Add a SetDoNotFragment() method to DatagramSocket, and call this for

net/socket/socket.h

Index: net/socket/socket.h
diff --git a/net/socket/socket.h b/net/socket/socket.h
index cda54063f3059e76726c896b5e6ae87508a5f483..b65e783071921e6c85a5eac848c53efe03533160 100644
--- a/net/socket/socket.h
+++ b/net/socket/socket.h
@@ -57,6 +57,10 @@ class NET_EXPORT Socket {
   // Note: changing this value can affect the TCP window size on some platforms.
   // Returns a net error code.
   virtual int SetSendBufferSize(int32_t size) = 0;
+
+  // Configures the socket to set or clear the DF (Do not Fragment) bit on
+  // packets, which prevents routers from fragmenting them.
+  virtual int SetDoNotFragment(bool do_not_fragment) = 0;
 };
 
 }  // namespace net