Avoid all 'unhandled exceptions' from h2spec run

They're mostly related to broken IO (EPIPE, ECONNRESET, EOF) or
pending fibers (e.g. waiting to write data to `stream.data`).

src/connection.cr

@@ -227,7 +227,7 @@ module HTTP2
 
       when Frame::Type::GOAWAY
         _, last_stream_id = read_stream_id
-        error_code = Error::Code.from_value(io.read_bytes(UInt32, IO::ByteFormat::BigEndian))
+        error_code = Error::Code.new(io.read_bytes(UInt32, IO::ByteFormat::BigEndian))
         io.read_fully(buf = Slice(UInt8).new(frame.size - 8))
         error_message = String.new(buf)
 
@@ -332,7 +332,7 @@ module HTTP2
     # synchronisation could end up corrupted if another HEADERS frame for
     # another stream was sent in between.
     def send(frame : Frame | Array(Frame))
-      @channel.send(frame)
+      @channel.send(frame) unless @channel.closed?
     end
 
     def write_settings

src/hpack/huffman.cr

@@ -76,7 +76,7 @@ module HTTP2
               eos_padding = false
             end
 
-            raise Exception.new("node is nil!") unless node
+            raise Error.new("node is nil!") unless node
 
             if value = node.value
               io.write_byte(value)
@@ -88,11 +88,11 @@ module HTTP2
           end
 
           # RFC 7541, section 5.2
-          raise Exception.new("huffman string padding is larger than 7-bits") unless byte_has_value
+          raise Error.new("huffman string padding is larger than 7-bits") unless byte_has_value
         end
 
         # RFC 7541, section 5.2
-        raise Exception.new("huffman string padding must use MSB of EOS symbol") unless eos_padding
+        raise Error.new("huffman string padding must use MSB of EOS symbol") unless eos_padding
 
         io.to_s
       end

src/server/request_processor.cr

@@ -78,19 +78,22 @@ class HTTP::Server::RequestProcessor
         # didn't read it all, for the next request
         request.body.try(&.close)
       end
+    ensure
+      io.close if must_close
+    end
 
-    rescue ex : Errno
-      # FIXME: calling with curl results in EPIPE (certainly related to
-      #        SSL::Error below)
-      raise ex unless ex.errno == Errno::EPIPE
+  rescue ex : IO::EOFError | IO::Error
+    # silence
 
-    rescue ex : OpenSSL::SSL::Error
-      # FIXME: calling with curl results in "SSL_read: ZERO_RETURN" exception
-      #        (certainly related to EPIPE above)
-      raise ex unless ex.message.try(&.includes?("ZERO_RETURN"))
+  rescue ex : Errno
+    raise ex unless {Errno::EPIPE, Errno::ECONNRESET}.includes?(ex.errno)
 
-    ensure
-      io.close if must_close
+  rescue ex : OpenSSL::SSL::Error
+    # NOTE: curl calls may result in "SSL_read: ZERO_RETURN" exceptions
+    # NOTE: unexpectedly closed connections may result in OpenSSL hitting EOF early
+    unless ex.message.try(&.includes?("ZERO_RETURN")) ||
+        ex.message.try(&.includes?("Unexpected EOF"))
+      raise ex
     end
   end
 

src/stream.cr

@@ -112,7 +112,7 @@ module HTTP2
 
     protected def send_window_update_frame(increment)
       unless MINIMUM_WINDOW_SIZE <= increment <= MAXIMUM_WINDOW_SIZE
-        raise Exception.new("invalid WINDOW_UPDATE increment: #{increment}")
+        raise Error.protocol_error("invalid WINDOW_UPDATE increment: #{increment}")
       end
       io = IO::Memory.new
       io.write_bytes(increment.to_u32 & 0x7fffffff_u32, IO::ByteFormat::BigEndian)