Eu já tinha descrito em atualizando mapas de DNS no estilo do DynDNS como fazia o sistema de DNS dinâmico que uso pra manter o nome bolha.linux-br.org atualizado, entre alguns outros, com o link residencial que tenho em casa.
Funcionava mas não era aquela maravilha. Atualizava a cada 5 minutos e pegava a mudança de IP pelos logs do Apache.
Até aí, sem grandes problemas.
Mas daí o Guto, da instância bolha.us, disse que estava tendo problemas de conexão com a bolha.linux-br.org.
Minha suspeita foi DNS. Então dei uma olhada nos logs.
starting: 20251228T18:45:01
finished: 20251228T18:45:01
starting: 20251228T18:50:01
finished: 20251228T18:50:01
starting: 20251228T18:55:01
updating IPv4 for raspberry3: old=83.233.219.150 new=51.75.236.128
updating: filename=/etc/bind/master/db.linux-br.org old_serial=2025122854 new_serial=2025122855
restarting named.service
finished: 20251228T18:55:01
starting: 20251228T19:00:01
updating IPv4 for raspberry3: old=51.75.236.128 new=83.233.219.150
updating: filename=/etc/bind/master/db.linux-br.org old_serial=2025122855 new_serial=2025122856
restarting named.service
finished: 20251228T19:00:01
starting: 20251228T19:05:01
finished: 20251228T19:05:01
starting: 20251228T19:10:01
finished: 20251228T19:10:01
starting: 20251228T19:15:01
finished: 20251228T19:15:01
starting: 20251228T19:20:01
updating IPv4 for raspberry3: old=83.233.219.150 new=51.68.247.213
updating: filename=/etc/bind/master/db.linux-br.org old_serial=2025122856 new_serial=2025122857
restarting named.service
finished: 20251228T19:20:01
starting: 20251228T19:25:01
updating IPv4 for raspberry3: old=51.68.247.213 new=83.233.219.150
updating: filename=/etc/bind/master/db.linux-br.org old_serial=2025122857 new_serial=2025122858
restarting named.service
finished: 20251228T19:25:01
starting: 20251228T19:30:01
finished: 20251228T19:30:01O código mostra que IPv4 mudou várias vezes no mesmo dia.
Então entrei em contato com o provedor e perguntei se não era possível deixar o lease do DHCP mais longo. A resposta foi que um desses IPs nem era deles.
Um bug na lógica.
Então resolvi escrever algo em Go pra tomar o lugar desse sistema pereba de atualização de DNS. Fiz o dns-monitor.
Agora o dns-monitor funciona ouvido numa API REST, que recebe JSON, atualiza no banco de dados, faz o update dos mapas de DNS e reinicia o serviço de DNS via systemd.
E vejo logs assim:
Feb 24 18:15:02 dns-monitor[1139847]: [2026-02-24T18:15:02] (INFO): [RESP] remote_addr=127.0.0.1:59286, real_ip=2a00:1598:23af:4900:5fe7:c566:dbbd:7b35 status_code=200 hostname=www.bolha message=unchanged
Feb 24 18:15:02 dns-monitor[1139847]: [2026-02-24T18:15:02] (INFO): [REQ] remote_addr=127.0.0.1:59312 real_ip=2a00:1598:23af:4900:5fe7:c566:dbbd:7b35 host=api.linux-br.org uri=/api/register method=POST user_agent=curl/8.5.0
Feb 24 18:17:27 dns-monitor[1139847]: [2026-02-24T18:17:27] (INFO): [REQ] remote_addr=127.0.0.1:52066 real_ip=2a00:1598:23af:4900::b55 host=api.linux-br.org uri=/api/register method=POST user_agent=curl/8.18.0
