dsct 0.2.8

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

//! Snapshot / schema-stability tests for `dsct read` and `dsct stats` JSON output.
//!
//! Existing integration tests assert the *presence* of individual fields.
//! This file fixes the top-level **key set and order** of the JSON produced
//! by `write_packet_json` (`src/serialize.rs`) and `StatsOutput`
//! (`src/stats/mod.rs`) so that any accidental rename, reorder, or removal
//! of a top-level key is caught as a regression.
//!
//! `serde_json` is configured with `preserve_order` in `Cargo.toml`, so the
//! key iteration order is deterministic and reflects the write order used by
//! `serialize.rs` / `Serialize` impls.

use assert_cmd::Command;
use serde_json::{Map, Value};
use std::io::Write;
use tempfile::NamedTempFile;

/// Build a minimal pcap containing `n` identical Ethernet+IPv4+UDP packets.
///
/// Matches the format used by `tests/cli_read_test.rs` so we exercise the
/// same shared code path.
fn build_udp_pcap(n: usize) -> Vec<u8> {
    let mut pcap = Vec::new();
    // pcap global header (little-endian, Ethernet link type)
    pcap.extend_from_slice(&0xA1B2C3D4u32.to_le_bytes());
    pcap.extend_from_slice(&2u16.to_le_bytes()); // version major
    pcap.extend_from_slice(&4u16.to_le_bytes()); // version minor
    pcap.extend_from_slice(&0i32.to_le_bytes()); // thiszone
    pcap.extend_from_slice(&0u32.to_le_bytes()); // sigfigs
    pcap.extend_from_slice(&65535u32.to_le_bytes()); // snaplen
    pcap.extend_from_slice(&1u32.to_le_bytes()); // Ethernet link type

    let pkt: &[u8] = &[
        // Ethernet
        0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x00, 0x11, 0x22, 0x33, 0x44, 0x55, 0x08, 0x00,
        // IPv4: TTL=64, protocol=17 (UDP), src=10.0.0.1, dst=10.0.0.2
        0x45, 0x00, 0x00, 0x1c, 0x00, 0x00, 0x00, 0x00, 0x40, 0x11, 0x00, 0x00, 0x0a, 0x00, 0x00,
        0x01, 0x0a, 0x00, 0x00, 0x02, // UDP: sport=4096, dport=4097
        0x10, 0x00, 0x10, 0x01, 0x00, 0x08, 0x00, 0x00,
    ];

    for i in 0..n {
        pcap.extend_from_slice(&(i as u32).to_le_bytes()); // ts_sec
        pcap.extend_from_slice(&0u32.to_le_bytes()); // ts_usec
        pcap.extend_from_slice(&(pkt.len() as u32).to_le_bytes()); // caplen
        pcap.extend_from_slice(&(pkt.len() as u32).to_le_bytes()); // origlen
        pcap.extend_from_slice(pkt);
    }
    pcap
}

fn write_pcap(n: usize) -> NamedTempFile {
    let mut tmp = NamedTempFile::with_suffix(".pcap").unwrap();
    tmp.write_all(&build_udp_pcap(n)).unwrap();
    tmp
}

/// Return the ordered list of keys in a JSON object value.
fn object_keys(value: &Value) -> Vec<String> {
    value
        .as_object()
        .map(|m: &Map<String, Value>| m.keys().cloned().collect())
        .unwrap_or_default()
}

// ---------------------------------------------------------------------------
// `dsct read` — packet record schema
// ---------------------------------------------------------------------------

#[test]
fn read_jsonl_top_level_keys_are_stable() {
    let tmp = write_pcap(1);
    let output = Command::cargo_bin("dsct")
        .unwrap()
        .args(["read", tmp.path().to_str().unwrap()])
        .output()
        .unwrap();
    assert!(output.status.success(), "read must exit 0");

    let stdout = String::from_utf8(output.stdout).unwrap();
    let first_line = stdout.lines().next().expect("at least one JSONL line");
    let value: Value = serde_json::from_str(first_line).unwrap();

    // Fix the exact top-level key order. Any rename / reorder / removal trips.
    let expected = [
        "number",
        "timestamp",
        "length",
        "original_length",
        "stack",
        "layers",
    ];
    assert_eq!(
        object_keys(&value),
        expected,
        "read JSONL top-level key order changed"
    );

    // Type invariants.
    assert!(value["number"].is_u64());
    let ts = value["timestamp"].as_str().expect("timestamp is string");
    assert!(
        ts.ends_with('Z') && ts.len() >= 20,
        "timestamp must be ISO 8601 Z-terminated, got {ts:?}"
    );
    assert!(value["length"].is_u64());
    assert!(value["original_length"].is_u64());
    assert!(value["stack"].is_string());
    assert!(value["layers"].is_array());

    // Stack summary must reflect the packet we built.
    assert_eq!(value["stack"], "Ethernet:IPv4:UDP");

