add IP_MULTICAST_IF for sockopt

src/sys/socket/mod.rs

@@ -375,6 +375,32 @@ impl Ipv6MembershipRequest {
     }
 }
 
+cfg_if! {
+    if #[cfg(not(all(target_os = "linux",
+                     target_env = "gnu",
+                     any(target_arch = "mips",
+                         target_arch = "mips64",
+                         target_arch = "aarch64",
+                         target_arch = "arm",
+                         target_arch = "powerpc64"))))] {
+        /// Request for multicast socket's outgoing interface
+        ///
+        /// The value is a `libc::in_addr` structure, which is the most common.
+        /// `ip_mreqn` or `ip_mreq` structure are not supported at this point, one
+        /// reason is that if we use enum to represent all possible structures,
+        /// `#[repr(transparent)]` does not support enum.
+        #[repr(transparent)]
+        #[derive(Clone, Copy, Debug, Eq, PartialEq)]
+        pub struct IpMulticastIfInAddr(libc::in_addr);
+
+        impl IpMulticastIfInAddr {
+            pub fn new(interface: Ipv4Addr) -> Self {
+                IpMulticastIfInAddr(interface.0)
+            }
+        }
+    }
+}
+
 /// Create a buffer large enough for storing some control messages as returned
 /// by [`recvmsg`](fn.recvmsg.html).
 ///

src/sys/socket/sockopt.rs

@@ -233,6 +233,17 @@ cfg_if! {
         sockopt_impl!(SetOnly, Ipv6DropMembership, libc::IPPROTO_IPV6, libc::IPV6_LEAVE_GROUP, super::Ipv6MembershipRequest);
     }
 }
+cfg_if! {
+    if #[cfg(not(all(target_os = "linux",
+                     target_env = "gnu",
+                     any(target_arch = "mips",
+                         target_arch = "mips64",
+                         target_arch = "aarch64",
+                         target_arch = "arm",
+                         target_arch = "powerpc64"))))] {
+        sockopt_impl!(Both, IpMulticastIf, libc::IPPROTO_IP, libc::IP_MULTICAST_IF, super::IpMulticastIfInAddr);
+    }
+}
 sockopt_impl!(Both, IpMulticastTtl, libc::IPPROTO_IP, libc::IP_MULTICAST_TTL, u8);
 sockopt_impl!(Both, IpMulticastLoop, libc::IPPROTO_IP, libc::IP_MULTICAST_LOOP, bool);
 sockopt_impl!(Both, ReceiveTimeout, libc::SOL_SOCKET, libc::SO_RCVTIMEO, TimeVal);

test/sys/test_sockopt.rs

@@ -1,5 +1,14 @@
 use rand::{thread_rng, Rng};
 use nix::sys::socket::{socket, sockopt, getsockopt, setsockopt, AddressFamily, SockType, SockFlag, SockProtocol};
+#[cfg(not(all(target_os = "linux",
+                     target_env = "gnu",
+                     any(target_arch = "mips",
+                         target_arch = "mips64",
+                         target_arch = "aarch64",
+                         target_arch = "arm",
+                         target_arch = "powerpc64"))))]
+use nix::{ifaddrs::getifaddrs, sys::socket::{IpAddr, IpMulticastIfInAddr, SockAddr}};
+
 #[cfg(any(target_os = "android", target_os = "linux"))]
 use crate::*;
 
@@ -94,3 +103,26 @@ fn test_so_tcp_keepalive() {
         assert_eq!(getsockopt(fd, sockopt::TcpKeepInterval).unwrap(), x + 1);
     }
 }
+
+#[test]
+#[cfg(not(all(target_os = "linux",
+                     target_env = "gnu",
+                     any(target_arch = "mips",
+                         target_arch = "mips64",
+                         target_arch = "aarch64",
+                         target_arch = "arm",
+                         target_arch = "powerpc64"))))]
+fn test_so_multicast_if() {
+    let fd = socket(AddressFamily::Inet, SockType::Datagram, SockFlag::empty(), None).unwrap();
+    let addrs = getifaddrs().unwrap();
+
+    for if_addr in addrs {
+        if let Some(SockAddr::Inet(inet_addr)) = if_addr.address {
+            if let IpAddr::V4(ipv4_addr) = inet_addr.ip() {
+                let request = IpMulticastIfInAddr::new(ipv4_addr);
+                setsockopt(fd, sockopt::IpMulticastIf, &request).unwrap();
+                assert_eq!(getsockopt(fd, sockopt::IpMulticastIf).unwrap(), request);
+            }
+        }
+    }
+}