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• IIS not responding with SSL Server Hello

  - by Damien_The_Unbeliever

  I'm having difficulty getting a particular IIS machine to "do" SSL. This is a test environment (one of many) which we've set up "the same" as we have many times previously, but it just doesn't seem to be working. The server is Windows Server 2003 (Version 5.2 (Build 3790.srv03_sp2_gdr.100216-1301 : Service Pack 2)) IIS is hosting 4 sites (including the default site), but only one site is configured for SSL. We're using the same SSL certificate we use on all of our other servers (it's a wildcard cert). (Don't think this is relevant, but including anyway) We've configured the site to require SSL, it has a subdirectory that doesn't require SSL but has an asp page that redirects into SSL. The 403;4 error page for the site is hooked up to this asp page (this is how we do our non-HTTPS into HTTPS transition). Using Microsoft Network Monitor (3.3), I've just run a session against a server where SSL is working. It can pull apart the SSL exchange as the following messages: SSL: Client Hello SSL: Server Hello. Certificate. Server Hello Done SSL: Client Key Exchange. Change Cipher Spec. Encrypted Handshake Message. SSL: Change Cipher Spec. Encrypted Handshake Message However, on our problem server, I only see: SSL: Client Hello. The next packet from the server (from port 443, so it's listening and responding there) contains only 60 bytes, and just seems to have the Tcp headers and not much else (but I'm by no means an expert at deciphering these things). So, where do I look next? Or what additional information do I need to add to this question, and where do I find it?

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• iptables to block VPN-traffic if not through tun0

  - by dacrow

  I have a dedicated Webserver running Debian 6 and some Apache, Tomcat, Asterisk and Mail-stuff. Now we needed to add VPN support for a special program. We installed OpenVPN and registered with a VPN provider. The connection works well and we have a virtual tun0 interface for tunneling. To archive the goal for only tunneling a single program through VPN, we start the program with sudo -u username -g groupname command and added a iptables rule to mark all traffic coming from groupname iptables -t mangle -A OUTPUT -m owner --gid-owner groupname -j MARK --set-mark 42 Afterwards we tell iptables to to some SNAT and tell ip route to use special routing table for marked traffic packets. Problem: if the VPN failes, there is a chance that the special to-be-tunneled program communicates over the normal eth0 interface. Desired solution: All marked traffic should not be allowed to go directly through eth0, it has to go through tun0 first. I tried the following commands which didn't work: iptables -A OUTPUT -m owner --gid-owner groupname ! -o tun0 -j REJECT iptables -A OUTPUT -m owner --gid-owner groupname -o eth0 -j REJECT It might be the problem, that the above iptable-rules didn't work due to the fact, that the packets are first marked, then put into tun0 and then transmitted by eth0 while they are still marked.. I don't know how to de-mark them after in tun0 or to tell iptables, that all marked packet may pass eth0, if they where in tun0 before or if they going to the gateway of my VPN provider. Does someone has any idea to a solution? Some config infos: iptables -nL -v --line-numbers -t mangle Chain OUTPUT (policy ACCEPT 11M packets, 9798M bytes) num pkts bytes target prot opt in out source destination 1 591K 50M MARK all -- * * 0.0.0.0/0 0.0.0.0/0 owner GID match 1005 MARK set 0x2a 2 82812 6938K CONNMARK all -- * * 0.0.0.0/0 0.0.0.0/0 owner GID match 1005 CONNMARK save iptables -nL -v --line-numbers -t nat Chain POSTROUTING (policy ACCEPT 393 packets, 23908 bytes) num pkts bytes target prot opt in out source destination 1 15 1052 SNAT all -- * tun0 0.0.0.0/0 0.0.0.0/0 mark match 0x2a to:VPN_IP ip rule add from all fwmark 42 lookup 42 ip route show table 42 default via VPN_IP dev tun0

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• Routing / binding 128 IPs to one server

  - by Andrew

  I have a Ubuntu server with 128 ip's (static external ips 86.xx.xx.16), and I want to crawl pages thru different ip's. The gateway is xx.xxx.xxx.1, the main ip is xx.xxx.xxx.16, and the other 128 ip's are xx.xxx.xxx.129/255. I tried this configuration in /etc/network/interfaces but I doesn't work. It work if I remove the gateway for the aliases eth0:0 and eth0:1. I think this is routing problem. auto lo iface lo inet loopback auto eth0 auto eth0:0 auto eth0:1 iface eth0 inet static address xx.xxx.xxx.16 netmask 255.255.255.128 gateway xx.xxx.xxx.1 iface eth0:0 inet static address xx.xxx.xxx.129 netmask 255.255.255.128 gateway xx.xxx.xxx.1 iface eth0:1 inet static address xx.xxx.xxx.130 netmask 255.255.255.128 gateway xx.xxx.xxx.1 Also, please tell me how to "reset" every changes that I made in networking and routing. Update: I removed the gateway and now it works. I can reach the website thru all 128 ip's. But when I try to bind a socket connection in php to a specific ip I get no answer. socket_bind($sock, "xx.xxx.xx.xxx"); socket_connect($sock, 'google.com', 80); I tryed to use a sniffer to see the packets, and I see the packet sent from binded ip to google.com but the "connection" can't be established. I don't know anything about "route" command, but I have a feeling that this is the solution.

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• Looking for a real DisplayPort hub/splitter

  - by squircle

  In my search for a new display, I came across the Dell Multi-Monitor Hub MMH11, which seemed to be an alternative to my search for daisy-chainable DisplayPort displays. However, before I cave and spend $179 on this device, I am wondering if this will be similar to other splitting devices where it appears to the computer as one big monitor and the device does the splitting (which I don't want). Or, does this use the packet-based nature of DisplayPort to present two/three separate displays to the computer? Also, would this device work on my MacBook Pro? (I know the Dell site says it's for Windows, but it also says that no driver installation is required. I'd assume since the MBP supports DP 1.2 it would work, but it's better to ask). Thanks! Edit: I've checked out the similar-looking Cirago DisplayPort splitter, but I have extreme doubts as to whether or not it's a genuine displayport splitter, or just another monitor-conglomerate. Their DVI solution looks identical to Dell's, which I'm pretty sure won't do what I want. I also don't want to order this DisplayPort "hub" and find that it doesn't do what I want it to.

