V6R1 B2B connection error 400

Hi,
After upgrading a machine from V5R4 to V6R1 some B2B clients are now receiving an HTTP 400 error.
The new version of Apache does not appear to be doing anything different when one looks at the trace but there appears to be something that the client now sees differently.
The client is making a B2B connection using a .Net client and has not changed anything at their end so I'm wondering if there is something wrong with the way .Net talks to Apache 2.2.

At V5R4 the client makes an initial POST without authorization credentials. Apache responds with a 401, the client repeats the POST with credentials and all goes well.
It should be noted that the POST actually contains an Expect 100 header so Apache actually responds to the authenticated request with an 100 Continue header which causes the client to then POST the body of the request.

At V6R1 the client makes an initial POST without authorization credentials. Apache responds with a 401, but the client does not appear to accommodate this and immediately responds by a POST with the body of the request.
Apache is expecting to see a valid HTTP header and throws a 400 error when it sees the xml in the body of the request instead.
It's kind of like it is treating the 401 like a 100 response.

Anyone seen anything like this?

Cheers, Peter



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