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  • How do you return stolen packets back to Netfilter

    - by meg18019
    Let's say I have intercepted a packet from Netfilter and subsequently returned NF_STOLEN. At some point I want to re-inject that packet back to, in this case, the TCP stream it came from. I want to do this from Kernel space. So far I have been unable to find a way to do this. Thanks for the help.

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  • error: "net.netfilter.nf_conntrack_acct" is an unknown key

    - by anonymous
    Hello, i have the next error when i run 'sysctl -p' error: "net.netfilter.nf_conntrack_acct" is an unknown key net.netfilter.nf_conntrack_acct = 1 net.ipv4.netfilter.ip_conntrack_max = 9527600 net.ipv4.netfilter.ip_conntrack_tcp_timeout_established = 7200 lsmod ipv6 289352 34 loop 19724 0 nf_conntrack_ipv4 19352 0 nf_conntrack 71440 1 nf_conntrack_ipv4 joydev 15232 0 evdev 14592 0 ext3 125456 3 jbd 54696 1 ext3 mbcache 13188 1 ext3 raid1 24832 4 md_mod 81700 5 raid1 thermal_sys 17728 0 Debian 5.0.8 Any idea? Thanks

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  • openstack, bridging, netfilter and dnat

    - by Craig Sanders
    In a recent upgrade (from Openstack Diablo on Ubuntu Lucid to Openstack Essex on Ubuntu Precise), we found that DNS packets were frequently (almost always) dropped on the bridge interface (br100). For our compute-node hosts, that's a Mellanox MT26428 using the mlx4_en driver module. We've found two workarounds for this: Use an old lucid kernel (e.g. 2.6.32-41-generic). This causes other problems, in particular the lack of cgroups and the old version of the kvm and kvm_amd modules (we suspect the kvm module version is the source of a bug we're seeing where occasionally a VM will use 100% CPU). We've been running with this for the last few months, but can't stay here forever. With the newer Ubuntu Precise kernels (3.2.x), we've found that if we use sysctl to disable netfilter on bridge (see sysctl settings below) that DNS started working perfectly again. We thought this was the solution to our problem until we realised that turning off netfilter on the bridge interface will, of course, mean that the DNAT rule to redirect VM requests for the nova-api-metadata server (i.e. redirect packets destined for 169.254.169.254:80 to compute-node's-IP:8775) will be completely bypassed. Long-story short: with 3.x kernels, we can have reliable networking and broken metadata service or we can have broken networking and a metadata service that would work fine if there were any VMs to service. We haven't yet found a way to have both. Anyone seen this problem or anything like it before? got a fix? or a pointer in the right direction? Our suspicion is that it's specific to the Mellanox driver, but we're not sure of that (we've tried several different versions of the mlx4_en driver, starting with the version built-in to the 3.2.x kernels all the way up to the latest 1.5.8.3 driver from the mellanox web site. The mlx4_en driver in the 3.5.x kernel from Quantal doesn't work at all) BTW, our compute nodes have supermicro H8DGT motherboards with built-in mellanox NIC: 02:00.0 InfiniBand: Mellanox Technologies MT26428 [ConnectX VPI PCIe 2.0 5GT/s - IB QDR / 10GigE] (rev b0) we're not using the other two NICs in the system, only the Mellanox and the IPMI card are connected. Bridge netfilter sysctl settings: net.bridge.bridge-nf-call-arptables = 0 net.bridge.bridge-nf-call-iptables = 0 net.bridge.bridge-nf-call-ip6tables = 0 Since discovering this bridge-nf sysctl workaround, we've found a few pages on the net recommending exactly this (including Openstack's latest network troubleshooting page and a launchpad bug report that linked to this blog-post that has a great description of the problem and the solution)....it's easier to find stuff when you know what to search for :), but we haven't found anything on the DNAT issue that it causes.

