Administrace komentářů

Tento post je o čiastkovom probléme, na ktorý som narazil pri jedom svojom experimente.

Chcem v docker kontajneri bežať BIND DNS server a použiť ho z VM bežiacom pod VirtualBox-om.

Setup:

Host:

# ip -4 addr  show dev docker0
5: docker0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default 
    inet 192.168.1.1/24 scope global docker0
       valid_lft forever preferred_lft forever

Docker kontajner:

# ip -4 addr show dev eth0
13: eth0@if14: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default 
    inet 192.168.1.2/24 scope global eth0
       valid_lft forever preferred_lft forever

VM: Linux (VirtualBox - network adapter mode: Bridge na interface docker0)

# ip -4 addr show
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default 
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
2: enp0s3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
    inet 192.168.1.3/24 brd 192.168.1.255 scope global enp0s3
       valid_lft forever preferred_lft forever

Ping v guest-ovi:

# ping -c 3 192.168.1.2
PING 192.168.1.2 (192.168.1.2) 56(84) bytes of data.
64 bytes from 192.168.1.2: icmp_seq=1 ttl=64 time=0.707 ms
64 bytes from 192.168.1.2: icmp_seq=2 ttl=64 time=0.294 ms
64 bytes from 192.168.1.2: icmp_seq=3 ttl=64 time=1.28 ms

--- 192.168.1.2 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2006ms
rtt min/avg/max/mdev = 0.294/0.762/1.286/0.407 ms

Resolvovanie:

Docker container:

# host container.samdom.example.org
container.samdom.example.org has address 192.168.1.2

Host:

# host container.samdom.example.org 192.168.1.2
Using domain server:
Name: 192.168.1.2
Address: 192.168.1.2#53
Aliases: 

container.samdom.example.org has address 192.168.1.2

Guest:

# host container.samdom.example.org 192.168.1.2
;; connection timed out; no servers could be reached

VM guest vie pingnúť kontajner, ale nevie kontaktovať DNS server bežiaci v tom kontajneri. Ale to nie je tak celkom pravda. Tcpdump/wireshark bežiaci v tom VM guestovi vidí, ako odíde DNS paket s DNS query a vidí aj paket s DNS odpoveďou. Ale napriek tomu resolvovanie zlyhá z timeout-om.

Kde je zádrhel?