ruleset: skip _iifname match for !tcp in mss fix

[brada4]

Add explicit l4proto match before _ifname to avoid burning cycles for other protocols, eliminating measurable (iperf3) udp re-ordering Displayed back rules show pessimal combo even new one is loaded.

Fixes: couple of issues pertaining UDP ordering in games and cheap loudspeakers TBA
Signed-off-by: Andris PE neandris@gmail.com

[brada4]

in

table inet t {
chain c {
oifname "eth1" tcp flags & (fin | syn | rst) == syn tcp option maxseg size set rt mtu
meta l4proto tcp oifname "eth1" tcp flags & (fin | syn | rst) == syn tcp option maxseg size set rt mtu
}
}

out

inet t c
  [ meta load oifname => reg 1 ]
  [ cmp eq reg 1 0x31687465 0x00000000 0x00000000 0x00000000 ]
  [ meta load l4proto => reg 1 ]
  [ cmp eq reg 1 0x00000006 ]
...
inet t c
  [ meta load l4proto => reg 1 ]
  [ cmp eq reg 1 0x00000006 ]
  [ meta load oifname => reg 1 ]
  [ cmp eq reg 1 0x31687465 0x00000000 0x00000000 0x00000000 ]
...

[brada4]

Kind of still sucks for tcp established connections.

[Djfe]

do you mean by that that this is just a workaround?

[brada4]

tcp mss fix will still do the name comparison for each tcp packet. This just removes useless check for measurably bad offloaded udp streams. just a side observation in the context.

[brada4]

Swapped to draft, i got better idea, but this is still minimally intrusive for stable trains