Initial commit, see README.md for details

README.md

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+# Docker DNS Lab
+
+```mermaid
+flowchart TD
+  client["client<br/>172.20.0.100"]
+  subgraph main["example.com"]
+    maindns[(maindns<br/>ns1.example.com<br/>172.20.0.10)]
+    subgraph sub["sub.example.com"]
+      subdns[(subdns<br/>ns1.sub.example.com<br/>172.20.0.20)]
+    end
+  end
+
+  client -->|"DNS"| maindns
+  maindns -->|"delegate:sub"| subdns
+```
+
+## Running
+
+```shell
+#start the containers
+./start-dnslab.sh
+
+# do your tests
+./dnslab dig ns1.example.com
+./dnslab dig ns1.sub.example.com
+
+./dnslab ip -br a
+```
+
+## Cleaning up
+
+```
+./cleanup-dnslab.sh
+```

cleanup-dnslab.sh

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+#! /usr/bin/env bash
+
+set -e
+
+docker compose down --remove-orphans
+
+[[ $# -eq 0 ]] || docker run --rm -v .:/tmp/x bash -vc "cd /tmp/x; ${*:-ls -la --color}"
+

client_Dockerfile

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+FROM ubuntu
+
+RUN apt-get update \
+    && apt-get install --yes dnsutils iputils-arping iputils-ping iproute2
+

compose.yaml

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+services:
+  maindns:
+    image: internetsystemsconsortium/bind9:9.18
+    container_name: maindns
+    command: -u root -g -d 9 -f -c /etc/bind/named.conf
+    volumes:
+      - maindns_etc_bind:/etc/bind
+      - ./maindns_named.conf:/etc/bind/named.conf:ro
+      - ./db.example.com:/etc/bind/db.example.com:ro
+    tmpfs:
+      - /var/cache/bind
+      - /var/log
+    depends_on:
+      - subdns
+    networks:
+      dnsnet:
+        ipv4_address: 172.20.0.10
+
+  subdns:
+    image: internetsystemsconsortium/bind9:9.18
+    command: -u root -g -d 9 -f -c /etc/bind/named.conf
+    container_name: subdns
+    volumes:
+      - subdns_etc_bind:/etc/bind
+      - ./subdns_named.conf:/etc/bind/named.conf:ro
+      - ./db.sub.example.com:/etc/bind/db.sub.example.com:ro
+    tmpfs:
+      - /var/cache/bind
+      - /var/log
+    networks:
+      dnsnet:
+        ipv4_address: 172.20.0.20
+
+  client:
+    build:
+      dockerfile: client_Dockerfile
+    container_name: client
+    command: sleep infinity
+    depends_on:
+      - maindns
+    dns:
+      - 172.20.0.10
+    networks:
+      dnsnet:
+        ipv4_address: 172.20.0.100
+
+networks:
+  dnsnet:
+    driver: bridge
+    ipam:
+      config:
+        - subnet: 172.20.0.0/24
+
+volumes:
+  maindns_etc_bind:
+  subdns_etc_bind:

db.example.com

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+$TTL    86400
+@       IN      SOA     ns1.example.com. admin.example.com. (
+                            1         ; Serial
+                            3600      ; Refresh
+                            1800      ; Retry
+                            604800    ; Expire
+                            86400 )   ; Minimum TTL
+        IN      NS      ns1.example.com.
+ns1     IN      A       172.20.0.10
+
+; Delegate subdomain to subdns
+sub     IN      NS      ns1.sub.example.com.
+ns1.sub IN      A       172.20.0.20

db.sub.example.com

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+$TTL    86400
+@       IN      SOA     ns1.sub.example.com. admin.sub.example.com. (
+                            1         ; Serial
+                            3600      ; Refresh
+                            1800      ; Retry
+                            604800    ; Expire
+                            86400 )   ; Minimum TTL
+        IN      NS      ns1.sub.example.com.
+ns1     IN      A       172.20.0.20
+client  IN      A       172.20.0.100

dnslab

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+#! /usr/bin/env bash
+
+set -e
+
+docker exec -it client "${@:-bash}"
+

maindns_named.conf

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+options {
+  directory "/var/cache/bind";
+  listen-on port 53 { any; };
+  allow-query { any; };
+  recursion no;
+};
+
+zone "example.com" {
+  type master;
+  file "/etc/bind/db.example.com";
+};
+
+zone "sub.example.com" {
+  type delegation-only;
+};
+
+logging {
+  channel default_log {
+    file "/var/log/named.log";
+    severity info;
+    print-time yes;
+  };
+  category default { default_log; };
+};

start-dnslab.sh

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+#! /usr/bin/env bash
+
+set -e
+
+docker compose down --remove-orphans \
+&& docker compose build \
+&& docker compose up -d
+

subdns_named.conf

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+options {
+  directory "/var/cache/bind";
+  listen-on port 53 { any; };
+  allow-query { any; };
+  recursion no;
+};
+
+zone "sub.example.com" {
+  type master;
+  file "/etc/bind/db.sub.example.com";
+};
+
+logging {
+  channel default_log {
+    file "/var/log/named.log";
+    severity info;
+    print-time yes;
+  };
+  category default { default_log; };
+};