Add support for Netlink socket addresses

src/backend/libc/net/read_sockaddr.rs

@@ -8,6 +8,8 @@ use crate::backend::c;
 #[cfg(not(windows))]
 use crate::ffi::CStr;
 use crate::io::Errno;
+#[cfg(linux_kernel)]
+use crate::net::netlink::SocketAddrNetlink;
 #[cfg(target_os = "linux")]
 use crate::net::xdp::{SockaddrXdpFlags, SocketAddrXdp};
 use crate::net::{AddressFamily, Ipv4Addr, Ipv6Addr, SocketAddrAny, SocketAddrV4, SocketAddrV6};
@@ -239,3 +241,14 @@ pub(crate) fn read_sockaddr_xdp(addr: &SocketAddrAny) -> Result<SocketAddrXdp, E
         u32::from_be(decode.sxdp_shared_umem_fd),
     ))
 }
+
+#[cfg(linux_kernel)]
+#[inline]
+pub(crate) fn read_sockaddr_netlink(addr: &SocketAddrAny) -> Result<SocketAddrNetlink, Errno> {
+    if addr.address_family() != AddressFamily::NETLINK {
+        return Err(Errno::AFNOSUPPORT);
+    }
+    assert!(addr.len() >= size_of::<c::sockaddr_nl>());
+    let decode = unsafe { &*addr.as_ptr().cast::<c::sockaddr_nl>() };
+    Ok(SocketAddrNetlink::new(decode.nl_pid, decode.nl_groups))
+}

src/backend/linux_raw/net/read_sockaddr.rs

@@ -4,6 +4,7 @@
 
 use crate::backend::c;
 use crate::io::Errno;
+use crate::net::netlink::SocketAddrNetlink;
 #[cfg(target_os = "linux")]
 use crate::net::xdp::{SockaddrXdpFlags, SocketAddrXdp};
 use crate::net::{AddressFamily, SocketAddrAny};
@@ -133,3 +134,13 @@ pub(crate) fn read_sockaddr_xdp(addr: &SocketAddrAny) -> Result<SocketAddrXdp, E
         u32::from_be(decode.sxdp_shared_umem_fd),
     ))
 }
+
+#[inline]
+pub(crate) fn read_sockaddr_netlink(addr: &SocketAddrAny) -> Result<SocketAddrNetlink, Errno> {
+    if addr.address_family() != AddressFamily::NETLINK {
+        return Err(Errno::AFNOSUPPORT);
+    }
+    assert!(addr.len() >= size_of::<c::sockaddr_nl>());
+    let decode = unsafe { &*addr.as_ptr().cast::<c::sockaddr_nl>() };
+    Ok(SocketAddrNetlink::new(decode.nl_pid, decode.nl_groups))
+}

src/net/socket_addr_any.rs

@@ -191,6 +191,12 @@ impl fmt::Debug for SocketAddrAny {
                     return addr.fmt(f);
                 }
             }
+            #[cfg(linux_kernel)]
+            AddressFamily::NETLINK => {
+                if let Ok(addr) = crate::net::netlink::SocketAddrNetlink::try_from(self.clone()) {
+                    return addr.fmt(f);
+                }
+            }
             _ => {}
         }
 

src/net/types.rs

@@ -1003,6 +1003,12 @@ pub mod netlink {
     use {
         super::{new_raw_protocol, Protocol},
         crate::backend::c,
+        crate::backend::net::read_sockaddr::read_sockaddr_netlink,
+        crate::net::{
+            addr::{call_with_sockaddr, SocketAddrArg, SocketAddrOpaque},
+            SocketAddrAny,
+        },
+        core::mem,
     };
 
