From cc7559e9e41bbebc3a58d55ad52707b3cff8d952 Mon Sep 17 00:00:00 2001
From: Andrew Cady <d@samizdat>
Date: Tue, 28 Sep 2021 20:30:21 -0400
Subject: cryptonomic-dyndns will prefer IPv6 if no public IPv4 address is
 available

---
 selfpublish.sh | 42 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)

diff --git a/selfpublish.sh b/selfpublish.sh
index 521d9da..fa366a8 100644
--- a/selfpublish.sh
+++ b/selfpublish.sh
@@ -83,6 +83,7 @@ fortune-mod
 fortunes-min
 gnupg (>= 2.2.14)
 libssl1.1 (>= 1.1.1d)
+netmask
 openssl
 ssh
 EOF
@@ -178,6 +179,44 @@ EOF
 # File: /usr/share/doc/selfpublish-dot-sh/README.Debian 644
 #  This gets overwritten :(
 # EOF
+    control_file_file /usr/lib/cryptonomic/cryptonomic-ipv4 755 <<'EOF'
+#!/bin/bash
+
+ipv4_check_masks_()
+{
+      ip=$(netmask -x "$1"/32) || return
+      ip=${ip%/*}
+      shift
+      for cidr in "$@"
+      do
+            prefix=${cidr%/*}
+            mask=${cidr#*/}
+            if (( (ip & mask) == prefix ))
+            then
+                  return 1
+            fi
+      done
+      true
+}
+
+ipv4_address_is_public()
+{
+      ipv4_check_masks_ "$1" $CIDR_NONPUBLIC
+}
+
+CIDR_NONPUBLIC=$(netmask -x 127.0/8 10.0/8 192.168.0/16 172.16.0/20 169.254.0/16)
+
+ip -4 -oneline addr |
+while read n dev _ inet _
+do
+    a=${inet%%/*}
+    if ipv4_address_is_public "$a"; then
+        echo "$a"
+    fi
+done
+
+
+EOF
     control_file_file /usr/lib/cryptonomic/cryptonomic-gpg 755 <<'EOF'
 #!/bin/sh
 
@@ -407,6 +446,9 @@ elif [ "$1" = dyndns ]
 then
     shift
     # further command line options are ssh options
+    if [ -z "$(cryptonomic ipv4)" ]
+    then set -- "$@" -6
+    fi
     set -- ssh -i "$KEY_FILE" dyndns@"$DOMAIN" "$@" -- "$(hostname)"
 
     if [ -r "$KEY_FILE" ]
-- 
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