ksmbd (actualy: nf-nathelper-extra = conntrack modules) slows down NAT

[Rafał Miłecki]

I realized that my custom images for BCM47094 based on bcm53xx OpenWrt
21.02 can't reach 940 Mb/s NAT speeds. Such 940 Mb/s speeds are totally
possible with clean OpenWrt builds.

After some debugging I discovered that it's because I include ksmbd.
Package kmod-fs-ksmbd selects kmod-nf-nathelper-extra which provides a
few conntrack modules. It seems each one slows down handling network
traffic by some small percentage.

Base NAT speed in my custom fw is 880 Mb/s (not 940 for some reason).

Then it slows down to:
860 Mb/s with added: nf_conntrack_tftp, nf_nat_tftp
862 Mb/s with nf_nat_snmp_basic nf_conntrack_snmp nf_conntrack_broadcast
843 Mb/s with nf_nat_sip, nf_conntrack_sip
825 Mb/s with nf_nat_pptp, nf_conntrack_pptp
821 Mb/s with nf_nat_irc, nf_conntrack_irc
817 Mb/s with nf_nat_h323, nf_conntrack_h323
800 Mb/s with nf_nat_amanda, nf_conntrack_amanda

I'm planning to reduce ksmbd dependencies to minimalize its negative
effect on NAT.

It's a heads-up and my debugging summary for others that may find it helpful.

-- 
Rafał