Fail 2 ban not banning an IP when found

Question

When testing my applications fail2ban from another server I see these logs:

2021-08-01 18:48:37,692 fail2ban.filter         [1]: INFO    [nginx] Found 51.195.221.70 - 2021-08-01 18:48:37
2021-08-01 18:48:37,897 fail2ban.filter         [1]: INFO    [nginx] Found 51.195.221.70 - 2021-08-01 18:48:37
2021-08-01 18:48:38,496 fail2ban.filter         [1]: INFO    [nginx] Found 51.195.221.70 - 2021-08-01 18:48:38
2021-08-01 18:48:38,671 fail2ban.filter         [1]: INFO    [nginx] Found 51.195.221.70 - 2021-08-01 18:48:38
2021-08-01 18:48:38,860 fail2ban.filter         [1]: INFO    [nginx] Found 51.195.221.70 - 2021-08-01 18:48:38
2021-08-01 18:48:38,976 fail2ban.actions        [1]: NOTICE  [nginx] Ban 51.195.221.70
2021-08-01 18:48:39,234 fail2ban.filter         [1]: INFO    [nginx] Found 51.195.221.70 - 2021-08-01 18:48:39
[SNIP]
2021-08-01 18:48:41,686 fail2ban.filter         [1]: INFO    [nginx] Found 51.195.221.70 - 2021-08-01 18:48:41
2021-08-01 18:48:41,872 fail2ban.filter         [1]: INFO    [nginx] Found 51.195.221.70 - 2021-08-01 18:48:41
2021-08-01 18:48:41,897 fail2ban.actions        [1]: NOTICE  [nginx] 51.195.221.70 already banned

The requests can keep continuing even when found and banned. My Docker container looks like this:

 fail2ban:
    image: 'crazymax/fail2ban:latest'
    restart: 'always'
    network_mode: 'host'
    cap_add:
      - 'NET_ADMIN'
      - 'NET_RAW'
    volumes:
      - 'nginx-log:/var/log:ro'
      - 'fail2ban-data:/data'
    env_file:
      - './fail2ban.env'

My configuration is:

jail.d/nginx.conf

[nginx]
enabled = true
logpath = /var/log/access.log
port = http,https

filter.d/nginx.conf

[Definition]
failregex = ^<HOST> \- \S+ \[\] \"(GET|POST|HEAD) .+\" 419 .+$
ignoreregex =

Any help appreciated. Do I need to configure IP tables?

Answer 1

https://github.com/crazy-max/docker-fail2ban/blob/master/examples/jails/traefik/jail.d/traefik.conf

I found I needed to add chain = DOCKER-USER to my jail.d/nginx.conf to make this work.