udp: add experimental io_uring implementation (#131)

* WIP: add udp uring support

* WIP: fix udp uring address parsing

* WIP: udp uring: resubmit recv when needed

* WIP: udp uring: add OutMessageStorage, send swarm responses

* WIP: udp uring: increase ring entries to 1024

* WIP: udp uring: add constants

* WIP: udp uring: use sqpoll, avoid kernel calls

* WIP: udp uring: disable sqpoll

* WIP: udp uring: use VecDeque for local responses

* udp uring: enable setup_coop_taskrun

* udp uring: add RecvMsgStorage

* udp: improve split of uring and mio implementations

* udp uring: clean up

* udp uring: initial ipv6 support

* udp uring: improve helper structs

* udp uring: clean up, use constants for important data

* udp: share create_socket fn between implementations

* udp uring: improve send buffer free index finding

* udp uring: work on SendBuffers.try_add

* udp uring: split into modules

* udp uring: Rename RecvMsgMultiHelper to RecvHelper

* udp uring: improve SendBuffers

* udp uring: fix copyright attribution in buf_ring module

* udp uring: stop always consuming 100% cpu

* udp uring: clean up

* udp uring: add handle_recv_cqe

* udp uring: move local_responses into SocketWorker

* udp uring: move timeout_timespec into SocketWorker

* Update TODO

* udp: make io-uring optional

* Update TODO

* udp uring: enqueue timeout before sends

* udp uring: move likely empty buffer tracking logic into SendBuffers

* udp uring: improve error handling and logging

* udp uring: keep one timeout submitted at a time

* udp uring: update pending_scrape_valid_until

* udp uring: add second timeout for cleaning

* Update TODO

* udp uring: store resubmittable squeue entries in a Vec

* udp uring: add comment, remove a log statement

* Update TODO

* Update TODO

* udp: io_uring: fall back to mio if io_uring support not recent enough

* udp: uring: add bytes_received statistics

* udp: uring: add bytes_sent statistics

* udp: uring: add more statistics

* Update TODO

* udp: uring: improve SendBuffers code

* udp: uring: remove unneeded squeue sync calls

* udp: uring: replace buf_ring impl with one from tokio-uring

* udp: uring: store ring in TLS so it can be used in Drop impls

* udp: uring: store BufRing in SocketWorker

* udp: uring: silence buf_ring dead code warnings, improve comment

* Update TODO

* udp: uring: improve CurrentRing docs, use anonymous struct field

* udp: uring: improve ring setup

* udp: uring: get ipv6 working

* udp: uring: make ring entry count configurable, use more send entries

* udp: uring: log number of pending responses (info level)

* udp: uring: improve comment on send_buffer_entries calculation

* udp: improve config comments

* udp: uring: add to responses stats when they are confirmed as sent

* Update TODO

* udp: uring: enable IoUring setup_submit_all

* Update README

Cargo.lock

@@ -229,6 +229,7 @@ dependencies = [
  "hashbrown 0.13.2",
  "hdrhistogram",
  "hex",
+ "io-uring",
  "libc",
  "log",
  "metrics",
@@ -1489,6 +1490,16 @@ dependencies = [
  "memoffset 0.8.0",
 ]
 
+[[package]]
+name = "io-uring"
+version = "0.5.13"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "dd1e1a01cfb924fd8c5c43b6827965db394f5a3a16c599ce03452266e1cf984c"
+dependencies = [
+ "bitflags 1.3.2",
+ "libc",
+]
+
 [[package]]
 name = "ipnet"
 version = "2.7.1"