alt Hacker NewsYou can also use TCP_CORK to reduce the number of packets without any increased latency.
Disabling TCP_NODELAY would also reduce number of packets + be portable & simpler to implement - but would incur a latency penalty.
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Oh wow - I've never heard of TCP_CORK before. Without disabling pings I'd still pay the cost of receiving way more packets, but maybe that'd be tolerable if I didn't have to send so many pongs. This is super handy; excited to play around with it.
I am aware of TCP_NODELAY (funny enough I recently posted about TCP_NODELAY to HN[1] when I was thinking about it for the same game that I wrote about here). But I think the latency hit from disabling it just doesn't work for me.
Can you explain how TCP_CORK helps here? The chaff packets are spaced 20ms apart and sent per socket, so I don’t see how TCP_CORK could help unless it coalesced across 20ms intervals? But coalescing is clearly not an option for the intended obfuscation effect of the original feature.
Haven't heard of TCP_CORK, very interesting.
For people who don't feel like googling it:
1. You TCP_CORK a socket
2. You put data into it and the kernel buffers it
3. If you uncork the socket, or if the buffer hits MSS, the kernel sends the packet
Basically, the kernel waits until it has a full packet worth of data, or until you say you don't have any more data to send, and then it sends. Sort of an extreme TCP_YESDELAY.
See https://catonmat.net/tcp-cork for where I learned it all from.