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  • performance block countries using iptables /netfilter

    - by markus
    It's easy to block IPs from country using iptables (e.g. like http://www.cyberciti.biz/faq/block-entier-country-using-iptables/). However I read that the performance can go down if the deny list get too large. An alternative is installing the iptables geoip patch or using ipset ( http://www.jsimmons.co.uk/2010/06/08/using-ipset-with-iptables-in-ubuntu-lts-1004-to-block-large-ip-ranges/) instead of iptables. Does anyone have experience with the various approaches and can say something about the performance differences ? Are there are other ways to block country IPs in linux which I did't mentioned above?

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  • Slow manipulation of netfilter rules

    - by Ole Martin Eide
    I have a script maintaining gre tunnels and firewall rules using the "ip" and "iptables" tools. Setting up hundreds of tunnels, and adresses per interface runs just fine. Takes less than 0.1 second per interface, however when I get around to do the firewall rules everything slows down spending 0.5 per insertion. Why is it running so slow? What can I do to improve the speed? It seems like I could try ipset instead, but I really feel there is something wrong with the kernel or something. The interesting thing is that the first 10 rules runs fast, then it slows down.. mybox(root) foo# iptables -V iptables v1.3.5 mybox(root) foo# uname -a Linux foo 2.6.18-164.el5 #1 SMP Tue Aug 18 15:51:48 EDT 2009 x86_64 x86_64 x86_64 GNU/Linux mybox(root) foo# cat test.sh #!/bin/sh for n in {1..100} do /sbin/iptables -A OUTPUT -s ${n} -j ACCEPT /sbin/iptables -D OUTPUT -s ${n} -j ACCEPT done mybox(root) foo# time ./test.sh real 1m38.839s user 0m0.100s sys 1m38.724s Appriciate any help. Cheers!

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  • sysctl.conf ignore net settings

    - by Steffen Unland
    I have a little problem with sysctl on a Ubuntu 10.04 LTS system. When I set the sysctl values with "sysctl -w " all work fine, but when I try to use the sysctl.conf file. the net settings will be ignored. For example my sysctl.conf # /etc/sysctl.conf - Configuration file for setting system variables kernel.domainname=findme.sysctl # Corefiles information fs.suid_dumpable=2 kernel.core_pattern=/cores/core-%e-%s-%u-%g-%p-%t ##############################################################3 # Functions previously found in netbase net.ipv4.netfilter.ip_conntrack_tcp_timeout_fin_wait=1 net.ipv4.netfilter.ip_conntrack_tcp_timeout_close_wait=1 when I grep to the values, I can see that the sysctl settings for net.ipv4.netfilter don't set. [host:~ ] $ sysctl -a | grep domainname kernel.domainname = findme.sysctl [host:~ ] $ sysctl -a | grep "core_pattern" kernel.core_pattern = /cores/core-%e-%s-%u-%g-%p-%t [host:~ ] $ sysctl -a | grep "timeout_fin_wait" net.netfilter.nf_conntrack_tcp_timeout_fin_wait = 120 net.ipv4.netfilter.ip_conntrack_tcp_timeout_fin_wait = 120 [host:~ ] $ sysctl -a | grep "timeout_close_wait" net.netfilter.nf_conntrack_tcp_timeout_close_wait = 60 net.ipv4.netfilter.ip_conntrack_tcp_timeout_close_wait = 60 can somebody help me to solve the problem? If you need more information I can post it. Cheers, Steffen

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  • Linux IPTables / routing issue

