Evaluate uv_udp_try_send2 available in libuv 1.50.0

[ibc]

Details

• libuv 1.50.0 comes with a new function uv_udp_try_send2.
• https://github.com/libuv/libuv/releases/tag/v1.50.0
• unix,win: add uv_udp_try_send2 libuv/libuv#4644

Add a version of uv_udp_try_send that can send multiple datagrams.

Uses sendmmsg on platforms that support it (Linux, FreeBSD, macOS), falls back to a regular sendmsgloop elsewhere.

[jmillan]

The only use case I find is when sending NACK-ed RTP packets. In that case we may want to send N packets at once to a single socket.

[ibc]

Or when we send RTCP compound packets.

[fippo]

how would compound RTCP which needs to be SRTP-encrypted in a single call work?
NACK, FEC and maybe pacing... I hear @ggarber ponders re-pacing ;-)

[ibc]

how would compound RTCP which needs to be SRTP-encrypted in a single call work?

I fail to understand the problem you mean. The RTCP compound packet is not split into N datagrams. It's not that way. When mediasoup needs to generate RTCP compound packets it calculates the total size it would need and instead generates N RTCP compound packets of size less than hardcoded MTU (13XX bytes AFAIR) and then it encrypts each compound packet independently before sending each one. Nothing changes here regarding that.

[fippo]

yeah but how often does the get bigger than the MTU?

[ibc]

yeah but how often does the get bigger than the MTU?

How is that related to using this new UDP api in libuv? Absolutely nothing changes here no matter the total size of data to place in RTCP Compound packets.