From 4febe16e256fc26acfcd4111fdf76d1bb1405f98 Mon Sep 17 00:00:00 2001
From: Daniel Baumann <mail@daniel-baumann.ch>
Date: Sun, 5 Jun 2022 20:04:59 +0200
Subject: Handling ipv4-only/ipv6-only nameservers on ipv4-only/ipv6-only
 systems.

Signed-off-by: Daniel Baumann <mail@daniel-baumann.ch>
---
 dehydrated/bin/dehydrated-nsupdate             | 35 ++++++++++++++++++++++++--
 dehydrated/share/man/dehydrated-nsupdate.1.rst |  3 ++-
 2 files changed, 35 insertions(+), 3 deletions(-)

diff --git a/dehydrated/bin/dehydrated-nsupdate b/dehydrated/bin/dehydrated-nsupdate
index fa421ea..96c95eb 100755
--- a/dehydrated/bin/dehydrated-nsupdate
+++ b/dehydrated/bin/dehydrated-nsupdate
@@ -88,9 +88,9 @@ else
 	TXT_RECORD="_acme-challenge.${DOMAIN}"
 fi
 
-# find nameservers to update
 ZONE="${TXT_RECORD}"
 
+# find all nameservers to update
 while true
 do
 	NAMESERVERS="$(${DIG} +nocomments +noquestion NS "${ZONE}" 2>&1 | grep -v '^;' | awk '/NS/ { print $5 }')"
@@ -104,12 +104,43 @@ do
 	fi
 done
 
+NAMESERVERS_IPV6=""
+NAMESERVERS_IPV4=""
+
+for NAMESERVER in ${NAMESERVERS}
+do
+	if [ -n "$(${DIG} +nocomments +noquestion +short AAAA ${NAMESERVER})" ]
+	then
+		NAMESERVERS_IPV6="${NAMESERVERS_IPV6} ${NAMESERVER}"
+	fi
+
+	if [ -n "$(${DIG} +nocomments +noquestion +short A ${NAMESERVER})" ]
+	then
+		NAMESERVERS_IPV4="${NAMESERVERS_IPV4} ${NAMESERVER}"
+	fi
+done
+
+# filter nameservers by available IP protocol
+NAMESERVERS=""
+
+if hostname -I | grep -qs ':'
+then
+	NAMESERVERS="${NAMESERVERS} ${NAMESERVERS_IPV6}"
+fi
+
+if hostname -I | grep -qs '\.'
+then
+	NAMESERVERS="${NAMESERVERS} ${NAMESERVERS_IPV4}"
+fi
+
+NAMESERVERS="$(echo ${NAMESERVERS} | sed -e 's| |\n|g' | sort -u -V)"
+
+# update nameservers
 if [ -n "${TSIG_KEYFILE}" ] && [ -e "${TSIG_KEYFILE}" ]
 then
 	NSUPDATE_OPTIONS="-k ${TSIG_KEYFILE}"
 fi
 
-# update nameservers
 for NAMESERVER in ${NAMESERVERS}
 do
 	echo -n "   + sending '${HOOK_ACTION}' for ${TXT_RECORD} to ${NAMESERVER}..."
diff --git a/dehydrated/share/man/dehydrated-nsupdate.1.rst b/dehydrated/share/man/dehydrated-nsupdate.1.rst
index 058785f..db58d5c 100644
--- a/dehydrated/share/man/dehydrated-nsupdate.1.rst
+++ b/dehydrated/share/man/dehydrated-nsupdate.1.rst
@@ -54,7 +54,8 @@ Features
 
 | **automatic nameserver detection**
 | **dehydrated-nsupdate** automatically finds and updates all authoritative
-| nameservers for a given record by looking up the records in the DNS by itself.
+| nameservers for a given record by looking up the records in the DNS by itself,
+| supporting IPv6-only, IPv4-only, and dual-stacked environments.
 
 | **proper CNAME support**
 | **dehydrated-nsupdate** follows CNAMEs delegating the TXT record creation to
-- 
cgit v1.2.3