`BaseHTTPRequestHandler` incorrectly expects headers from HTTP/0.9 requests

[Carmina16]

Bug report

Bug description:

The HTTPServer class seems to have issues with pre-HTTP 1.0 type requests. The request is not passed to the GET handler until the client closes the connection.

Maybe the BaseHTTPRequestHandler tries to read non-existent headers or wants an empty line in the request?

CPython versions tested on:

3.12

Operating systems tested on:

Windows

Linked PRs

• gh-70765: avoid waiting for HTTP headers when parsing HTTP/0.9 requests #139514

[picnixz]

Can you show the server and client code? We need a reproducer to understand your issue.

[Carmina16]

from http.server import *
from sys import stderr, stdout

class MyHandler(BaseHTTPRequestHandler):
	def do_GET(self):
		print("Request:",repr(self.requestline),file=stderr)
		return

srv=HTTPServer(
	RequestHandlerClass=MyHandler,
	server_address=('',8080)
	)
srv.serve_forever()

[picnixz]

What is the request you are sending? Make sure that request is a well-formed HTTP/0.9 as well

[Carmina16]

Sending GET /foo\r\n and not closing connection afterwards should work.

[picnixz]

HTTP/0.9 is a one-line protocol. The connection is terminated after the response has been sent. See https://www.w3.org/Protocols/HTTP/AsImplemented. So it's working as intended.

[picnixz]

Btw, if you need to keep alive your connection, you need to use HTTP/1.1.

[picnixz]

Sending GET /foo\r\n and not closing connection afterwards should work.

I'm not sure whether you meant the connection on the client or the server, but note that it's possible to see a hang if you use echo. For instance echo "GET /index.html\r\n"| nc 127.0.0.1 8080 would make it hang but not with echo -e "GET /index.html\r\n" | nc 127.0.0.1 8080 and that's because the client request is not completed

[Carmina16]

The connection is terminated after the response has been sent.

But it is not terminated. The server hangs (probably misreading the request) until the client aborts the connection, then the request is finally processed but obviously there is nowhere to send the response.

[picnixz]

Ah! I see what you mean. Sorry for misunderstanding the issue. Indeed, it's stuck in http.client.parse_headers.