xtap 0.2.0

An LD_PRELOAD interception library for runtime hooking of network calls in Unix-like systems.
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

use std::net::IpAddr;

use netdev::{Interface, get_interfaces};

use crate::debug_log;
use crate::log::{log_and_none, log_and_some};

/// Log helper for interface addresses
fn log_interface_addrs(interface: &Interface) {
    debug_log!(
        "Interface: {:<10} | Addr(v4): {:?}",
        interface.name,
        interface.ipv4_addrs()
    );
    debug_log!(
        "Interface: {:<10} | Addr(v6): {:?}",
        interface.name,
        interface.ipv6_addrs()
    );
}

/// Return the first IP address of an `Interface`, preferring IPv4 over IPv6 or `None`
pub(crate) fn first_ip(interface: &Interface) -> Option<IpAddr> {
    log_interface_addrs(interface);

    interface
        .ipv4_addrs()
        .first()
        .map(|ip| IpAddr::V4(*ip))
        .or_else(|| interface.ipv6_addrs().first().map(|ip| IpAddr::V6(*ip)))
        .or_else(|| {
            log_and_none(&format!(
                "Interface '{}' has no IP addresses",
                interface.name
            ))
        })
}

/// Find an interface by its `IpAddr`.
pub(crate) fn interface_by(ip: IpAddr) -> Option<Interface> {
    for interface in get_interfaces() {
        log_interface_addrs(&interface);

        if interface.ip_addrs().contains(&ip) {
            return log_and_some(
                &format!("Found interface '{}' for address '{}'", interface.name, ip),
                interface,
            );
        }
    }

    log_and_none(&format!("No interface found for address '{ip}'"))
}

#[cfg(test)]
mod tests {
    use super::*;
    use netdev::{
        Interface,
        ipnet::{Ipv4Net, Ipv6Net},
    };
    use std::net::{IpAddr, Ipv4Addr, Ipv6Addr};

    fn make_interface(name: &str, v4_addrs: Vec<Ipv4Net>, v6_addrs: Vec<Ipv6Net>) -> Interface {
        Interface {
            name: name.to_string(),
            ipv4: v4_addrs,
            ipv6: v6_addrs,
            ..Interface::dummy()
        }
    }

    #[test]
    fn test_first_interface_ip_with_ipv4() {
        let interface = make_interface(
            "eth0",
            vec![Ipv4Net::new(Ipv4Addr::new(192, 168, 1, 100), 24).unwrap()],
            vec![],
        );
        let ip = first_ip(&interface);

        assert_eq!(ip, Some(IpAddr::V4(Ipv4Addr::new(192, 168, 1, 100))));
    }

    #[test]
    fn test_first_interface_ip_with_ipv6_only() {
        let interface = make_interface(
            "eth1",
            vec![],
            vec![Ipv6Net::new(Ipv6Addr::LOCALHOST, 128).unwrap()],
        );
        let ip = first_ip(&interface);

        assert_eq!(ip, Some(IpAddr::V6(Ipv6Addr::LOCALHOST)));
    }

    #[test]
    fn test_first_interface_ip_with_no_addrs() {
        let interface = make_interface("lo", vec![], vec![]);
        let ip = first_ip(&interface);

        assert_eq!(ip, None);
    }

    #[test]
    fn test_interface_by_ip_found() {
        fn mock_get_interfaces() -> Vec<Interface> {
            vec![
                make_interface(
                    "eth0",
                    vec![Ipv4Net::new(Ipv4Addr::new(10, 0, 0, 1), 24).unwrap()],
                    vec![],
                ),
                make_interface(
                    "eth1",
                    vec![Ipv4Net::new(Ipv4Addr::new(192, 168, 1, 1), 24).unwrap()],
                    vec![],
                ),
            ]
        }

        let target_ip = IpAddr::V4(Ipv4Addr::new(192, 168, 1, 1));
        let result = mock_get_interfaces()
            .into_iter()
            .find(|iface| iface.ipv4.iter().any(|net| net.addr() == target_ip))
            .map(|iface| iface.name);

        assert_eq!(result, Some("eth1".to_string()));
    }

    #[test]
    fn test_interface_by_ip_not_found() {
        let iface = make_interface(
            "eth0",
            vec![Ipv4Net::new(Ipv4Addr::new(10, 0, 0, 1), 24).unwrap()],
            vec![],
        );
        let target_ip = IpAddr::V4(Ipv4Addr::new(127, 0, 0, 1));
        let matches = iface.ipv4.iter().any(|net| net.addr() == target_ip);

        assert!(!matches);
    }
}