Get rid of hard coded IPs (#441)

Replace them with:
* containers' hostnames
* gateway's IP address for default SMTP_HOST
* Core: when SMTP_HOST undef, echo the default value
* docker-compose: add port mapping
* docker-compose: drop network driver conf
* Exim macro: use localhost as LMTP host
* Update README.md
* docker-compose: Limit port mapping to loopback
* Update other docker-compose example files

core/README.md

@@ -40,8 +40,8 @@ These are the variables that you MUST change before deploying:
 These are the variables that you don't need to change if you are using a
 standard version of docker-compose.yaml from this repository.
 
-- `MM_HOSTNAME`: Which IP should Core bind to for REST API and LMTP. If not
-  defined output for `hostname -i` command is used.
+- `MM_HOSTNAME`: Which hostname or IP should Core bind to for REST API and
+  LMTP. If not defined output from `hostname` command is used.
 
 - `MAILMAN_REST_PORT`: Which port should Core use for the REST API. If not defined
   the default is `8001`.
@@ -55,7 +55,8 @@ standard version of docker-compose.yaml from this repository.
 - `MTA`: Mail Transfer Agent to use. Either `exim` or `postfix`. Default value is `exim`.
 
 - `SMTP_HOST`: IP Address/hostname from which you will be sending
-  emails. Default value is `172.19.199.1`, which is the address of the Host OS.
+  emails. Default value is the container's gateway retrieved from:
+    /sbin/ip route | awk '/default/ { print $3 }'
 
 - `SMTP_PORT`: Port used for SMTP. Default is `25`.
 

core/assets/exim/25_mm3_macros

@@ -2,7 +2,9 @@
 # /etc/exim4/conf.d/main/25_mm3_macros
 
 domainlist mm3_domains=MY_DOMAIN_NAME
-MM3_LMTP_HOST=172.19.199.2
+# Depending on your network configuration
+#MM3_LMTP_HOST=mailman-core
+MM3_LMTP_HOST=localhost
 MM3_LMTP_PORT=8024
 MM3_HOME=/opt/mailman/core/var
 

core/docker-entrypoint.sh

@@ -27,14 +27,16 @@ function wait_for_mysql () {
 echo "# This file is autogenerated at container startup." > /etc/mailman.cfg
 
 # Check if $MM_HOSTNAME is set, if not, set it to the value returned by
-# `hostname -i` command to set it to whatever IP address is assigned to the
+# `hostname` command to set it to whatever hostname is assigned to the
 # container.
 if [[ ! -v MM_HOSTNAME ]]; then
-	export MM_HOSTNAME=`hostname -i`
+	export MM_HOSTNAME=`hostname`
 fi
 
+# SMTP_HOST defaults to the gateway
 if [[ ! -v SMTP_HOST ]]; then
-	export SMTP_HOST='172.19.199.1'
+	export SMTP_HOST=$(/sbin/ip route | awk '/default/ { print $3 }')
+	echo "SMPT_HOST not specified, using the gateway ($SMTP_HOST) as default"
 fi
 
 if [[ ! -v SMTP_PORT ]]; then