Remove default for destination lookup subnets (#399)

Related to #3807, but serves as a more temporary fix until the proxy injector
provides a way for this to be configured from an install.

Signed-off-by: Kevin Leimkuhler <[email protected]>

Author: kleimkuhler

linkerd/app/src/env.rs

@@ -196,10 +196,6 @@ const DEFAULT_OUTBOUND_MAX_IN_FLIGHT: usize = 10_000;
 const DEFAULT_DESTINATION_GET_SUFFIXES: &str = "svc.cluster.local.";
 const DEFAULT_DESTINATION_PROFILE_SUFFIXES: &str = "svc.cluster.local.";
 
-// RFC6890 private networks
-// Doesn't make sense to include the IPv6 network yet (fd00::/8).
-const DEFAULT_DESTINATION_GET_NETWORKS: &str = "10.0.0.0/8,172.16.0.0/12,192.168.0.0/16";
-
 const DEFAULT_IDENTITY_MIN_REFRESH: Duration = Duration::from_secs(10);
 const DEFAULT_IDENTITY_MAX_REFRESH: Duration = Duration::from_secs(60 * 60 * 24);
 
@@ -408,8 +404,7 @@ pub fn parse_config<S: Strings>(strings: &S) -> Result<super::Config, EnvError>
             context: dst_token?.unwrap_or_default(),
             get_suffixes: dst_get_suffixes?
                 .unwrap_or(parse_dns_suffixes(DEFAULT_DESTINATION_GET_SUFFIXES).unwrap()),
-            get_networks: dst_get_networks?
-                .unwrap_or(parse_networks(DEFAULT_DESTINATION_GET_NETWORKS).unwrap()),
+            get_networks: dst_get_networks?.unwrap_or_default(),
             profile_suffixes: dst_profile_suffixes?
                 .unwrap_or(parse_dns_suffixes(DEFAULT_DESTINATION_PROFILE_SUFFIXES).unwrap()),
             control: ControlConfig {