I'm using an OpenVPN server in a Docker container for multiple client connections.
This container is located in a specific Docker network in which I have a web server as client target.
I want to publish the host name of my web server to clients so that they won't need to know its IP address in order to reach it.
To do so, I want to open the Docker's native DNS server to the OpenVPN clients and push to them the OpenVPN's IP as DNS server.
However, the Docker DNS server resides in the OpenVPN container, listening on 127.0.0.11 (with iptables internal redirections but that's another story).
Thus, in the OpenVPN server container, I need to add an iptables rule in order to forward a DNS request coming from the external OpenVPN IP to the internal 127.0.0.11 one.
But such an internal forward requires me to execute the following command:
sysctl -w net.ipv4.conf.tun0.route_localnet=1
Using the only NET_ADMIN capability when running docker run (--cap-add=NET_ADMIN), I get the following error message:
sysctl: error setting key 'net.ipv4.conf.tun0.route_localnet': Read-only file system
However, this perfectly works using the --privileged flag, but the one is too permissive.
Is there any Linux capability that can do the trick without using the --privileged flag?
I couldn't find the answer in the Linux capabilities manual.
I found a solution, using the --sysctl's docker run option
Solution in docker-compose.yml:
sysctls:
- net.ipv4.conf.tun0.route_localnet=1 # Doesn't work as tun0 doesn't
# exist yet at container start time
- net.ipv4.conf.default.route_localnet=1 # Workaround.
Related
I have a NAS where I am running various web apps in docker containers through docker-compose. I want some of these web apps to be accessible through the internet, not only when I am connected to my home network.
The problem I'm currently facing is that while cloudflare is able to expose the default web apps (default NAS management 192.168.1.135:80 can be mapped to subdomain.domain.com, for instance), it is unable to expose any docker container I try to run (192.168.1.135:4444 cannot be mapped to subdomain2.domain.com), and I receive a 502 bad gateway error with every app I have tried so far.
The configuration shouldn't be the issue, and it's definitely not the NoTLSVerify flag because the apps run on HTTP and I have configured it that way, so I am out of options to know what is going on and how to solve it.
Looks like the apps you're running on your NAS are proxied through the docker runtime. Consequently, the IP:port you need to add to the cloudflare tunnel config is the one that is reachable from the Host (not the IP of the host itself).
If the host is 192.168.1.135, you need to know which the the IP (internal to the docker network) of the app that you want to access from the outside, typically in the 172.0.0.1/24 range.
Example: If the containers running the apps you want to access are running on 172.0.0.2:4444 for app1 and 172.0.0.3:5555 for app2, the cloudflare config would look like this:
tunnel: the_ID_of_the_tunnel
credentials-file: /root/.cloudflared/the_ID_of_the_tunnel.json
ingress:
- hostname: yourapp1.example.com
service: http://172.0.0.2:4444
- hostname: ypurapp2.example.com
service: http://172.0.0.3:5555
- service: http_status:404
See more details and a video here: How to redirect subdomain to port (docker)
Turns out the problem is due to how docker works with networks, not with how Cloudflare accesses them. I first had to create a network that connected both containers, since adding cloudflare to my docker-compose file didn't work for some reason.
Create a docker network docker network create tunnel
Run docker without specifying the network docker run -d --name cloudflare cloudflare/cloudflared:latest tunnel --no-autoupdate run --token
Add the docker to the network docker network connect tunnel cloudflare
Run the container (note the container should have, as you specified, the network name identical to the one you created earlier, but cloudflare should not be in your docker-compose file) docker-compose up
In the cloudflare tunnel config, you will have to specify the docker internal address of your container (as #lu4t suggested). You can identify the address with docker inspect -f '{{range.NetworkSettings.Networks}}{{.IPAddress}}{{end}}' container
I have a container for which I expose my port to access a service running within the container. I am not exposing my ports outside the container i.e. to the host (using host network on mac). On getting inside the container using exec -t and running a curl for a post request, I get the error:
curl command: curl http://localhost:19999
Failed connect to localhost:19999; Connection refused.
