From b9f5f230a2697abc268cf385ff771c2c183ccbe8 Mon Sep 17 00:00:00 2001
From: zzz <zzz@mail.i2p>
Date: Wed, 8 Aug 2012 23:36:11 +0000
Subject: [PATCH] stub out local MTU detection (ticket 682)
---
.../src/net/i2p/router/transport/udp/MTU.java | 84 +++++++++++++++++++
.../i2p/router/transport/udp/UDPEndpoint.java | 11 +++
2 files changed, 95 insertions(+)
create mode 100644 router/java/src/net/i2p/router/transport/udp/MTU.java
diff --git a/router/java/src/net/i2p/router/transport/udp/MTU.java b/router/java/src/net/i2p/router/transport/udp/MTU.java
new file mode 100644
index 0000000000..22001b13fa
--- /dev/null
+++ b/router/java/src/net/i2p/router/transport/udp/MTU.java
@@ -0,0 +1,84 @@
+package net.i2p.router.transport.udp;
+
+import java.net.InetAddress;
+import java.net.NetworkInterface;
+import java.net.SocketException;
+import java.util.Enumeration;
+
+import net.i2p.util.VersionComparator;
+
+/**
+ * Get the MTU for the network interface of an address.
+ * Not available until Java 6 / Android API 9.
+ * @since 0.9.2
+ */
+abstract class MTU {
+
+ private static final boolean hasMTU =
+ (new VersionComparator()).compare(System.getProperty("java.version"), "1.6") >= 0;
+
+ /**
+ * The MTU for the socket interface, if available.
+ * Not available for Java 5.
+ * @param ia null ok
+ * @return 0 if Java 5, or if not bound to an address;
+ * limited to range MIN_MTU to LARGE_MTU.
+ */
+ public static int getMTU(InetAddress ia) {
+ if (ia == null || !hasMTU)
+ return 0;
+ Enumeration<NetworkInterface> ifcs;
+ try {
+ ifcs = NetworkInterface.getNetworkInterfaces();
+ } catch (SocketException se) {
+ return 0;
+ }
+ if (ifcs != null) {
+ while (ifcs.hasMoreElements()) {
+ NetworkInterface ifc = ifcs.nextElement();
+ for(Enumeration<InetAddress> addrs = ifc.getInetAddresses(); addrs.hasMoreElements();) {
+ InetAddress addr = addrs.nextElement();
+ if (ia.equals(addr)) {
+ try {
+ // testing
+ //return ifc.getMTU();
+ return rectify(ifc.getMTU());
+ } catch (SocketException se) {
+ // ignore
+ } catch (Throwable t) {
+ // NoSuchMethodException or NoSuchMethodError if we somehow got the
+ // version detection wrong or the JVM doesn't support it
+ return 0;
+ }
+ }
+ }
+ }
+ }
+ return 0;
+ }
+
+ /**
+ * @return min of PeerState.MIN_MTU, max of PeerState.LARGE_MTU,
+ * rectifyed so rv % 16 == 12
+ */
+ public static int rectify(int mtu) {
+ int rv = mtu;
+ int mod = rv % 16;
+ if (mod > 12)
+ rv -= mod - 12;
+ else if (mod < 12)
+ rv -= mod + 4;
+ return Math.max(PeerState.MIN_MTU, Math.min(PeerState.LARGE_MTU, rv));
+ }
+
+/****
+ public static void main(String args[]) {
+ try {
+ InetAddress test = InetAddress.getByName(args[0]);
+ System.out.println("MTU is " + getMTU(test));
+ } catch (Exception e) {
+ e.printStackTrace();
+ }
+ }
+****/
+}
diff --git a/router/java/src/net/i2p/router/transport/udp/UDPEndpoint.java b/router/java/src/net/i2p/router/transport/udp/UDPEndpoint.java
index 9531335b42..2723c3ac79 100644
--- a/router/java/src/net/i2p/router/transport/udp/UDPEndpoint.java
+++ b/router/java/src/net/i2p/router/transport/udp/UDPEndpoint.java
@@ -154,4 +154,15 @@ class UDPEndpoint {
return null;
return _receiver.receiveNext();
}
+
+ /**
+ * The MTU for the socket interface, if available.
+ * Not available for Java 5.
+ * @return 0 if Java 5, or if bound to an address;
+ * limited to range MIN_MTU to LARGE_MTU.
+ * @since 0.9.2
+ */
+ public int getMTU() {
+ return MTU.getMTU(_bindAddress);
+ }
}
--
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