feat(client): filter remote IP addresses by family of given local IP address

It is not possible to connect to an IPv4 address from an IPv6 address or
vice-versa so don't waste time trying. If no remote addresses match then a
"missing connect error" will now occur.

src/client/connect/dns.rs

@@ -194,7 +194,14 @@ impl IpAddrs {
         None
     }
 
-    pub(super) fn split_by_preference(self) -> (IpAddrs, IpAddrs) {
+    pub(super) fn split_by_preference(self, local_addr: Option<IpAddr>) -> (IpAddrs, IpAddrs) {
+        if let Some(local_addr) = local_addr {
+            let preferred = self.iter
+                .filter(|addr| addr.is_ipv6() == local_addr.is_ipv6())
+                .collect();
+
+            (IpAddrs::new(preferred), IpAddrs::new(vec![]))
+        } else {
             let preferring_v6 = self.iter
                 .as_slice()
                 .first()
@@ -206,6 +213,7 @@ impl IpAddrs {
 
             (IpAddrs::new(preferred), IpAddrs::new(fallback))
         }
+    }
 
     pub(super) fn is_empty(&self) -> bool {
         self.iter.as_slice().is_empty()
@@ -325,14 +333,24 @@ mod tests {
         let v6_addr = (Ipv6Addr::new(0, 0, 0, 0, 0, 0, 0, 1), 80).into();
 
         let (mut preferred, mut fallback) =
-            IpAddrs { iter: vec![v4_addr, v6_addr].into_iter() }.split_by_preference();
+            IpAddrs { iter: vec![v4_addr, v6_addr].into_iter() }.split_by_preference(None);
         assert!(preferred.next().unwrap().is_ipv4());
         assert!(fallback.next().unwrap().is_ipv6());
 
         let (mut preferred, mut fallback) =
-            IpAddrs { iter: vec![v6_addr, v4_addr].into_iter() }.split_by_preference();
+            IpAddrs { iter: vec![v6_addr, v4_addr].into_iter() }.split_by_preference(None);
         assert!(preferred.next().unwrap().is_ipv6());
         assert!(fallback.next().unwrap().is_ipv4());
+
+        let (mut preferred, fallback) =
+            IpAddrs { iter: vec![v4_addr, v6_addr].into_iter() }.split_by_preference(Some(v4_addr.ip()));
+        assert!(preferred.next().unwrap().is_ipv4());
+        assert!(fallback.is_empty());
+
+        let (mut preferred, fallback) =
+            IpAddrs { iter: vec![v4_addr, v6_addr].into_iter() }.split_by_preference(Some(v6_addr.ip()));
+        assert!(preferred.next().unwrap().is_ipv6());
+        assert!(fallback.is_empty());
     }
 
     #[test]

src/client/connect/http.rs

@@ -501,7 +501,7 @@ impl ConnectingTcp {
         reuse_address: bool,
     ) -> ConnectingTcp {
         if let Some(fallback_timeout) = fallback_timeout {
-            let (preferred_addrs, fallback_addrs) = remote_addrs.split_by_preference();
+            let (preferred_addrs, fallback_addrs) = remote_addrs.split_by_preference(local_addr);
             if fallback_addrs.is_empty() {
                 return ConnectingTcp {
                     local_addr,