Why is set-listen-backlog-size a function?

[sunfishcode]

If I understand correctly, set-listen-backlog-size corresponds to the backlog parameter in the listen function in POSIX. I'm curious why it's a function here instead of being a listen parameter.

[badeend]

Although not part of the official POSIX documentation, many implementations allow listen to be called multiple times:

• The first invocation performs the actual listen and sets the initial backlog size.
• Any future invocation just updates the backlog size.

Splitting out these concerns into distinct functions simplifies the WASI interface.

• tcp-socket::listen performs the actual listener transition, permission checks, etc. Additionally:
  • is async
  • can be called exactly once (successfully)
  • can potentially return an "accept stream" in the future.
• tcp-socket::set-listen-backlog-size behaves just like any other socket option (which it effectively is, in my mind)
  • is sync
  • can be called multiple times
  • on non-listening sockets, stashes the value on the internal socket instance, to be passed on to the native listen call part of tcp-socket::listen
  • on already listening socket, calls out to the native listen

[sunfishcode]

Cool, thanks!