assert_eq!(encoded[0], IcmpV4::ECHO_REQUEST_TYPE);
130        assert_eq!(encoded[1], IcmpV4::ECHO_REQUEST_CODE);
131        assert_eq!(&encoded[4..8], &[0x12, 0x34, 0, 7]);
132        assert_eq!(&encoded[8..], &payload);
133        assert_eq!(checksum_sum(&encoded), 0xffff);
134    }
135
136    #[test]
137    fn rejects_wrong_echo_reply_code() {
138        let packet = [IcmpV4::ECHO_REPLY_TYPE, 1, 0, 0, 0, 1, 0, 1];
139
140        assert!(matches!(
141            EchoReply::decode::<IcmpV4>(&packet),
142            Err(Error::InvalidPacket)
143        ));
144    }
145
146    #[test]
147    fn decodes_icmpv6_echo_reply() {
148        let packet = [IcmpV6::ECHO_REPLY_TYPE, 0, 0, 0, 0x12, 0x34, 0, 9, 1, 2];
149        let reply = EchoReply::decode::<IcmpV6>(&packet).unwrap();
150
151        assert_eq!(reply.ident, 0x1234);
152        assert_eq!(reply.seq_cnt, 9);
153        assert_eq!(reply.payload, &[1, 2]);
154    }
155
156    fn checksum_sum(buffer: &[u8]) -> u16 {
157        let mut sum = 0u32;
158        for word in buffer.chunks(2) {
159            let mut part = u16::from(word[0]) << 8;
160            if word.len() > 1 {
161                part += u16::from(word[1]);
162            }
163            sum = sum.wrapping_add(u32::from(part));
164        }
165        while (sum >> 16) > 0 {
166            sum = (sum & 0xffff) + (sum >> 16);
167        }
168        sum as u16
169    }
170}
tiny_ping/packet/icmp.rs

tiny_ping/packet/
icmp.rs
