Ignore unknown address types when looking up hosts

Previously, any function using a `ToSocketAddrs` input would fail if
passed a hostname that resolves to an address type different from the
ones recognized by Rust.

This also changes the `LookupHost` iterator to only include the known
address types, as a result, it doesn't have to return `Result`s any
more, which are likely misinterpreted as failed name lookups.

Author: tbu-

src/libstd/net/addr.rs

@@ -448,12 +448,7 @@ impl ToSocketAddrs for (Ipv6Addr, u16) {
 
 fn resolve_socket_addr(s: &str, p: u16) -> io::Result<vec::IntoIter<SocketAddr>> {
     let ips = lookup_host(s)?;
-    let v: Vec<_> = ips.map(|a| {
-        a.map(|mut a| {
-            a.set_port(p);
-            a
-        })
-    }).collect()?;
+    let v: Vec<_> = ips.map(|mut a| { a.set_port(p); a }).collect();
     Ok(v.into_iter())
 }
 

src/libstd/net/mod.rs

@@ -98,8 +98,8 @@ pub struct LookupHost(net_imp::LookupHost);
                                               addresses",
            issue = "27705")]
 impl Iterator for LookupHost {
-    type Item = io::Result<SocketAddr>;
-    fn next(&mut self) -> Option<io::Result<SocketAddr>> { self.0.next() }
+    type Item = SocketAddr;
+    fn next(&mut self) -> Option<SocketAddr> { self.0.next() }
 }
 
 /// Resolve the host specified by `host` as a number of `SocketAddr` instances.

src/libstd/sys/common/net.rs

@@ -119,14 +119,18 @@ pub struct LookupHost {
 }
 
 impl Iterator for LookupHost {
-    type Item = io::Result<SocketAddr>;
-    fn next(&mut self) -> Option<io::Result<SocketAddr>> {
+    type Item = SocketAddr;
+    fn next(&mut self) -> Option<SocketAddr> {
+        let result;
         unsafe {
             if self.cur.is_null() { return None }
-            let ret = sockaddr_to_addr(mem::transmute((*self.cur).ai_addr),
-                                       (*self.cur).ai_addrlen as usize);
+            result = sockaddr_to_addr(mem::transmute((*self.cur).ai_addr),
+                                      (*self.cur).ai_addrlen as usize).ok();
             self.cur = (*self.cur).ai_next as *mut c::addrinfo;
-            Some(ret)
+        }
+        match result {
+            Some(r) => Some(r),
+            None => self.next(),
         }
     }
 }