Merge #1857

1857: Add better support for unnamed unix socket addrs r=asomers a=stevenengler

This adds the following 2 functions/methods: `UnixAddr::new_unnamed` and `UnixAddr::is_unnamed`.

Closes #1585

unix(7) on Linux:

> unnamed: A stream socket that has not been bound to a pathname using bind(2) has no name. Likewise, the two sockets created by socketpair(2) are unnamed. When the address of an unnamed socket is returned, its length is `sizeof(sa_family_t)`, and `sun_path` should not be inspected.

**Edit:** This currently isn't working on BSD, but I see why. Will fix it shortly.

Co-authored-by: Steven Engler <opara@cs.georgetown.edu>

1 files changed, 22 insertions, 0 deletions

diff --git a/src/sys/socket/addr.rs b/src/sys/socket/addr.rs
index b80d78c1..2b3e4919 100644
--- a/src/sys/socket/addr.rs
+++ b/src/sys/socket/addr.rs
@@ -885,6 +885,20 @@ impl UnixAddr {
         }
     }
 
+    /// Create a new `sockaddr_un` representing an "unnamed" unix socket address.
+    #[cfg(any(target_os = "android", target_os = "linux"))]
+    #[cfg_attr(docsrs, doc(cfg(all())))]
+    pub fn new_unnamed() -> UnixAddr {
+        let ret = libc::sockaddr_un {
+            sun_family: AddressFamily::Unix as sa_family_t,
+            .. unsafe { mem::zeroed() }
+        };
+
+        let sun_len: u8 = offset_of!(libc::sockaddr_un, sun_path).try_into().unwrap();
+
+        unsafe { UnixAddr::from_raw_parts(ret, sun_len) }
+    }
+
     /// Create a UnixAddr from a raw `sockaddr_un` struct and a size. `sun_len`
     /// is the size of the valid portion of the struct, excluding any trailing
     /// NUL.
@@ -941,6 +955,14 @@ impl UnixAddr {
         }
     }
 
+    /// Check if this address is an "unnamed" unix socket address.
+    #[cfg(any(target_os = "android", target_os = "linux"))]
+    #[cfg_attr(docsrs, doc(cfg(all())))]
+    #[inline]
+    pub fn is_unnamed(&self) -> bool {
+        matches!(self.kind(), UnixAddrKind::Unnamed)
+    }
+
     /// Returns the addrlen of this socket - `offsetof(struct sockaddr_un, sun_path)`
     #[inline]
     pub fn path_len(&self) -> usize {