Re: [Bloat] [Cerowrt-devel] talking at linux plumbers in portugal next week

[Sebastian Moeller <moeller0@gmx.de>]

Not sure this is on-topic, but:

https://www.prnewswire.com/news-releases/root-cause-analysis-and-incident-report-on-the-august-ddos-attack-300905405.html

https://lists.gt.net/nanog/users/206044


> On Sep 3, 2019, at 16:21, Dave Taht <dave.taht@gmail.com> wrote:
> 
> On Tue, Sep 3, 2019 at 5:23 AM Mikael Abrahamsson <swmike@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?
> 
> Like I said, though, my big question was is there a browser stat or
> some other easily accessible stat to see how
> often syns are rejected? Another context for this was syn negotiation
> with ecn on and the fallback.
> 
> Interestingly, I've also seen a pretty big uptick in ecn marking over
> the last year or so, on one uplink (we do have a lot of guests that
> run apple gear), it's now at over 10% of of the drop ratio on
> outbound.
> 
> This box is - I hope - the last cerowrt box running in the universe -
> and the only reason it ever goes down is because of a long duration
> power failure. I've been meaning to replace it for ages...
> 
> root@lounge:~# uptime
> 07:14:53 up 55 days, 17:14,  load average: 0.16, 0.09, 0.10
> 
> outbound:
> 
> qdisc fq_codel 120: parent 1:12 limit 1001p flows 1024 quantum 300
> target 5.0ms interval 100.0ms ecn
> Sent 159378714029 bytes 1038654784 pkt (dropped 426065, overlimits 0
> requeues 0)
> backlog 0b 0p requeues 0
>  maxpacket 1514 drop_overlimit 0 new_flow_count 213282954 ecn_mark 48220
>  new_flows_len 0 old_flows_len 1
> 
> inbound: (where comcast remarks most packets to CS1)
> 
> qdisc fq_codel 120: parent 1:12 limit 1001p flows 1024 quantum 1500
> target 5.0ms interval 100.0ms ecn
> Sent 40391986695 bytes 34710741 pkt (dropped 420, overlimits 0 requeues 0)
> backlog 0b 0p requeues 0
>  maxpacket 1514 drop_overlimit 0 new_flow_count 5687382 ecn_mark 0
>  new_flows_len 0 old_flows_len 2
> qdisc fq_codel 130: parent 1:13 limit 1001p flows 1024 quantum 300
> target 5.0ms interval 100.0ms ecn
> Sent 2285974845172 bytes 1748071724 pkt (dropped 61231, overlimits 0
> requeues 0)
> backlog 0b 0p requeues 0
>  maxpacket 1514 drop_overlimit 0 new_flow_count 229072930 ecn_mark 344
>  new_flows_len 0 old_flows_len 1
> 
> 
>> 
>> --
>> Mikael Abrahamsson    email: swmike@swm.pp.se
> 
> 
> 
> -- 
> 
> Dave Täht
> CTO, TekLibre, LLC
> http://www.teklibre.com
> Tel: 1-831-205-9740
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