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. -Toke _______________________________________________ Bloat mailing list Bloat@lists.bufferbloat.net https://lists.bufferbloat.net/listinfo/bloat