IPTABLES - How does the Docker port a:b work?
I am learning iptables in combination with Docker. I am figuring out how the docker-compose host:port:port for port forwarding actually works. I understood it does some iptables magic. So I did a little test.
First I had this docker-compose.yml:
version: "3"
services:
postgres:
image: postgres:latest
ports:
- 127.0.0.1:5432:5432
networks:
- network
network:
network:
When running this, iptables -S gives:
-P INPUT ACCEPT
-P FORWARD DROP
-P OUTPUT ACCEPT
-N DOCKER
-N DOCKER-ISOLATION
-N DOCKER-USER
-A FORWARD -j DOCKER-USER
-A FORWARD -j DOCKER-ISOLATION
-A FORWARD -o br-bd4b05981a0f -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
-A FORWARD -o br-bd4b05981a0f -j DOCKER
-A FORWARD -i br-bd4b05981a0f ! -o br-bd4b05981a0f -j ACCEPT
-A FORWARD -i br-bd4b05981a0f -o br-bd4b05981a0f -j ACCEPT
-A FORWARD -o docker0 -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
-A FORWARD -o docker0 -j DOCKER
-A FORWARD -i docker0 ! -o docker0 -j ACCEPT
-A FORWARD -i docker0 -o docker0 -j ACCEPT
-A DOCKER -d 172.18.0.2/32 ! -i br-bd4b05981a0f -o br-bd4b05981a0f -p tcp -m tcp --dport 5432 -j ACCEPT
-A DOCKER-ISOLATION -i docker0 -o br-bd4b05981a0f -j DROP
-A DOCKER-ISOLATION -i br-bd4b05981a0f -o docker0 -j DROP
-A DOCKER-ISOLATION -j RETURN
-A DOCKER-USER -j RETURN
I verified that port 5432 was indeed not accessible over the internet and only on localhost. Great!
After this, I rebooted, cleared docker (docker system prune --all --volumes --force) and started with following docker-compose.yml:
version: "3"
services:
postgres:
image: postgres:latest
ports:
- 5432:5432
networks:
- network
network:
network:
Note that 127.0.0.1: is no long present in this configuration. Now, when running iptables -S, I am getting exact the same configuration:
-P INPUT ACCEPT
-P FORWARD DROP
-P OUTPUT ACCEPT
-N DOCKER
-N DOCKER-ISOLATION
-N DOCKER-USER
-A FORWARD -j DOCKER-USER
-A FORWARD -j DOCKER-ISOLATION
-A FORWARD -o br-6ada9a016213 -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
-A FORWARD -o br-6ada9a016213 -j DOCKER
-A FORWARD -i br-6ada9a016213 ! -o br-6ada9a016213 -j ACCEPT
-A FORWARD -i br-6ada9a016213 -o br-6ada9a016213 -j ACCEPT
-A FORWARD -o docker0 -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
-A FORWARD -o docker0 -j DOCKER
-A FORWARD -i docker0 ! -o docker0 -j ACCEPT
-A FORWARD -i docker0 -o docker0 -j ACCEPT
-A DOCKER -d 172.18.0.2/32 ! -i br-6ada9a016213 -o br-6ada9a016213 -p tcp -m tcp --dport 5432 -j ACCEPT
-A DOCKER-ISOLATION -i docker0 -o br-6ada9a016213 -j DROP
-A DOCKER-ISOLATION -i br-6ada9a016213 -o docker0 -j DROP
-A DOCKER-ISOLATION -j RETURN
-A DOCKER-USER -j RETURN
However, this time, the service is accessible via internet. This is intended as per the docker-compose.yml I am using this time. However, the iptables configuration is exact the same as the one above. Strange?
How is it possible that two exact iptables configurations have different behavior? I guess I am missing some piece to understand the specifics of the Docket port forwarding functionality.
linux networking firewall iptables docker
edited Feb 12 at 18:03
Flux
1145
asked Nov 21 '17 at 13:03
Dave TeezoDave Teezo
104
add a comment |
I am learning iptables in combination with Docker. I am figuring out how the docker-compose host:port:port for port forwarding actually works. I understood it does some iptables magic. So I did a little test.
