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#!/bin/bash | |
# Configure the instance to run as a Port Address Translator (PAT) to provide | |
# Internet connectivity to private instances. | |
function log { logger -t "vpc" -- $1; } | |
function die { | |
[ -n "$1" ] && log "$1" | |
log "Configuration of PAT failed!" | |
exit 1 | |
} | |
# Sanitize PATH | |
PATH="/usr/sbin:/sbin:/usr/bin:/bin" | |
log "Determining the MAC address on eth0..." | |
ETH0_MAC=$(cat /sys/class/net/eth0/address) || | |
die "Unable to determine MAC address on eth0." | |
log "Found MAC ${ETH0_MAC} for eth0." | |
VPC_CIDR_URI="http://169.254.169.254/latest/meta-data/network/interfaces/macs/${ETH0_MAC}/vpc-ipv4-cidr-block" | |
log "Metadata location for vpc ipv4 range: ${VPC_CIDR_URI}" | |
VPC_CIDR_RANGE=$(curl --retry 3 --silent --fail ${VPC_CIDR_URI}) | |
if [ $? -ne 0 ]; then | |
log "Unable to retrive VPC CIDR range from meta-data, using 0.0.0.0/0 instead. PAT may masquerade traffic for Internet hosts!" | |
VPC_CIDR_RANGE="0.0.0.0/0" | |
else | |
log "Retrieved VPC CIDR range ${VPC_CIDR_RANGE} from meta-data." | |
fi | |
log "Enabling PAT..." | |
sysctl -q -w net.ipv4.ip_forward=1 net.ipv4.conf.eth0.send_redirects=0 && ( | |
iptables -t nat -C POSTROUTING -o eth0 -s ${VPC_CIDR_RANGE} -j MASQUERADE 2> /dev/null || | |
iptables -t nat -A POSTROUTING -o eth0 -s ${VPC_CIDR_RANGE} -j MASQUERADE ) || | |
die | |
sysctl net.ipv4.ip_forward net.ipv4.conf.eth0.send_redirects | log | |
iptables -n -t nat -L POSTROUTING | log | |
log "Configuration of PAT complete." | |
exit 0 |
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