Fix setting sockopt::IpMulticastTtl (#2072)

* Fix the value of optlen as passed to libc::setsockopt

Ever since the sockopt macro was written in
979faf0 we've been passing the wrong
size for u8 and usize sockopts.

* Add tests for sockopt::IpMulticastTtl #2073

On Linux and Android, sockopt::IpMulticastTtl can be set for both IPv4
and IPv6 sockets, but not on FreeBSD.

---------

Co-authored-by: Alan Somers <asomers@gmail.com>
Co-authored-by: Simon B. Gasse <sgasse@users.noreply.github.com>

Author: sgasse

changelog/2072.fixed.md

@@ -0,0 +1 @@
+Fixed `::sys::socket::sockopt::IpMulticastTtl` by fixing the value of optlen passed to `libc::setsockopt` and added tests.

src/sys/socket/sockopt.rs

@@ -1247,7 +1247,7 @@ impl<'a> Set<'a, bool> for SetBool {
     }
 
     fn ffi_len(&self) -> socklen_t {
-        mem::size_of::<c_int>() as socklen_t
+        mem::size_of_val(&self.val) as socklen_t
     }
 }
 
@@ -1298,7 +1298,7 @@ impl<'a> Set<'a, u8> for SetU8 {
     }
 
     fn ffi_len(&self) -> socklen_t {
-        mem::size_of::<c_int>() as socklen_t
+        mem::size_of_val(&self.val) as socklen_t
     }
 }
 
@@ -1349,7 +1349,7 @@ impl<'a> Set<'a, usize> for SetUsize {
     }
 
     fn ffi_len(&self) -> socklen_t {
-        mem::size_of::<c_int>() as socklen_t
+        mem::size_of_val(&self.val) as socklen_t
     }
 }
 

test/sys/test_sockopt.rs

@@ -320,6 +320,34 @@ fn test_ttl_opts() {
         .expect("setting ipv6ttl on an inet6 socket should succeed");
 }
 
+#[test]
+#[cfg(any(linux_android, target_os = "freebsd"))]
+fn test_multicast_ttl_opts_ipv4() {
+    let fd4 = socket(
+        AddressFamily::Inet,
+        SockType::Datagram,
+        SockFlag::empty(),
+        None,
+    )
+    .unwrap();
+    setsockopt(&fd4, sockopt::IpMulticastTtl, &2)
+        .expect("setting ipmulticastttl on an inet socket should succeed");
+}
+
+#[test]
+#[cfg(linux_android)]
+fn test_multicast_ttl_opts_ipv6() {
+    let fd6 = socket(
+        AddressFamily::Inet6,
+        SockType::Datagram,
+        SockFlag::empty(),
+        None,
+    )
+    .unwrap();
+    setsockopt(&fd6, sockopt::IpMulticastTtl, &2)
+        .expect("setting ipmulticastttl on an inet6 socket should succeed");
+}
+
 #[test]
 fn test_ipv6_multicast_hops() {
     let fd6 = socket(