[tor-bugs] #9166 [Tor]: Write a UTP-based channel implementation

Tor Bug Tracker & Wiki blackhole at torproject.org
Tue Jul 16 17:57:28 UTC 2013

#9166: Write a UTP-based channel implementation
 Reporter:  nickm          |          Owner:                  
     Type:  defect         |         Status:  new             
 Priority:  normal         |      Milestone:  Tor: unspecified
Component:  Tor            |        Version:                  
 Keywords:  tor-relay utp  |         Parent:  #9165           
   Points:                 |   Actualpoints:                  

Comment(by karsten):

 I finally got Shadow simulations of Steven's utp branch running (with help
 by Steven and Rob).  See
 -utp-combined.pdf attached simulation results] of a variant that uses uTP
 for all links and one that uses it for none of the links.  This was in a
 "tiny" Shadow network with 20 relays, which took almost 2.5 hours per

 Here's the code change I made to enable (`if (1 ||`) or disable uTP (`if
 (0 &&`):

 diff --git a/src/or/channeltls.c b/src/or/channeltls.c
 index 0551b73..b7b36e1 100644
 --- a/src/or/channeltls.c
 +++ b/src/or/channeltls.c
 @@ -418,7 +418,7 @@ channel_tls_connect(const tor_addr_t *addr, uint16_t
    /* Create a uTP connection */
    tor_addr_to_sockaddr(addr, port, (struct sockaddr*)&sin, sizeof(sin));
    tor_addr_to_str(addr_str, addr, sizeof(addr_str), 0);
 -  if (!strncmp(addr_str, "", sizeof(addr_str))) {
 +  if (1 || !strncmp(addr_str, "", sizeof(addr_str))) {
               "Trying uTP connection to %s", addr_str);
      tlschan->utp = UTP_Create(tor_UTPSendToProc, tlschan, (const struct

 Am I doing the simulation right?  Should I apply different code changes to
 turn uTP on/off?  Should I run this in a larger Shadow network?

Ticket URL: <https://trac.torproject.org/projects/tor/ticket/9166#comment:7>
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