A One Line Kernel Patch Appears To Solve The Recent Linux + Steam Networking Regression
Linus Torvalds got involved and pointed out a brand new kernel patch that may solve the issue. That patch was quickly reaffirmed by Linux gamers as well as prominent Valve Linux developer Pierre-Loup A. Griffais.
The patch simply refines the memory limit test within the kernel's tcp_fragment() function. The patch was originally devised by a Google developer and quickly tested as well by an Apple developer, surprisingly.
Hopefully this patch will soon appear in kernel stable releases, "Memory limits might have been exceeded because tcp_sendmsg() only checks limits at full skb (64KB) boundaries. Therefore, we need to make sure tcp_fragment() wont punish applications that might have setup very low SO_SNDBUF values."
It was pointed out by Pierre of Valve that Linux desktop distributions should have caught onto such a regression:
The regression highlights the fact that there are currently no true desktop distributions. A desktop product would have seen the server-centric security fix get queued, tested and found the fact that it breaks Steam, and held it off for the two days it needed to get fixed.— Pierre-Loup Griffais (@Plagman2) June 22, 2019