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• Can't get DNS Alias work on Ubuntu 10.04 with Apache 2

  - by Johnny

  I want to use the DNS Alias to configure one of my domain pointing to a specific directory on the server. Here is what I've done: Change the IP address in domain setting, and it works $ ping www.example.com PING example.com (124.205.62.xxx): 56 data bytes 64 bytes from 124.205.62.xxx: icmp_seq=0 ttl=48 time=53.088 ms 64 bytes from 124.205.62.xxx: icmp_seq=1 ttl=48 time=52.125 ms ^C --- example.com ping statistics --- 2 packets transmitted, 2 packets received, 0.0% packet loss round-trip min/avg/max/stddev = 52.125/52.606/53.088/0.482 ms Add sites-available and sites-enabled $ ls -l /etc/apache2/sites-available/ total 16 -rw-r--r-- 1 root root 948 2010-04-14 03:27 default -rw-r--r-- 1 root root 7467 2010-04-14 03:27 default-ssl -rw-r--r-- 1 root root 365 2010-06-09 18:27 example.com $ ls -l /etc/apache2/sites-enabled/ total 0 lrwxrwxrwx 1 root root 26 2010-06-09 15:46 000-default -> ../sites-available/default lrwxrwxrwx 1 root root 33 2010-06-09 18:17 001-example.com -> ../sites-available/example.com But it doesn't work and when I open the browser for www.example.com, it shows an 111 error: The following error was encountered: Connection to 124.205.62.48 Failed The system returned: (111) Connection refused Here is how example.com's config: $ cat /etc/apache2/sites-enabled/001-example.com <virtualhost *:80> DocumentRoot "/vhosts/example.com/htdocs/" ServerName www.example.com ServerAlias example.com <Location /> Order Deny,Allow Deny from None Allow from all </Location> #Include /etc/phpmyadmin/apache.conf ErrorLog /vhosts/example.com/logs/error.log CustomLog /vhosts/example.com/logs/access.log combined Could you please tell me how to solve this?

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• Network Security Device/Software

  - by Campo

  We currently run Symantec Antivirus Corporate 10.2. The software is really easy to manage on a network but the actual virus detection isn't bad but the malware detection is crap. We recently were infected with a email bot that got us put on some block lists. This has been resolved. I cannot have that happen again. I would like to find a program as easy to manage as symantec that I can install on all the user's workstations as well as the servers. We run a windows 2003 domain. We have a couple 2008 test servers in the environment. Most of the workstations are xp though I am using windows 7 and symantect is not compatible with this OS... So we need a solution that would cover all those operating systems. If it could be installed on macs too that would be a bonus though not necessary at all. This software must detect: Viruses AND Malware I am looking for something that combines the features in anti-malware programs like malwarebytes or spybot with an antivirus program like symantec or AVG. Alternatively if there is a piece of hardware that is a firewall, router, and packet inspection for virus/spam that would be the most ideal solution. I then could supplement with a piece of software that could pickup what the hardware misses. Thank you for your suggestions.

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• Windows 8 using as a webserver

  - by Jason

  I have a few hobby websites that I currently host on CentOS 6. Apache, mail serving, PHP, MySQL nothing special. In the past I used Windows XP to do this same task, for years, and I was OK. I switched to Linux and for the last few years it has been such a pain. updates break, certain apps only support certain distros without compiling from source. It prevents me from working on my hobby sites more because I am always fixing something. With Windows I locked it down, I run a hardware firewall and packet analyser, kept up on updates and A/V and never had a problem. I dont allow RDC from outside the local LAN, no FTP open, run OpenSSH on an obscure port.. I am considering switching to Windows 8 (since it is a cheaper license now that Windows 7) and running apache, HMailServer, PHP, MySQL, just like my CentOS install. My questions: I am not familiar with Windows 8, can the above be done like XP? No new security restrictions or the OS preventing this from happening? The machine is a Athlon 64-bit X2 with 32GB of RAM. Will Windows 8 see all of the RAM? Technically the machine came with Windows 7, and there is a serial number on it but I am sure I wiped away the Windows 7 recovery partition when I switched to Linux....

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• Port knocking via SSH tunnels

  - by j0ker

  I have a server running in my university's internal network. There is only one SSH daemon running which is secured by port knocking with knockd. Works fine if I try to connect from within the internal network. But since the server has no external IP, I have to tunnel into the internal network every time I want to access the server from outside. And since tunneling only works for a single port I cannot do the port knocking as easily as from an internal client. In fact, I don't get it to work at all. What I'm trying is opening tunnels for all the different ports that have to be knocked. Then I send TCP-SYN packets into the tunnels. But that doesn't work even for a single port. If I establish the tunnel on the first port in the knock sequence and send a packet through it, it doesn't reach the server. There is no entry in the log file of knockd, while there should be something like 123.45.67.89: openSSH: Stage 1 (as shown with internal knocks). So I guess, the problem doesn't exist within my knocking script but is a more general one. Are there any known problems with what I'm trying to do? Is it even possible or am I missing something? Thanks in advance!

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• Hyper-V with multiple physical networks

  - by Yaman

  I have Hyper-V on my laptop with a wireless and Ethernet card, sometimes I connect using wireless card, and sometimes using the Ethernet cable. I am trying to configure Hyper-v to work always with internet provided to virtual machine. I have tried to create 2 virtual switches, one external to the Wireless network card, and the other one external to the Ethernet card. What happens is that the wireless network creates a bridge object in the network and sharing center\Network connections of windows 8, while the Ethernet does not. Unfortunately, they do not work together as external, i have to set the connected one to external and the other one as external, I also have to go to the properties of the bridge and virtual Ethernet properties to uncheck and check some components like: Client for Microsoft Networks Deterministic Network Enhancer VMWare Bridge Protocol QoS Packet Scheduler File and Printer Sharing for Microsoft Networks In order to make things work. Sometimes I keep the wireless network switch external, and go to another location (another wireless network), and it disconnects, i have to reconfigure the switches. Is there a way to do the configuration once and remain working wherever I connect, whether its Wireless or Ethernet and on any network with DHCP?

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• Requests are making it to my app server, but not into node.js -- why?