Feb 24 18:17:28 dns-monitor[1139847]: [2026-02-24T18:17:28] (INFO): [REQ] remote_addr=127.0.0.1:52074 real_ip=83.233.219.150 host=api.linux-br.org uri=/api/register method=POST user_agent=curl/8.18.0
Feb 24 18:20:01 dns-monitor[1139847]: [2026-02-24T18:20:01] (INFO): [REQ] remote_addr=127.0.0.1:47990 real_ip=83.233.219.150 host=api.linux-br.org uri=/api/register method=POST user_agent=curl/8.5.0
Feb 24 18:20:01 dns-monitor[1139847]: [2026-02-24T18:20:01] (INFO): [RESP] remote_addr=127.0.0.1:47990, real_ip=83.233.219.150 status_code=200 hostname=bolha message=unchanged
Feb 24 18:20:01 dns-monitor[1139847]: [2026-02-24T18:20:01] (INFO): [REQ] remote_addr=127.0.0.1:48006 real_ip=2a00:1598:23af:4900:3e52:82ff:fe62:ff11 host=api.linux-br.org uri=/api/register method=POST user_agent=curl/8.5.0
Feb 24 18:20:01 dns-monitor[1139847]: [2026-02-24T18:20:01] (INFO): trigger update on ipv6
Feb 24 18:20:01 dns-monitor[1139847]: [2026-02-24T18:20:01] (INFO): Updating DNS maps: hostname=www.bolha ip_version=6 ip_address=2a00:1598:23af:4900:3e52:82ff:fe62:ff11
Feb 24 18:20:01 dns-monitor[1139847]: [2026-02-24T18:20:01] (INFO): dns maps to be udpated: [/etc/bind/master/db.truta.org /etc/bind/master/db.linux-br.org]
Feb 24 18:20:01 dns-monitor[1139847]: [2026-02-24T18:20:01] (INFO): updated serial: 2026022400
Feb 24 18:20:01 dns-monitor[1139847]: [2026-02-24T18:20:01] (INFO): updated serial: 2026022400
Feb 24 18:20:01 dns-monitor[1139847]: [2026-02-24T18:20:01] (INFO): dns submap to also be update: /etc/bind/master/dyndns.map
Feb 24 18:20:01 dns-monitor[1139847]: [2026-02-24T18:20:01] (INFO): [RESP] remote_addr=127.0.0.1:48006, real_ip=2a00:1598:23af:4900:3e52:82ff:fe62:ff11 status_code=200 hostname=www.bolha message=IPv6_updated
Feb 24 18:20:01 dns-monitor[1139847]: [2026-02-24T18:20:01] (INFO): restart service named via systemd
Feb 24 18:20:01 dns-monitor[1139847]: [2026-02-24T18:20:01] (INFO): [REQ] remote_addr=127.0.0.1:48010 real_ip=83.233.219.150 host=api.linux-br.org uri=/api/register method=POST user_agent=curl/8.5.0
Feb 24 18:20:01 dns-monitor[1139847]: [2026-02-24T18:20:01] (INFO): [REQ] remote_addr=127.0.0.1:48034 real_ip=83.233.219.150 host=api.linux-br.org uri=/api/register method=POST user_agent=curl/8.5.0
Feb 24 18:20:01 dns-monitor[1139847]: [2026-02-24T18:20:01] (INFO): [REQ] remote_addr=127.0.0.1:48020 real_ip=2a00:1598:23af:4900:3e52:82ff:fe62:ff11 host=api.linux-br.org uri=/api/register method=POST user_agent=curl/8.5.0
Feb 24 18:20:01 dns-monitor[1139847]: [2026-02-24T18:20:01] (INFO): [RESP] remote_addr=127.0.0.1:48034, real_ip=83.233.219.150 status_code=200 hostname=www.bolha message=unchanged
Feb 24 18:20:01 dns-monitor[1139847]: [2026-02-24T18:20:01] (INFO): trigger update on ipv6
Feb 24 18:20:01 dns-monitor[1139847]: [2026-02-24T18:20:01] (INFO): Updating DNS maps: hostname=bolha ip_version=6 ip_address=2a00:1598:23af:4900:3e52:82ff:fe62:ff11
Feb 24 18:20:01 dns-monitor[1139847]: [2026-02-24T18:20:01] (INFO): dns maps to be udpated: [/etc/bind/master/db.truta.org /etc/bind/master/db.linux-br.org]
Feb 24 18:20:01 dns-monitor[1139847]: [2026-02-24T18:20:01] (INFO): updated serial: 2026022401