First I had this docker-compose.yml:
version: "3"
services:
postgres:
image: postgres:latest
ports:
- 127.0.0.1:5432:5432
networks:
- network
network:
network:
When running this, iptables -S gives:
-P INPUT ACCEPT
-P FORWARD DROP
-P OUTPUT ACCEPT
-N DOCKER
-N DOCKER-ISOLATION
-N DOCKER-USER
-A FORWARD -j DOCKER-USER
-A FORWARD -j DOCKER-ISOLATION
-A FORWARD -o br-bd4b05981a0f -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
-A FORWARD -o br-bd4b05981a0f -j DOCKER
-A FORWARD -i br-bd4b05981a0f ! -o br-bd4b05981a0f -j ACCEPT
-A FORWARD -i br-bd4b05981a0f -o br-bd4b05981a0f -j ACCEPT
-A FORWARD -o docker0 -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
-A FORWARD -o docker0 -j DOCKER
-A FORWARD -i docker0 ! -o docker0 -j ACCEPT
-A FORWARD -i docker0 -o docker0 -j ACCEPT
-A DOCKER -d 172.18.0.2/32 ! -i br-bd4b05981a0f -o br-bd4b05981a0f -p tcp -m tcp --dport 5432 -j ACCEPT
-A DOCKER-ISOLATION -i docker0 -o br-bd4b05981a0f -j DROP
-A DOCKER-ISOLATION -i br-bd4b05981a0f -o docker0 -j DROP
-A DOCKER-ISOLATION -j RETURN
-A DOCKER-USER -j RETURN
I verified that port 5432 was indeed not accessible over the internet and only on localhost. Great!
After this, I rebooted, cleared docker (docker system prune --all --volumes --force) and started with following docker-compose.yml:
version: "3"
services:
postgres:
image: postgres:latest
ports:
- 5432:5432
networks:
- network
network:
network:
Note that 127.0.0.1: is no long present in this configuration. Now, when running iptables -S, I am getting exact the same configuration:
-P INPUT ACCEPT
-P FORWARD DROP
-P OUTPUT ACCEPT
-N DOCKER
-N DOCKER-ISOLATION
-N DOCKER-USER
-A FORWARD -j DOCKER-USER
-A FORWARD -j DOCKER-ISOLATION
-A FORWARD -o br-6ada9a016213 -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
-A FORWARD -o br-6ada9a016213 -j DOCKER
-A FORWARD -i br-6ada9a016213 ! -o br-6ada9a016213 -j ACCEPT
-A FORWARD -i br-6ada9a016213 -o br-6ada9a016213 -j ACCEPT
-A FORWARD -o docker0 -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
-A FORWARD -o docker0 -j DOCKER
-A FORWARD -i docker0 ! -o docker0 -j ACCEPT
-A FORWARD -i docker0 -o docker0 -j ACCEPT
-A DOCKER -d 172.18.0.2/32 ! -i br-6ada9a016213 -o br-6ada9a016213 -p tcp -m tcp --dport 5432 -j ACCEPT
-A DOCKER-ISOLATION -i docker0 -o br-6ada9a016213 -j DROP
-A DOCKER-ISOLATION -i br-6ada9a016213 -o docker0 -j DROP
-A DOCKER-ISOLATION -j RETURN
-A DOCKER-USER -j RETURN
However, this time, the service is accessible via internet. This is intended as per the docker-compose.yml I am using this time. However, the iptables configuration is exact the same as the one above. Strange?
How is it possible that two exact iptables configurations have different behavior? I guess I am missing some piece to understand the specifics of the Docket port forwarding functionality.
linux networking firewall iptables docker
edited Feb 12 at 18:03
Flux
1145
asked Nov 21 '17 at 13:03
Dave TeezoDave Teezo
104
add a comment |
I am learning iptables in combination with Docker. I am figuring out how the docker-compose host:port:port for port forwarding actually works. I understood it does some iptables magic. So I did a little test.
