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8241786: Improve heuristic to determine default network interface on macOS

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DefaultInetrface.getDefault is updated to prefer interfaces that have non link-local addresses. NetworkConfiguration is updated to skip interface that have only link-local addresses, whether IPv4 or IPv6, for multicasting.

Reviewed-by: chegar, alanb
This commit is contained in:
Daniel Fuchs 2020-04-03 14:27:03 +01:00
parent 553ea1e891
commit f541970b31
8 changed files with 243 additions and 107 deletions
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53
src/java.base/macosx/classes/java/net/DefaultInterface.java
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@ -1,5 +1,5 @@
/*
* Copyright (c) 2011, 2019, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2011, 2020, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
@ -54,11 +54,30 @@ class DefaultInterface {
/**
* Choose a default interface. This method returns the first interface that
* is both "up" and supports multicast. This method chooses an interface in
* order of preference:
* 1. neither loopback nor point to point
* ( prefer interfaces with dual IP support )
* 2. point to point
* 3. loopback
* order of preference, using the following algorithm:
*
* <pre>
* Interfaces that are down, or don't support multicasting, are skipped.
* In steps 1-4 below, PPP and loopback interfaces are skipped.
*
* 1. The first interface that has at least an IPv4 address, and an IPv6 address,
* and a non link-local IP address, is picked.
*
* 2. If none is found, then the first interface that has at least an
* IPv4 address, and an IPv6 address is picked.
*
* 3. If none is found, then the first interface that has at least a
* non link local IP address is picked.
*
* 4. If none is found, then the first non loopback and non PPP interface
* is picked.
*
* 5. If none is found then first PPP interface is picked.
*
* 6. If none is found, then the first loopback interface is picked.
*
* 7. If none is found, then null is returned.
* </pre>
*
* @return the chosen interface or {@code null} if there isn't a suitable
* default
@ -74,6 +93,8 @@ class DefaultInterface {
}
NetworkInterface preferred = null;
NetworkInterface dual = null;
NetworkInterface nonLinkLocal = null;
NetworkInterface ppp = null;
NetworkInterface loopback = null;
@ -83,7 +104,7 @@ class DefaultInterface {
if (!ni.isUp() || !ni.supportsMulticast())
continue;
boolean ip4 = false, ip6 = false;
boolean ip4 = false, ip6 = false, isNonLinkLocal = false;
PrivilegedAction<Enumeration<InetAddress>> pa = ni::getInetAddresses;
Enumeration<InetAddress> addrs = AccessController.doPrivileged(pa);
while (addrs.hasMoreElements()) {
@ -94,6 +115,9 @@ class DefaultInterface {
} else if (addr instanceof Inet6Address) {
ip6 = true;
}
if (!addr.isLinkLocalAddress()) {
isNonLinkLocal = true;
}
}
}
@ -104,8 +128,13 @@ class DefaultInterface {
// point-to-point interface
if (preferred == null) {
preferred = ni;
} else if (ip4 && ip6){
return ni;
}
if (ip4 && ip6) {
if (isNonLinkLocal) return ni;
if (dual == null) dual = ni;
}
if (nonLinkLocal == null) {
if (isNonLinkLocal) nonLinkLocal = ni;
}
}
if (ppp == null && isPPP)
@ -116,7 +145,11 @@ class DefaultInterface {
} catch (IOException skip) { }
}
if (preferred != null) {
if (dual != null) {
return dual;
} else if (nonLinkLocal != null) {
return nonLinkLocal;
} else if (preferred != null) {
return preferred;
} else {
return (ppp != null) ? ppp : loopback;