How do I allow a Cloud Composer Airflow DAG to connect to a REST API via VPN gateway? The cluster is connected to the according VPC.
The kube-proxy is able to reach the API, yet the containers can not.
I have SSH'd into the kube-proxy and containers and tried a traceroute. The containers' traceroute ends with the kube-proxy. The kube-proxy has 4 hops before reaching destination.
I have dumped the iptables from the kube-proxy, they do not specify anything in regards to NATing the VPCs subnet with the containers.
The VPC subnet also does not show up in the containers, which is by design.
Some reading material:
https://www.stackrox.com/post/2020/01/kubernetes-networking-demystified/
EDIT1: More info:
Let's assume the VPN connects the VPC to the remote 10.200.0.0 network.
The VPC has multiple subnets. The primary range is e.g. 10.10.0.0/20. For each Kubernetes cluster we have two more subnet, one for each pod (10.16.0.0/14) and another for services (10.20.0.0/20). The gateway is 10.10.0.1.
Each pod again has it's own range, where pod_1 is 10.16.0.0/14, pod_2 is 10.16.1.0/14, pod_3 10.16.3.0/14 and so on.
One of the kube-proxies has multiple network adapters. It resides in the 10.10.0.0 network with eth0 and has a cbr0 bridge to 10.16.0.0. Through said kube-proxy via the bridge the workers for Airflow are connecting to the network. One worker e.g. 10.16.0.1 has only one network adapter.
The kube-proxy can reach the 10.200.0.0 network. The Airflow workers can not.
How do we get the worker to access the 10.200.0.0 network? Do we need to change the iptables of the kube-proxy?
One of the possible solutions would be to forward the packages from the kube virtual interface to the node's real one. E.g. adding the following rules to ip tables:
iptables -A FORWARD -i cbr0 -o eth0 -d 10.200.0.0/25 -j ACCEPT
iptables -A FORWARD -i eth0 -o cbr0 -s 10.200.0.0/25 -m state --state ESTABLISHED,RELATED -j ACCEPT
iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
Related
We run K8S cluster in private network behind firewall with nasty reverse NAT rules that prevent our hosts to connect to themselves over public IPs.
Problem
From inside a pod I need to connect to the service that is resolved to public IP 203.X.X.X that is not possible. However I can connect to this service over private IP 192.Y.Y.Y
I can setup iptables rule on the node running pod as follows:
iptables -A OUTPUT -t nat -p tcp -d 203.X.X.X --dport 80 -j DNAT --to-destination 192.Y.Y.Y:80
Then I can successfully connect to the service from node, but not from pod running on this node.
Solution with hostAliases would not work as we:
do not know the host names in advance
would like to reroute all traffic to known public (unreachable) IPs to the respective private IPs
PS:
We use calico as networking plugin
I am trying to understand how the bridged docker0 interface works.
When docker daemon starts up, it creates a bridged device docker0;
When a container starts up, it creates a interface vthn and bind to docker0
say we issue a ping command from inside the container to a external host
[root#f505f022eb5b app]# ping 130.49.40.130
PING 130.49.40.130 (130.49.40.130) 56(84) bytes of data.
64 bytes from 130.49.40.130: icmp_seq=1 ttl=52 time=11.9 ms
so apprently my host eth0 is receiving this ping back, but how does this package get forwarded to the container? There are serveral questions to ask
eth0 and docker0 are not bridged, how come docker0 get the packets from eth0?
even if docker0 got the packets, how it works internally sending packets to vth0? does it internally maintains some Maps so it can convert packets to between different mac address?
how is iptables related here?
Cheers.
Docker is not doing anything specifically magical here and your question is not really docker dependant/related.
docker0 is just a network bridge. As soon as this bridge is created (upon starting the docker service) you can assume that a new machine (in this case in a VM/docker form) has joined the your network.
When pinging the docker container from host or vice versa you are basically pinging another machine inside your network.
Regarding docker, unless you have created a new network interface (which I doubt so since you are pinging eth0) you are basically pinging yourself.
If you run the container as:
docker run -i -t --rm -p 10.0.0.99:80:8080 ubuntu:16.04
You are telling docker to create a NAT rule in iptables to forward any packets going to 10.0.0.99:80 to your docker container on port 8080.
When you run the container as:
docker run -i -t --rm -p --net=host ubuntu:16.04
Then you are saying the docker container should have the same network stack as the host so all the packets going to host will also arrive to your docker container via the docker0 bridge.
To answer your question, how does a container ping an external host, this is also achieved via NAT.
If you list your Iptables / NAT rules using: sudo iptables -t nat -L
You will likely see, something similar to the below (docker subnet may be different)
Chain POSTROUTING (policy ACCEPT)
target prot opt source destination
MASQUERADE all -- 172.17.0.0/16 anywhere
This is basically saying NAT any outgoing packets originating from the docker subnet. So the outgoing packets will appear to originate from the docker host machine. When the ping packets return, the NAT table will be used to determine that a docker host actually made the request, and the packet gets forwarded to the docker veth.
I got a problem at the moment and really don't know where the mistake is. I got a Root-Server from my ISP. This Root-Server has already one IP included and today i booked two more IP-Addresses. So what I want to do now is to map this two new IP-Adresses to two virtual Machines but also hold the included IP for the Root-Server. So how I realize this?
I thought something like:
br0 - holds the original IP of the Root-Server
br0:0 - holds first IP of first virtual Machine
br0:1 - holds second IP of second virtual Machine
But this doesn't work. Any Ideas. I'm really frustrated. Worked the hole Day on it and no solution.