Feb 24 18:20:01 dns-monitor[1139847]: [2026-02-24T18:20:01] (INFO): updated serial: 2026022401
Feb 24 18:20:01 dns-monitor[1139847]: [2026-02-24T18:20:01] (INFO): [REQ] remote_addr=127.0.0.1:48036 real_ip=2a00:1598:23af:4900:3e52:82ff:fe62:ff11 host=api.linux-br.org uri=/api/register method=POST user_agent=curl/8.5.0
Feb 24 18:20:01 dns-monitor[1139847]: [2026-02-24T18:20:01] (INFO): trigger update on ipv6
Feb 24 18:20:01 dns-monitor[1139847]: [2026-02-24T18:20:01] (INFO): dns submap to also be update: /etc/bind/master/dyndns.map
Feb 24 18:20:01 dns-monitor[1139847]: [2026-02-24T18:20:01] (INFO): dns maps to be udpated: [/etc/bind/master/db.truta.org /etc/bind/master/db.linux-br.org]
Feb 24 18:20:01 dns-monitor[1139847]: [2026-02-24T18:20:01] (INFO): updated serial: 2026022402
Feb 24 18:20:01 dns-monitor[1139847]: [2026-02-24T18:20:01] (INFO): updated serial: 2026022402
Feb 24 18:20:01 dns-monitor[1139847]: [2026-02-24T18:20:01] (INFO): [RESP] remote_addr=127.0.0.1:48020, real_ip=2a00:1598:23af:4900:3e52:82ff:fe62:ff11 status_code=200 hostname=bolha message=IPv6_updated
Feb 24 18:20:01 dns-monitor[1139847]: [2026-02-24T18:20:01] (INFO): restart service named via systemd
Feb 24 18:20:01 dns-monitor[1139847]: [2026-02-24T18:20:01] (INFO): dns submap to also be update: /etc/bind/master/dyndns.map
Feb 24 18:20:01 dns-monitor[1139847]: [2026-02-24T18:20:01] (INFO): restart service named via systemd
Feb 24 18:22:28 dns-monitor[1139847]: [2026-02-24T18:22:28] (INFO): [REQ] remote_addr=127.0.0.1:48738 real_ip=2a00:1598:23af:4900::b55 host=api.linux-br.org uri=/api/register method=POST user_agent=curl/8.18.0
Feb 24 18:22:28 dns-monitor[1139847]: [2026-02-24T18:22:28] (INFO): [REQ] remote_addr=127.0.0.1:48740 real_ip=83.233.219.150 host=api.linux-br.org uri=/api/register method=POST user_agent=curl/8.18.0
Feb 24 18:25:02 dns-monitor[1139847]: [2026-02-24T18:25:02] (INFO): [REQ] remote_addr=127.0.0.1:52456 real_ip=83.233.219.150 host=api.linux-br.org uri=/api/register method=POST user_agent=curl/8.5.0
Feb 24 18:25:02 dns-monitor[1139847]: [2026-02-24T18:25:02] (INFO): [RESP] remote_addr=127.0.0.1:52456, real_ip=83.233.219.150 status_code=200 hostname=bolha message=unchanged
Feb 24 18:25:02 dns-monitor[1139847]: [2026-02-24T18:25:02] (INFO): [REQ] remote_addr=127.0.0.1:52468 real_ip=83.233.219.150 host=api.linux-br.org uri=/api/register method=POST user_agent=curl/8.5.0
Feb 24 18:25:02 dns-monitor[1139847]: [2026-02-24T18:25:02] (INFO): [REQ] remote_addr=127.0.0.1:52476 real_ip=83.233.219.150 host=api.linux-br.org uri=/api/register method=POST user_agent=curl/8.5.0
Feb 24 18:25:02 dns-monitor[1139847]: [2026-02-24T18:25:02] (INFO): [RESP] remote_addr=127.0.0.1:52476, real_ip=83.233.219.150 status_code=200 hostname=www.bolha message=unchanged
Feb 24 18:25:02 dns-monitor[1139847]: [2026-02-24T18:25:02] (INFO): [REQ] remote_addr=127.0.0.1:52482 real_ip=2a00:1598:23af:4900:3e52:82ff:fe62:ff11 host=api.linux-br.org uri=/api/register method=POST user_agent=curl/8.5.0
Feb 24 18:25:02 dns-monitor[1139847]: [2026-02-24T18:25:02] (INFO): [REQ] remote_addr=127.0.0.1:52484 real_ip=2a00:1598:23af:4900:3e52:82ff:fe62:ff11 host=api.linux-br.org uri=/api/register method=POST user_agent=curl/8.5.0
