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Re: App fails when rebuilt with newer library, but only when MTU is small

From: Dan Fandrich via curl-library <>
Date: Thu, 29 Sep 2022 15:08:50 -0700

On Thu, Sep 29, 2022 at 09:58:58PM +0000, Mark Fanara wrote:
>> Some servers have an issue with 100-continue, and I don't recall which version
>> of libcurl enabled it by default. You could try disabling it and see what
>> happens. It theoretically shouldn't have anything to do with MTU, though.
>> What happens in this case when the MTU is greater? How do the client and server
>> handle this 100-continue?
> I don't know how to disable it. Change the timeout to 0ms ?

It's a FAQ:

> When the MTU is larger, the TLS packet sequence continues

This seems unlikely to me to be a curl issue. It sounds more likely to be
something lower in the networking stack that's interfering. Try using Wireshark
to sniff the traffic to see if the short application data packets are getting
through, and if they are, if they're being acked.

Received on 2022-09-30