  - by Zane Claes

  I detailed in this question on StackOverflow how some random requests are not making it from the client to my Node.js app server, resulting in a gateway timeout. In summary, identical requests are, at random, not even making it far enough to trigger a console.log() in my first line of express middleware. I need to narrow down the problem, though, to find out WHERE the traffic is being lost and it was suggested that I try a packet sniffer on my app servers. Here's my setup: 2x Load Balancers (m1.larges) 2x node.js servers (also m1.large) Here's what's interesting/unusual: the node.js servers started as PHP servers with an Apache stack and continue to serve PHP files for my domain (streamified.me). However, I use a little httpd.conf magic on the app servers so that requests to api.streamified.me get routed over port 8888 to the node.js server: RewriteCond %{HTTP_HOST} ^api.streamified.me RewriteRule ^(.*) http://localhost:8888$1 [P] So, the request hits the load balancer = goes to an app server = gets routed to port 8888 if it's intended for the API = gets handled by node.js So, in the same httpd.conf file, I turned on RewriteLogLevel 5 and then created a simple PHP+CURL script on my localhost to hit my api.streamified.me with a random URL (which should cause node.js to trigger a simple "not found" response) until it resulted in a Gateway timeout. Here, you can see that it has happened -- and the rewrite log shows that the request was definitely received by the app server and forwarded to port 8888... but it was never received by node.js (or, at least, the first line of code in the first line of middleware never gets it...) Image Link: http://i.stack.imgur.com/3OQxS.png

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• Configure static IPv6 on Ubuntu

  - by Charles Offenbacher

  I'm trying to configure IPv6 on a dedicated Ubuntu server. My provider gave me a "/64" (whatever that is - I'm still confused) of IPv6 addresses. However, when I try to use them, I can't ping anything. What do I do? :( # ping6 ipv6.google.com PING ipv6.google.com(vx-in-x63.1e100.net) 56 data bytes From fe80::219:d1ff:fefb:42d8 icmp_seq=1 Destination unreachable: Address unreachable From fe80::219:d1ff:fefb:42d8 icmp_seq=2 Destination unreachable: Address unreachable From fe80::219:d1ff:fefb:42d8 icmp_seq=3 Destination unreachable: Address unreachable --- ipv6.google.com ping statistics --- 3 packets transmitted, 0 received, +3 errors, 100% packet loss, time 2014ms # tracepath6 ipv6.google.com 1?: [LOCALHOST] 0.025ms pmtu 1500 1: fe80::219:d1ff:fefb:42d8%eth0 2000.022ms !H Resume: pmtu 1500 # cat /etc/network/interfaces # The loopback network interface auto lo iface lo inet loopback # The primary network interface auto eth0 iface eth0 inet static address 64.***.***.*** netmask 255.255.255.248 gateway 64.***.***.*** iface eth0 inet6 static pre-up modprobe ipv6 address 2607:F878:1:***::1 netmask 64 gateway 2607:F878:1:***(same as address)::1 # ifconfig eth0 Link encap:Ethernet HWaddr 00:19:d1:fb:42:d8 inet addr:64.***.***.*** Bcast:64.***.***.*** Mask:255.255.255.248 inet6 addr: fe80::219:d1ff:fefb:42d8/64 Scope:Link inet6 addr: 2607:f878:1:***::1/64 Scope:Global UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:52451 errors:0 dropped:0 overruns:0 frame:0 TX packets:39729 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:6817761 (6.8 MB) TX bytes:6153835 (6.1 MB) Interrupt:41 Base address:0xc000 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:166 errors:0 dropped:0 overruns:0 frame:0 TX packets:166 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:31714 (31.7 KB) TX bytes:31714 (31.7 KB)

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• tc u32 --- how to match L2 protocols in recent kernels?

  - by brownian

  I have a nice shaper, with hashed filtering, built at a linux bridge. In short, br0 connects external and internal physical interfaces, VLAN tagged packets are bridged "transparently" (I mean, no VLAN interfaces are there). Now, different kernels do it differently. I can be wrong with exact kernel verions ranges, please forgive me. Thanks. 2.6.26 So, in debian, 2.6.26 and up (up to 2.6.32, I believe) --- this works: tc filter add dev internal protocol 802.1q parent 1:0 prio 100 \ u32 ht 1:64 match ip dst 192.168.1.100 flowid 1:200 Here, "kernel" matches two bytes in "protocol" field with 0x8100, but counts the beginning of ip packet as a "zero position" (sorry for my English, if I'm a bit unclear). 2.6.32 Again, in debian (I've not built vanilla kernel), 2.6.32-5 --- this works: tc filter add dev internal protocol 802.1q parent 1:0 prio 100 \ u32 ht 1:64 match ip dst 192.168.1.100 at 20 flowid 1:200 Here, "kernel" matches the same for protocol, but counts offset from the beginning of this protocol's header --- I have to add 4 bytes to offset (20, not 16 for dst address). It's ok, seems more logical, as for me. 3.2.11, the latest stable now This works --- as if there is no 802.1q tag at all: tc filter add dev internal protocol ip parent 1:0 prio 100 \ u32 ht 1:64 match ip dst 192.168.1.100 flowid 1:200 The problem is that I couldn't find a way to match 802.1q tag so far. Matching 802.1q tag at past I could do this before as follows: tc filter add dev internal protocol 802.1q parent 1:0 prio 100 \ u32 match u16 0x0ed8 0x0fff at -4 flowid 1:300 Now I'm unable to match 802.1q tag with at 0, at -2, at -4, at -6 or like that. The main issue that I have zero hits count --- this filter is not being checked at all, "wrong protocol", in other words. Please, anyone, help me :-) Thanks!

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• ping incorrectly pinging 127.0.0.1

  - by AlexW

  I've got an odd DNS issue. I'm running a dual ipv4/ipv6 environment on Linux. Pinging some sites results in ping pinging 127.0.0.1. e.g. #> ping authserver.mojang.com PING authserver.mojang.com (127.0.0.1) 56(84) bytes of data. 64 bytes from localhost.localdomain (127.0.0.1): icmp_seq=1 ttl=64 time=0.045 ms 64 bytes from localhost.localdomain (127.0.0.1): icmp_seq=2 ttl=64 time=0.043 ms 64 bytes from localhost.localdomain (127.0.0.1): icmp_seq=3 ttl=64 time=0.058 ms --- authserver.mojang.com ping statistics --- 3 packets transmitted, 3 received, 0% packet loss, time 2000ms rtt min/avg/max/mdev = 0.043/0.048/0.058/0.010 ms Dig, however correctly returns the following: # dig authserver.mojang.com ; <<>> DiG 9.9.3-P2 <<>> authserver.mojang.com ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 15800 ;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1 ;; OPT PSEUDOSECTION: ; EDNS: version: 0, flags:; udp: 512 ;; QUESTION SECTION: ;authserver.mojang.com. IN A ;; ANSWER SECTION: authserver.mojang.com. 5 IN A 54.235.119.47 ;; Query time: 14 msec ;; SERVER: 2001:4860:4860::8888#53(2001:4860:4860::8888) ;; WHEN: Sat Nov 09 15:34:40 GMT 2013 ;; MSG SIZE rcvd: 66 I'm confused! My web browser returns the correct website, and the same computer booted into Windows also works correctly.