    - by Jon
    Hi all, EDIT 1/3/10 22:00 GMT - rewrote some of it after further investigation It has been a while since I looked at IPtables and I seem to be worse than before as I can not seem to get my webserver online. Below is my firewall rules on the gateway server that is running the dhcp server accessing the net. The webserver is inside my network on a static IP (192.168.0.98, default port). When I use Nmap or GRC.com I see that port 80 is open on the gateway server but when I browse to it, (via public URL. http://www.houseofhawkins.com) it always fails with a connection error, (nmap cannot connect and figure out what the web server is either). I can nmap the webserver and browse to it just fine via same IP inside my network. I believe it is my IPTable rules that are not letting it through. Internally I can route all my requests. Each machine can browse to the website and traffic works just fine. I can MSTSC / ssh to all the webservers internally and they inturn can connect to the web. IPTABLE: *EDIT - Added new firewall rules 2/3/10 * #!/bin/sh iptables="/sbin/iptables" modprobe="/sbin/modprobe" depmod="/sbin/depmod" EXTIF="eth2" INTIF="eth1" load () { $depmod -a $modprobe ip_tables $modprobe ip_conntrack $modprobe ip_conntrack_ftp $modprobe ip_conntrack_irc $modprobe iptable_nat $modprobe ip_nat_ftp echo "enable forwarding.." echo "1" > /proc/sys/net/ipv4/ip_forward echo "enable dynamic addr" echo "1" > /proc/sys/net/ipv4/ip_dynaddr # start firewall # default policies $iptables -P INPUT DROP $iptables -F INPUT $iptables -P OUTPUT DROP $iptables -F OUTPUT $iptables -P FORWARD DROP $iptables -F FORWARD $iptables -t nat -F #echo " Opening loopback interface for socket based services." $iptables -A INPUT -i lo -j ACCEPT $iptables -A OUTPUT -o lo -j ACCEPT #echo " Allow all connections OUT and only existing and related ones IN" $iptables -A INPUT -i $INTIF -j ACCEPT $iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT $iptables -A OUTPUT -o $EXTIF -j ACCEPT $iptables -A OUTPUT -m state --state ESTABLISHED,RELATED -j ACCEPT $iptables -A FORWARD -i $EXTIF -o $INTIF -m state --state ESTABLISHED,RELATED -j ACCEPT $iptables -A FORWARD -i $INTIF -o $EXTIF -j ACCEPT $iptables -A FORWARD -j LOG --log-level 7 --log-prefix "Dropped by firewall: " $iptables -A INPUT -j LOG --log-level 7 --log-prefix "Dropped by firewall: " $iptables -A OUTPUT -j LOG --log-level 7 --log-prefix "Dropped by firewall: " #echo " Enabling SNAT (MASQUERADE) functionality on $EXTIF" $iptables -t nat -A POSTROUTING -o $EXTIF -j MASQUERADE $iptables -A INPUT -i $INTIF -j ACCEPT $iptables -A OUTPUT -o $INTIF -j ACCEPT #echo " Allowing packets with ICMP data (i.e. ping)." $iptables -A INPUT -p icmp -j ACCEPT $iptables -A OUTPUT -p icmp -j ACCEPT $iptables -A INPUT -p udp -i $INTIF --dport 67 -m state --state NEW -j ACCEPT #echo " Port 137 is for NetBIOS." $iptables -A INPUT -i $INTIF -p udp --dport 137 -j ACCEPT $iptables -A OUTPUT -o $INTIF -p udp --dport 137 -j ACCEPT #echo " Opening port 53 for DNS queries." $iptables -A INPUT -p udp -i $EXTIF --sport 53 -j ACCEPT #echo " opening Apache webserver" $iptables -A PREROUTING -t nat -i $EXTIF -p tcp --dport 80 -j DNAT --to 192.168.0.96:80 $iptables -A FORWARD -p tcp -m state --state NEW -d 192.168.0.96 --dport 80 -j ACCEPT } flush () { echo "flushing rules..." $iptables -P FORWARD ACCEPT $iptables -F INPUT $iptables -P INPUT ACCEPT echo "rules flushed" } case "$1" in start|restart) flush load ;; stop) flush ;; *) echo "usage: start|stop|restart." ;; esac exit 0 route info: Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 5e0412a6.bb.sky * 255.255.255.255 UH 0 0 0 eth2 192.168.0.0 * 255.255.255.0 U 0 0 0 eth1 default 5e0412a6.bb.sky 0.0.0.0 UG 100 0 0 eth2 ifconfig: eth1 Link encap:Ethernet HWaddr 00:22:b0:cf:4a:1c inet addr:192.168.0.1 Bcast:192.168.0.255 Mask:255.255.255.0 inet6 addr: fe80::222:b0ff:fecf:4a1c/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:79023 errors:0 dropped:0 overruns:0 frame:0 TX packets:57786 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:11580918 (11.5 MB) TX bytes:22872030 (22.8 MB) Interrupt:17 Base address:0x2b00 eth2 Link encap:Ethernet HWaddr 00:0c:f1:7c:45:5b inet addr:94.4.18.166 Bcast:94.4.18.166 Mask:255.255.255.255 inet6 addr: fe80::20c:f1ff:fe7c:455b/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:57038 errors:0 dropped:0 overruns:0 frame:0 TX packets:34532 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:21631721 (21.6 MB) TX bytes:7685444 (7.6 MB) lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:16 errors:0 dropped:0 overruns:0 frame:0 TX packets:16 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:1517 (1.5 KB) TX bytes:1517 (1.5 KB) EDIT OK so as requested I will try and expand on my infrastructure: I previously had it setup with a Sky broadband modem router that did the DHCP and I used its web interface to port forward the web across to the web server. The network looked something like this: I have now replaced the sky modem with a dlink modem which gives the IP to the gateway server that now does the DHCP. It looks like: The internet connection is a standard broadband connection with a dynamic IP, (use zoneedit.com to keep it updated). I have tried it on each of the webservers(one Ubuntu Apache server and one WS2008 IIS7). I think there must also be an issue with my IPTable rules as it can route to my win7 box which has the default IIS7 page and that would not display when I forwarded all port 80 to it. I would be really grateful for any and all help with this. Thanks Jon

