fixing TCP connection inprogress on SSL connection bug

The Errno::INPROGRESS error signals that the TCP handshake has been
signaled to the peer already, by which locally we just have wait for it
to be writable.

For simple plaintext requests, this was working correctly, because the
interest was always writable no matter what. However, when wrapped in
the SSL conn, and with the OS tcp stack under more stress, the interest
could be switched to readable, and by reuse, never reset; if, by
subsequent reconnection, EINPROGRESS would be emitted, the socket would
wait for readable instead, resulting in a loop and subsequent
connectionnn timeout.

lib/httpx/io/ssl.rb

@@ -21,10 +21,6 @@ module HTTPX
       @state = :negotiated if @keep_open
     end
 
-    def interests
-      @interests || super
-    end
-
     def protocol
       @io.alpn_protocol || super
     rescue StandardError
@@ -66,6 +62,7 @@ module HTTPX
       @io.connect_nonblock
       @io.post_connection_check(@sni_hostname) if @ctx.verify_mode != OpenSSL::SSL::VERIFY_NONE
       transition(:negotiated)
+      @interests = :w
     rescue ::IO::WaitReadable
       @interests = :r
     rescue ::IO::WaitWritable

lib/httpx/io/tcp.rb

@@ -7,7 +7,7 @@ module HTTPX
   class TCP
     include Loggable
 
-    attr_reader :ip, :port, :addresses, :state
+    attr_reader :ip, :port, :addresses, :state, :interests
 
     alias_method :host, :ip
 
@@ -18,6 +18,7 @@ module HTTPX
       @options = Options.new(options)
       @fallback_protocol = @options.fallback_protocol
       @port = origin.port
+      @interests = :w
       if @options.io
         @io = case @options.io
               when Hash
@@ -39,10 +40,6 @@ module HTTPX
       @io ||= build_socket
     end
 
-    def interests
-      :w
-    end
-
     def to_io
       @io.to_io
     end
@@ -62,6 +59,8 @@ module HTTPX
         @io.connect_nonblock(Socket.sockaddr_in(@port, @ip.to_s))
       rescue Errno::EISCONN
       end
+      @interests = :w
+
       transition(:connected)
     rescue Errno::EHOSTUNREACH => e
       raise e if @ip_index <= 0
@@ -74,8 +73,10 @@ module HTTPX
       @ip_index -= 1
       retry
     rescue Errno::EINPROGRESS,
-           Errno::EALREADY,
-           ::IO::WaitReadable
+           Errno::EALREADY
+      @interests = :w
+    rescue ::IO::WaitReadable
+      @interests = :r
     end
 
     if RUBY_VERSION < "2.3"