Broken off network sends since Boost (probably ASIO) 1.74

[ghost]

@audaki commented on Sep 12, 2020, 1:07 PM UTC:

3 Years ago we have developed a small (TLS 1.2+ only) HTTPs server for our web application.

We are using Boost for that since 1.64 (development started May 2017) and we never had a problem. Now I have a problem with Boost 1.74, which is always 100% reproducible. When I compile my application with Boost 1.73 the problem is gone, when I compile it with Boost 1.74 it's back. I have tried this 6 times and even tried again with backported TLS libraries in the meantime (didn't change a thing sadly). It is always reproducible when switching the Boost version and recompiling everything and it is the same problem on 2 different PCs and internet connections. I am 100% sure this is a software bug.

With Boost 1.74 our HTTPs server responses occasionally "stops" at some 4 KiB boundary. And I mean literally stops, the browser thinks it is a succcessful response. Let's say we have a javascript file that is 73 KiB. With all other Boost versions the user always receives all 73 KiB.

But with Boost 1.74 in 95% of responses it works. But in about 5% of the responses (and yes, it is that often) the response is cut short. I've seen for example response sizes of exactly 20 KiB, exactly 24 KiB and exactly 40 KiB (I could've probably find more sizes but I had to fix our production service ;-) ). I can easily reproduce the issue by pressing F5 between 5 and 10 times until some resource is broken off.

It is noteworthy that the problem is on exact 4 KiB boundaries!

This issue was moved by chriskohlhoff from boostorg/asio#363.