test/scripts/1990-TCP-Fast-Open/1990

   1 # TCP Fast Open
   2 #
   3 # Linux:
   4 # Both server and client-side TFO support must be enabled in the
   5 # kernel, 'sudo sh -c "echo 3 > /proc/sys/net/ipv4/tcp_fastopen"'.
   6 #
   7 # A packet capture on the loopback interface will show the TFO
   8 # option on the SYN, but the fast-output SMTP banner will not
   9 # be seen unless you also deliberately emulate a long path:
  10 # 'sudo tc qdisc add dev lo root netem delay 50ms'
  11 # You'll need iproute-tc installed, for the tc command.
  12 # You'll need kernel-modules-extra installed, or you get
  13 # an unhelpful error from RTNETLINK.
  14 # To tidy up:  'sudo tc qdisc delete dev lo root'
  15 #
  16 # MacOS:
  17 # The kernel seems to have TFO enabled both ways as default.
  18 # There is a net.inet.tcp.clear_tfocache parameter
  19 ## sysctl -w foo-val
  20 #
  21 # For network delays there is something called 'Network Link Conditioner'
  22 # which might do the job.  But how to manipulate it?
  23 #
  24 #
  25 sudo perl
  26 system ("tc qdisc add dev lo root netem delay 50ms");
  27 ****
  28 #
  29 #
  30 # Disable the TFO blackhole detection, as we seem to be running foul of it.
  31 # If bitten, we see the expected EINPROGRESS for sendto, yet no TFO cookie
  32 # option on the SYN.
  33 #
  34 sudo perl
  35 system ("[ -e /proc/sys/net/ipv4/tcp_fastopen_blackhole_timeout_sec ] && echo 0 > /proc/sys/net/ipv4/tcp_fastopen_blackhole_timeout_sec");
  36 ****
  37 #
  38 # First time runs will see a TFO request option only; subsequent
  39 # ones should see the TFO cookie and fast-output SMTP banner
  40 # (currently on a separate packet after the server SYN,ACK but before
  41 # the client ACK).
  42 #
  43 # The client log => line  should have a "TFO" element.
  44 # The server log <= line for a@test.ex  should not.
  45 #
  46 # First clear any previously-obtained cookie:
  47 sudo perl
  48 system ("ip tcp_metrics delete 127.0.0.1");
  49 ****
  50 #
  51 #
  52 #
  53 # FreeBSD: it looks like you have to compile a custom kernel, with
  54 # 'options TCP_RFC7413' in the config.  Also set
  55 # 'net.inet.tcp.fastopen.enabled=1' in /etc/sysctl.conf
  56 # Untested.
  57 #
  58 exim -DSERVER=server -bd -oX PORT_D
  59 ****
  60 #
  61 exim a@test.ex
  62 Testing
  63 ****
  64 sleep 3
  65 #
  66 # The server log <= line for b@test.ex  should have a "TFO" element, but
  67 # this will only be obtained when the above delay is inserted into the
  68 # loopback net path.
  69 #
  70 exim b@test.ex
  71 Testing
  72 ****
  73 sleep 3
  74 #
  75 #
  76 sudo perl
  77 system ("tc qdisc delete dev lo root");
  78 system ("[ -e /proc/sys/net/ipv4/tcp_fastopen_blackhole_timeout_sec ] && echo 3600 > /proc/sys/net/ipv4/tcp_fastopen_blackhole_timeout_sec");
  79 ****
  80 #
  81 killdaemon
  82 no_msglog_check