search for: tcp_syncookies

Greetings, all: OS: CentOS 6.4 x86_64 Kernel: 2.6.32-358.14.1 I could use some assistance with setting up pulse to load balance my dns servers. I've configured tcp and udp port 53 with the piranha gui, set up arptable rules on the real servers and added the virtual ip to the bond0 interface on the real servers, but I'm still having no luck in getting things going. A dig against the

Hello everyone, is a pleasure to be here. I have a problem with my server, it runs qmail SMTP and protect it with shorewall. Since yesterday I get syn flood attacks on port 25, which means that no longer meet. How can I stop this with shorewall? my setup is as follows. zones: #ZONE DISPLAY COMMENTS net Net Internet loc Local Local networks dmz DMZ

Hello, I current have a FreeBSD 4.8 bridge firewall that sits between 7 servers and the internet. The servers are being attacked with syn floods and go down multiple times a day. The 7 servers belong to a client, who runs redhat. I am trying to find a way to do some kind of syn flood protection inside the firewall. Any suggestions would be greatly appreciated. -- Ryan James ryan@mac2.net

...dge_ports bond0 bond-miimon 100 bond-lacp_rate 1 bond-downdelay 200 bond-updelay 200 address 0.0.0.0 netmask 0.0.0.0 *** *** /etc/sysctl.conf #kernel.printk = 3 4 1 3 #net.ipv4.conf.default.rp_filter=1 #net.ipv4.conf.all.rp_filter=1 #net.ipv4.tcp_syncookies=1 net.ipv4.ip_forward=1 #net.ipv4.conf.br0.proxy_arp=1 #net.ipv4.conf.eth0.proxy_arp=1 #net.ipv4.conf.eth1.proxy_arp=1 #net.ipv6.conf.all.forwarding=1 #net.ipv4.conf.all.accept_redirects = 0 #net.ipv6.conf.all.accept_redirects = 0 #net.ipv4.conf.all.send_redirects = 0 #net.ipv4.conf.all.accept_sour...

...blic internet, e.g. 8.8.8.8 the only EM I'm seeing is when executing command : [root at centoshofkwartier ~]# sysctl -p /etc/sysctl.conf net.ipv4.ip_forward = 1 net.ipv4.conf.default.rp_filter = 1 net.ipv4.conf.default.accept_source_route = 0 kernel.sysrq = 0 kernel.core_uses_pid = 1 net.ipv4.tcp_syncookies = 1 error: "net.bridge.bridge-nf-call-ip6tables" is an unknown key error: "net.bridge.bridge-nf-call-iptables" is an unknown key error: "net.bridge.bridge-nf-call-arptables" is an unknown key kernel.msgmnb = 65536 kernel.msgmax = 65536 kernel.shmmax = 68719476736 kerne...

...s ~]# uname -r 2.6.32-042stab108.7 [root at vps ~]# sysctl -a | grep ack_limit net.ipv4.tcp_challenge_ack_limit = 100 [root at vps ~]# vi /etc/sysctl.conf > Append > net.ipv4.tcp_challenge_ack_limit = 999999999 > to end of file [root at vps ~]# sysctl -p net.ipv4.ip_forward = 0 net.ipv4.tcp_syncookies = 1 error: permission denied on key 'net.bridge.bridge-nf-call-ip6tables' error: permission denied on key 'net.bridge.bridge-nf-call-iptables' error: permission denied on key 'net.bridge.bridge-nf-call-arptables' error: permission denied on key 'net.ipv4.tcp_challenge_ac...

.... iptables -F INPUT iptables -F OUTPUT iptables -F FORWARD iptables -F -t nat iptables -F -t mangle #Enabling ip forwarding echo "1" > /proc/sys/net/ipv4/ip_forward #enable syn cookies (prevent against the common 'syn flood attack') echo "1" > /proc/sys/net/ipv4/tcp_syncookies #do source validation by reversed path echo "1" > /proc/sys/net/ipv4/conf/all/rp_filter #Enable tracking mechanism /sbin/modprobe -a ip_conntrack_ftp ip_nat_ftp iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT iptables -A FORWARD -m state --state ESTABLISHED,RELATED...