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• Steps to deploy a custom routing protocol

  - by user134589

  I'm a Ph.D Student and I'm researching a Service Centric Networking architecture with resourceallocation on a large scale. What I'm looking to do is expand an existing routing protocol like OSPF with extra fields and some new message types that I need for communication between Nodes. I want to manipulate the cost of a network link and I want paths to be calculated like in OSPF V2/v3, but using the cost that my algorithms have calculated. What I have I have the source code of OSPF from Quagga. I am assuming I can edit this code how I want, including packet structures and creating new types. Yes, I am aware it won't be easy but this is a 6 years research project and I am eager to develop something new, to move forward. What I need I would like to know how I can deploy the edited OSPF source files I have (written in C) on any type of server. I have a large testbed environment available with hundreds of virtual nodes and pretty much any OS out there. So if I want to test my extended protocol, how do I make all the nodes in a network use this to communicate? I do not understand what parts of the kernel I need to edit here. I tried searching for days now and I am unable to find how to deploy a non-existing routing protocol, without the use of an application-level framework. If somebody could push me in the right direction that'd be awesome. note: I need this to be a routingprotocol and not an application, since I want this to work on op of the network layer for performance reasons. Thanks!

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• virtualized windows 2003 domain with CentOS 5.3 and poor connectivity

  - by Chris Gow

  I have a test lab set up running a virtualized windows 2003 domain on a CentOS 5.3(xen) host and am experiencing connectivity problems with guests running on other hosts that are part of the same domain. Here's the setup: On Computer A I have CentOS 5.3 running as the host and have virtualized windows 2003 servers for a primary domain controller, a backup domain controller and an exchange server. The primary domain controller also acts as a WINS and dns server. The windows domain appears on a separate subnet from my company's corporate network. Connectivity to any of the virtualized guests on Computer A is fine (remote desktop, ping, what have you). I have another host computer (Computer B) that also has a virtualized Windows 2003 server guest that is part of the same domain. However, connectivity to that guest is flaky at best. I continuously get at least 60% packet loss when I try to ping the guest, and due to that flakiness I can not access any of the services that it runs (remote desktop, web). Now here's the interesting part. It seems to affect only machines running on a different computer than the domain controller that are in the same domain. On Computer B there is another Windows 2003 guest that is not part of the test domain and is on my corporate network. There's no connectivity issues with that guest machine. The problem does not seem to be specific to Computer B either. I created a test VM on my local computer within the test domain and it exhibits the same behaviour as the guest in Computer B. A couple of items to note: - Host OS on both Computer A and B are the same CentOS 5.3 64 bit - Guest OS is Windows 2003 64 bit and 32 bit (the guest on Computer B is 32 bit) - Guest OSes are all up to date (as of Monday) - Host OS on Computer A was upgraded from CentOS 5.2 to 5.3 Update: Sorry I did not follow up with the comments from below. Computer A and B have been moved to their own dedicated switch and the problem has gone away. I'm not sure what the underlying problem(s) were though

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• Xen virtual host can reach some sites but not others

  - by Tun H S Lee

  Okay, this is killing me. Debian Squeeze, Xen 4.0, brand new install. No iptables rules whatsoever except for the ones added by the default xen bridge script. Dom0 can reach the entire world, no problems. DomU can receive packets from some hosts, but not from others. For instance, if I ping Host A, it works fine. If I ping Host B, the DomU reports 100% packet loss. The hosts are random, but consistent (even after reboots). I can see no pattern to why some work and others don't. In fact, in some cases, different virtual hosts on the same server (an other server at a different data center) are divided; some work and others do not. I can reboot (DomU or Dom0 too) and the same hosts will work or fail as before. If I tcpdump on the Host B while pinging from the DomU, everything looks fine. It sees the echo request coming in and says it's sending one back. However, if I tcpdump peth0 on the Dom0, it never sees the echo reply. Any ideas what could be happening? I'm tearing my hair out here.

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• Windows Server 2003 IPSec Tunnel Connected, But Not Working (Possibly NAT/RRAS Related)

  - by Kevinoid

  Configuration I have setup a "raw" IPSec tunnel between a Windows Server 2003 (SBS) machine and a Netgear FVG318 according to the instructions in Microsoft KB816514. The configuration is as follows (using the same conventions as the article): NetA | SBS2003 | FVG318 | NetB 10.0.0.0/24 | 216.x.x.x | 69.y.y.y | 10.0.254.0/24 Both the Main Mode and Quick Mode Security Associations are successfully completed and appear in the IP Security Monitor. I am also able to ping the SBS2003 server on its private address from any computer on NetB. The Problem Any traffic sent from a computer on NetA to NetB, or from SBS2003 to NetB (excluding ICMP Ping responses), is sent out on the public network interface outside the IPSec tunnel (no encryption or header authentication, as if the tunnel were not there). Pings sent from a computer on NetB to a computer on NetA successfully reach computers on NetA, but the responses are silently discarded by SBS2003 (they do not go out in the clear and do not generate any encrypted traffic). Possible Solutions Incorrect Configuration I could have mistyped something, somewhere, or KB816514 could be incorrect in some way. I have tried very hard to eliminate the first option. Have re-created the configuration several times, tried tweaking and adjusting all the settings I could without success (most prevent the SA from being established). NAT/RRAS I have seen multiple posts elsewhere suggesting that this could be due to interaction between NAT and the IPSec filters. Possibly the NetA private addresses get rewritten to 216.x.x.x before being compared with the Quick Mode IPSec filters and don't get tunneled because of the mismatch. In fact, The Cable Guy article from June 2005 "TCP/IP Packet Processing Paths" suggests that this is the case, (see step 2 and 4 of the Transit Traffic path). If this is the case, is there a way to exclude NetA-NetB traffic from NAT? Any thoughts, ideas, suggestions, and/or comments are appreciated.