First I had this docker-compose.yml:
version: "3"
services:
postgres:
image: postgres:latest
ports:
- 127.0.0.1:5432:5432
networks:
- network
network:
network:
When running this, iptables -S gives:
-P INPUT ACCEPT
-P FORWARD DROP
-P OUTPUT ACCEPT
-N DOCKER
-N DOCKER-ISOLATION
-N DOCKER-USER
-A FORWARD -j DOCKER-USER
-A FORWARD -j DOCKER-ISOLATION
-A FORWARD -o br-bd4b05981a0f -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
-A FORWARD -o br-bd4b05981a0f -j DOCKER
-A FORWARD -i br-bd4b05981a0f ! -o br-bd4b05981a0f -j ACCEPT
-A FORWARD -i br-bd4b05981a0f -o br-bd4b05981a0f -j ACCEPT
-A FORWARD -o docker0 -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
-A FORWARD -o docker0 -j DOCKER
-A FORWARD -i docker0 ! -o docker0 -j ACCEPT
-A FORWARD -i docker0 -o docker0 -j ACCEPT
-A DOCKER -d 172.18.0.2/32 ! -i br-bd4b05981a0f -o br-bd4b05981a0f -p tcp -m tcp --dport 5432 -j ACCEPT
-A DOCKER-ISOLATION -i docker0 -o br-bd4b05981a0f -j DROP
-A DOCKER-ISOLATION -i br-bd4b05981a0f -o docker0 -j DROP
-A DOCKER-ISOLATION -j RETURN
-A DOCKER-USER -j RETURN
I verified that port 5432 was indeed not accessible over the internet and only on localhost. Great!
After this, I rebooted, cleared docker (docker system prune --all --volumes --force) and started with following docker-compose.yml:
version: "3"
services:
postgres:
image: postgres:latest
ports:
- 5432:5432
networks:
- network
network:
network:
Note that 127.0.0.1: is no long present in this configuration. Now, when running iptables -S, I am getting exact the same configuration:
-P INPUT ACCEPT
-P FORWARD DROP
-P OUTPUT ACCEPT
-N DOCKER
-N DOCKER-ISOLATION
-N DOCKER-USER
-A FORWARD -j DOCKER-USER
-A FORWARD -j DOCKER-ISOLATION
-A FORWARD -o br-6ada9a016213 -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
-A FORWARD -o br-6ada9a016213 -j DOCKER
-A FORWARD -i br-6ada9a016213 ! -o br-6ada9a016213 -j ACCEPT
-A FORWARD -i br-6ada9a016213 -o br-6ada9a016213 -j ACCEPT
-A FORWARD -o docker0 -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
-A FORWARD -o docker0 -j DOCKER
-A FORWARD -i docker0 ! -o docker0 -j ACCEPT
-A FORWARD -i docker0 -o docker0 -j ACCEPT
-A DOCKER -d 172.18.0.2/32 ! -i br-6ada9a016213 -o br-6ada9a016213 -p tcp -m tcp --dport 5432 -j ACCEPT
-A DOCKER-ISOLATION -i docker0 -o br-6ada9a016213 -j DROP
-A DOCKER-ISOLATION -i br-6ada9a016213 -o docker0 -j DROP
-A DOCKER-ISOLATION -j RETURN
-A DOCKER-USER -j RETURN
However, this time, the service is accessible via internet. This is intended as per the docker-compose.yml I am using this time. However, the iptables configuration is exact the same as the one above. Strange?
How is it possible that two exact iptables configurations have different behavior? I guess I am missing some piece to understand the specifics of the Docket port forwarding functionality.
linux networking firewall iptables docker
edited Feb 12 at 18:03
Flux
1145
asked Nov 21 '17 at 13:03
Dave TeezoDave Teezo
104
I am learning iptables in combination with Docker. I am figuring out how the docker-compose host:port:port for port forwarding actually works. I understood it does some iptables magic. So I did a little test.
First I had this docker-compose.yml:
version: "3"
services:
postgres:
image: postgres:latest
ports:
- 127.0.0.1:5432:5432
networks:
- network
network:
network:
When running this, iptables -S gives:
-P INPUT ACCEPT
-P FORWARD DROP
-P OUTPUT ACCEPT
-N DOCKER
-N DOCKER-ISOLATION
-N DOCKER-USER
-A FORWARD -j DOCKER-USER
-A FORWARD -j DOCKER-ISOLATION
-A FORWARD -o br-bd4b05981a0f -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
-A FORWARD -o br-bd4b05981a0f -j DOCKER
-A FORWARD -i br-bd4b05981a0f ! -o br-bd4b05981a0f -j ACCEPT
-A FORWARD -i br-bd4b05981a0f -o br-bd4b05981a0f -j ACCEPT
-A FORWARD -o docker0 -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
-A FORWARD -o docker0 -j DOCKER
-A FORWARD -i docker0 ! -o docker0 -j ACCEPT
-A FORWARD -i docker0 -o docker0 -j ACCEPT
-A DOCKER -d 172.18.0.2/32 ! -i br-bd4b05981a0f -o br-bd4b05981a0f -p tcp -m tcp --dport 5432 -j ACCEPT
-A DOCKER-ISOLATION -i docker0 -o br-bd4b05981a0f -j DROP
-A DOCKER-ISOLATION -i br-bd4b05981a0f -o docker0 -j DROP
-A DOCKER-ISOLATION -j RETURN
-A DOCKER-USER -j RETURN
I verified that port 5432 was indeed not accessible over the internet and only on localhost. Great!
