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
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
use crate::ffi::OsStr;
#[cfg(any(doc, target_os = "android", target_os = "linux"))]
use crate::os::net::linux_ext;
use crate::os::unix::ffi::OsStrExt;
use crate::path::Path;
use crate::sealed::Sealed;
use crate::sys::cvt;
use crate::{fmt, io, mem, ptr};

// FIXME(#43348): Make libc adapt #[doc(cfg(...))] so we don't need these fake definitions here?
#[cfg(not(unix))]
#[allow(non_camel_case_types)]
mod libc {
    pub use libc::c_int;
    pub type socklen_t = u32;
    pub struct sockaddr;
    #[derive(Clone)]
    pub struct sockaddr_un;
}

fn sun_path_offset(addr: &libc::sockaddr_un) -> usize {
    // Work with an actual instance of the type since using a null pointer is UB
    let base = (addr as *const libc::sockaddr_un).addr();
    let path = (&addr.sun_path as *const libc::c_char).addr();
    path - base
}

pub(super) fn sockaddr_un(path: &Path) -> io::Result<(libc::sockaddr_un, libc::socklen_t)> {
    // SAFETY: All zeros is a valid representation for `sockaddr_un`.
    let mut addr: libc::sockaddr_un = unsafe { mem::zeroed() };
    addr.sun_family = libc::AF_UNIX as libc::sa_family_t;

    let bytes = path.as_os_str().as_bytes();

    if bytes.contains(&0) {
        return Err(io::const_io_error!(
            io::ErrorKind::InvalidInput,
            "paths must not contain interior null bytes",
        ));
    }

    if bytes.len() >= addr.sun_path.len() {
        return Err(io::const_io_error!(
            io::ErrorKind::InvalidInput,
            "path must be shorter than SUN_LEN",
        ));
    }
    // SAFETY: `bytes` and `addr.sun_path` are not overlapping and
    // both point to valid memory.
    // NOTE: We zeroed the memory above, so the path is already null
    // terminated.
    unsafe {
        ptr::copy_nonoverlapping(bytes.as_ptr(), addr.sun_path.as_mut_ptr().cast(), bytes.len())
    };

    let mut len = sun_path_offset(&addr) + bytes.len();
    match bytes.get(0) {
        Some(&0) | None => {}
        Some(_) => len += 1,
    }
    Ok((addr, len as libc::socklen_t))
}

enum AddressKind<'a> {
    Unnamed,
    Pathname(&'a Path),
    Abstract(&'a [u8]),
}

/// An address associated with a Unix socket.
///
/// # Examples
///
/// ```
/// use std::os::unix::net::UnixListener;
///
/// let socket = match UnixListener::bind("/tmp/sock") {
///     Ok(sock) => sock,
///     Err(e) => {
///         println!("Couldn't bind: {e:?}");
///         return
///     }
/// };
/// let addr = socket.local_addr().expect("Couldn't get local address");
/// ```
#[derive(Clone)]
#[stable(feature = "unix_socket", since = "1.10.0")]
pub struct SocketAddr {
    pub(super) addr: libc::sockaddr_un,
    pub(super) len: libc::socklen_t,
}

impl SocketAddr {
    pub(super) fn new<F>(f: F) -> io::Result<SocketAddr>
    where
        F: FnOnce(*mut libc::sockaddr, *mut libc::socklen_t) -> libc::c_int,
    {
        unsafe {
            let mut addr: libc::sockaddr_un = mem::zeroed();
            let mut len = mem::size_of::<libc::sockaddr_un>() as libc::socklen_t;
            cvt(f(&mut addr as *mut _ as *mut _, &mut len))?;
            SocketAddr::from_parts(addr, len)
        }
    }

    pub(super) fn from_parts(
        addr: libc::sockaddr_un,
        mut len: libc::socklen_t,
    ) -> io::Result<SocketAddr> {
        if len == 0 {
            // When there is a datagram from unnamed unix socket
            // linux returns zero bytes of address
            len = sun_path_offset(&addr) as libc::socklen_t; // i.e., zero-length address
        } else if addr.sun_family != libc::AF_UNIX as libc::sa_family_t {
            return Err(io::const_io_error!(
                io::ErrorKind::InvalidInput,
                "file descriptor did not correspond to a Unix socket",
            ));
        }

        Ok(SocketAddr { addr, len })
    }

    /// Constructs a `SockAddr` with the family `AF_UNIX` and the provided path.
    ///
    /// # Errors
    ///
    /// Returns an error if the path is longer than `SUN_LEN` or if it contains
    /// NULL bytes.
    ///
    /// # Examples
    ///
    /// ```
    /// use std::os::unix::net::SocketAddr;
    /// use std::path::Path;
    ///
    /// # fn main() -> std::io::Result<()> {
    /// let address = SocketAddr::from_pathname("/path/to/socket")?;
    /// assert_eq!(address.as_pathname(), Some(Path::new("/path/to/socket")));
    /// # Ok(())
    /// # }
    /// ```
    ///
    /// Creating a `SocketAddr` with a NULL byte results in an error.
    ///
    /// ```
    /// use std::os::unix::net::SocketAddr;
    ///
    /// assert!(SocketAddr::from_pathname("/path/with/\0/bytes").is_err());
    /// ```
    #[stable(feature = "unix_socket_creation", since = "1.61.0")]
    pub fn from_pathname<P>(path: P) -> io::Result<SocketAddr>
    where
        P: AsRef<Path>,
    {
        sockaddr_un(path.as_ref()).map(|(addr, len)| SocketAddr { addr, len })
    }