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• Bandwidth monitoring with iptables for non-router machine

  - by user1591276

  I came across this tutorial here that describes how to monitor bandwidth using iptables. I wanted to adapt it for a non-router machine, so I want to know how much data is going in/coming out and not passing through. Here are the rules I added: iptables -N ETH0_IN iptables -N ETH0_OUT iptables -I INPUT -i eth0 -j ETH0_IN iptables -I OUTPUT -o eth0 -j ETH0_OUT And here is a sample of the output: user@host:/tmp$ sudo iptables -x -vL -n Chain INPUT (policy ACCEPT 1549 packets, 225723 bytes) pkts bytes target prot opt in out source destination 199 54168 ETH0_IN all -- eth0 * 0.0.0.0/0 0.0.0.0/0 Chain FORWARD (policy ACCEPT 0 packets, 0 bytes) pkts bytes target prot opt in out source destination Chain OUTPUT (policy ACCEPT 1417 packets, 178128 bytes) pkts bytes target prot opt in out source destination 201 19597 ETH0_OUT all -- * eth0 0.0.0.0/0 0.0.0.0/0 Chain ETH0_IN (1 references) pkts bytes target prot opt in out source destination Chain ETH0_OUT (1 references) pkts bytes target prot opt in out source destination As seen above, there are no packet and byte values for ETH0_IN and ETH0_OUT, which is not the same result in the tutorial I referenced. Is there a mistake that I made somewhere? Thanks for your time.

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• VMWare use of Gratuitous ARP REPLY

  - by trs80

  I have an ESXi cluster that hosts several Windows Server VMs and around 30 Windows workstation VMs. Packet captures show a high number of ARP replies of the form: -sender_ip: VM IP -sender_mac: VM virtual MAC -target_ip: 0.0.0.0 -target_mac: Switch interface MAC The specific addresses aren't really a concern -- they're all legitimate and we're not having any problems with communications (most of the questions surrounding GARP and VMWare have to do with ping issues, a problem we don't have). I'm looking for an explanation of the traffic pattern in an environment that functions as expected. So the question is why would I see a high number of unsolicited ARP replies? Is this a mechanism VMWare uses for some purpose? What is it? Is there an alternative? EDIT: Quick diagram: [esxi]--[switch vlan]--[inline IDS]--[fw]--(rest of network) The IDS is complaining about these unsolicited ARPs. Several IDS vendors trigger on ARP replies without a prior request, or for ARP replies that have a target IP of 0.0.0.0. The target MAC in these replies is the VLAN interface on the switch. Capture points: -The IDS grabs the offending packets -The FW can see the same ones -A VM on the ESXi host does not see these, although there is an ARP request for a specific IP on the ESXi host that has source_ip=0.0.0.0 and source_mac=[switch vlan interface]. I can't share the captures, unfortunately. Really I'm interested in finding out if this is normal for an ESXi deployment.

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• Is this a good starting point for iptables in Linux?

  - by sbrattla

  Hi, I'm new to iptables, and i've been trying to put together a firewall which purpose is to protect a web server. The below rules are the ones i've put together so far, and i would like to hear if the rules makes sense - and wether i've left out anything essential? In addition to port 80, i also need to have port 3306 (mysql) and 22 (ssh) open for external connections. Any feedback is highly appreciated! #!/bin/sh # Clear all existing rules. iptables -F # ACCEPT connections for loopback network connection, 127.0.0.1. iptables -A INPUT -i lo -j ACCEPT # ALLOW established traffic iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT # DROP packets that are NEW but does not have the SYN but set. iptables -A INPUT -p tcp ! --syn -m state --state NEW -j DROP # DROP fragmented packets, as there is no way to tell the source and destination ports of such a packet. iptables -A INPUT -f -j DROP # DROP packets with all tcp flags set (XMAS packets). iptables -A INPUT -p tcp --tcp-flags ALL ALL -j DROP # DROP packets with no tcp flags set (NULL packets). iptables -A INPUT -p tcp --tcp-flags ALL NONE -j DROP # ALLOW ssh traffic (and prevent against DoS attacks) iptables -A INPUT -p tcp --dport ssh -m limit --limit 1/s -j ACCEPT # ALLOW http traffic (and prevent against DoS attacks) iptables -A INPUT -p tcp --dport http -m limit --limit 5/s -j ACCEPT # ALLOW mysql traffic (and prevent against DoS attacks) iptables -A INPUT -p tcp --dport mysql -m limit --limit 25/s -j ACCEPT # DROP any other traffic. iptables -A INPUT -j DROP

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• Redirecting or routing all traffic to OpenVPN on a Mac OS X client