    // Every layer must expose `protocol` then `fields`, in that order.
    for layer in value["layers"].as_array().unwrap() {
        let layer_keys = object_keys(layer);
        assert_eq!(
            layer_keys,
            ["protocol", "fields"],
            "layer object key order changed"
        );
        assert!(layer["protocol"].is_string());
        assert!(layer["fields"].is_object());
    }
}

#[test]
fn read_verbose_adds_fields_to_ipv4_layer() {
    let tmp = write_pcap(1);

    // Default run.
    let default_out = Command::cargo_bin("dsct")
        .unwrap()
        .args(["read", tmp.path().to_str().unwrap()])
        .output()
        .unwrap();
    assert!(default_out.status.success());
    let default_line = String::from_utf8(default_out.stdout).unwrap();
    let default_value: Value = serde_json::from_str(default_line.lines().next().unwrap()).unwrap();

    // Verbose run.
    let verbose_out = Command::cargo_bin("dsct")
        .unwrap()
        .args(["read", "--verbose", tmp.path().to_str().unwrap()])
        .output()
        .unwrap();
    assert!(verbose_out.status.success());
    let verbose_line = String::from_utf8(verbose_out.stdout).unwrap();
    let verbose_value: Value = serde_json::from_str(verbose_line.lines().next().unwrap()).unwrap();

    // Top-level key order must be identical regardless of verbosity.
    assert_eq!(object_keys(&default_value), object_keys(&verbose_value));

    // Find the IPv4 layer in both outputs and compare field counts.
    let ipv4_fields_count = |v: &Value| -> usize {
        v["layers"]
            .as_array()
            .unwrap()
            .iter()
            .find(|l| l["protocol"] == "IPv4")
            .and_then(|l| l["fields"].as_object())
            .map(|fs| fs.len())
            .unwrap_or(0)
    };

    let default_count = ipv4_fields_count(&default_value);
    let verbose_count = ipv4_fields_count(&verbose_value);
    assert!(
        verbose_count > default_count,
        "--verbose must expose more IPv4 fields (default={default_count}, verbose={verbose_count})"
    );
}

// ---------------------------------------------------------------------------
// `dsct stats` — StatsOutput schema
// ---------------------------------------------------------------------------

#[test]
fn stats_top_level_keys_are_stable() {
    let tmp = write_pcap(3);
    let output = Command::cargo_bin("dsct")
        .unwrap()
        .args(["stats", tmp.path().to_str().unwrap()])
        .output()
        .unwrap();
    assert!(output.status.success());

    let value: Value = serde_json::from_slice(&output.stdout).unwrap();

    // StatsOutput field order per `#[derive(Serialize)]`:
    //   type, total_packets, time_start?, time_end?, duration_secs, protocols,
    //   ...protocol_stats (flattened), top_talkers?, tcp_streams?
    // Optional keys are skipped when None; with the UDP-only pcap built above
    // we expect time_start / time_end to be present (ts_sec=0..n).
    let keys = object_keys(&value);
    let expected_prefix = [
        "type",
        "total_packets",
        "time_start",
        "time_end",
        "duration_secs",
        "protocols",
    ];
    assert!(
        keys.starts_with(&expected_prefix.map(String::from)),
        "stats top-level key prefix changed; got {keys:?}"
    );

    // Invariants.
    assert_eq!(value["type"], "stats");
    assert_eq!(value["total_packets"].as_u64().unwrap(), 3);
    assert!(value["duration_secs"].is_number());
    assert!(value["protocols"].is_object());
    let protocols = value["protocols"].as_object().unwrap();
    assert!(
        protocols.contains_key("Ethernet")
            && protocols.contains_key("IPv4")
            && protocols.contains_key("UDP"),
        "protocols map missing expected entries: {protocols:?}"
    );

    // top_talkers / tcp_streams must NOT appear unless their flags are set.
    assert!(!keys.iter().any(|k| k == "top_talkers"));
    assert!(!keys.iter().any(|k| k == "tcp_streams"));
}

#[test]
fn stats_with_top_talkers_flag_adds_key() {
    let tmp = write_pcap(3);
    let output = Command::cargo_bin("dsct")
        .unwrap()
        .args(["stats", "--top-talkers", tmp.path().to_str().unwrap()])
        .output()
        .unwrap();
    assert!(output.status.success());

    let value: Value = serde_json::from_slice(&output.stdout).unwrap();
    assert!(
        value.get("top_talkers").is_some(),
        "--top-talkers must add top_talkers key; got {value:?}"
    );
    let talkers = value["top_talkers"]
        .as_array()
        .expect("top_talkers must be an array");
    assert!(!talkers.is_empty(), "top_talkers must not be empty");

    // Every talker entry must carry the TalkerEntry contract.
    for entry in talkers {
        let entry_keys = object_keys(entry);
        assert_eq!(
            entry_keys,
            ["src", "dst", "packets", "bytes"],
            "TalkerEntry key order changed"
        );
    }
}