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  • Configuring my Linux firewall for Tomcat

    - by David Pinn
    I'm following some instructions for Installing Tomcat. They require me to add the following line to my iptables file: -A RH-Lokkit-0-50-INPUT -p tcp -m tcp --dport 8080 --syn -j ACCEPT Having carefully read the man page for iptables, I have learned what the parameters do, except for the first one. What does -A RH-Lokkit-0-50-INPUT do, and can you confirm that it is sensible in this case?

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  • How to configure iptables to use apt-get in a server?

    - by segaco
    I'm starting using iptables (newbie) to protect a linux server (specifically Debian 5.0). Before I configure the iptables settings, I can use apt-get without a problem. But after I configure the iptables, the apt-get stop working. For example I use this script in iptables: #!/bin/sh IPT=/sbin/iptables ## FLUSH $IPT -F $IPT -X $IPT -t nat -F $IPT -t nat -X $IPT -t mangle -F $IPT -t mangle -X $IPT -P INPUT DROP $IPT -P OUTPUT DROP $IPT -P FORWARD DROP $IPT -A INPUT -i lo -j ACCEPT $IPT -A OUTPUT -o lo -j ACCEPT $IPT -A INPUT -p tcp --dport 22 -j ACCEPT $IPT -A OUTPUT -p tcp --sport 22 -j ACCEPT $IPT -A INPUT -p tcp --dport 80 -j ACCEPT $IPT -A OUTPUT -p tcp --sport 80 -j ACCEPT $IPT -A INPUT -p tcp --dport 443 -j ACCEPT $IPT -A OUTPUT -p tcp --sport 443 -j ACCEPT # Allow FTP connections @ port 21 $IPT -A INPUT -p tcp --sport 21 -m state --state ESTABLISHED -j ACCEPT $IPT -A OUTPUT -p tcp --dport 21 -m state --state NEW,ESTABLISHED -j ACCEPT # Allow Active FTP Connections $IPT -A INPUT -p tcp --sport 20 -m state --state ESTABLISHED,RELATED -j ACCEPT $IPT -A OUTPUT -p tcp --dport 20 -m state --state ESTABLISHED -j ACCEPT # Allow Passive FTP Connections $IPT -A INPUT -p tcp --sport 1024: --dport 1024: -m state --state ESTABLISHED -j ACCEPT $IPT -A OUTPUT -p tcp --sport 1024: --dport 1024: -m state --state ESTABLISHED,RELATED -j ACCEPT #DNS $IPT -A OUTPUT -p udp --dport 53 --sport 1024:65535 -j ACCEPT $IPT -A INPUT -p tcp --dport 1:1024 $IPT -A INPUT -p udp --dport 1:1024 $IPT -A INPUT -p tcp --dport 3306 -j DROP $IPT -A INPUT -p tcp --dport 10000 -j DROP $IPT -A INPUT -p udp --dport 10000 -j DROP then when I run apt-get I obtain: core:~# apt-get update 0% [Connecting to ftp.us.debian.org] [Connecting to security.debian.org] [Conne and it stalls. What rules I need to configure to make it works. Thanks