I have the expose command in my dockerfile and do not want to expose ports to my host. My service is also up and running inside the container. I also have the property within config set as
"ExposedPorts": {"19999/tcp": {}}
(obtained through `docker inspect <container id/name>\ Any idea on why this is not working? Using docker for Mac
I'd post my docker-compose file too but this is being built through maven. I can ensure that I am exposing my port using 19999:19999. Another weird issue is that on disabling my proxies it would run a very light weight command for my custom service and wouldn't run it again returning the same error as above. The issue only occurs on my machine and not others
Hints:
The app must be listening on port 19999 which is probably not.
The EXPOSE that you're using inside the Dockerfile does nothing.
Usually there is no need to change the default port on which an application is listening, hence each container has its own IP and you shouldn't run in a port conflict.
Answer:
Instead of curling 19999 try to use the default port on which your app would normally be listening to(it's hard to guess what you are trying to run).
If you don't publish a port (with the docker run -p option or the Docker Compose ports: option), you cannot directly reach the container on Docker for Mac. See the Known limitations, use cases, and workarounds in the Docker Desktop for Mac documentation: the "per-container IP addressing is not possible" item ism what you're trying to attempt.
The docker inspect IP address is basically useless, except in one very specific Docker configuration (on a native-Linux host, calling from outside of Docker, on the same host); I wouldn't bother looking it up.
The Dockerfile EXPOSE directive and similar runtime options do very little and mostly serve as documentation. Even if you have that configured you still need to separately publish the port when you start the container to reach it from outside of Docker space.
I have a mongodb docker container I only want to have access to it from inside of my server, not out side. even I blocked the port 27017/tcp with firewall-cmd but it seems that docker is still available to public.
I am using linux centos 7
and docker-compose for setting up docker
I resolved the same problem adding an iptables rule that blocks 27017 port on public interface (eth0) at the top of chain DOCKER:
iptables -I DOCKER 1 -i eth0 -p tcp --dport 27017 -j DROP
Set the rule after docker startup
Another thing to do is to use non-default port for mongod, modify docker-compose.yml (remember to add --port=XXX in command directive)
For better security I suggest to put your server behind an external firewall
If you have your application in one container and MongoDb in other container what you need to do is to connect them together by using a network that is set to be internal.
See Documentation:
Internal
By default, Docker also connects a bridge network to it to provide
external connectivity. If you want to create an externally isolated
overlay network, you can set this option to true.
See also this question
Here's the tutorial on networking (not including internal but good for understanding)
You may also limit traffic on MongoDb by Configuring Linux iptables Firewall for MongoDB
for creating private networks use some IPs from these ranges:
10.0.0.0 – 10.255.255.255
172.16.0.0 – 172.31.255.255
192.168.0.0 – 192.168.255.255
more read on Wikipedia
You may connect a container to more than one network so typically an application container is connected to the outside world network (external) and internal network. The application communicates with database on internal network and returns some data to the client via external network. Database is connected only to the internal network so it is not seen from the outside (internet)
I found a post here may help enter link description here. Just post it here for people who needed it in future.
For security concern we need both hardware firewall and OS firewall enabled and configured properly. I found that firewall protection is ineffective for ports opened in docker container listened on 0.0.0.0 though firewalld service was enabled at that time.
My situation is :
A server with Centos 7.9 and Docker version 20.10.17 installed
A docker container was running with port 3000 opened on 0.0.0.0
The firewalld service had started with the command systemctl start firewalld
Only ports 22 should be allow access outside the server as the firewall configured.
It was expected that no one others could access port 3000 on that server, but the testing result was opposite. Port 3000 on that server was accessed successfully from any other servers. Thanks to the blog post, I have had my server under firewall protected.
I'm seeing problems mounting local volumes when running docker on Windows 10. The problems only appear when I have my company VPN enabled.
