75 lines
3.3 KiB
Plaintext
75 lines
3.3 KiB
Plaintext
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1. PUT/POST without a known auth to use (possibly no auth required):
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(When explicitly set to use a multi-pass auth when doing a POST/PUT,
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libcurl should immediately go the Content-Length: 0 bytes route to avoid
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the first send all data phase, step 2. If told to use a single-pass auth,
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goto step 3.)
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Issue the proper PUT/POST request immediately, with the correct
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Content-Length and Expect: headers.
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If a 100 response is received or the wait for one times out, start sending
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the request-body.
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If a 401 (or 407 when talking through a proxy) is received, then:
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If we have "more than just a little" data left to send, close the
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connection. Exactly what "more than just a little" means will have to be
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determined. Possibly the current transfer speed should be taken into
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account as well.
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NOTE: if the size of the POST data is less than MAX_INITIAL_POST_SIZE (when
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CURLOPT_POSTFIELDS is used), libcurl will send everything in one single
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write() (all request-headers and request-body) and thus it will
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unconditionally send the full post data here.
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2. PUT/POST with multi-pass auth but not yet completely negotiated:
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Send a PUT/POST request, we know that it will be rejected and thus we claim
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Content-Length zero to avoid having to send the request-body. (This seems
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to be what IE does.)
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3. PUT/POST as the last step in the auth negotiation, that is when we have
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what we believe is a completed negotiation:
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Send a full and proper PUT/POST request (again) with the proper
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Content-Length and a following request-body.
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NOTE: this may very well be the second (or even third) time the whole or at
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least parts of the request body is sent to the server. Since the data may
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be provided to libcurl with a callback, we need a way to tell the app that
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the upload is to be restarted so that the callback will provide data from
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the start again. This requires an API method/mechanism that libcurl
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doesn't have today. See below.
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Data Rewind
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It will be troublesome for some apps to deal with a rewind like this in all
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circumstances. I'm thinking for example when using 'curl' to upload data
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from stdin. If libcurl ends up having to rewind the reading for a request
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to succeed, of course a lack of this callback or if it returns failure, will
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cause the request to fail completely.
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The new callback is set with CURLOPT_IOCTLFUNCTION (in an attempt to add a
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more generic function that might be used for other IO-related controls in
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the future):
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curlioerr curl_ioctl(CURL *handle, curliocmd cmd, void *clientp);
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And in the case where the read is to be rewinded, it would be called with a
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cmd named CURLIOCMD_RESTARTREAD. The callback would then return CURLIOE_OK,
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if things are fine, or CURLIOE_FAILRESTART if not.
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Backwards Compatibility
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The approach used until now, that issues a HEAD on the given URL to trigger
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the auth negotiation could still be supported and encouraged, but it would
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be up to the app to first fetch a URL with GET/HEAD to negotiate on, since
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then a following PUT/POST wouldn't need to negotiate authentication and
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thus avoid double-sending data.
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Optionally, we keep the current approach if some option is set
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(CURLOPT_HEADBEFOREAUTH or similar), since it seems to work fairly well for
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POST on most servers.
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