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  • How to filter and intercept Linux packets by using net_dev_add() API?

    - by Khajavi
    I'm writing ethernet network driver for linux. I want to receive packets, edit and resend them. I know how to edit the packet in packet_interceptor function, but how can I drop incoming packets in this function?? #include <linux/netdevice.h> #include <linux/skbuff.h> #include <linux/ip.h> #include <net/sock.h> struct packet_type my_proto; int packet_interceptor(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt, struct net_device *orig_dev) { // I dont want certain packets go to upper in net_devices for further processing. // How can I drop sk_buff here?! return 0; } static int hello_init( void ) { printk(KERN_INFO "Hello, world!\n"); my_proto.type = htons(ETH_P_ALL); my_proto.dev = NULL; my_proto.func = packet_interceptor; dev_add_pack(&my_proto); return 0; } static void hello_exit(void) { dev_remove_pack(&my_proto); printk(KERN_INFO "Bye, world\n"); } module_init(hello_init); module_exit(hello_exit);

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  • logging conntrack connection values into log file

    - by seaquest
    Linux netfilter iptables Conntrack table already has records for bytes and packets on both directions. Is there any way to log those values to a log file while a connection is closing by netfilter. tcp 6 430619 ESTABLISHED src=192.168.0.145 dst=33.42.42.42 sport=53601 dport=22 packets=66560 bytes=14800077 src=33.42.42.42 dst=192.168.1.2 sport=22 dport=53601 packets=89726 bytes=68403910 [ASSURED] mark=0 use=1

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  • 32bit domU on 64bit dom0

    - by ModuleC
    I'm using 64bit Centos Dom0 with: 2.6.18-164.15.1.el5xen #1 SMP Wed Mar 17 12:04:23 EDT 2010 x86_64 x86_64 x86_64 GNU/Linux recently i migrated some 32bit Centos domUs on this node. As by specs 32bit domUs should work with 64bit dom0. DomUs are paravirtualized, and everything works, except iptables limit. Anyways runing csf on domU will return following messages in dmesg: ip_tables: (C) 2000-2006 Netfilter Core Team Netfilter messages via NETLINK v0.30. ip_conntrack version 2.4 (2080 buckets, 16640 max) - 304 bytes per conntrack ip_tables: limit match: invalid size 40 != 28 ip_tables: limit match: invalid size 40 != 28 ip_tables: limit match: invalid size 40 != 28 ip_tables: limit match: invalid size 40 != 28 ip_tables: limit match: invalid size 40 != 28 ip_tables: limit match: invalid size 40 != 28 ip_tables: limit match: invalid size 40 != 28 Doing lsmod on both dom0 and domU is listing all iptables modules required as loaded. I've found this http://www.mail-archive.com/[email protected]/msg189433.html But didn't find anything for centos on this issue. Am I missing something?

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  • iproute2 premptive route creation, i think....