...it connect to a switch which connect 4 access points (linksys), each giving connection for every eth2 "C" class Along a week I''ve changed my syslog.ctl like: net.ipv4.ip_forward = 1 net.ipv4.icmp_ignore_bogus_error_responses = 1 net.ipv4.icmp_echo_ignore_broadcasts = 1 net.ipv4.tcp_syncookies = 1 net.ipv4.tcp_timestamps = 0 net.ipv4.tcp_window_scaling = 0 net.ipv4.tcp_sack = 0 net.ipv4.tcp_fin_timeout = 30 net.ipv4.tcp_keepalive_time = 1800 net.ipv4.tcp_low_latency = 1 net.ipv4.tcp_ecn = 0 net.ipv4.conf.all.accept_source_route = 0 net.ipv4.conf.all.accept_redirects = 0 net.ipv4.conf.all...

...rce_route = 0 # Controls the System Request debugging functionality of the kernel kernel.sysrq = 0 # Controls whether core dumps will append the PID to the core filename. # Useful for debugging multi-threaded applications. kernel.core_uses_pid = 1 # Controls the use of TCP syncookies net.ipv4.tcp_syncookies = 1 # Disable netfilter on bridges. # Controls the default maxmimum size of a mesage queue kernel.msgmnb = 65536 # Controls the maximum size of a message, in bytes kernel.msgmax = 65536 # Controls the maximum shared segment size, in bytes kernel.shmmax = 68719476736 # Controls the maximum...

...ame>.conf file # # For more information, see sysctl.conf(5) and sysctl.d(5). net.ipv4.ip_forward = 0 kernel.panic = 20 kernel.sem = 250 65000 32 256 vm.swappiness = 10 net.ipv4.conf.all.log_martians = 1 kernel.dmesg_restrict = 1 vm.dirty_ratio = 15 net.ipv6.conf.default.disable_ipv6 = 1 net.ipv4.tcp_syncookies = 1 net.ipv6.conf.all.disable_ipv6 = 1 kernel.kptr_restrict = 1 [root at web-devel-local-1 ~]# systemctl status systemd-sysctl ? systemd-sysctl.service - Apply Kernel Variables Loaded: loaded (/usr/lib/systemd/system/systemd-sysctl.service; static; vendor preset: disabled) Active: active (e...

also in /etc/sysctl.d/ On Thu, Dec 24, 2015 at 8:58 AM, Gordon Messmer <gordon.messmer at gmail.com> wrote: > On 12/23/2015 05:08 AM, Ofer Hasson wrote: > >> By running "systemctl status systemd-sysctl" I also receive the same >> output, but a simple "cat /proc/sys/vm/swappiness" returns the default >> value, and not the one set by my conf file.

...will write also). I guess the read-rate is about 80%. - The filesystem was online extended 2 times after initial setup. - sysctl.conf parameters are set (for the webserver): -- net.ipv4.ip_nonlocal_bind=1 net.ipv4.tcp_fin_timeout=10 net.ipv4.ip_local_port_range=1024 65535 vm.swappiness=10 net.ipv4.tcp_syncookies = 1 net.ipv4.tcp_tw_reuse = 1 net.ipv4.tcp_tw_recycle = 1 -- Now, the problem: The cluster runs well, but some times a day the systemload grows up from ~0-1 to 40, 500, 2000! CPU is fine, no problems. RAM is free, no problems. "ps -e -o pid,stat,comm,wchan=WIDE-WCHAN-COLUMN | grep D" sho...

Good Evening, I am trying to forward packages on an internal device using iptables: /sbin/iptables -A FORWARD -i eth0 -o eth0 -m state --state NEW,RELATED,ESTABLISHED -j ACCEPT but the packages are still blocked, e.g.: Feb 6 20:58:28 firewall kernel: DROP-TCP IN=eth0 OUT=eth0 SRC=192.168.100.177 DST=172.28.2.184 LEN=40 TOS=0x00 PREC=0x00 TTL=127 ID=16609 PROTO=TCP SPT=7166 DPT=3590 WINDOW=0

...found that SYN-ACK generation was moved to tcp_syncache.c I did not managed to find any rfc1948 related info in CVS log for this file. Maybe I just missed it. Then I just looked into my copy of tcp_syncache.c and found that: ;------------------Begin clipboard---------------------------- if (tcp_syncookies) sc->sc_iss = syncookie_generate(sc); else sc->sc_iss = arc4random(); ;--------------------End clipboard---------------------------- Is it the place where synack iss is generated? If yes, then why net.inet.tcp.syncookies sysctl is turned on by default?...

