On Tue, Sep 3, 2019 at 7:45 AM Toke Høiland-Jørgensen <t...@toke.dk> wrote: > > Dave Taht <dave.t...@gmail.com> writes: > > > On Tue, Sep 3, 2019 at 5:23 AM Mikael Abrahamsson <swm...@swm.pp.se> wrote: > >> > >> On Mon, 2 Sep 2019, Dave Taht wrote: > >> > >> > with copy-pasted parameters set in the 90s - openwrt's default, last I > >> > looked, was 25/sec. > >> > >> -A syn_flood -p tcp -m tcp --tcp-flags FIN,SYN,RST,ACK SYN -m limit > >> --limit 25/sec --limit-burst 50 -m comment --comment "!fw3" -j RETURN > >> -A syn_flood -m comment --comment "!fw3" -j DROP > >> > >> Well, it's got a burst-size of 50. I agree that this is quite > >> conservative. > >> > >> However, at least in my home we're not seeing drops: > >> > >> # iptables -nvL | grep -A 4 "Chain syn_flood" > >> Chain syn_flood (1 references) > >> pkts bytes target prot opt in out source > >> destination > >> 2296 113K RETURN tcp -- * * 0.0.0.0/0 > >> 0.0.0.0/0 tcp flags:0x17/0x02 limit: avg 25/sec burst 50 /* > >> !fw3 */ > >> 0 0 DROP all -- * * 0.0.0.0/0 > >> 0.0.0.0/0 /* !fw3 */ > >> > >> But you might be right that in places with a lot more clients then this > >> might indeed cause problems. > > > > Well, *I* long ago had upped those params by 10x and don't see syn > > drops either on my backbone. But I rather suspect the rest of the > > world just copy-pasted it. It should scale as a function of bandwidth, > > I suppose, or get updated as a side effect of setting QoS - or just > > get bumped up. Start a bug over with openwrt? Take a hard look at > > other firewall designs? > > FWIW: > > # iptables -nvL syn_flood > Chain syn_flood (1 references) > pkts bytes target prot opt in out source > destination > 195K 12M RETURN tcp -- * * 0.0.0.0/0 0.0.0.0/0 > tcp flags:0x17/0x02 limit: avg 25/sec burst 50 /* !fw3 */ > 0 0 DROP all -- * * 0.0.0.0/0 0.0.0.0/0 > /* !fw3 */ > > # ip6tables -nvL syn_flood > Chain syn_flood (1 references) > pkts bytes target prot opt in out source > destination > 396 41508 RETURN tcp * * ::/0 ::/0 > tcp flags:0x17/0x02 limit: avg 25/sec burst 50 /* !fw3 */ > 0 0 DROP all * * ::/0 ::/0 > /* !fw3 */ > > rebooted this box today; don't seem to have hit the limit thus far, > though... This is on a gigabit link.
Hmm. Try to trigger it with --te=upload_streams=200 ? > > -Toke -- Dave Täht CTO, TekLibre, LLC http://www.teklibre.com Tel: 1-831-205-9740 _______________________________________________ Bloat mailing list Bloat@lists.bufferbloat.net https://lists.bufferbloat.net/listinfo/bloat