From 131962c86ab0a31c2413261cf4532eca88d67dcb Mon Sep 17 00:00:00 2001
From: James Le Cuirot <james.lecuirot@metaswitch.com>
Date: Wed, 13 Nov 2019 14:56:53 +0000
Subject: [PATCH] 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  | 44 +++++++++++++++++++++++++++-----------
 src/client/connect/http.rs |  2 +-
 2 files changed, 32 insertions(+), 14 deletions(-)

diff --git a/src/client/connect/dns.rs b/src/client/connect/dns.rs
index 17d3c7df67..e50382ab3a 100644
--- a/src/client/connect/dns.rs
+++ b/src/client/connect/dns.rs
@@ -194,17 +194,25 @@ impl IpAddrs {
         None
     }
 
-    pub(super) fn split_by_preference(self) -> (IpAddrs, IpAddrs) {
-        let preferring_v6 = self.iter
-            .as_slice()
-            .first()
-            .map(SocketAddr::is_ipv6)
-            .unwrap_or(false);
-
-        let (preferred, fallback) = self.iter
-            .partition::<Vec<_>, _>(|addr| addr.is_ipv6() == preferring_v6);
-
-        (IpAddrs::new(preferred), IpAddrs::new(fallback))
+    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()
+                .map(SocketAddr::is_ipv6)
+                .unwrap_or(false);
+
+            let (preferred, fallback) = self.iter
+                .partition::<Vec<_>, _>(|addr| addr.is_ipv6() == preferring_v6);
+
+            (IpAddrs::new(preferred), IpAddrs::new(fallback))
+        }
     }
 
     pub(super) fn is_empty(&self) -> bool {
@@ -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]
diff --git a/src/client/connect/http.rs b/src/client/connect/http.rs
index 7a4c9cccc7..336945eb26 100644
--- a/src/client/connect/http.rs
+++ b/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,