Feb 24 18:25:02 dns-monitor[1139847]: [2026-02-24T18:25:02] (INFO): [RESP] remote_addr=127.0.0.1:52484, real_ip=2a00:1598:23af:4900:3e52:82ff:fe62:ff11 status_code=200 hostname=www.bolha message=unchanged
Feb 24 18:25:02 dns-monitor[1139847]: [2026-02-24T18:25:02] (INFO): [REQ] remote_addr=127.0.0.1:52498 real_ip=2a00:1598:23af:4900:3e52:82ff:fe62:ff11 host=api.linux-br.org uri=/api/register method=POST user_agent=curl/8.5.0
Feb 24 18:25:02 dns-monitor[1139847]: [2026-02-24T18:25:02] (INFO): [RESP] remote_addr=127.0.0.1:52498, real_ip=2a00:1598:23af:4900:3e52:82ff:fe62:ff11 status_code=200 hostname=bolha message=unchanged
Feb 24 18:27:28 dns-monitor[1139847]: [2026-02-24T18:27:28] (INFO): [REQ] remote_addr=127.0.0.1:46772 real_ip=2a00:1598:23af:4900::b55 host=api.linux-br.org uri=/api/register method=POST user_agent=curl/8.18.0
Feb 24 18:27:29 dns-monitor[1139847]: [2026-02-24T18:27:29] (INFO): [REQ] remote_addr=127.0.0.1:46774 real_ip=83.233.219.150 host=api.linux-br.org uri=/api/register method=POST user_agent=curl/8.18.0
Feb 24 18:30:01 dns-monitor[1139847]: [2026-02-24T18:30:01] (INFO): [REQ] remote_addr=127.0.0.1:37288 real_ip=83.233.219.150 host=api.linux-br.org uri=/api/register method=POST user_agent=curl/8.5.0
Feb 24 18:30:01 dns-monitor[1139847]: [2026-02-24T18:30:01] (INFO): [REQ] remote_addr=127.0.0.1:37294 real_ip=83.233.219.150 host=api.linux-br.org uri=/api/register method=POST user_agent=curl/8.5.0
Feb 24 18:30:01 dns-monitor[1139847]: [2026-02-24T18:30:01] (INFO): [RESP] remote_addr=127.0.0.1:37294, real_ip=83.233.219.150 status_code=200 hostname=bolha message=unchanged
Feb 24 18:30:01 dns-monitor[1139847]: [2026-02-24T18:30:01] (INFO): [REQ] remote_addr=127.0.0.1:37302 real_ip=83.233.219.150 host=api.linux-br.org uri=/api/register method=POST user_agent=curl/8.5.0
Ficou mais fácil acompanhar as mudanças e o sistema ficou mais estável.
No servidor eu fiz um reverse proxy no Apache pra chegar no serviço dns-monitor.
Do lado do cliente, eu uso curl, como é possível ver pelos logs com user_agent. Envio algo como isso abaixo mas na crontab a cada 5 minutos:
❯ curl -6 -o /dev/null -s "https://api.linux-br.org/api/register" -d '{"hostname": "bolha", "token": "abcdefgh123456"}'
❯ curl -4 -o /dev/null -s "https://api.linux-br.org/api/register" -d '{"hostname": "bolha", "token": "abcdefgh123456"}'
O sistema está longe de estar perfeito. Roda vários updates no mapa seguidamente se o endereço mudar tanto no IPv4 quanto no IPv6, que aconteceu quando mudei o servidor fisicamente do quarto pra sala. Mas está funcionando e com menos erros que antes.
Quem quiser olhar o código, já esta no Codeberg:
https://codeberg.org/helioloureiro/dns_monitor
Não tem muita descrição, mas está lá e está funcionando em produção.
Nota: depois de tudo isso, o Guto falou que o problema era do lado da bolha.us. Ao menos serviu pra eu sair da inércia e escrever um pouco de Go, o que foi bem divertido.
Nota 2: nenhum código de AI foi usando durante o desenvolvimento desse programa.