    - by Bryan Hunt
    Firstly: I know could do this the easy way with SSH but I want to learn how to route. I want to route packets back through the same tun0 interface from which they came into my system. I can do it for single routes. This works: sudo ip route add 74.52.23.120 metric 2 via 10.8.0.1 But i'd have to add them manually for each request that came down the pipe I've taken the blue pill and followed the http://lartc.org/howto/lartc.netfilter.html: Netfilter & iproute - marking packets tutorial But it's oriented towards redirecting OUTGOING packets based upon markers What I want is for a packet that comes in via tun0 not to be dropped which is what's happening right now, running scappy or suchlike to receive packets it doesn't seem to be receiving anything. Watching in wireshark I see the initial SYN packets coming in on the tun0 interface but that's as far as it gets without a static route as shown above. Am I nuts?

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  • books about Firewall development

    - by VP
    Hi, i was just asked today, but i couldn't answer precisely so that's why i'm asking here :-) There is any book about Firewall design and implementations (Unix environment and C)? For sure, i could recommend TCP/IP books, and what i did, but there is some design decisions, that are not related with TCP/IP. For sure, i said about the netfilter/iptables (RTFSC) but as well we cannot assume that the netfilter/iptables is the best approach since we don't have too many baselines (ok, we could compare it with PF, but again, read source code to understand design decisions is not always the best way). So if anybody knows a book about this theme, please shoot it!

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  • Using u32 together with extension headers (how to jump over them?)

    - by bortzmeyer
    I'm trying to filter on some parts of the payload, for an IPv6 packet with extension headers (for instance Destination Options). ip6tables works fine with conditions like --proto udp or --dport 109, even when the packet has extension headers. Netfilter clearly knows how to jump over Destination Options to find the UDP header. Now, I would like to use the u32 module to match a byte in the payload (say "I want the third byte of the payload to be 42). If the packet has no extension headers something like --u32 "48&0x0000ff00=0x2800"` (48 = 40 bytes for the IPv6 header + 8 for the UDP header) works fine, If the packet has a Destination Options, it no longer matches. I would like to write a rule that will work whether the packet has Destination Options or not. I do not find a way to tell Netfilter to parse until the UDP header (something that it is able to do, otherwise --dport 109 would not work) then to leave u32 parse the rest. I'm looking for a simple way, otherwise, as BatchyX mentions, I could write a kernel module doing what I want.

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  • Will running CSF & Bastille cause any conflicts?

    - by MatW
    I'm taking my first steps into the world of un-managed servers, and have confused myself whilst reading through the 101 tutorials on server hardening that Google spews out! The most recent advice I have been given is to install both CSF and Bastille on my server (used to serve a consumer-facing ecommerce site and act as the business' email server), but my understanding was that both of these tools were an abstraction layer above netfilter / iptables. Will installing both packages cause any conflicts, or do they play well together?

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  • Is there a decent diagram of packet flow for a modern era (2.6+) iptables setup?

    - by stsquad
    I'm currently trying to debug a particularly hairy set of DNAT based iptables rules (the UDP reply never makes it back to the original requester) and I'm struggling to visualise the packet flow through all the numerous tables involved. So far Google'ing has shown me old 2.4 based ipchains ones. The netfilter site has some good text docs but is short on diagrams and a number of the external links are now dead. So is there a canonical diagram for iptables packet flow, preferably showing how NAT/Masqueraded packets are also dealt with?

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  • ipv6 just wont go away 12.10 server

    - by VladoPortos
    After very long time using Ubuntu old LTS version I have re-installed to new LTS 12.10, but I can't get rid of ipv6 ! I have did: in /etc/modprobe.d/blacklist.conf: blacklist ipv6 blacklist ip6table_filter blacklist ip6_tables in /etc/sysctl.conf net.ipv6.conf.all.disable_ipv6 = 1 net.ipv6.conf.default.disable_ipv6 = 1 net.ipv6.conf.lo.disable_ipv6 = 1 But ufw happily use v6 protocol, and in dmesg: ip6_tables: (C) 2000-2006 Netfilter Core Team . . IPv6: ADDRCONF(NETDEV_CHANGE): em1: link becomes ready What is going to take to get rid of IPv6 ? I swear Terminator didn't put so much fight.

