Enable IPv4 configuration on macOS

This enables getting and setting the IPv4 address on tun interfaces
on macOS

tun/src/unix/apple/mod.rs

@@ -1,15 +1,16 @@
 use fehler::throws;
 use libc::c_char;
-use std::io::Error;
-use std::net::Ipv4Addr;
-use std::os::fd::AsRawFd;
+use socket2::{Domain, SockAddr, Socket, Type};
+use std::net::{Ipv4Addr, SocketAddrV4};
+use std::os::fd::{AsRawFd, RawFd};
+use std::{io::Error, mem};
 
 mod kern_control;
 mod sys;
 
 pub use super::queue::TunQueue;
 
-use super::ifname_to_string;
+use super::{ifname_to_string, string_to_ifname};
 use kern_control::SysControlSocket;
 
 #[derive(Debug)]
@@ -53,12 +54,33 @@ impl TunInterface {
     }
 
     #[throws]
-    pub fn set_ipv4_addr(&self, _addr: Ipv4Addr) {
-        todo!()
+    fn ifreq(&self) -> sys::ifreq {
+        let mut iff: sys::ifreq = unsafe { mem::zeroed() };
+        iff.ifr_name = string_to_ifname(&self.name()?);
+        iff
+    }
+
+    #[throws]
+    pub fn set_ipv4_addr(&self, addr: Ipv4Addr) {
+        let addr = SockAddr::from(SocketAddrV4::new(addr, 0));
+
+        let mut iff = self.ifreq()?;
+        iff.ifr_ifru.ifru_addr = unsafe { *addr.as_ptr() };
+
+        self.perform(|fd| unsafe { sys::if_set_addr(fd, &iff) })?;
     }
 
     #[throws]
     pub fn ipv4_addr(&self) -> Ipv4Addr {
-        todo!()
+        let mut iff = self.ifreq()?;
+        self.perform(|fd| unsafe { sys::if_get_addr(fd, &mut iff) })?;
+        let addr = unsafe { *(&iff.ifr_ifru.ifru_addr as *const _ as *const sys::sockaddr_in) };
+        Ipv4Addr::from(u32::from_be(addr.sin_addr.s_addr))
+    }
+
+    #[throws]
+    fn perform<R>(&self, perform: impl FnOnce(RawFd) -> Result<R, nix::Error>) -> R {
+        let socket = Socket::new(Domain::IPV4, Type::DGRAM, None)?;
+        perform(socket.as_raw_fd())?
     }
 }

tun/src/unix/apple/sys.rs

@@ -1,5 +1,11 @@
-pub use libc::{c_void, socklen_t, SYSPROTO_CONTROL, IFNAMSIZ, sockaddr_ctl, AF_SYSTEM, AF_SYS_CONTROL};
-use nix::ioctl_readwrite;
+use std::mem;
+
+use libc::{c_char, c_int, c_short, c_uint, c_ulong, sockaddr};
+pub use libc::{
+    c_void, sockaddr_ctl, sockaddr_in, socklen_t, AF_SYSTEM, AF_SYS_CONTROL, IFNAMSIZ,
+    SYSPROTO_CONTROL,
+};
+use nix::{ioctl_read_bad, ioctl_readwrite, ioctl_write_ptr_bad, request_code_write};
 
 pub const UTUN_CONTROL_NAME: &str = "com.apple.net.utun_control";
 pub const UTUN_OPT_IFNAME: libc::c_int = 2;
@@ -7,29 +13,68 @@ pub const UTUN_OPT_IFNAME: libc::c_int = 2;
 pub const MAX_KCTL_NAME: usize = 96;
 
 #[repr(C)]
+#[derive(Copy, Clone, Debug)]
 pub struct ctl_info {
     pub ctl_id: u32,
     pub ctl_name: [u8; MAX_KCTL_NAME],
 }
 
 #[repr(C)]
-pub struct ifreq {}
+#[derive(Copy, Clone, Debug)]
+pub struct ifkpi {
+    pub ifk_module_id: c_uint,
+    pub ifk_type: c_uint,
+    pub ifk_ptr: *mut c_void,
+}
 
-ioctl_readwrite!(resolve_ctl_info, b'N', 3, ctl_info);
+#[repr(C)]
+#[derive(Copy, Clone, Debug)]
+pub struct ifdevmtu {
+    pub ifdm_current: c_int,
+    pub ifdm_min: c_int,
+    pub ifdm_max: c_int,
+}
+
+#[repr(C)]
+pub union ifr_ifru {
+    pub ifru_addr: sockaddr,
+    pub ifru_dstaddr: sockaddr,
+    pub ifru_broadaddr: sockaddr,
+    pub ifru_flags: c_short,
+    pub ifru_metric: c_int,
+    pub ifru_mtu: c_int,
+    pub ifru_phys: c_int,
+    pub ifru_media: c_int,
+    pub ifru_intval: c_int,
+    pub ifru_data: *mut c_char,
+    pub ifru_devmtu: ifdevmtu,
+    pub ifru_kpi: ifkpi,
+    pub ifru_wake_flags: u32,
+    pub ifru_route_refcnt: u32,
+    pub ifru_cap: [c_int; 2],
+    pub ifru_functional_type: u32,
+}
+
+#[repr(C)]
+pub struct ifreq {
+    pub ifr_name: [c_char; IFNAMSIZ],
+    pub ifr_ifru: ifr_ifru,
+}
+
+pub const SIOCSIFADDR: c_ulong = request_code_write!(b'i', 12, mem::size_of::<ifreq>());
 
-/// Copied from https://github.com/rust-lang/socket2/blob/61314a231f73964b3db969ef72c0e9479df320f3/src/sys/unix.rs#L168-L178
-/// getsockopt is not exposed by socket2
 #[macro_export]
 macro_rules! syscall {
-    ($fn: ident ( $($arg: expr),* $(,)* ) ) => {{
-        #[allow(unused_unsafe)]
-        let res = unsafe { libc::$fn($($arg, )*) };
-        if res == -1 {
-            Err(std::io::Error::last_os_error())
-        } else {
-            Ok(res)
+    ($call: ident ( $($arg: expr),* $(,)* ) ) => {{
+        match unsafe { ::libc::$call($($arg, )*) } {
+            -1 => Err(::std::io::Error::last_os_error()),
+            res => Ok(res),
         }
     }};
 }
 
 pub use syscall;
+
+ioctl_readwrite!(resolve_ctl_info, b'N', 3, ctl_info);
+ioctl_read_bad!(if_get_addr, libc::SIOCGIFADDR, ifreq);
+ioctl_write_ptr_bad!(if_set_addr, SIOCSIFADDR, ifreq);