From 43ef49c73722174d37047efd53441a429fa9a932 Mon Sep 17 00:00:00 2001
From: Michael Kropat <mail@michael.kropat.name>
Date: Sat, 7 Jun 2014 13:54:58 -0400
Subject: [PATCH] Improve hostname/IP default values

Default IP+hostname values were incorrect for my VPS provider. I
improved the detection, which should give correct results results for
almost any provider. Specific issues addressed:

- icanhazip.com detection was only enabled in non-interactive mode
- `hostname` is by convention a short (non-fqdn) name in Ubuntu
- `hostname --fqdn` fails if provider does not pouplate `hosts` file
- `hostname -i` fails if provider does not populate `hosts` file
- `curl` without `--fail` will someday return crazy results
  when icanhazip.com returns 500 errors or similar
---
 setup/functions.sh | 28 ++++++++++++++++++++++++++++
 setup/start.sh     | 14 ++++++++------
 2 files changed, 36 insertions(+), 6 deletions(-)

diff --git a/setup/functions.sh b/setup/functions.sh
index 426f914a..d98405fd 100644
--- a/setup/functions.sh
+++ b/setup/functions.sh
@@ -19,6 +19,34 @@ function apt_install {
 	DEBIAN_FRONTEND=noninteractive apt-get -qq -y install $PACKAGES > /dev/null;
 }
 
+function get_default_hostname {
+	set -- $(hostname --fqdn      2>/dev/null ||
+                 hostname --all-fqdns 2>/dev/null ||
+                 hostname             2>/dev/null)
+	printf '%s\n' "$1"
+}
+
+function get_default_publicip {
+	get_publicip_from_web_service || get_publicip_from_dns
+}
+
+function get_publicip_from_web_service {
+	curl --fail --silent icanhazip.com 2>/dev/null
+}
+
+function get_publicip_from_dns {
+	set -- $(hostname --ip-address       2>/dev/null) \
+	       $(hostname --all-ip-addresses 2>/dev/null)
+	while (( $# )) && is_loopback_ip "$1"; do
+		shift
+	done
+	printf '%s\n' "$1"
+}
+
+function is_loopback_ip {
+	[[ "$1" == 127.* ]]
+}
+
 function ufw_allow {
 	if [ -z "$DISABLE_FIREWALL" ]; then
 		# ufw has completely unhelpful output
diff --git a/setup/start.sh b/setup/start.sh
index e9ccd552..cec5c90b 100755
--- a/setup/start.sh
+++ b/setup/start.sh
@@ -2,6 +2,8 @@
 # This is the entry point for configuring the system.
 #####################################################
 
+source setup/functions.sh # load our functions
+
 # Check system setup.
 
 if [ "`lsb_release -d | sed 's/.*:\s*//'`" != "Ubuntu 14.04 LTS" ]; then
@@ -31,7 +33,7 @@ if [ -z "$PUBLIC_HOSTNAME" ]; then
 
 	if [ -z "$DEFAULT_PUBLIC_HOSTNAME" ]; then
 		# set a default on first run
-		DEFAULT_PUBLIC_HOSTNAME=`hostname`
+		DEFAULT_PUBLIC_HOSTNAME=`get_default_hostname`
 	fi
 
 	read -e -i "$DEFAULT_PUBLIC_HOSTNAME" -p "Hostname: " PUBLIC_HOSTNAME
@@ -46,7 +48,7 @@ if [ -z "$PUBLIC_IP" ]; then
 
 	if [ -z "$DEFAULT_PUBLIC_IP" ]; then
 		# set a default on first run
-		DEFAULT_PUBLIC_IP=`hostname -i`
+		DEFAULT_PUBLIC_IP=`get_default_publicip`
 	fi
 
 	read -e -i "$DEFAULT_PUBLIC_IP" -p "Public IP: " PUBLIC_IP
@@ -69,18 +71,18 @@ fi
 
 # Automatic configuration, e.g. as used in our Vagrant configuration.
 if [ "$PUBLIC_IP" == "auto" ]; then
-	# Assume `hostname -i` gives the correct public IP address for the machine.
-	PUBLIC_IP=`hostname -i`
+	# Assume `get_publicip_from_dns` gives the correct public IP address for the machine.
+	PUBLIC_IP=`get_publicip_from_dns`
 	echo "IP Address: $PUBLIC_IP"
 fi
 if [ "$PUBLIC_IP" == "auto-web" ]; then
 	# Use a public API to get our public IP address.
-	PUBLIC_IP=`curl -s icanhazip.com`
+	PUBLIC_IP=`get_publicip_from_web_service`
 	echo "IP Address: $PUBLIC_IP"
 fi
 if [ "$PUBLIC_HOSTNAME" == "auto-easy" ]; then
 	# Generate a probably-unique subdomain under our justtesting.email domain.
-	PUBLIC_HOSTNAME=m`hostname -i | sha1sum | cut -c1-5`.justtesting.email
+	PUBLIC_HOSTNAME=m`get_publicip_from_dns | sha1sum | cut -c1-5`.justtesting.email
 	echo "Public Hostname: $PUBLIC_HOSTNAME"
 fi