Listen on both loopback addresses, and name them

README.rst

@@ -54,10 +54,14 @@ Upstream's ``conf.d/main`` sets ``listen_addresses = '*'`` and appends
 ``host all all 0.0.0.0/0 md5`` to ``pg_hba.conf``, so the appliance accepts
 password authentication for every database from anywhere. On an IPv6 first,
 publicly routable appliance (brief section 5.3) that is not a default this
-project can inherit quietly. This layer keeps Debian's
-``listen_addresses = 'localhost'``, which is the loopback of both families,
-and asserts at build time that neither of upstream's two changes is
-present. An appliance that really has remote clients opens the port, says
+project can inherit quietly. This layer listens on
+``'::1,127.0.0.1'``, the loopback of both families and nothing else, and
+asserts at build time that neither of upstream's two changes is present.
+Both addresses are written out rather than left to Debian's default of
+``'localhost'``: that default binds the IPv4 loopback alone, because
+Debian's ``/etc/hosts`` maps ``::1`` to ``ip6-localhost`` and never to
+``localhost``, which is a defect this layer shipped once and its own boot
+test caught. An appliance that really has remote clients opens the port, says
 who may connect and terminates TLS. That is a decision an appliance makes,
 not one a database layer makes for everything built on it.
 

changelog

@@ -1,3 +1,13 @@
+turnkey-postgresql-19.0 (2) turnkey; urgency=low
+
+  * Listen on both loopback addresses, named literally:
+    listen_addresses = '::1,127.0.0.1'. Debian's default, 'localhost',
+    binds the IPv4 loopback alone, because Debian's /etc/hosts maps ::1 to
+    ip6-localhost and never to localhost, so an appliance built on this
+    layer and reaching its database over IPv6 found nothing listening.
+
+ -- Keel Linux maintainers <admin@keellinux.org>  Sun, 27 Sep 2026 07:30:00 +0000
+
 turnkey-postgresql-19.0 (1) turnkey; urgency=low
 
   * Initial release of the PostgreSQL database layer for Keel, compatible

conf.d/main

@@ -41,12 +41,30 @@ EOF
 
 systemctl stop postgresql
 
-# The cluster listens on the loopback of both families and nowhere else.
-# Debian's default, listen_addresses = 'localhost', is exactly that, so it
-# is asserted rather than changed: upstream's postgresql appliance replaces
-# it with '*' and appends a pg_hba line accepting password authentication
-# from 0.0.0.0/0, and this layer must not inherit that by accident.
-grep -qE "^#?listen_addresses = 'localhost'" "$CONF_DIR/postgresql.conf"
+# The cluster listens on the loopback of both families and nowhere else,
+# and both are named as literal addresses.
+#
+# Debian's default is listen_addresses = 'localhost', and that was taken
+# for "the loopback of both families" when this layer was written. It is
+# not. Debian's /etc/hosts maps ::1 to ip6-localhost and ip6-loopback and
+# never to localhost, so getaddrinfo("localhost") answers 127.0.0.1 alone
+# and the cluster binds the IPv4 loopback only. Measured on the booted
+# layer: "LISTEN 127.0.0.1:5432" and nothing on [::1]:5432, with ::1 up on
+# lo and pg_hba.conf already holding its scram-sha-256 line for ::1/128.
+# An appliance built on this layer and reaching its database over IPv6,
+# which is the default this project builds for (brief section 10), found
+# nothing listening.
+#
+# Two literal addresses cannot resolve into something else, which is the
+# whole point of writing them out; what they bind to is then proved on the
+# booted machine by the boot test rather than assumed here.
+sed -i "s|^#\?listen_addresses = .*|listen_addresses = '::1,127.0.0.1'\t\t# set by conf.d/main of keel-postgresql: see the comment there|" \
+    "$CONF_DIR/postgresql.conf"
+grep -qE "^listen_addresses = '::1,127\.0\.0\.1'" "$CONF_DIR/postgresql.conf"
+
+# Upstream's postgresql appliance replaces listen_addresses with '*' and
+# appends a pg_hba line accepting password authentication from 0.0.0.0/0.
+# This layer must not inherit either by accident.
 ! grep -qE "^listen_addresses = '\*'" "$CONF_DIR/postgresql.conf"
 ! grep -qE '^host\s+all\s+all\s+0\.0\.0\.0/0' "$CONF_DIR/pg_hba.conf"