Dynamically choose the Docker network subnet

generate_config.sh

@@ -158,6 +158,24 @@ if [ ! -z "${MAILCOW_BRANCH}" ]; then
   git_branch=${MAILCOW_BRANCH}
 fi
 
+if [[ $(docker network ls -q \
+                | xargs docker network inspect --format $'{{range .IPAM.Config}}{{.Subnet}}\n{{end}}' \
+                | grep -qsP '172\.22.*' )$? \
+        -eq 0 ]]; then
+
+        max_octet=$(docker network ls -q \
+                        | xargs -I {} docker network inspect {} --format $'{{range .IPAM.Config}}{{.Subnet}}\n{{end}}' \
+                        | grep -P '172\.[0-9]+\.[0-9]+\.[0-9]+/[0-9]+$' \
+                        | sort \
+                        | tail -n 1 \
+                        | sed -e 's~\(172\)\.\([0-9]\+\).*~\2~g')
+
+        DOCKER_NETWORK="172.$(($max_octet+1)).1"
+else
+        DOCKER_NETWORK='172.22.1'
+fi
+
+
 git fetch --all
 git checkout -f $git_branch
 
@@ -361,7 +379,7 @@ LOG_LINES=9999
 # Internal IPv4 /24 subnet, format n.n.n (expands to n.n.n.0/24)
 # Use private IPv4 addresses only, see https://en.wikipedia.org/wiki/Private_network#Private_IPv4_addresses
 
-IPV4_NETWORK=172.22.1
+IPV4_NETWORK=${DOCKER_NETWORK}
 
 # Internal IPv6 subnet in fc00::/7
 # Use private IPv6 addresses only, see https://en.wikipedia.org/wiki/Private_network#Private_IPv6_addresses