  - by sdr56p

  I have configured an OpenVPN (2.2.1) server on an Ubuntu virtual machine in the Amazon elastic compute cloud. The server is up and running. I have installed OpenVPN (2.2.1) on a Mac OS X (10.8.2) client and I am using the openvpn2 binary to connect (in opposition to other clients like Tunnelblick or Viscosity). I can connect with the client and successfully ping or ssh the server through the tunnel. However, I can't redirect all internet traffic through the VPN even if I use the push "redirect-gateway def1 bypass-dhcp" option in the server.conf configurations. When I connect to the server with these configurations, I get a successful connection, but then an infinite series of error messages: "write UDPv4: No route to host (code=65)". Traffic routing seems to be compromised because I am not able to access anything anymore, not even the OpenVPN server (by pinging 10.8.0.1 for instance). This is beyond me. I am finding little help on the web and don't know what to try next. I don't think it is a problem of forwarding the traffic on the server since, first, I have also took care of that and, second, I can't even ping the VPN server locally through the tunnel (or ping anything at all for that matter). Thank you for your help. Here is the server.conf. file: port 1194 proto udp dev tun ca ca.crt cert ec2-server.crt key ec2-server.key # This file should be kept secret dh dh1024.pem server 10.8.0.0 255.255.255.0 ifconfig-pool-persist ipp.txt push "redirect-gateway def1 bypass-dhcp" client-to-client keepalive 10 120 comp-lzo persist-key persist-tun status openvpn-status.log verb 3 And the client.conf file: client dev tun proto udp remote servername.com 1194 resolv-retry infinite nobind persist-key persist-tun ca ca.crt cert Toto5.crt key Toto5.key ns-cert-type server comp-lzo verb 3 Here is the connection log with the error messages: $ sudo openvpn2 --config client.conf Wed Mar 13 22:58:22 2013 OpenVPN 2.2.1 x86_64-apple-darwin12.2.0 [SSL] [LZO2] [eurephia] built on Mar 4 2013 Wed Mar 13 22:58:22 2013 NOTE: OpenVPN 2.1 requires '--script-security 2' or higher to call user-defined scripts or executables Wed Mar 13 22:58:22 2013 LZO compression initialized Wed Mar 13 22:58:22 2013 Control Channel MTU parms [ L:1542 D:138 EF:38 EB:0 ET:0 EL:0 ] Wed Mar 13 22:58:22 2013 Socket Buffers: R=[196724->65536] S=[9216->65536] Wed Mar 13 22:58:22 2013 Data Channel MTU parms [ L:1542 D:1450 EF:42 EB:135 ET:0 EL:0 AF:3/1 ] Wed Mar 13 22:58:22 2013 Local Options hash (VER=V4): '41690919' Wed Mar 13 22:58:22 2013 Expected Remote Options hash (VER=V4): '530fdded' Wed Mar 13 22:58:22 2013 UDPv4 link local: [undef] Wed Mar 13 22:58:22 2013 UDPv4 link remote: 54.234.43.171:1194 Wed Mar 13 22:58:22 2013 TLS: Initial packet from 54.234.43.171:1194, sid=ffbaf343 d0c1a266 Wed Mar 13 22:58:22 2013 VERIFY OK: depth=1, /C=US/ST=CA/L=SanFrancisco/O=Fort-Funst ... ost.domain Wed Mar 13 22:58:22 2013 VERIFY OK: nsCertType=SERVER Wed Mar 13 22:58:22 2013 VERIFY OK: depth=0, /C=US/ST=CA/L=SanFrancisco/O=Fort-Funst ... ost.domain Wed Mar 13 22:58:23 2013 Data Channel Encrypt: Cipher 'BF-CBC' initialized with 128 bit key Wed Mar 13 22:58:23 2013 Data Channel Encrypt: Using 160 bit message hash 'SHA1' for HMAC authentication Wed Mar 13 22:58:23 2013 Data Channel Decrypt: Cipher 'BF-CBC' initialized with 128 bit key Wed Mar 13 22:58:23 2013 Data Channel Decrypt: Using 160 bit message hash 'SHA1' for HMAC authentication Wed Mar 13 22:58:23 2013 Control Channel: TLSv1, cipher TLSv1/SSLv3 DHE-RSA-AES256-SHA, 1024 bit RSA Wed Mar 13 22:58:23 2013 [ec2-server] Peer Connection Initiated with 54.234.43.171:1194 Wed Mar 13 22:58:25 2013 SENT CONTROL [ec2-server]: 'PUSH_REQUEST' (status=1) Wed Mar 13 22:58:25 2013 PUSH: Received control message: 'PUSH_REPLY,route 10.8.0.0 255.255.255.0,topology net30,ping 10,ping-restart 120,ifconfig 10.8.0.6 10.8.0.5' Wed Mar 13 22:58:25 2013 OPTIONS IMPORT: timers and/or timeouts modified Wed Mar 13 22:58:25 2013 OPTIONS IMPORT: --ifconfig/up options modified Wed Mar 13 22:58:25 2013 OPTIONS IMPORT: route options modified Wed Mar 13 22:58:25 2013 ROUTE default_gateway=0.0.0.0 Wed Mar 13 22:58:25 2013 TUN/TAP device /dev/tun0 opened Wed Mar 13 22:58:25 2013 /sbin/ifconfig tun0 delete ifconfig: ioctl (SIOCDIFADDR): Can't assign requested address Wed Mar 13 22:58:25 2013 NOTE: Tried to delete pre-existing tun/tap instance -- No Problem if failure Wed Mar 13 22:58:25 2013 /sbin/ifconfig tun0 10.8.0.6 10.8.0.5 mtu 1500 netmask 255.255.255.255 up Wed Mar 13 22:58:25 2013 /sbin/route add -net 10.8.0.0 10.8.0.5 255.255.255.0 add net 10.8.0.0: gateway 10.8.0.5 Wed Mar 13 22:58:25 2013 Initialization Sequence Completed ^CWed Mar 13 22:58:30 2013 event_wait : Interrupted system call (code=4) Wed Mar 13 22:58:30 2013 TCP/UDP: Closing socket Wed Mar 13 22:58:30 2013 /sbin/route delete -net 10.8.0.0 10.8.0.5 255.255.255.0 delete net 10.8.0.0: gateway 10.8.0.5 Wed Mar 13 22:58:30 2013 Closing TUN/TAP interface Wed Mar 13 22:58:30 2013 SIGINT[hard,] received, process exiting toto5:ttntec2 Dominic$ sudo openvpn2 --config client.conf --remote ec2-54-234-43-171.compute-1.amazonaws.com Wed Mar 13 22:58:57 2013 OpenVPN 2.2.1 x86_64-apple-darwin12.2.0 [SSL] [LZO2] [eurephia] built on Mar 4 2013 Wed