dsct 0.2.5

LLM-friendly packet dissector CLI
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
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259

use std::net::{IpAddr, Ipv4Addr, Ipv6Addr};

use packet_dissector_core::field::{Field, FieldValue};
use packet_dissector_core::packet::{Layer, Packet};

use super::{CountEntry, ResponseTimeStats};

/// Extract (src_ip, dst_ip) as [`IpAddr`] from IPv4 or IPv6 layers.
pub(super) fn extract_ip_addr_pair(packet: &Packet) -> Option<(IpAddr, IpAddr)> {
    if let Some(ipv4) = packet.layer_by_name("IPv4") {
        let fields = packet.layer_fields(ipv4);
        let src = match find_field(fields, "src").map(|f| &f.value) {
            Some(FieldValue::Ipv4Addr(b)) => IpAddr::V4(Ipv4Addr::from(*b)),
            _ => return None,
        };
        let dst = match find_field(fields, "dst").map(|f| &f.value) {
            Some(FieldValue::Ipv4Addr(b)) => IpAddr::V4(Ipv4Addr::from(*b)),
            _ => return None,
        };
        return Some((src, dst));
    }
    if let Some(ipv6) = packet.layer_by_name("IPv6") {
        let fields = packet.layer_fields(ipv6);
        let src = match find_field(fields, "src").map(|f| &f.value) {
            Some(FieldValue::Ipv6Addr(b)) => IpAddr::V6(Ipv6Addr::from(*b)),
            _ => return None,
        };
        let dst = match find_field(fields, "dst").map(|f| &f.value) {
            Some(FieldValue::Ipv6Addr(b)) => IpAddr::V6(Ipv6Addr::from(*b)),
            _ => return None,
        };
        return Some((src, dst));
    }
    None
}

/// Extract the transport layer name and (src_port, dst_port).
pub(super) fn extract_transport(packet: &Packet) -> Option<(&'static str, u16, u16)> {
    for name in &["UDP", "TCP"] {
        if let Some(layer) = packet.layer_by_name(name) {
            let fields = packet.layer_fields(layer);
            let src_port = field_u16(fields, "src_port")?;
            let dst_port = field_u16(fields, "dst_port")?;
            return Some((name, src_port, dst_port));
        }
    }
    None
}

/// Extract (src_ip, dst_ip) strings from IPv4 or IPv6 layers.
pub(super) fn extract_ip_pair(packet: &Packet) -> Option<(String, String)> {
    let (src, dst) = extract_ip_addr_pair(packet)?;
    Some((src.to_string(), dst.to_string()))
}

/// Resolve a display name for a field via `Packet::resolve_display_name`.
///
/// Falls back to the raw field value formatted as a string when no
/// `display_fn` is registered for the base field.
pub(super) fn display_name(
    packet: &Packet,
    layer: &Layer,
    fields: &[Field<'_>],
    name_field: &str,
    base_field: &str,
) -> Option<String> {
    if let Some(name) = packet.resolve_display_name(layer, name_field) {
        return Some(name.to_owned());
    }
    find_field(fields, base_field).map(|f| field_value_to_string(&f.value))
}

pub(super) fn find_field<'a, 'b>(fields: &'a [Field<'b>], name: &str) -> Option<&'a Field<'b>> {
    fields.iter().find(|f| f.name() == name)
}

pub(super) fn field_u8(fields: &[Field<'_>], name: &str) -> Option<u8> {
    match find_field(fields, name).map(|f| &f.value) {
        Some(FieldValue::U8(v)) => Some(*v),
        _ => None,
    }
}

pub(super) fn field_str<'a>(fields: &'a [Field<'_>], name: &str) -> Option<&'a str> {
    match find_field(fields, name).map(|f| &f.value) {
        Some(FieldValue::Str(s)) => Some(s),
        _ => None,
    }
}

/// Convert a [`FieldValue`] to a display string for stats aggregation.
pub(super) fn field_value_to_string(value: &FieldValue) -> String {
    match value {
        FieldValue::Str(s) => (*s).to_string(),
        FieldValue::U8(v) => v.to_string(),
        FieldValue::U16(v) => v.to_string(),
        FieldValue::U32(v) => v.to_string(),
        FieldValue::U64(v) => v.to_string(),
        FieldValue::I32(v) => v.to_string(),
        FieldValue::Ipv4Addr(b) => Ipv4Addr::from(*b).to_string(),
        FieldValue::Ipv6Addr(b) => Ipv6Addr::from(*b).to_string(),
        FieldValue::Bytes(b) => String::from_utf8_lossy(b).into_owned(),
        FieldValue::MacAddr(m) => m.to_string(),
        _ => String::new(),
    }
}

pub(super) fn field_u16(fields: &[Field<'_>], name: &str) -> Option<u16> {
    match find_field(fields, name).map(|f| &f.value) {
        Some(FieldValue::U16(v)) => Some(*v),
        _ => None,
    }
}

pub(super) fn field_u32(fields: &[Field<'_>], name: &str) -> Option<u32> {
    match find_field(fields, name).map(|f| &f.value) {
        Some(FieldValue::U32(v)) => Some(*v),
        _ => None,
    }
}

