Add a function for SO_DOMAIN. (#779)

Add a `get_socket_domain` function for using `SO_DOMAIN` on a socket.

src/backend/libc/net/syscalls.rs

@@ -517,6 +517,19 @@ pub(crate) mod sockopt {
     use super::{c, in6_addr_new, in_addr_new, BorrowedFd};
     use crate::io;
     use crate::net::sockopt::Timeout;
+    #[cfg(not(any(
+        apple,
+        solarish,
+        windows,
+        target_os = "dragonfly",
+        target_os = "emscripten",
+        target_os = "espidf",
+        target_os = "haiku",
+        target_os = "netbsd",
+        target_os = "nto",
+        target_os = "openbsd"
+    )))]
+    use crate::net::AddressFamily;
     use crate::net::{Ipv4Addr, Ipv6Addr, SocketType};
     use crate::utils::as_mut_ptr;
     use core::time::Duration;
@@ -809,6 +822,26 @@ pub(crate) mod sockopt {
         getsockopt(fd, c::SOL_SOCKET as _, c::SO_SNDBUF).map(|size: u32| size as usize)
     }
 
+    #[inline]
+    #[cfg(not(any(
+        apple,
+        solarish,
+        windows,
+        target_os = "dragonfly",
+        target_os = "emscripten",
+        target_os = "espidf",
+        target_os = "haiku",
+        target_os = "netbsd",
+        target_os = "nto",
+        target_os = "openbsd"
+    )))]
+    pub(crate) fn get_socket_domain(fd: BorrowedFd<'_>) -> io::Result<AddressFamily> {
+        let domain: c::c_int = getsockopt(fd, c::SOL_SOCKET as _, c::SO_DOMAIN)?;
+        Ok(AddressFamily(
+            domain.try_into().map_err(|_| io::Errno::OPNOTSUPP)?,
+        ))
+    }
+
     #[inline]
     pub(crate) fn set_ip_ttl(fd: BorrowedFd<'_>, ttl: u32) -> io::Result<()> {
         setsockopt(fd, c::IPPROTO_IP as _, c::IP_TTL, ttl)

src/backend/linux_raw/c.rs

@@ -65,10 +65,10 @@ pub(crate) use linux_raw_sys::{
         IP_MULTICAST_TTL, IP_TTL, MSG_CMSG_CLOEXEC, MSG_CONFIRM, MSG_DONTROUTE, MSG_DONTWAIT,
         MSG_EOR, MSG_ERRQUEUE, MSG_MORE, MSG_NOSIGNAL, MSG_OOB, MSG_PEEK, MSG_TRUNC, MSG_WAITALL,
         SCM_CREDENTIALS, SCM_RIGHTS, SHUT_RD, SHUT_RDWR, SHUT_WR, SOCK_DGRAM, SOCK_RAW, SOCK_RDM,
-        SOCK_SEQPACKET, SOCK_STREAM, SOL_SOCKET, SO_BROADCAST, SO_ERROR, SO_KEEPALIVE, SO_LINGER,
-        SO_PASSCRED, SO_RCVBUF, SO_RCVTIMEO_NEW, SO_RCVTIMEO_NEW as SO_RCVTIMEO, SO_RCVTIMEO_OLD,
-        SO_REUSEADDR, SO_SNDBUF, SO_SNDTIMEO_NEW, SO_SNDTIMEO_NEW as SO_SNDTIMEO, SO_SNDTIMEO_OLD,
-        SO_TYPE, TCP_NODELAY,
+        SOCK_SEQPACKET, SOCK_STREAM, SOL_SOCKET, SO_BROADCAST, SO_DOMAIN, SO_ERROR, SO_KEEPALIVE,
+        SO_LINGER, SO_PASSCRED, SO_RCVBUF, SO_RCVTIMEO_NEW, SO_RCVTIMEO_NEW as SO_RCVTIMEO,
+        SO_RCVTIMEO_OLD, SO_REUSEADDR, SO_SNDBUF, SO_SNDTIMEO_NEW, SO_SNDTIMEO_NEW as SO_SNDTIMEO,
+        SO_SNDTIMEO_OLD, SO_TYPE, TCP_NODELAY,
     },
     netlink::*,
 };

src/backend/linux_raw/net/syscalls.rs

@@ -920,7 +920,7 @@ pub(crate) mod sockopt {
     use super::{c, BorrowedFd};
     use crate::io;
     use crate::net::sockopt::Timeout;
-    use crate::net::{Ipv4Addr, Ipv6Addr, SocketType};
+    use crate::net::{AddressFamily, Ipv4Addr, Ipv6Addr, SocketType};
     use c::{SO_RCVTIMEO_NEW, SO_RCVTIMEO_OLD, SO_SNDTIMEO_NEW, SO_SNDTIMEO_OLD};
     use core::time::Duration;
     use linux_raw_sys::general::{__kernel_timespec, timeval};
@@ -1271,6 +1271,14 @@ pub(crate) mod sockopt {
         getsockopt(fd, c::SOL_SOCKET as _, c::SO_SNDBUF).map(|size: u32| size as usize)
     }
 