Mar 13 22:58:57 2013 NOTE: OpenVPN 2.1 requires '--script-security 2' or higher to call user-defined scripts or executables Wed Mar 13 22:58:57 2013 LZO compression initialized Wed Mar 13 22:58:57 2013 Control Channel MTU parms [ L:1542 D:138 EF:38 EB:0 ET:0 EL:0 ] Wed Mar 13 22:58:57 2013 Socket Buffers: R=[196724->65536] S=[9216->65536] Wed Mar 13 22:58:57 2013 Data Channel MTU parms [ L:1542 D:1450 EF:42 EB:135 ET:0 EL:0 AF:3/1 ] Wed Mar 13 22:58:57 2013 Local Options hash (VER=V4): '41690919' Wed Mar 13 22:58:57 2013 Expected Remote Options hash (VER=V4): '530fdded' Wed Mar 13 22:58:57 2013 UDPv4 link local: [undef] Wed Mar 13 22:58:57 2013 UDPv4 link remote: 54.234.43.171:1194 Wed Mar 13 22:58:57 2013 TLS: Initial packet from 54.234.43.171:1194, sid=a0d75468 ec26de14 Wed Mar 13 22:58:58 2013 VERIFY OK: depth=1, /C=US/ST=CA/L=SanFrancisco/O=Fort-Funst ... ost.domain Wed Mar 13 22:58:58 2013 VERIFY OK: nsCertType=SERVER Wed Mar 13 22:58:58 2013 VERIFY OK: depth=0, /C=US/ST=CA/L=SanFrancisco/O=Fort-Funst ... ost.domain Wed Mar 13 22:58:58 2013 Data Channel Encrypt: Cipher 'BF-CBC' initialized with 128 bit key Wed Mar 13 22:58:58 2013 Data Channel Encrypt: Using 160 bit message hash 'SHA1' for HMAC authentication Wed Mar 13 22:58:58 2013 Data Channel Decrypt: Cipher 'BF-CBC' initialized with 128 bit key Wed Mar 13 22:58:58 2013 Data Channel Decrypt: Using 160 bit message hash 'SHA1' for HMAC authentication Wed Mar 13 22:58:58 2013 Control Channel: TLSv1, cipher TLSv1/SSLv3 DHE-RSA-AES256-SHA, 1024 bit RSA Wed Mar 13 22:58:58 2013 [ec2-server] Peer Connection Initiated with 54.234.43.171:1194 Wed Mar 13 22:59:00 2013 SENT CONTROL [ec2-server]: 'PUSH_REQUEST' (status=1) Wed Mar 13 22:59:00 2013 PUSH: Received control message: 'PUSH_REPLY,redirect-gateway def1 bypass-dhcp,route 10.8.0.0 255.255.255.0,topology net30,ping 10,ping-restart 120,ifconfig 10.8.0.6 10.8.0.5' Wed Mar 13 22:59:00 2013 OPTIONS IMPORT: timers and/or timeouts modified Wed Mar 13 22:59:00 2013 OPTIONS IMPORT: --ifconfig/up options modified Wed Mar 13 22:59:00 2013 OPTIONS IMPORT: route options modified Wed Mar 13 22:59:00 2013 ROUTE default_gateway=0.0.0.0 Wed Mar 13 22:59:00 2013 TUN/TAP device /dev/tun0 opened Wed Mar 13 22:59:00 2013 /sbin/ifconfig tun0 delete ifconfig: ioctl (SIOCDIFADDR): Can't assign requested address Wed Mar 13 22:59:00 2013 NOTE: Tried to delete pre-existing tun/tap instance -- No Problem if failure Wed Mar 13 22:59:00 2013 /sbin/ifconfig tun0 10.8.0.6 10.8.0.5 mtu 1500 netmask 255.255.255.255 up Wed Mar 13 22:59:00 2013 /sbin/route add -net 54.234.43.171 0.0.0.0 255.255.255.255 add net 54.234.43.171: gateway 0.0.0.0 Wed Mar 13 22:59:00 2013 /sbin/route add -net 0.0.0.0 10.8.0.5 128.0.0.0 add net 0.0.0.0: gateway 10.8.0.5 Wed Mar 13 22:59:00 2013 /sbin/route add -net 128.0.0.0 10.8.0.5 128.0.0.0 add net 128.0.0.0: gateway 10.8.0.5 Wed Mar 13 22:59:00 2013 /sbin/route add -net 10.8.0.0 10.8.0.5 255.255.255.0 add net 10.8.0.0: gateway 10.8.0.5 Wed Mar 13 22:59:00 2013 Initialization Sequence Completed Wed Mar 13 22:59:00 2013 write UDPv4: No route to host (code=65) Wed Mar 13 22:59:00 2013 write UDPv4: No route to host (code=65) Wed Mar 13 22:59:01 2013 write UDPv4: No route to host (code=65) Wed Mar 13 22:59:01 2013 write UDPv4: No route to host (code=65) Wed Mar 13 22:59:01 2013 write UDPv4: No route to host (code=65) Wed Mar 13 22:59:02 2013 write UDPv4: No route to host (code=65) Wed Mar 13 22:59:02 2013 write UDPv4: No route to host (code=65) Wed Mar 13 22:59:02 2013 write UDPv4: No route to host (code=65) Wed Mar 13 22:59:02 2013 write UDPv4: No route to host (code=65) Wed Mar 13 22:59:02 2013 write UDPv4: No route to host (code=65) ... The routing table after a connection WITHOUT the push redirect-gateway (all traffic is not redirected to the VPN and everything is working fine, I can ping or ssh the OpenVPN server and access all other Internet resources through my default gateway): Destination Gateway Flags Refs Use Netif Expire default user148-1.wireless UGSc 50 0 en1 10.8/24 10.8.0.5 UGSc 2 7 tun0 10.8.0.5 10.8.0.6 UH 3 2 tun0 127 localhost UCS 0 0 lo0 localhost localhost UH 6 6692 lo0 client.openvpn.net client.openvpn.net UH 3 18 lo0 142.1.148/22 link#5 UCS 2 0 en1 user148-1.wireless 0:90:b:27:10:71 UHLWIir 50 0 en1 76 user150-173.wirele localhost UHS 0 0 lo0 142.1.151.255 ff:ff:ff:ff:ff:ff UHLWbI 0 2 en1 169.254 link#5 UCS 1 0 en1 169.254.255.255 0:90:b:27:10:71 UHLSWi 0 0 en1 71 The routing table after a connection with the push redirect-gateway option enable as in the server.conf file above (all internet traffic should be redirected to the VPN tunnel, but nothing is working, I can't access any Internet ressources at all): Destination Gateway Flags Refs Use Netif Expire 0/1 10.8.0.5 UGSc 1 0 tun0 default user148-1.wireless UGSc 7 0 en1 10.8/24 10.8.0.5 UGSc 0 0 tun0 10.8.0.5 10.8.0.6 UHr 6 0 tun0 54.234.43.171/32 0.0.0.0 UGSc 1 0 en1 127 localhost UCS 0 0 lo0 localhost localhost UH 3 6698 lo0 client.openvpn.net client.openvpn.net UH 0 27 lo0 128.0/1 10.8.0.5 UGSc 2 0 tun0 142.1.148/22 link#5 UCS 1 0 en1 user148-1.wireless 0:90:b:27:10:71 UHLWIir 1 0 en1 833 user150-173.wirele localhost UHS 0 0 lo0 169.254 link#5 UCS 1 0 en1 169.254.255.255 0:90:b:27:10:71 UHLSW 0 0 en1

