feat: Limit the range of randomly generated fd in the WASI component

[hydai]

Motivation

Due to some applications using the old select API, our current implementation follows the standard of WASI which means we will have a map to handle the randomly generated fd number (<= 2**31) to the actual fd number. However, in some cases, the application only accepts the fd number which is less than FD_SETSIZE (usually 1024).

It would be nice to have an API to set the range of the randomly generated fd numbers.

Details

• Implement an internal function to control the range
• Export this function as a configuration option in C API
• Export a CLI option to control this flag
• Write a section in the document

Appendix

• https://github.com/WebAssembly/WASI/blob/main/phases/snapshot/docs.md#-path_openfd-fd-dirflags-lookupflags-path-string-oflags-oflags-fs_rights_base-rights-fs_rights_inheriting-rights-fdflags-fdflags---resultfd-errno

[uddhavphatak]

Hi @hydai, I wish to work on this issue, but have a confusion, is this still a pending feature, can I work for this for the upcoming release?

[hydai]

This is still available.

[uddhavphatak]

Thank you,
is there any documentation related to this issue, the appendix written in the issue description is giving error-404

[uddhavphatak]

I am assuming the 404'd appendix referred to the FD_SETSIZE (1024) limitation in the select() syscall.

I plan to implement a configuration option that constrains the randomized FDs to be within the FD_SETSIZE range.

I'll start by looking at how the WASI implementation currently maps FDs in "lib/host/wasi". Does that sound like the right direction? Please correct me if I am going in the wrong direction