From fda53416d37f409d64f1a689f4517fbed67a3ec5 Mon Sep 17 00:00:00 2001
From: zzz <zzz@i2pmail.org>
Date: Thu, 4 Mar 2021 08:42:08 -0500
Subject: [PATCH] Transports: Prefer IPv6 temporary addresses if the kernel
 does

This helps us pick the right address at startup,
so we don't switch after peer testing.
---
 core/java/src/net/i2p/util/Addresses.java     | 19 +++++++++++++------
 .../router/transport/TransportManager.java    |  4 ++--
 2 files changed, 15 insertions(+), 8 deletions(-)

diff --git a/core/java/src/net/i2p/util/Addresses.java b/core/java/src/net/i2p/util/Addresses.java
index 2077ac265..e008019b5 100644
--- a/core/java/src/net/i2p/util/Addresses.java
+++ b/core/java/src/net/i2p/util/Addresses.java
@@ -898,17 +898,15 @@ public abstract class Addresses {
     }
 
     /**
-     * RFC 4941
-     * @since 0.9.34
+     * @return "true", "false", or "unknown"
+     * @since 0.9.50
      */
-    private static String getPrivacyStatus() {
+    public static String useIPv6TempAddresses() {
         // Windows: netsh interface ipv6 show privacy
         // Mac: sysctl net.inet6.ip6.use_tempaddr (1 is enabled)
         if (SystemVersion.isMac() || SystemVersion.isWindows())
             return "unknown";
         long t = getLong("/proc/sys/net/ipv6/conf/all/use_tempaddr");
-        if (t < 0)
-            return "unknown";
         String rv;
         if (t == 0)
             rv = "false";
@@ -916,7 +914,16 @@ public abstract class Addresses {
             rv = "true";
         else
             rv = "unknown";
-        if (t == 2) {
+        return rv;
+    }
+
+    /**
+     * RFC 4941
+     * @since 0.9.34
+     */
+    private static String getPrivacyStatus() {
+        String rv = useIPv6TempAddresses();
+        if (Boolean.valueOf(rv)) {
             long pref = getLong("/proc/sys/net/ipv6/conf/all/temp_prefered_lft");
             if (pref > 0)
                 rv += ", preferred lifetime " + DataHelper.formatDuration(pref * 1000);
diff --git a/router/java/src/net/i2p/router/transport/TransportManager.java b/router/java/src/net/i2p/router/transport/TransportManager.java
index fa44aa304..c852b359a 100644
--- a/router/java/src/net/i2p/router/transport/TransportManager.java
+++ b/router/java/src/net/i2p/router/transport/TransportManager.java
@@ -326,10 +326,10 @@ public class TransportManager implements TransportEventListener {
         Set<String> ipset = Addresses.getAddresses(_context.getBooleanProperty("i2np.allowLocal"), false, true);
         String lastv4 = _context.getProperty(UDPTransport.PROP_IP);
         String lastv6 = _context.getProperty(UDPTransport.PROP_IPV6);
-        boolean preferTemp = _context.getBooleanProperty(UDPTransport.PROP_LAPTOP_MODE);
+        boolean preferTemp = Boolean.valueOf(Addresses.useIPv6TempAddresses());
         //
         // Avoid IPv6 temporary addresses if we have a non-temporary one,
-        // unless laptop mode
+        // unless the kernel prefers them
         //
         boolean hasPreferredV6Address = false;
         List<InetAddress> addresses = new ArrayList<InetAddress>(4);