From: "Maciej Żenczykowski" <zenczykow...@gmail.com> Date: Sun, 3 Jun 2018 10:41:17 -0700
> From: Maciej Żenczykowski <m...@google.com> > > This changes the /proc/sys/net/ipv4/tcp_tw_reuse from a boolean > to an integer. > > It now takes the values 0, 1 and 2, where 0 and 1 behave as before, > while 2 enables timewait socket reuse only for sockets that we can > prove are loopback connections: > ie. bound to 'lo' interface or where one of source or destination > IPs is 127.0.0.0/8, ::ffff:127.0.0.0/104 or ::1. > > This enables quicker reuse of ephemeral ports for loopback connections > - where tcp_tw_reuse is 100% safe from a protocol perspective > (this assumes no artificially induced packet loss on 'lo'). > > This also makes estblishing many loopback connections *much* faster > (allocating ports out of the first half of the ephemeral port range > is significantly faster, then allocating from the second half) > > Without this change in a 32K ephemeral port space my sample program > (it just establishes and closes [::1]:ephemeral -> [::1]:server_port > connections in a tight loop) fails after 32765 connections in 24 seconds. > With it enabled 50000 connections only take 4.7 seconds. > > This is particularly problematic for IPv6 where we only have one local > address and cannot play tricks with varying source IP from 127.0.0.0/8 > pool. > > Signed-off-by: Maciej Żenczykowski <m...@google.com> Applied, thank you.
