Date: Fri, 16 Mar 2012 00:57:36 +0200 From: Nikolay Denev <ndenev@gmail.com> To: =?iso-8859-1?Q?Seyit_=D6zg=FCr?= <seyit.ozgur@istanbul.net> Cc: "freebsd-net@freebsd.org" <freebsd-net@freebsd.org> Subject: Re: Malformed syn packet cause %100 cpu and interrupts FreeBSD 9.0 release Message-ID: <14B45EAA-EC95-463B-A4C0-4CE9090FA274@gmail.com> In-Reply-To: <3807CE6F3BF4B04EB897F4EBF2D258CE5C05F2D0@yuhanna.magnetdigital.local> References: <3807CE6F3BF4B04EB897F4EBF2D258CE5C05F221@yuhanna.magnetdigital.local> <38FA7BAB-AC2B-4515-85CF-27F77C3F4313@mac.com> <3807CE6F3BF4B04EB897F4EBF2D258CE5C05F28C@yuhanna.magnetdigital.local>, <13511933-562D-4887-951B-5BB01F62AB00@mac.com> <3807CE6F3BF4B04EB897F4EBF2D258CE5C05F2D0@yuhanna.magnetdigital.local>
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On Mar 15, 2012, at 10:40 PM, Seyit =D6zg=FCr wrote: > sori my opinion but i m not a BSD guru.. i just working on BSD like 2 = months.. > i know that PF or IPFW isn't build multicore arhitecture... As i know = if my server got on heavy Syn flood traffic PF or IPFW don't enough 1 = core..=20 > i also tried Syn_cookie, Syn_cookie_only and syn_cache.. if i set up = syn_cookie start input errors after 600.000 syn packets per second. But = while i set off syn cookie protection.. my server can handle much more = syn packets then 600.000..=20 > Also thats why i don't use syncookies too.. > If there is any statefull Firewall software on freeBSD which support = multicore process? (you know ?). i m up to set up.. >=20 > i will get tcpdump again with -X param.. then i will post it again.. >=20 > Thanks for your comments.=20 >=20 > ________________________________________ > From: Chuck Swiger [cswiger@mac.com] > Sent: Thursday, March 15, 2012 10:30 PM > To: Seyit =D6zg=FCr > Cc: freebsd-net@freebsd.org > Subject: Re: Malformed syn packet cause %100 cpu and interrupts = FreeBSD 9.0 release >=20 > On Mar 15, 2012, at 1:17 PM, Seyit =D6zg=FCr wrote: >> Thanks for quick reply.. but i don't use firewall. i tried to use = PF.. >> Packer filter stucks up to 100.000 syn packets flooding(on open = port).. Without packet filter it handle much more syn flooding. Like = 1Mpps can handle w/o interrupts that i see on my equiment >> But in this case "malformed packets" i got interrupts also input = packet error.. cause %100 cpu.. >> Is there any way to stop them without firewall ? Any rfc kernel = feature can check and stop those bogus packets ? >> Or do i something wrong on PF ? >=20 > I prefer IPFW myself, but you probably ran out of stateful rule slots. = For a high-volume services which is expected to be Internet-reachable = (ie, port 80 to a busy webserver), you really just don't want to have = stateful rules-- it's too easy to DoS the firewall itself, as you = noticed. In any event, you don't need state if you are just = blacklisting attack sources. >=20 > You haven't really identified what you mean by "malformed", but maybe = you are talking about a SYN flood, in which case make sure that SYN = cookies and SYN cache are enabled... >=20 > Regards, > -- > -Chuck >=20 >=20 In my experience you will endure a lot more SYN flood traffic if you use = only syncache, and also increase the syncache sysctls. Sycookies are somewhat more expensive to calculate and they cause 100% = CPU load much sooner. I use : net.inet.tcp.syncache.hashsize=3D2048 net.inet.tcp.syncache.cachelimit=3D61440 net.inet.tcp.syncache.bucketlimit=3D30 Does this works better for you?
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