After this, I rebooted, cleared docker (docker system prune --all --volumes --force) and started with following docker-compose.yml:
version: "3"
services:
postgres:
image: postgres:latest
ports:
- 5432:5432
networks:
- network
network:
network:
Note that 127.0.0.1: is no long present in this configuration. Now, when running iptables -S, I am getting exact the same configuration:
-P INPUT ACCEPT
-P FORWARD DROP
-P OUTPUT ACCEPT
-N DOCKER
-N DOCKER-ISOLATION
-N DOCKER-USER
-A FORWARD -j DOCKER-USER
-A FORWARD -j DOCKER-ISOLATION
-A FORWARD -o br-6ada9a016213 -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
-A FORWARD -o br-6ada9a016213 -j DOCKER
-A FORWARD -i br-6ada9a016213 ! -o br-6ada9a016213 -j ACCEPT
-A FORWARD -i br-6ada9a016213 -o br-6ada9a016213 -j ACCEPT
-A FORWARD -o docker0 -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
-A FORWARD -o docker0 -j DOCKER
-A FORWARD -i docker0 ! -o docker0 -j ACCEPT
-A FORWARD -i docker0 -o docker0 -j ACCEPT
-A DOCKER -d 172.18.0.2/32 ! -i br-6ada9a016213 -o br-6ada9a016213 -p tcp -m tcp --dport 5432 -j ACCEPT
-A DOCKER-ISOLATION -i docker0 -o br-6ada9a016213 -j DROP
-A DOCKER-ISOLATION -i br-6ada9a016213 -o docker0 -j DROP
-A DOCKER-ISOLATION -j RETURN
-A DOCKER-USER -j RETURN
However, this time, the service is accessible via internet. This is intended as per the docker-compose.yml I am using this time. However, the iptables configuration is exact the same as the one above. Strange?
How is it possible that two exact iptables configurations have different behavior? I guess I am missing some piece to understand the specifics of the Docket port forwarding functionality.
linux networking firewall iptables docker
linux networking firewall iptables docker
edited Feb 12 at 18:03
Flux
1145
asked Nov 21 '17 at 13:03
Dave TeezoDave Teezo
104
edited Feb 12 at 18:03
Flux
1145
asked Nov 21 '17 at 13:03
Dave TeezoDave Teezo
104
edited Feb 12 at 18:03
Flux
1145
edited Feb 12 at 18:03
Flux
1145
edited Feb 12 at 18:03
Flux
1145
1145
asked Nov 21 '17 at 13:03
Dave TeezoDave Teezo
104
asked Nov 21 '17 at 13:03
Dave TeezoDave Teezo
104
asked Nov 21 '17 at 13:03
Dave TeezoDave Teezo
104
104
add a comment |
add a comment |
1 Answer
1
active
oldest
votes
Have a look at the nat table with iptables -L -t nat.
answered Nov 21 '17 at 13:14
towotowo
50938
add a comment |
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1 Answer
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1 Answer
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Have a look at the nat table with iptables -L -t nat.
answered Nov 21 '17 at 13:14
towotowo
50938
add a comment |
Have a look at the nat table with iptables -L -t nat.
answered Nov 21 '17 at 13:14
towotowo
50938
add a comment |
Have a look at the nat table with iptables -L -t nat.
answered Nov 21 '17 at 13:14
towotowo
50938
Have a look at the nat table with iptables -L -t nat.
answered Nov 21 '17 at 13:14
towotowo
50938
answered Nov 21 '17 at 13:14
towotowo
50938
answered Nov 21 '17 at 13:14
towotowo
50938
answered Nov 21 '17 at 13:14
towotowo
50938
50938
add a comment |
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