Set/get broadcast address in TunInterface

Modelled after TunInterface's IPV4 logic.
Uses SIOCGIFBRDADDR & SIOCSIFBRDADDR.
View https://man7.org/linux/man-pages/man7/netdevice.7.html.

tun/src/unix/linux/mod.rs

@@ -103,6 +103,28 @@ impl TunInterface {
         Ipv4Addr::from(u32::from_be(addr.sin_addr.s_addr))
     }
 
+    #[throws]
+    pub fn set_broadcast_addr(&self, addr: Ipv4Addr) {
+        let addr = SockAddr::from(SocketAddrV4::new(addr, 0));
+        let mut iff = self.ifreq()?;
+        iff.ifr_ifru.ifru_broadaddr = unsafe { *addr.as_ptr() };
+        self.perform(|fd| unsafe { sys::if_set_brdaddr(fd, &iff) })?;
+        info!(
+            "broadcast_addr_set: {:?} (fd: {:?})",
+            addr,
+            self.as_raw_fd()
+        )
+    }
+
+    #[throws]
+    pub fn broadcast_addr(&self) -> Ipv4Addr {
+        let mut iff = self.ifreq()?;
+        self.perform(|fd| unsafe { sys::if_get_brdaddr(fd, &mut iff) })?;
+        let addr =
+            unsafe { *(&iff.ifr_ifru.ifru_broadaddr as *const _ as *const sys::sockaddr_in) };
+        Ipv4Addr::from(u32::from_be(addr.sin_addr.s_addr))
+    }
+
     #[throws]
     pub fn set_ipv6_addr(&self, addr: Ipv6Addr) {
         let mut iff = self.in6_ifreq()?;

tun/src/unix/linux/sys.rs

@@ -18,10 +18,12 @@ ioctl_read_bad!(
 );
 ioctl_read_bad!(if_get_index, libc::SIOCGIFINDEX, libc::ifreq);
 ioctl_read_bad!(if_get_addr, libc::SIOCGIFADDR, libc::ifreq);
+ioctl_read_bad!(if_get_brdaddr, libc::SIOCGIFBRDADDR, libc::ifreq);
 ioctl_read_bad!(if_get_mtu, libc::SIOCGIFMTU, libc::ifreq);
 ioctl_read_bad!(if_get_netmask, libc::SIOCGIFNETMASK, libc::ifreq);
 
 ioctl_write_ptr_bad!(if_set_addr, libc::SIOCSIFADDR, libc::ifreq);
 ioctl_write_ptr_bad!(if_set_addr6, libc::SIOCSIFADDR, libc::in6_ifreq);
+ioctl_write_ptr_bad!(if_set_brdaddr, libc::SIOCSIFBRDADDR, libc::ifreq);
 ioctl_write_ptr_bad!(if_set_mtu, libc::SIOCSIFMTU, libc::ifreq);
 ioctl_write_ptr_bad!(if_set_netmask, libc::SIOCSIFNETMASK, libc::ifreq);

tun/tests/configure.rs

@@ -9,6 +9,21 @@ fn test_create() {
     TunInterface::new()?;
 }
 
+#[test]
+#[throws]
+#[cfg(not(any(target_os = "windows", target_vendor = "apple")))]
+fn test_set_get_broadcast_addr() {
+    let tun = TunInterface::new()?;
+    let addr = Ipv4Addr::new(10, 0, 0, 1);
+    tun.set_ipv4_addr(addr)?;
+
+    let broadcast_addr = Ipv4Addr::new(255, 255, 255, 0);
+    tun.set_broadcast_addr(broadcast_addr)?;
+    let result = tun.broadcast_addr()?;
+
+    assert_eq!(broadcast_addr, result);
+}
+
 #[test]
 #[throws]
 #[cfg(not(target_os = "windows"))]