    /// Returns `true` if the address is unnamed.
    ///
    /// # Examples
    ///
    /// A named address:
    ///
    /// ```no_run
    /// use std::os::unix::net::UnixListener;
    ///
    /// fn main() -> std::io::Result<()> {
    ///     let socket = UnixListener::bind("/tmp/sock")?;
    ///     let addr = socket.local_addr().expect("Couldn't get local address");
    ///     assert_eq!(addr.is_unnamed(), false);
    ///     Ok(())
    /// }
    /// ```
    ///
    /// An unnamed address:
    ///
    /// ```
    /// use std::os::unix::net::UnixDatagram;
    ///
    /// fn main() -> std::io::Result<()> {
    ///     let socket = UnixDatagram::unbound()?;
    ///     let addr = socket.local_addr().expect("Couldn't get local address");
    ///     assert_eq!(addr.is_unnamed(), true);
    ///     Ok(())
    /// }
    /// ```
    #[must_use]
    #[stable(feature = "unix_socket", since = "1.10.0")]
    pub fn is_unnamed(&self) -> bool {
        matches!(self.address(), AddressKind::Unnamed)
    }

    /// Returns the contents of this address if it is a `pathname` address.
    ///
    /// # Examples
    ///
    /// With a pathname:
    ///
    /// ```no_run
    /// use std::os::unix::net::UnixListener;
    /// use std::path::Path;
    ///
    /// fn main() -> std::io::Result<()> {
    ///     let socket = UnixListener::bind("/tmp/sock")?;
    ///     let addr = socket.local_addr().expect("Couldn't get local address");
    ///     assert_eq!(addr.as_pathname(), Some(Path::new("/tmp/sock")));
    ///     Ok(())
    /// }
    /// ```
    ///
    /// Without a pathname:
    ///
    /// ```
    /// use std::os::unix::net::UnixDatagram;
    ///
    /// fn main() -> std::io::Result<()> {
    ///     let socket = UnixDatagram::unbound()?;
    ///     let addr = socket.local_addr().expect("Couldn't get local address");
    ///     assert_eq!(addr.as_pathname(), None);
    ///     Ok(())
    /// }
    /// ```
    #[stable(feature = "unix_socket", since = "1.10.0")]
    #[must_use]
    pub fn as_pathname(&self) -> Option<&Path> {
        if let AddressKind::Pathname(path) = self.address() { Some(path) } else { None }
    }

    fn address(&self) -> AddressKind<'_> {
        let len = self.len as usize - sun_path_offset(&self.addr);
        let path = unsafe { mem::transmute::<&[libc::c_char], &[u8]>(&self.addr.sun_path) };

        // macOS seems to return a len of 16 and a zeroed sun_path for unnamed addresses
        if len == 0
            || (cfg!(not(any(target_os = "linux", target_os = "android")))
                && self.addr.sun_path[0] == 0)
        {
            AddressKind::Unnamed
        } else if self.addr.sun_path[0] == 0 {
            AddressKind::Abstract(&path[1..len])
        } else {
            AddressKind::Pathname(OsStr::from_bytes(&path[..len - 1]).as_ref())
        }
    }
}

#[stable(feature = "unix_socket_abstract", since = "1.70.0")]
impl Sealed for SocketAddr {}

#[doc(cfg(any(target_os = "android", target_os = "linux")))]
#[cfg(any(doc, target_os = "android", target_os = "linux"))]
#[stable(feature = "unix_socket_abstract", since = "1.70.0")]
impl linux_ext::addr::SocketAddrExt for SocketAddr {
    fn as_abstract_name(&self) -> Option<&[u8]> {
        if let AddressKind::Abstract(name) = self.address() { Some(name) } else { None }
    }

    fn from_abstract_name<N>(name: N) -> crate::io::Result<Self>
    where
        N: AsRef<[u8]>,
    {
        let name = name.as_ref();
        unsafe {
            let mut addr: libc::sockaddr_un = mem::zeroed();
            addr.sun_family = libc::AF_UNIX as libc::sa_family_t;

            if name.len() + 1 > addr.sun_path.len() {
                return Err(io::const_io_error!(
                    io::ErrorKind::InvalidInput,
                    "abstract socket name must be shorter than SUN_LEN",
                ));
            }

            crate::ptr::copy_nonoverlapping(
                name.as_ptr(),
                addr.sun_path.as_mut_ptr().add(1) as *mut u8,
                name.len(),
            );
            let len = (sun_path_offset(&addr) + 1 + name.len()) as libc::socklen_t;
            SocketAddr::from_parts(addr, len)
        }
    }
}

#[stable(feature = "unix_socket", since = "1.10.0")]
impl fmt::Debug for SocketAddr {
    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self.address() {
            AddressKind::Unnamed => write!(fmt, "(unnamed)"),
            AddressKind::Abstract(name) => write!(fmt, "\"{}\" (abstract)", name.escape_ascii()),
            AddressKind::Pathname(path) => write!(fmt, "{path:?} (pathname)"),
        }
    }
}