lsnet 0.7.0

See what's on your local network: fast, zero-config device discovery and identification
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

//! SSDP / UPnP discovery. Routers, TVs, media players and NASes answer an
//! M-SEARCH with the URL of an XML description that names their maker and model.

use crate::http;
use ipnetwork::Ipv4Network;
use serde::Serialize;
use std::collections::HashMap;
use std::net::{Ipv4Addr, SocketAddr};
use std::time::Duration;
use tokio::net::UdpSocket;
use tokio::task::JoinSet;
use tokio::time::{Instant, timeout_at};

const SSDP: (Ipv4Addr, u16) = (Ipv4Addr::new(239, 255, 255, 250), 1900);
const SEARCH: &str = "M-SEARCH * HTTP/1.1\r\nHOST: 239.255.255.250:1900\r\n\
    MAN: \"ssdp:discover\"\r\nMX: 1\r\nST: ssdp:all\r\n\r\n";

#[derive(Default, Clone, Serialize)]
pub struct SsdpInfo {
    pub server: Option<String>,
    pub friendly_name: Option<String>,
    pub manufacturer: Option<String>,
    pub model_name: Option<String>,
    pub model_number: Option<String>,
    pub device_type: Option<String>,
}

/// Collect responses for `wait`, fetching each device's description as soon
/// as it answers, then allow `fetch_grace` for the last fetches to finish.
pub async fn discover(
    local_ip: Ipv4Addr,
    net: Ipv4Network,
    own_ips: &[Ipv4Addr],
    wait: Duration,
    fetch_grace: Duration,
) -> HashMap<Ipv4Addr, SsdpInfo> {
    let Ok(sock) = UdpSocket::bind((local_ip, 0)).await else {
        return HashMap::new();
    };
    let _ = sock.send_to(SEARCH.as_bytes(), SSDP).await;

    let deadline = Instant::now() + wait;
    let resend_at = Instant::now() + wait / 3;
    let mut resent = false;
    let mut seen: HashMap<Ipv4Addr, Option<String>> = HashMap::new();
    let mut fetches = JoinSet::new();
    let mut buf = vec![0u8; 4096];

    loop {
        let until = if resent { deadline } else { resend_at };
        match timeout_at(until, sock.recv_from(&mut buf)).await {
            Ok(Ok((n, SocketAddr::V4(src)))) => {
                let ip = *src.ip();
                if !net.contains(ip) || seen.contains_key(&ip) {
                    continue;
                }
                let resp = String::from_utf8_lossy(&buf[..n]).to_string();
                let header = |name: &str| {
                    resp.lines().find_map(|l| {
                        let (k, v) = l.split_once(':')?;
                        k.trim()
                            .eq_ignore_ascii_case(name)
                            .then(|| v.trim().to_string())
                    })
                };
                seen.insert(ip, header("server"));
                if let Some((host, port, path)) =
                    header("location").and_then(|l| description_url(&l, ip, own_ips))
                {
                    fetches.spawn(async move {
                        (ip, http::get(host, port, &path, wait + fetch_grace).await)
                    });
                }
            }
            Ok(_) => {}
            Err(_) if !resent => {
                resent = true;
                let _ = sock.send_to(SEARCH.as_bytes(), SSDP).await;
            }
            Err(_) => break,
        }
    }

    let mut out: HashMap<Ipv4Addr, SsdpInfo> = seen
        .into_iter()
        .map(|(ip, server)| {
            (
                ip,
                SsdpInfo {
                    server,
                    ..Default::default()
                },
            )
        })
        .collect();

    let grace_end = Instant::now() + fetch_grace;
    while let Ok(Some(joined)) = timeout_at(grace_end, fetches.join_next()).await {
        let Ok((ip, Some(resp))) = joined else {
            continue;
        };
        let info = out.entry(ip).or_default();
        let x = &resp.body;
        info.friendly_name = http::tag(x, "friendlyName");
        info.manufacturer = http::tag(x, "manufacturer");
        info.model_name = http::tag(x, "modelName");
        info.model_number = http::tag(x, "modelNumber");
        info.device_type = http::tag(x, "deviceType");
    }
    out
}

/// Where to fetch a responder's description, if its LOCATION is safe to follow.
///
/// Only the device that answered is asked, and never this machine; otherwise
/// anyone on the LAN could point us at 127.0.0.1 or the internet. Queries are
/// refused too: description URLs don't have them, but "do something on GET"
/// endpoints usually take their parameters that way.
fn description_url(
    location: &str,
    responder: Ipv4Addr,
    own_ips: &[Ipv4Addr],
) -> Option<(Ipv4Addr, u16, String)> {
    let (host, port, path) = http::parse_url(location)?;
    (host == responder && !own_ips.contains(&host) && !path.contains('?'))
        .then_some((host, port, path))
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn follows_only_safe_locations() {
        let dev: Ipv4Addr = "192.168.1.57".parse().unwrap();
        let me: Ipv4Addr = "192.168.1.179".parse().unwrap();
        let ok = |l: &str, from: Ipv4Addr| description_url(l, from, &[me]).is_some();

        assert!(ok("http://192.168.1.57:49152/description.xml", dev));
        assert!(!ok("http://127.0.0.1:8080/description.xml", dev));
        assert!(!ok("http://192.168.1.1/description.xml", dev));
        assert!(!ok("http://192.168.1.57/cgi-bin/reboot?now=1", dev));
        assert!(!ok("http://192.168.1.179/description.xml", me));
    }
}