...th0 scope link metric 1002 169.254.0.0/16 dev eth1 scope link metric 1003 default via x.x.x.z dev eth0 </pre> Here is a *sysctl -p* <pre> # sysctl -p net.ipv4.conf.default.rp_filter = 1 net.ipv4.conf.default.accept_source_route = 0 kernel.sysrq = 0 kernel.core_uses_pid = 1 net.ipv4.tcp_syncookies = 1 kernel.msgmnb = 65536 kernel.msgmax = 65536 kernel.shmmax = 68719476736 kernel.shmall = 4294967296 net.ipv4.ip_forward = 1 net.ipv6.conf.all.forwarding = 1 net.ipv4.conf.default.proxy_arp = 1 net.ipv4.conf.all.rp_filter = 1 kernel.sysrq = 1 net.ipv4.conf.default.send_redirects = 1 net.ipv4.conf...

...ngs (Smurf-Amplifier-Protection) echo "1" > /proc/sys/net/ipv4/icmp_echo_ignore_broadcasts #Block source routing echo 0 > /proc/sys/net/ipv4/conf/all/accept_source_route #Kill timestamps echo 0 > /proc/sys/net/ipv4/tcp_timestamps #Enable SYN Cookies echo 1 > /proc/sys/net/ipv4/tcp_syncookies #Kill redirects echo 0 > /proc/sys/net/ipv4/conf/all/accept_redirects #Enable bad error message protection echo 1 > /proc/sys/net/ipv4/icmp_ignore_bogus_error_responses #Log martians (packets with impossible addresses) echo 1 > /proc/sys/net/ipv4/conf/all/log_martians # 3.2 Non-Required p...

...ages previous to linux-2.4.2-14S OpenLinux Workstation 3.1 All packages previous to linux-2.4.2-14D 3. Solution Workaround Disable syncookies by doing: echo -n 0 > /proc/sys/net/ipv4/tcp_syncookies The proper solution is to upgrade to the latest packages. 4. OpenLinux 2.3 4.1 Location of Fixed Packages The upgrade packages can be found on Caldera's FTP site at: ftp://ftp.caldera.com/pub/updates/OpenLinux/2.3/current/RPMS The corresponding source code pack...

...et line isn''t loaded up, server load fine. QOS isn''t used, qdiscs default. I don''t realize what the problem is and even how to debug it. Sysctl config: net/ipv4/ip_forward = 1 net/ipv4/icmp_ignore_bogus_error_responses = 1 net/ipv4/icmp_echo_ignore_broadcasts = 1 net/ipv4/tcp_syncookies = 1 net/ipv4/tcp_timestamps = 0 net/ipv4/tcp_window_scaling = 0 net/ipv4/tcp_sack = 0 net/ipv4/tcp_fin_timeout = 30 net/ipv4/tcp_keepalive_time = 1800 net/ipv4/tcp_low_latency = 1 Thanks for any thoughts. _______________________________________________ LARTC mailing list / LARTC@mailman.ds9a.nl...

...aight (domain->ip) and reverse (address->ip).It is well tested. Also i've made /etc/hosts and /etc/samba/lmhosts files. They contains same ip=domain setup as named. Next thing was an firewall on my server (smbd and nmbd runs on it) but i found that it does not matter. Even turning off tcp_syncookies and rp_filter. Without success. I have found an article suggesting that windows xp firewall is to blame. I dont think it is a true, because workstations runs diffrent types of firewall. One of them use windows firewall but others use another firewalling sollution. Both of theese disapear from...

https://bugzilla.netfilter.org/cgi-bin/bugzilla/show_bug.cgi?id=40 laforge@netfilter.org changed: What |Removed |Added ---------------------------------------------------------------------------- Status|NEW |ASSIGNED ------- Additional Comments From laforge@netfilter.org 2003-02-03 16:49 ------- We haven't seen this