I was also struggling with similar scenario, I've got server and got to point that setting up bridge did cut me out and had to restart to be able to reach it , anyway I've managed to handle it by iptables ..
#create alias for your second ip address (lets say its 111.222.333.2 , local address 192.168.1.2)
ifconfig eth0:1 111.222.333.2
#you should add netmask to be proper if you've got subnet
#now you should be able to ping this second address from outside world - try it,
#that is if you have not set up firewall to block pings ... flush iptables rules if you are not sure...
#set up NAT rule (network-address-translate : outside ip-> local ip and back local ip->outside ip)
#assumes your virtual machines lives as 192.168.1.2
iptables -t nat -A PREROUTING -d 111.222.333.2 -j DNAT --to-destination 192.168.1.2
iptables -t nat -A POSTROUTING -s 192.168.1.2 -j SNAT --to-source 111.222.333.2
This did help me with server which has multiple IP addresses and KVM virtual machines,
which were originally run in default network (forward mode=nat), so they had internet through NAT and internal IP at first , this also gives them outside-world public IP address.
You can also do these redirects on port-by-port basis by adjusting iptables rule to set address like -d 111.222.333.2:80 -p tcp and also adding port to local address ...
You may also need to turn on device IP forwarding, you can check that by for example sysctl -a | grep forward (where you should see it on for your eth0 device) , optionally adjusting it by proper sysctl command like
sysctl -w net.ipv4.ip_forward=1
Map br0 to VM1 and VM2 as TAP DEVICE and in VM1 and VM2 you can see that as eth device;
Assign IP1 and IP2 to VM1 and VM2 respectively; With this configuration you can ping from VM1 to VM2 and from host machine to any guest machine(VM1 or VM2);
The following link will help you setting up TAP device for VM via bridge; See qemu-ifup script specified there and understand it well.
I don't know if the question is related to the topics on stackoverflow so, if not sorry in advance.
I have the following problem that I'm trying to solve :
I am connected to my university network that requires me to configure my browser to use a proxy. I want to set up a router in my house ( D-Link Dir-300 with Firmware: DD-WRT v24-sp2) and because I am using multiple Android devices that are not rooted ( I can't use global proxy apps ) I was thinking about the following solution :
Question Can I make my router redirect all the traffic from my wireless network to the proxy server that I'm using ( allowing the devices not to configure a proxy server) ?
I have a HTTP redirect tool available on the router configuration page
I looked up the destination IP address from the proxy URL that I was using and I get 4 IP addresses for that node, I tried to use two of them with the source network set to 192.168.1.0 but it didn't work -my browser on the android devices doesn't work without setting up the proxy.
____________________________________ EDIT ____________________________
After looking some more I found this link
#!/bin/sh
PROXY_IP=[IP]
PROXY_PORT=[PORT]
LAN_IP=`nvram get lan_ipaddr`
LAN_NET=$LAN_IP/`nvram get lan_netmask`
iptables -t nat -A PREROUTING -i br0 -s $LAN_NET -d ! $LAN_IP -p tcp --dport 80 -j DNAT --to $PROXY_IP:$PROXY_PORT
iptables -t nat -A POSTROUTING -o br0 -s $PROXY_IP -p tcp -d $LAN_NET -j SNAT --to $PROXY_IP
iptables -A FORWARD -i vlan1 -o br0 -s $LAN_NET -d $PROXY_IP -p tcp --dport $PROXY_PORT -j ACCEPT
How can I modify it to redirect all the traffic udp/tcp etc coming from all the ports?
Easy option is to configure your proxy on your android device. When setting up the wireless connection select advanced options and enter your proxy settings, on older android devices it's somewhat hidden but I managed to do it on a 2.3 one.
For iOS you can add it later to your wifi settings.
If you router is not the main entry point for internet (if it's secondary) you can configure it to route to your PC/laptop. Configure a static IP op your PC/laptop, share internet over there, and configure that IP as gateway on your router.
You can install a proxy tool (charles proxy for example) on your PC and configure it to forward your traffic to the internet-proxy. On your devices you still need to setup the proxy, but this time it's your PC's proxy (gateway+8080).
I have X-Wrt based on OpenWrt 8.09 on my router
I have home LAN of few computers on which I have some network servers (SVN, web, etc). For each of service I made forwarding on my router (Linksys wrt54gl) to access it from the Internet (<my_external_ip>:<external_port> -> <some_internal_ip>:<internal_port>)
But within my local network this resources by above request is unreachable (so I need make some reconfiguration <some_internal_ip>:<internal_port> to access).
I added some line to my /etc/hosts
<my_external_ip> localhost
So now all requests from local network to <my_external_ip> forwards to my router but further redirection to appropriate port not works.
Advise proper redirection please.
You need to install an IP redirect for calls going out of the internal network and directed to the public IP. Normally these packets get discarded. You want to reroute them, DNATting to the destination server, but also masqueraded so that the server, seeing as you, its client, are in its same network, doesn't respond directly to you with its internal IP (which you, the client, not having sent the packet there, would discard).
I found this on OpenWRT groups:
iptables -t nat -A prerouting_rule -d YOURPUBLICIP -p tcp --dport PORT -j DNAT --to YOURSERVER
iptables -A forwarding_rule -p tcp --dport PORT -d YOURSERVER -j ACCEPT
iptables -t nat -A postrouting_rule -s YOURNETWORK -p tcp --dport PORT -d YOURSERVER -j MASQUERADE
https://forum.openwrt.org/viewtopic.php?id=4030
If I remember correctly OpenWrt allows you to define custom DNS entries. So maybe simply give a proper local names to your sources (ie. svnserver.local) and map them to specific local IPs. This way you do not even need to go through router to access local resources from local network.