Redirect (301) after POST re-reads file

[auselen]

I did this

Some python3 code to imitate the server I was working with

import sys
from http.server import HTTPServer, BaseHTTPRequestHandler
class Redirect(BaseHTTPRequestHandler):
   def do_POST(self):
       post_data = self.rfile.read(1)
       self.send_response(301)
       self.send_header('Location', 'http://no.no')
       self.end_headers()
HTTPServer(("", 9000), Redirect).serve_forever()

$ python3 server.py

$ curl -v -F content=@<(echo hello) -L localhost:9000
...
curl: (65) Cannot rewind mime/post data

I expected the following

Reading https://everything.curl.dev/http/redirects, I wouldn't expect curl to try to rewind my input file (process substitution) when redirect is just a 301 and switches to GET.

curl/libcurl version

I tried with a local build and some prebuilt binary.

curl 7.86.0-DEV, 7.68.0

operating system

.

[dfandrich]

The 301 doesn't come back until *after* the data is sent the first time. I think it might be possible to overcome this by forcing the 100-Continue logic which should send the redirect before the data is sent.

[bagder]

The problem is that curl considers and performs the rewind already when it sees the Location: header in the response to POST, before it has decided it should switch to GET...