# HG changeset patch
# User Tommaso Pecorella <tommaso.pecorella@unifi.it>
# Date 1386873376 -3600
# Node ID f222d52c616fc4acca5f576da9a31ef4271739fc
# Parent  3df0e5c2eed52b175aadba6d15fed46d7900ab45
Bug 1810 - IP packets can be sent on NetDevices not respecting the minimum MTU requirements

diff -r 3df0e5c2eed5 -r f222d52c616f RELEASE_NOTES
--- a/RELEASE_NOTES	Thu Dec 12 18:50:20 2013 +0100
+++ b/RELEASE_NOTES	Thu Dec 12 19:36:16 2013 +0100
@@ -50,6 +50,7 @@
 - Bug 1798 - Changing the rate of onOffApplication might stop transmission
 - Bug 1802 - FlowMon header deserialization problem with IPv4 fragments
 - Bug 1807 - Multiple bugs in Ipv4L3Protocol::LocalDeliver
+- Bug 1810 - IP packets can be sent on NetDevices not respecting the minimum MTU requirements
 
 Release 3.18.1
 ==============
diff -r 3df0e5c2eed5 -r f222d52c616f src/internet/model/ipv4-l3-protocol.cc
--- a/src/internet/model/ipv4-l3-protocol.cc	Thu Dec 12 18:50:20 2013 +0100
+++ b/src/internet/model/ipv4-l3-protocol.cc	Thu Dec 12 19:36:16 2013 +0100
@@ -1095,11 +1095,23 @@
 {
   NS_LOG_FUNCTION (this << i);
   Ptr<Ipv4Interface> interface = GetInterface (i);
-  interface->SetUp ();
+
+  // RFC 791, pg.25:
+  //  Every internet module must be able to forward a datagram of 68
+  //  octets without further fragmentation.  This is because an internet
+  //  header may be up to 60 octets, and the minimum fragment is 8 octets.
+  if (interface->GetDevice ()->GetMtu () >= 68)
+    {
+      interface->SetUp ();
 
-  if (m_routingProtocol != 0)
+      if (m_routingProtocol != 0)
+        {
+          m_routingProtocol->NotifyInterfaceUp (i);
+        }
+    }
+  else
     {
-      m_routingProtocol->NotifyInterfaceUp (i);
+      NS_LOG_LOGIC ("Interface " << int(i) << " is set to be down for IPv4. Reason: not respecting minimum IPv4 MTU (68 octects)");
     }
 }
 
diff -r 3df0e5c2eed5 -r f222d52c616f src/internet/model/ipv6-l3-protocol.cc
--- a/src/internet/model/ipv6-l3-protocol.cc	Thu Dec 12 18:50:20 2013 +0100
+++ b/src/internet/model/ipv6-l3-protocol.cc	Thu Dec 12 19:36:16 2013 +0100
@@ -486,11 +486,23 @@
   NS_LOG_FUNCTION (this << i);
   Ptr<Ipv6Interface> interface = GetInterface (i);
 
-  interface->SetUp ();
+  // RFC 2460, Section 5, pg. 24:
+  //  IPv6 requires that every link in the internet have an MTU of 1280
+  //  octets or greater.  On any link that cannot convey a 1280-octet
+  //  packet in one piece, link-specific fragmentation and reassembly must
+  //  be provided at a layer below IPv6.
+  if (interface->GetDevice ()->GetMtu () >= 1280)
+    {
+      interface->SetUp ();
 
-  if (m_routingProtocol != 0)
+      if (m_routingProtocol != 0)
+        {
+          m_routingProtocol->NotifyInterfaceUp (i);
+        }
+    }
+  else
     {
-      m_routingProtocol->NotifyInterfaceUp (i);
+      NS_LOG_LOGIC ("Interface " << int(i) << " is set to be down for IPv6. Reason: not respecting minimum IPv6 MTU (1280 octects)");
     }
 }