[PATCH (ccc)] http_request: support proposed Raindrops::TCP states on

[Eric Wong <e@80x24.org>]

TCP states names/numbers seem stable for each OS, but differ in
name and numeric values between them.  So I started upon this
patch series for raindrops last week:

  https://bogomips.org/raindrops-public/20170316031652.17433-1-e@80x24.org/T/

And things seem to be alright, for the most part.  Anyways
here's a proposed patch for unicorn which takes advantage of
the above (proposed) changes for raindrops and will allow
unicorn to support check_client_connection

Also Cc:-ing Jeremy to see if he has any input on the OpenBSD
side of things.

This goes on top of commit 20c66dbf1ebd0ca993e7a79c9d0d833d747df358
("http_request: reduce insn size for check_client_connection")
at: git://bogomips.org/unicorn ccc-tcp-v3

-------8<--------
Subject: [PATCH] http_request: support proposed Raindrops::TCP states on
 non-Linux

raindrops 0.18+ will have Raindrops::TCP state hash for portable
mapping of TCP states to their respective numeric values.  This
was necessary because TCP state numbers (and even macro names)
differ between FreeBSD and Linux (and possibly other OSes).

Favor using the Raindrops::TCP state hash if available, but
fall back to the hard-coded values since older versions of
raindrops did not support TCP_INFO on non-Linux systems.

While we're in the area, favor "const_defined?" over "defined?"
to reduce the inline constant cache footprint for branches
which are only evaluated once.

Patches to implement Raindrops::TCP for FreeBSD are available at:

  https://bogomips.org/raindrops-public/20170316031652.17433-1-e@80x24.org/T/
---
 lib/unicorn/http_request.rb | 38 +++++++++++++++++++++++++++++---------
 1 file changed, 29 insertions(+), 9 deletions(-)

diff --git a/lib/unicorn/http_request.rb b/lib/unicorn/http_request.rb
index 9010007..7253497 100644
--- a/lib/unicorn/http_request.rb
+++ b/lib/unicorn/http_request.rb
@@ -105,7 +105,7 @@ def hijacked?
     env.include?('rack.hijack_io'.freeze)
   end
 
-  if defined?(Raindrops::TCP_Info)
+  if Raindrops.const_defined?(:TCP_Info)
     TCPI = Raindrops::TCP_Info.allocate
 
     def check_client_connection(socket) # :nodoc:
@@ -118,14 +118,34 @@ def check_client_connection(socket) # :nodoc:
       end
     end
 
-    def closed_state?(state) # :nodoc:
-      case state
-      when 1 # ESTABLISHED
-        false
-      when 8, 6, 7, 9, 11 # CLOSE_WAIT, TIME_WAIT, CLOSE, LAST_ACK, CLOSING
-        true
-      else
-        false
+    if Raindrops.const_defined?(:TCP)
+      # raindrops 0.18.0+ supports FreeBSD + Linux using the same names
+      # Evaluate these hash lookups at load time so we can
+      # generate an opt_case_dispatch instruction
+      eval <<-EOS
+      def closed_state?(state) # :nodoc:
+        case state
+        when #{Raindrops::TCP[:ESTABLISHED]}
+          false
+        when #{Raindrops::TCP.values_at(
+              :CLOSE_WAIT, :TIME_WAIT, :CLOSE, :LAST_ACK, :CLOSING).join(',')}
+          true
+        else
+          false
+        end
+      end
+      EOS
+    else
+      # raindrops before 0.18 only supported TCP_INFO under Linux
+      def closed_state?(state) # :nodoc:
+        case state
+        when 1 # ESTABLISHED
+          false
+        when 8, 6, 7, 9, 11 # CLOSE_WAIT, TIME_WAIT, CLOSE, LAST_ACK, CLOSING
+          true
+        else
+          false
+        end
       end
     end
   else
-- 
EW