C:\Users\matt> docker run --rm -v d:/tmp:/data alpine ls /data
my_local_test_file.txt
When connected to VPN, I get this:
C:\Users\matt> docker run --rm -v d:/tmp:/data alpine ls /data
C:\Program Files\Docker\Docker\Resources\bin\docker.exe: Error response from daemon: error while creating mount source path '/host_mnt/d/tmp': mkdir /host_mnt/d: file exists.
Docker version is 17.12.0-ce-win47
I believe the problem is that docker uses the network when mounting local volumes, and the VPN routes ALL network traffic via the VPN gateway, so docker can't see the local drive.
Is there a workaround for this?
I'm aware I could run docker within a linux VM, or use docker toolbox. Neither of those are particularly good.
Is there another possible workaround?
the VPN routes ALL network traffic via the VPN gateway
You're probably right, in which case all traffic routed from Docker client to Docker daemon will also be through the VPN. When you use Docker CLI on Windows, it will connect to the Docker daemon which is accessible through the network. Using a VPN may disrupt this mechanism.
I think what's happening is:
When VPN is disabled, you use the Docker daemon on your machine and everything works
When VPN is enabled, another Docker daemon is used either because your VPN redirect traffic addressed to your Docker host (127.0.0.1 by default or set via -H flag or DOCKER_HOST env variable). This means that somehow this IP or host exists on your VPN network and there is a Docker daemon listening on it (which is kind of odd admittedly, it may be risky to use that daemon)
If that's really happening, you'll certainly see different output from docker ps -a, docker images, etc. because you are connecting to different daemons. (the daemon accessible through your VPN is actually being owned by someone else, you'd better not use it!)
What you can do:
Do not route 127.0.0.1 (or whatever is configured as Docker host) through your VPN
Action to take will depend on the VPN software you are using, or you can add route directly on your windows machine (here is a good article on the subject)
Find out your IP when VPN is enabled and configure Daemon to listen to this IP
When your VPN is enabled, run ipconfig /all and find the interface used by your VPN and it's IP address, for example 10.142.0.12 (you can compare output before/after enabling VPN to identify which one it is)
Configure your Docker daemon to listen this IP address and restart it. Either use the UI, or on Windows config file is located at %programdata%\docker\config\daemon.json by default, you need to specify "hosts": ["10.142.0.12", "127.0.0.1"] for example (see docs for details)
Configure Docker host to 10.142.0.12 when VPN is enabled, either by setting environment variable DOCKER_HOST=10.142.0.12 or with client docker -H 10.142.0.12 <cmd>
/!\ Security note: this may present a security issue as anyone knowing your IP on the VPN network will be able to use the Daemon on your machine
Hope this helps. I am not a Windows expert so I was not able to give details on Windows-related issues, but feel free to ask details if needed.
Hi can any one help me to tell the correct command to provide internet access to a running container ?
I know we have to specify --net in docker run command to access internet from inside container.
What if I want to provide internet access to container which I didn't ran with --net command (i.e to container which does not have internet access)
I got docker network connect NetworkName ContainerName/ID command from: https://docs.docker.com/engine/reference/commandline/network_connect/
but running above command does not providing internet access so requesting to share me correct command.
Note: Am trying this on centos container
Your docker containers should have internet access by default as that is the normal setup of docker, and by no means should they require providing --net to get that. If they don't then you probably have something mixed up on your host like ie. additional firewall rules or lack of ip forwarding enabled.
For starters, check if you have enabled ip forwarding, should look like following :
$ cat /proc/sys/net/ipv4/ip_forward
1
and verify if you don't have something funky in your iptables
Docker containers should resolve internet traffic once you configured properly. Please check the container network status by,
Enter public DNS (8.8.8.8)manually in /etc/resolve.conf.
If not working check the container network side.
#goto /etc/default/docker
#add public DNS values there (DOCKER_OPTS="--dns 208.67.222.222 --dns 208.67.220.220")
#sudo service docker restart
Login to the container and ping google.com