fix: use strict IPv4 regex in nginx resolver to prevent crash

    ### Problem
    The current logic filters IPv6 addresses by counting colons (NF-1 <= 2). However, compressed IPv6 addresses like `fd00::1` contain only two colons, causing them to be incorrectly identified as IPv4. This leads to an invalid `resolver.conf` and Nginx fails to start with:
    `[emerg] invalid port in resolver "fd00::1"`

    Solution

    Replaced the unreliable colon-counting logic with a strict IPv4 regex: ^[0-9]{1,3}(\.[0-9]{1,3}){3}$. This ensures only valid IPv4 addresses are added, maintaining the script's intent to "ignore ipv6 addresses" without crashing Nginx.

    Impact

    Fixes container startup failure on hosts with IPv6 ULA or compressed addresses in /etc/resolv.conf.

Author: d4c00

root/etc/s6-overlay/s6-rc.d/init-nginx/run

@@ -47,7 +47,7 @@ touch /config/nginx/resolver.conf
 if ! grep -q 'resolver' /config/nginx/resolver.conf; then
     RESOLVERRAW=$(awk 'BEGIN{ORS=" "} $1=="nameserver" {print $2}' /etc/resolv.conf)
     for i in ${RESOLVERRAW}; do
-        if [[ "$(awk -F ':' '{print NF-1}' <<<"${i}")" -le 2 ]]; then
+        if [[ "${i}" =~ ^[0-9]{1,3}(\.[0-9]{1,3}){3}$ ]]; then
             RESOLVER="${RESOLVER} ${i}"
         fi
     done