setting net.inet.tcp.inflight_* on 5.3-STABLE

[darren david]

hi all-

so i'm attempting to tweak my kernel to eke out a bit more oomph from my 
   Gigabit interface, but i can't seem to set any of the 
"net.inet.tcp.inflight_*" params with sysctl. i get:

sysctl: unknown oid 'net.inet.tcp.inflight_enable'

et al. all of the docs i've found seem to assume that it's enabled by 
default in the kernel. what do i need to enable in the kernel config to 
get it working?

perhaps a better long term question is "how do i find out what kernel 
config options are tied to which kernel params"?

thanks in advance,
darren david