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  • enable iptables firewall on linux

    - by user13278061
     Here is a very basic set of instruction to setup a simple iptables firewall configuration on linux (redhat) Enable firewall log as root thenenter the following command, it launch a text gui #> setup first screen: Choose firewall configuration second screen: choose "Enabled" then "Customize" third screen: select you interface in "Trusted Devices", select "Allow Incoming" for "SSH" "Telnet" "FTP" (add eventually other ports, then press "OK" (2 times, then "Quit") At that point the firewall is enabled. You can start/stop/monitor using service iptables start/stop/status Change timeout to changed the tcp established connection timeout #> echo 120 >    /proc/sys/net/ipv4/netfilter/ip_conntrack_tcp_timeout_established Monitor connection in iptables tables for example if you want to track a connection establish from a host  152.68.65.207 #> cat /proc/net/ip_conntrack |grep 152.68.65.207

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  • Diagnosing packet loss / high latency in Ubuntu

    - by Sam Gammon
    We have a Linux box (Ubuntu 12.04) running Nginx (1.5.2), which acts as a reverse proxy/load balancer to some Tornado and Apache hosts. The upstream servers are physically and logically close (same DC, sometimes same-rack) and show sub-millisecond latency between them: PING appserver (10.xx.xx.112) 56(84) bytes of data. 64 bytes from appserver (10.xx.xx.112): icmp_req=1 ttl=64 time=0.180 ms 64 bytes from appserver (10.xx.xx.112): icmp_req=2 ttl=64 time=0.165 ms 64 bytes from appserver (10.xx.xx.112): icmp_req=3 ttl=64 time=0.153 ms We receive a sustained load of about 500 requests per second, and are currently seeing regular packet loss / latency spikes from the Internet, even from basic pings: sam@AM-KEEN ~> ping -c 1000 loadbalancer PING 50.xx.xx.16 (50.xx.xx.16): 56 data bytes 64 bytes from loadbalancer: icmp_seq=0 ttl=56 time=11.624 ms 64 bytes from loadbalancer: icmp_seq=1 ttl=56 time=10.494 ms ... many packets later ... Request timeout for icmp_seq 2 64 bytes from loadbalancer: icmp_seq=2 ttl=56 time=1536.516 ms 64 bytes from loadbalancer: icmp_seq=3 ttl=56 time=536.907 ms 64 bytes from loadbalancer: icmp_seq=4 ttl=56 time=9.389 ms ... many packets later ... Request timeout for icmp_seq 919 64 bytes from loadbalancer: icmp_seq=918 ttl=56 time=2932.571 ms 64 bytes from loadbalancer: icmp_seq=919 ttl=56 time=1932.174 ms 64 bytes from loadbalancer: icmp_seq=920 ttl=56 time=932.018 ms 64 bytes from loadbalancer: icmp_seq=921 ttl=56 time=6.157 ms --- 50.xx.xx.16 ping statistics --- 1000 packets transmitted, 997 packets received, 0.3% packet loss round-trip min/avg/max/stddev = 5.119/52.712/2932.571/224.629 ms The pattern is always the same: things operate fine for a while (<20ms), then a ping drops completely, then three or four high-latency pings (1000ms), then it settles down again. Traffic comes in through a bonded public interface (we will call it bond0) configured as such: bond0 Link encap:Ethernet HWaddr 00:xx:xx:xx:xx:5d inet addr:50.xx.xx.16 Bcast:50.xx.xx.31 Mask:255.255.255.224 inet6 addr: <ipv6 address> Scope:Global inet6 addr: <ipv6 address> Scope:Link UP BROADCAST RUNNING MASTER MULTICAST MTU:1500 Metric:1 RX