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• Set primary group of file or directory on Samba share from Windows

  - by Hubert Kario

  Short version: I have such situation on a Samba share: $ ls -lha total 12K drwxr-xr-x 3 hka Domain Users 4.0K Jan 11 17:07 . drwxrwxrwt 19 root root 4.0K Jan 11 17:06 .. drwxr-xr-x 2 hka Domain Users 4.0K Jan 11 17:07 dir A -rw-r--r-- 1 hka Domain Users 0 Jan 11 17:07 file A How am I able to change this to following using only Windows SMB/CIFS client (using 3rd party applications is OK) $ ls -lha total 12K drwxr-xr-x 3 hka Domain Users 4.0K Jan 11 17:07 . drwxrwxrwt 19 root root 4.0K Jan 11 17:06 .. drwxr-xr-x 2 hka ntpoweruser 4.0K Jan 11 17:07 dir A -rw-r--r-- 1 hka ntpoweruser 0 Jan 11 17:07 file A Rationale and background info I'm using POSIX ACLs on Samba shares. Together with acl group control for Samba, it allows me to delegate management of permissions to different users based on group membership. Thing is, when I create a new file on a Samba share, I'm unable to set its primary group (the one that grants permission to change its permissions). It's being set to my primary group (Domain Users) or group set using force group option in smb.conf share definition. Removing all groups in windows except the one I want to become the new primary group doesn't work. I can change it using chgrp group folder/ as regular user though shell, but it's suboptimal (not all users are *nix users). Trying to set new owner to group from Windows file permission window makes the Samba to return permission denied with following log entry: [2012/01/05 21:13:03.349734, 3] smbd/nttrans.c:1899(call_nt_transact_set_security_desc) call_nt_transact_set_security_desc: file = projects/project A/New folder, sent 0x1 [2012/01/05 21:13:03.349774, 3] smbd/posix_acls.c:1208(unpack_nt_owners) unpack_nt_owners: unable to validate owner sid for S-1-5-21-4526631811-884521863-452487935-11025 [2012/01/05 21:13:03.349804, 3] smbd/error.c:80(error_packet_set) error packet at smbd/nttrans.c(1909) cmd=160 (SMBnttrans) NT_STATUS_INVALID_OWNER The SID is correct and belongs to group I specified in GUI.

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• Ping with explicit next-hop selection (aka Monitoring multiple default gateways)

  - by Michuelnik

  I have a linux (debian) router with two internet connections (A) and (B). (A) is preferred, (B) is fallback. I want to monitor the internet connection (and not only the availability of the gateways!) and change the default route appropriately. If (A) is not providing internet, switch to (B) If (A) is providing internet again, switch back to (A). Only problem I have is in case (2). My routing table points towards a working internet so I cannot easily detect whether internet is working over link (A) again. I am search for a ping or traceroute (or other diagnosis-tool) which can select the next-hop explicitly. ping -r looks promising, but can only ping a host on the lan. (It only has to write another destination address in the packet, damnit!) traceroute -g gateway looks even more promising and nearly does what I want - but sets source routing options which my next-hops deny. (Not within my administrative boundary...) I just want a $ping, that can: select a source interface (and address) select a next-hop on that interface ping any arbitrary ip address I could do evil trickery with policy-based routing but that would have production impact for all users. I would like to see a side-effect-free solution....

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• allow spoofing when using tun

  - by Johnny

  I have a working openvpn setup with a server and a number of clients. How would i go around allowing IP spoofing through the openvpn server? (to demonstrate security concepts)? A normal ping from client to server goes through all right: root@client: hping3 10.8.0.1 HPING 10.8.0.1 (tun0 10.8.0.1): NO FLAGS are set, 40 headers + 0 data bytes len=40 ip=10.8.0.1 ttl=64 DF id=0 sport=0 flags=RA seq=0 win=0 rtt=124.7 ms root@server:/etc/openvpn# tcpdump -n -i tun0 tcpdump: verbose output suppressed, use -v or -vv for full protocol decode listening on tun0, link-type RAW (Raw IP), capture size 65535 bytes 10:17:51.734167 IP 10.8.0.6.2146 > 10.8.0.1.0: Flags [], win 512, length 0 But when spoofing a packet, it does not arrive at the openvpn server: root@client: hping3 -a 10.0.8.120 10.8.0.1 HPING 10.8.0.1 (tun0 10.8.0.1): NO FLAGS are set, 40 headers + 0 data bytes root@server:/etc/openvpn# tcpdump -n -i tun0 tcpdump: verbose output suppressed, use -v or -vv for full protocol decode listening on tun0, link-type RAW (Raw IP), capture size 65535 bytes My current config files server.conf local X.Y.Z.P port 80 proto tcp dev tun ca ca.crt cert server.crt key server.key # This file should be kept secret dh dh1024.pem server 10.8.0.0 255.255.255.0 push "redirect-gateway def1 bypass-dhcp" keepalive 10 120 comp-lzo persist-key persist-tun persist-local-ip status openvpn-status.log verb 3 client.conf client dev tun proto tcp remote MYHOST..amazonaws.com 80 resolv-retry infinite nobind persist-key persist-tun ca ca.crt cert client.crt key client.key ns-cert-type server comp-lzo verb 3

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• Prevent Linux from processing incoming ICMP Host unreachable packets

  - by bbc

  I have a test setup with one host on a network (10.1.0.0/16) talking via TCP to another one on another network (10.2.0.0/16) and a gateway in the middle. Sometimes, the TCP connection is lost and while scanning the trace (pcap), I looks like it's because of just one ICMP Host unreachable message sent by the gateway to 10.1.0.1 at some point. 10.1.0.1 then sends a TCP RST to 10.2.0.1. In my opinion, the gateway (pfSense) is broken or not configured correctly but anyway, for testing purposes, I'd like to block this kind of ICMP on the host (10.1.0.1) before it has an influence on my TCP connection (or does it? I'm not even sure). I've tried iptables: iptables -I INPUT -i eth0 -p icmp --icmp-type host-unreachable -j DROP but while it does a good job at preventing userpace applications like ping from receiving these ICMP messages, my TCP connection still comes to an end when the alleged "killer ICMP packet" is sent by the gateway. Am I right about how it is processed? If yes, then what can I do to achieve my goal?

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