dnsdis TCP Fast Open / TCP_FASTOPEN on macOS?

[karelbilek]

I am trying to build and run dnsdist for regression tests on macOS.

I cannot figure out how to enable TCP_FASTOPEN.

I don't see any option in ./configure for fast open. I am trying to figure out where does the TCP_FASTOPEN come from.

Currently, it is undefined and I get this during regression tests:

TCP Fast Open has been configured on downstream server 127.0.0.1:22157 but is not supported

[karelbilek]

Ah, it seems this should be defined in #include <netinet/tcp.h>

but interestingly, I do see this defined there in macOS

[karelbilek]

Ah, the issue is actually MSG_FASTOPEN, not TCP_FASTOPEN, and that indeed is not defined

[karelbilek]

Yep the issue is macOS has different fastopen semantics.

unbound seems to do some magic there

NLnetLabs/unbound@ad939e5

[karelbilek]

yeah it seems to be the case that macOS and linux has different API for TCP Fast Open; this is how unbound does it

https://github.com/NLnetLabs/unbound/blob/8faa95354d9ce5cace6daeeba404c74f6a5027aa/services/outside_network.c#L677

I will open a new issue here

#16068