Rewrite in functional style

Author: Serock3

test/test-manager/src/vm/network/macos.rs

@@ -47,31 +47,29 @@ pub async fn setup_test_network() -> Result<()> {
 /// Returns the interface name and IP address of the bridge gateway, which is the (first) bridge
 /// network that the given `guest_ip` belongs to.
 pub(crate) fn find_vm_bridge(guest_ip: &Ipv4Addr) -> Result<(String, Ipv4Addr)> {
-    for addr in nix::ifaddrs::getifaddrs()
+    let to_sock_addr = |addr: Option<SockaddrStorage>| {
+        addr.as_ref()
+            .and_then(|addr| addr.as_sockaddr_in())
+            .map(|addr| *SocketAddrV4::from(*addr).ip())
+    };
+
+    nix::ifaddrs::getifaddrs()
         .unwrap()
         .filter(|addr| addr.interface_name.starts_with("bridge"))
-    {
-        let to_sock_addr = |addr: Option<SockaddrStorage>| {
-            addr.as_ref()
-                .and_then(|addr| addr.as_sockaddr_in())
-                .map(|addr| *SocketAddrV4::from(*addr).ip())
-        };
-
-        if let (Some(address), Some(netmask)) =
-            (to_sock_addr(addr.address), to_sock_addr(addr.netmask))
-        {
-            if let Ok(ip_v4_network) = ipnetwork::Ipv4Network::with_netmask(address, netmask) {
-                if ip_v4_network.contains(*guest_ip) {
-                    return Ok((addr.interface_name.to_owned(), address));
-                }
-            };
-        };
-    }
-
-    // This is probably either due to IP mismatch or Tart not running
-    Err(anyhow!(
-        "Failed to identify bridge used by tart -- not running?"
-    ))
+        .filter_map(|addr| {
+            let address = to_sock_addr(addr.address);
+            let netmask = to_sock_addr(addr.netmask);
+            address
+                .zip(netmask)
+                .map(|(address, netmask)| (addr.interface_name, address, netmask))
+        })
+        .find_map(|(interface_name, address, netmask)| {
+            ipnetwork::Ipv4Network::with_netmask(address, netmask)
+                .ok()
+                .filter(|ip_v4_network| ip_v4_network.contains(*guest_ip))
+                .map(|_| (interface_name.to_owned(), address))
+        })
+        .ok_or_else(|| anyhow!("Failed to identify bridge used by tart -- not running?"))
 }
 
 async fn enable_forwarding() -> Result<()> {