/// Sort entries by count descending and take top N.
pub(super) fn sorted_top_n(
    iter: impl Iterator<Item = (String, u64)>,
    top_n: usize,
) -> Vec<CountEntry> {
    let mut entries: Vec<CountEntry> = iter
        .map(|(name, count)| CountEntry { name, count })
        .collect();
    entries.sort_by(|a, b| b.count.cmp(&a.count).then_with(|| a.name.cmp(&b.name)));
    entries.truncate(top_n);
    entries
}

/// Compute percentile stats from a list of response times.
pub(super) fn compute_response_time_stats(mut times: Vec<f64>) -> Option<ResponseTimeStats> {
    if times.is_empty() {
        return None;
    }
    times.sort_by(|a, b| a.total_cmp(b));
    let n = times.len();
    let sum: f64 = times.iter().sum();
    Some(ResponseTimeStats {
        min: times[0],
        max: times[n - 1],
        mean: sum / n as f64,
        median: percentile(&times, 50.0),
        p95: percentile(&times, 95.0),
        p99: percentile(&times, 99.0),
        count: n as u64,
    })
}

/// Compute the p-th percentile from a sorted slice using linear interpolation.
pub(super) fn percentile(sorted: &[f64], p: f64) -> f64 {
    if sorted.len() == 1 {
        return sorted[0];
    }
    let rank = p / 100.0 * (sorted.len() - 1) as f64;
    let lower = rank.floor() as usize;
    let upper = rank.ceil() as usize;
    if lower == upper {
        sorted[lower]
    } else {
        let frac = rank - lower as f64;
        sorted[lower] * (1.0 - frac) + sorted[upper] * frac
    }
}

#[cfg(test)]
mod tests {
    use super::super::test_helpers::{add_ipv4_udp, pkt};
    use super::*;
    use packet_dissector_core::packet::DissectBuffer;

    #[test]
    fn sorted_top_n_orders_by_count_desc_then_name_asc() {
        let input = vec![
            ("b".to_string(), 1u64),
            ("a".to_string(), 2u64),
            ("c".to_string(), 2u64),
        ];
        let sorted = sorted_top_n(input.clone().into_iter(), 10);
        assert_eq!(sorted.len(), 3);
        assert_eq!(sorted[0].name, "a");
        assert_eq!(sorted[0].count, 2);
        assert_eq!(sorted[1].name, "c");
        assert_eq!(sorted[1].count, 2);
        assert_eq!(sorted[2].name, "b");
        assert_eq!(sorted[2].count, 1);

        let truncated = sorted_top_n(input.into_iter(), 2);
        assert_eq!(truncated.len(), 2);
        assert_eq!(truncated[0].name, "a");
        assert_eq!(truncated[1].name, "c");
    }

    #[test]
    fn percentile_linear_interpolation_basic() {
        let v = [1.0f64, 2.0, 3.0, 4.0];
        assert!((percentile(&v, 0.0) - 1.0).abs() < 1e-9);
        assert!((percentile(&v, 50.0) - 2.5).abs() < 1e-9);
        assert!((percentile(&v, 100.0) - 4.0).abs() < 1e-9);

        let single = [7.5f64];
        assert!((percentile(&single, 50.0) - 7.5).abs() < 1e-9);
    }

    #[test]
    fn compute_response_time_stats_none_for_empty() {
        assert!(compute_response_time_stats(Vec::new()).is_none());
    }

    #[test]
    fn compute_response_time_stats_basic() {
        let times = vec![0.5, 0.1, 0.3, 0.2, 0.4];
        let Some(stats) = compute_response_time_stats(times) else {
            panic!("expected Some stats for non-empty input");
        };
        assert_eq!(stats.count, 5);
        assert!((stats.min - 0.1).abs() < 1e-9);
        assert!((stats.max - 0.5).abs() < 1e-9);
        assert!((stats.mean - 0.3).abs() < 1e-9);
        assert!((stats.median - 0.3).abs() < 1e-9);
    }

    #[test]
    fn field_value_to_string_handles_common_variants() {
        assert_eq!(field_value_to_string(&FieldValue::Str("hello")), "hello");
        assert_eq!(field_value_to_string(&FieldValue::U8(42)), "42");
        assert_eq!(field_value_to_string(&FieldValue::U16(1024)), "1024");
        assert_eq!(field_value_to_string(&FieldValue::U32(70000)), "70000");
        assert_eq!(
            field_value_to_string(&FieldValue::Ipv4Addr([10, 0, 0, 1])),
            "10.0.0.1"
        );
        assert_eq!(field_value_to_string(&FieldValue::Bytes(b"raw")), "raw");
    }

    #[test]
    fn extract_ip_and_transport_from_udp_over_ipv4() {
        let mut buf = DissectBuffer::new();
        add_ipv4_udp(&mut buf, [10, 0, 0, 1], [10, 0, 0, 2], 53000, 53);
        let packet = pkt(&buf);

        let Some((src, dst)) = extract_ip_pair(&packet) else {
            panic!("expected extract_ip_pair to return Some");
        };
        assert_eq!(src, "10.0.0.1");
        assert_eq!(dst, "10.0.0.2");

        let Some((proto, sport, dport)) = extract_transport(&packet) else {
            panic!("expected extract_transport to return Some");
        };
        assert_eq!(proto, "UDP");
        assert_eq!(sport, 53000);
        assert_eq!(dport, 53);
    }
}