Consistently suggest ephemeral port for QUIC client

net/quic/quic_stream_factory.cc

Index: net/quic/quic_stream_factory.cc
diff --git a/net/quic/quic_stream_factory.cc b/net/quic/quic_stream_factory.cc
index 40f294821850e0a6fbffa5c9dc5a1d0fbb58d13c..c1c72322cef7ca7bcdc71c600d5d6735d9d74254 100644
--- a/net/quic/quic_stream_factory.cc
+++ b/net/quic/quic_stream_factory.cc
@@ -21,6 +21,7 @@
 #include "net/quic/congestion_control/tcp_receiver.h"
 #include "net/quic/crypto/proof_verifier_chromium.h"
 #include "net/quic/crypto/quic_random.h"
+#include "net/quic/port_suggester.h"
 #include "net/quic/quic_client_session.h"
 #include "net/quic/quic_clock.h"
 #include "net/quic/quic_connection.h"
@@ -256,7 +257,8 @@ QuicStreamFactory::QuicStreamFactory(
       random_generator_(random_generator),
       clock_(clock),
       max_packet_length_(max_packet_length),
-      weak_factory_(this) {
+      weak_factory_(this),
+      port_entropy_(random_generator_->RandUint64()) {
   config_.SetDefaults();
   config_.set_idle_connection_state_lifetime(
       QuicTime::Delta::FromSeconds(30),
@@ -447,9 +449,12 @@ QuicClientSession* QuicStreamFactory::CreateSession(
     const BoundNetLog& net_log) {
   QuicGuid guid = random_generator_->RandUint64();
   IPEndPoint addr = *address_list.begin();
+  scoped_refptr<PortSuggester> port_suggester =
+      new PortSuggester(host_port_proxy_pair.first, port_entropy_);
   scoped_ptr<DatagramClientSocket> socket(
       client_socket_factory_->CreateDatagramClientSocket(
-          DatagramSocket::DEFAULT_BIND, base::Bind(&base::RandInt),
+          DatagramSocket::RANDOM_BIND,
+          base::Bind(&PortSuggester::SuggestPort, port_suggester),

[Ryan Hamilton, 2013/12/07 01:46:14]

It would be super great if we had a test that verified we actually use the same
port when connecting to the same server.  Alas, that doesn't look trivial. :/ 
It's tempting to add a unit test of QuicStreamFactory, but that use the
MockSocket infrastructure, which doesn't call the rand_cb.  You could probably
tweak a test to use a real socket factory, but that'd be a a bunch of awkward. 
Probably the easiest thing would be to tweak the QuicServer to expose the
peer_address in some fashion, but even that's a bunch of yak-shaving, so perhaps
it's not worth it.

[jar (doing other things), 2013/12/07 03:12:18]

I added some code to DCHECK() that the port_suggester was at least being called
(recall that there was a bug previously where that didn't happen), and also to
verify that the last suggestion was actually used (I'm counting on not being
blocked from using the suggestions).

The only missing link would be if we're accidentally calling to seed_
differently when we are going to the same server (since the unit tests verify
that if you seed identically... you get identical suggestions).

[Ryan Hamilton, 2013/12/07 04:52:22]

If you reverted the changes to this file, would any tests break?

           net_log.net_log(), net_log.source()));
   socket->Connect(addr);