packets:527181270 errors:1 dropped:4 overruns:0 frame:1 TX packets:413335045 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:240016223540 (240.0 GB) TX bytes:104301759647 (104.3 GB) Requests are then submitted via HTTP to upstream servers on the private network (we can call it bond1), which is configured like so: bond1 Link encap:Ethernet HWaddr 00:xx:xx:xx:xx:5c inet addr:10.xx.xx.70 Bcast:10.xx.xx.127 Mask:255.255.255.192 inet6 addr: <ipv6 address> Scope:Link UP BROADCAST RUNNING MASTER MULTICAST MTU:1500 Metric:1 RX packets:430293342 errors:1 dropped:2 overruns:0 frame:1 TX packets:466983986 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:77714410892 (77.7 GB) TX bytes:227349392334 (227.3 GB) Output of uname -a: Linux <hostname> 3.5.0-42-generic #65~precise1-Ubuntu SMP Wed Oct 2 20:57:18 UTC 2013 x86_64 GNU/Linux We have customized sysctl.conf in an attempt to fix the problem, with no success. Output of /etc/sysctl.conf (with irrelevant configs omitted): # net: core net.core.netdev_max_backlog = 10000 # net: ipv4 stack net.ipv4.tcp_ecn = 2 net.ipv4.tcp_sack = 1 net.ipv4.tcp_fack = 1 net.ipv4.tcp_tw_reuse = 1 net.ipv4.tcp_tw_recycle = 0 net.ipv4.tcp_timestamps = 1 net.ipv4.tcp_window_scaling = 1 net.ipv4.tcp_no_metrics_save = 1 net.ipv4.tcp_max_syn_backlog = 10000 net.ipv4.tcp_congestion_control = cubic net.ipv4.ip_local_port_range = 8000 65535 net.ipv4.tcp_syncookies = 1 net.ipv4.tcp_synack_retries = 2 net.ipv4.tcp_thin_dupack = 1 net.ipv4.tcp_thin_linear_timeouts = 1 net.netfilter.nf_conntrack_max = 99999999 net.netfilter.nf_conntrack_tcp_timeout_established = 300 Output of dmesg -d, with non-ICMP UFW messages suppressed: [508315.349295 < 19.852453>] [UFW BLOCK] IN=bond1 OUT= MAC=<mac addresses> SRC=118.xx.xx.143 DST=50.xx.xx.16 LEN=68 TOS=0x00 PREC=0x00 TTL=51 ID=43221 PROTO=ICMP TYPE=3 CODE=1 [SRC=50.xx.xx.16 DST=118.xx.xx.143 LEN=40 TOS=0x00 PREC=0x00 TTL=249 ID=10220 DF PROTO=TCP SPT=80 DPT=53817 WINDOW=8190 RES=0x00 ACK FIN URGP=0 ] [517787.732242 < 0.443127>] Peer 190.xx.xx.131:59705/80 unexpectedly shrunk window 1155488866:1155489425 (repaired) How can I go about diagnosing the cause of this problem, on a Debian-family Linux box?

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  • How do I enable SELinux when booting a ramdisk from a CD/DVD?

    - by JeffG
    I have a bootable DVD which boots the same Kernel as the Hard Drive (which uses SELinux). I have copied /etc/selinux and all kernel modules to my ramdisk, and have tried various combinations of selinux=1 and selinux 1 with enforcing 1 and enforcing 0. as Kernel boot parameters. All files contained in the checkpolicy, libselinux, policycoreutils, selinux-policy and selinux-policy-targeted rpms have also been copied into the ramdisk tree. After the system boots from the ramdisk, I check dmesg: % dmesg | grep -i selinux Kernel command line: initrd=idrd.img ramdisk_size=110476 selinux=1 SELinux: Initializing. SELinux: Starting in permissive mode selinux_register_security: Registering secondary module capability SElinux: Registering netfilter hooks But SELinux isn't running: % /usr/sbin/getenforce Disabled % /usr/sbin/setenforce 1 /usr/sbin/setenforce: SELinux is disabled Neither /var/log/messages nor /proc/kmsg hold clues.

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