+    #[inline]
+    pub(crate) fn get_socket_domain(fd: BorrowedFd<'_>) -> io::Result<AddressFamily> {
+        let domain: c::c_int = getsockopt(fd, c::SOL_SOCKET as _, c::SO_DOMAIN)?;
+        Ok(AddressFamily(
+            domain.try_into().map_err(|_| io::Errno::OPNOTSUPP)?,
+        ))
+    }
+
     #[inline]
     pub(crate) fn set_ip_ttl(fd: BorrowedFd<'_>, ttl: u32) -> io::Result<()> {
         setsockopt(fd, c::IPPROTO_IP as _, c::IP_TTL, ttl)

src/net/sockopt.rs

@@ -6,6 +6,19 @@
 #![doc(alias = "getsockopt")]
 #![doc(alias = "setsockopt")]
 
+#[cfg(not(any(
+    apple,
+    solarish,
+    windows,
+    target_os = "dragonfly",
+    target_os = "emscripten",
+    target_os = "espidf",
+    target_os = "haiku",
+    target_os = "netbsd",
+    target_os = "nto",
+    target_os = "openbsd"
+)))]
+use crate::net::AddressFamily;
 use crate::net::{Ipv4Addr, Ipv6Addr, SocketType};
 use crate::{backend, io};
 use backend::c;
@@ -712,6 +725,57 @@ pub fn get_socket_send_buffer_size<Fd: AsFd>(fd: Fd) -> io::Result<usize> {
     backend::net::syscalls::sockopt::get_socket_send_buffer_size(fd.as_fd())
 }
 
+/// `getsockopt(fd, SOL_SOCKET, SO_DOMAIN)`
+///
+/// # References
+///  - [POSIX `getsockopt`]
+///  - [POSIX `sys/socket.h`]
+///  - [Linux `getsockopt`]
+///  - [Linux `socket`]
+///  - [Winsock2 `getsockopt`]
+///  - [Winsock2 `SOL_SOCKET` options]
+///  - [Apple]
+///  - [FreeBSD]
+///  - [NetBSD]
+///  - [OpenBSD]
+///  - [DragonFly BSD]
+///  - [illumos]
+///  - [glibc `getsockopt`]
+///  - [glibc `SOL_SOCKET` Options]
+///
+/// [POSIX `getsockopt`]: https://pubs.opengroup.org/onlinepubs/9699919799/functions/getsockopt.html
+/// [POSIX `sys/socket.h`]: https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/sys_socket.h.html
+/// [Linux `getsockopt`]: https://man7.org/linux/man-pages/man2/getsockopt.2.html
+/// [Linux `socket`]: https://man7.org/linux/man-pages/man7/socket.7.html
+/// [Winsock2 `getsockopt`]: https://docs.microsoft.com/en-us/windows/win32/api/winsock2/nf-winsock2-getsockopt
+/// [Winsock2 `SOL_SOCKET` options]: https://docs.microsoft.com/en-us/windows/win32/winsock/sol-socket-socket-options
+/// [Apple]: https://developer.apple.com/library/archive/documentation/System/Conceptual/ManPages_iPhoneOS/man2/getsockopt.2.html
+/// [FreeBSD]: https://man.freebsd.org/cgi/man.cgi?query=getsockopt&sektion=2
+/// [NetBSD]: https://man.netbsd.org/getsockopt.2
+/// [OpenBSD]: https://man.openbsd.org/getsockopt.2
+/// [DragonFly BSD]: https://man.dragonflybsd.org/?command=getsockopt&section=2
+/// [illumos]: https://illumos.org/man/3SOCKET/getsockopt
+/// [glibc `getsockopt`]: https://www.gnu.org/software/libc/manual/html_node/Socket-Option-Functions.html
+/// [glibc `SOL_SOCKET` options]: https://www.gnu.org/software/libc/manual/html_node/Socket_002dLevel-Options.html
+// TODO: OpenBSD and Solarish support submitted upstream: https://github.com/rust-lang/libc/pull/3316
+#[cfg(not(any(
+    apple,
+    solarish,
+    windows,
+    target_os = "dragonfly",
+    target_os = "emscripten",
+    target_os = "espidf",
+    target_os = "haiku",
+    target_os = "netbsd",
+    target_os = "nto",
+    target_os = "openbsd"
+)))]
+#[inline]
+#[doc(alias = "SO_DOMAIN")]
+pub fn get_socket_domain<Fd: AsFd>(fd: Fd) -> io::Result<AddressFamily> {
+    backend::net::syscalls::sockopt::get_socket_domain(fd.as_fd())
+}
+
 /// `setsockopt(fd, IPPROTO_IP, IP_TTL, ttl)`
 ///
 /// # References

tests/net/sockopt.rs

@@ -41,6 +41,22 @@ fn test_sockopts_ipv4() {
         rustix::net::sockopt::get_socket_send_buffer_size(&s).unwrap(),
         0
     );
+    #[cfg(not(any(
+        apple,
+        solarish,
+        windows,
+        target_os = "dragonfly",
+        target_os = "emscripten",
+        target_os = "espidf",
+        target_os = "haiku",
+        target_os = "netbsd",
+        target_os = "nto",
+        target_os = "openbsd"
+    )))]
+    assert_eq!(
+        rustix::net::sockopt::get_socket_domain(&s).unwrap(),
+        AddressFamily::INET
+    );
 
     // Set a timeout.
     rustix::net::sockopt::set_socket_timeout(