     /// `NETLINK_UNUSED`
@@ -1112,6 +1118,83 @@ pub mod netlink {
     /// `NETLINK_GET_STRICT_CHK`
     #[cfg(linux_kernel)]
     pub const GET_STRICT_CHK: Protocol = Protocol(new_raw_protocol(c::NETLINK_GET_STRICT_CHK as _));
+
+    /// A Netlink socket address.
+    ///
+    /// Used to bind to a Netlink socket.
+    ///
+    /// Not ABI compatible with `struct sockaddr_nl`
+    #[derive(Clone, Copy, PartialEq, PartialOrd, Eq, Ord, Hash, Debug)]
+    #[cfg(linux_kernel)]
+    pub struct SocketAddrNetlink {
+        /// Port ID
+        pid: u32,
+
+        /// Multicast groups mask
+        groups: u32,
+    }
+
+    #[cfg(linux_kernel)]
+    impl SocketAddrNetlink {
+        /// Construct a netlink address
+        #[inline]
+        pub fn new(pid: u32, groups: u32) -> Self {
+            Self { pid, groups }
+        }
+
+        /// Return port id.
+        #[inline]
+        pub fn pid(&self) -> u32 {
+            self.pid
+        }
+
+        /// Set port id.
+        #[inline]
+        pub fn set_pid(&mut self, pid: u32) {
+            self.pid = pid;
+        }
+
+        /// Return multicast groups mask.
+        #[inline]
+        pub fn groups(&self) -> u32 {
+            self.groups
+        }
+
+        /// Set multicast groups mask.
+        #[inline]
+        pub fn set_groups(&mut self, groups: u32) {
+            self.groups = groups;
+        }
+    }
+
+    #[cfg(linux_kernel)]
+    #[allow(unsafe_code)]
+    unsafe impl SocketAddrArg for SocketAddrNetlink {
+        fn with_sockaddr<R>(&self, f: impl FnOnce(*const SocketAddrOpaque, usize) -> R) -> R {
+            let mut addr: c::sockaddr_nl = unsafe { mem::zeroed() };
+            addr.nl_family = c::AF_NETLINK as _;
+            addr.nl_pid = self.pid;
+            addr.nl_groups = self.groups;
+            call_with_sockaddr(&addr, f)
+        }
+    }
+
+    #[cfg(linux_kernel)]
+    impl From<SocketAddrNetlink> for SocketAddrAny {
+        #[inline]
+        fn from(from: SocketAddrNetlink) -> Self {
+            from.as_any()
+        }
+    }
+
+    #[cfg(linux_kernel)]
+    impl TryFrom<SocketAddrAny> for SocketAddrNetlink {
+        type Error = crate::io::Errno;
+
+        fn try_from(addr: SocketAddrAny) -> Result<Self, Self::Error> {
+            read_sockaddr_netlink(&addr)
+        }
+    }
 }
 
 /// `ETH_P_*` constants.

tests/net/main.rs

@@ -10,6 +10,8 @@ mod addr;
 mod cmsg;
 mod connect_bind_send;
 mod dgram;
+#[cfg(linux_kernel)]
+mod netlink;
 #[cfg(feature = "event")]
 mod poll;
 #[cfg(unix)]

tests/net/netlink.rs

@@ -0,0 +1,64 @@
+use rustix::net::netlink::{self, SocketAddrNetlink};
+use rustix::net::{
+    bind, getsockname, recvfrom, sendto, socket_with, AddressFamily, RecvFlags, SendFlags,
+    SocketAddrAny, SocketFlags, SocketType,
+};
+
+#[test]
+fn encode_decode() {
+    let orig = SocketAddrNetlink::new(0x12345678, 0x9abcdef0);
+    let encoded = SocketAddrAny::from(orig);
+    let decoded = SocketAddrNetlink::try_from(encoded).unwrap();
+    assert_eq!(decoded, orig);
+}
+
+#[test]
+fn test_bind_kobject_uevent() {
+    let server = socket_with(
+        AddressFamily::NETLINK,
+        SocketType::RAW,
+        SocketFlags::CLOEXEC,
+        Some(netlink::KOBJECT_UEVENT),
+    )
+    .unwrap();
+
+    bind(&server, &SocketAddrNetlink::new(0, 1)).unwrap();
+}
+
+#[test]
+#[cfg_attr(
+    not(any(target_arch = "x86", target_arch = "x86_64")),
+    ignore = "qemu used in CI does not support NETLINK_USERSOCK"
+)]
+fn test_usersock() {
+    let server = socket_with(
+        AddressFamily::NETLINK,
+        SocketType::RAW,
+        SocketFlags::CLOEXEC,
+        Some(netlink::USERSOCK),
+    )
+    .unwrap();
+
+    bind(&server, &SocketAddrNetlink::new(0, 0)).unwrap();
+    let addr = getsockname(&server).unwrap();
+    let addr = SocketAddrNetlink::try_from(addr).unwrap();
+
+    let client = socket_with(
+        AddressFamily::NETLINK,
+        SocketType::RAW,
+        SocketFlags::CLOEXEC,
+        Some(netlink::USERSOCK),
+    )
+    .unwrap();
+
+    let data = b"ABCDEF";
+
+    sendto(client, data, SendFlags::empty(), &addr).unwrap();
+
+    let mut buffer = [0u8; 4096];
+    let (len, src) = recvfrom(&server, &mut buffer, RecvFlags::empty()).unwrap();
+
+    assert_eq!(&buffer[..len], data);
+    let src = SocketAddrNetlink::try_from(src.unwrap()).unwrap();
+    assert_eq!(src.groups(), 0);
+}