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AL2023 ec2-net-utils lib.sh
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lib.sh
#!/bin/bash
#
# Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License"). You may
# not use this file except in compliance with the License. A copy of the
# License is located at
#
# http://aws.amazon.com/apache2.0/
#
# or in the "license" file accompanying this file. This file is distributed
# on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
# express or implied. See the License for the specific language governing
# permissions and limitations under the License.
# These should be set by the calling program
declare ether
declare unitdir
declare lockdir
declare reload_flag
declare -r imds_endpoints=("http://169.254.169.254/latest" "http://[fd00:ec2::254]/latest")
declare -r imds_token_path="api/token"
declare -r syslog_facility="user"
declare -r syslog_tag="ec2net"
declare -i -r rule_base=10000
# Systemd installs routes with a metric of 1024 by default. We
# override to a lower metric to ensure that our fully configured
# interfaces are preferred over those in the process of being
# configured.
declare -i -r metric_base=512
declare imds_endpoint imds_token
get_token() {
# try getting a token early, using each endpoint in
# turn. Whichever endpoint responds will be used for the rest of
# the IMDS API calls. On initial interface setup, we'll retry
# this operation for up to 30 seconds, but on subsequent
# invocations we avoid retrying
local deadline
deadline=$(date -d "now+30 seconds" +%s)
local old_opts=$-
while [ "$(date +%s)" -lt $deadline ]; do
for ep in "${imds_endpoints[@]}"; do
set +e
imds_token=$(curl --max-time 5 --connect-timeout 0.15 -s --fail \
-X PUT -H "X-aws-ec2-metadata-token-ttl-seconds: 60" ${ep}/${imds_token_path})
[[ $old_opts = *e* ]] && set -e
if [ -n "$imds_token" ]; then
debug "Got IMDSv2 token from ${ep}"
imds_endpoint=$ep
return
fi
done
if [ ! -v EC2_IF_INITIAL_SETUP ]; then
break
fi
sleep 0.5
done
}
log() {
local priority
priority=$1 ; shift
logger --id=$$ --priority "${syslog_facility}.${priority}" --tag "$syslog_tag" "$@"
}
# debug-level messages
debug() {
log debug "$@"
}
# informational messages
info() {
log info "$@"
}
# warning conditions
warn() {
log warn "$@"
}
# error conditions
error() {
log err "$@"
}
get_meta() {
local key=$1
local max_tries=${2:-10}
local -i attempts=0 ms_per_backoff=100 backoff=0
debug "[get_meta] Querying IMDS for ${key}"
get_token
local url="${imds_endpoint}/meta-data/${key}"
local meta rc
while [ $attempts -lt $max_tries ]; do
meta=$(curl -s --max-time 5 -H "X-aws-ec2-metadata-token:${imds_token}" -f "$url")
rc=$?
if [ $rc -eq 0 ]; then
echo "$meta"
return 0
fi
if [ ! -v EC2_IF_INITIAL_SETUP ]; then
return 1
else
attempts+=1
backoff=$((attempts*ms_per_backoff))
sleep $((backoff/1000)).$((backoff%1000))
fi
done
return 1
}
get_imds() {
local key=$1
local max_tries=${2:-10}
get_meta $key $max_tries
}
get_iface_imds() {
local mac=$1
local key=$2
local max_tries=${3:-10}
get_imds network/interfaces/macs/${mac}/${key} $max_tries
}
_install_and_reload() {
local src=$1
local dest=$2
if [ -e "$dest" ]; then
if [ "$(md5sum < $dest)" = "$(md5sum < $src)" ]; then
# The config is unchanged since last run. Nothing left to do:
rm "$src"
echo 0
else
# The file content has changed, we need to reload:
mv "$src" "$dest"
echo 1
fi
return
fi
# If we're here then we're creating a new config file
if [ "$(stat --format=%s $src)" -gt 0 ]; then
mv "$src" "$dest"
echo 1
return
fi
rm "$src"
echo 0
}
ipv6_disabled() {
# Linux kernel tunable for ipv6: 0 = false, 1 = true
# returns: false = enabled, true = disabled
if grep -Pqs '^\h*1\b' /sys/module/ipv6/parameters/{disable,disable_ipv6} \
/proc/sys/net/ipv6/conf/{default,all}/disable_ipv6;
then
true
else
false
fi
}
create_ipv4_aliases() {
local iface=$1
local mac=$2
local addresses
subnet_supports_ipv4 "$iface" || return 0
addresses=$(get_iface_imds $mac local-ipv4s | tail -n +2 | sort)
local drop_in_dir="${unitdir}/70-${iface}.network.d"
mkdir -p "$drop_in_dir"
local file="$drop_in_dir/ec2net_alias.conf"
local work="${file}.new"
touch "$work"
for a in $addresses; do
cat <<EOF >> "$work"
[Address]
Address=${a}/32
AddPrefixRoute=false
EOF
done
_install_and_reload "$work" "$file"
}
subnet_supports_ipv4() {
local iface=$1
if [ -z "$iface" ]; then
error "${FUNCNAME[0]} called without an interface"
return 1
fi
! ip -4 addr show dev "$iface" scope global | \
sed -n -E 's,^.*inet (\S+).*,\1,p' | grep -E -q '^169\.254\.'
}
subnet_supports_ipv6() {
local iface=$1
if [ -z "$iface" ]; then
error "${FUNCNAME[0]} called without an interface"
return 1
fi
ip -6 addr show dev "$iface" scope global | grep -q inet6
}
subnet_prefixroutes() {
local ether=$1
local family=${2:-ipv4}
if [ -z "$ether" ]; then
err "${FUNCNAME[0]} called without an MAC address"
return 1
fi
case "$family" in
ipv4)
get_iface_imds "$ether" "subnet-${family}-cidr-block"
;;
ipv6)
get_iface_imds "$ether" "subnet-${family}-cidr-blocks"
;;
esac
}
create_rules() {
local iface=$1
local device_number=$2
local network_card=$3
local family=$4
local addrs prefixes
local local_addr_key subnet_pd_key
local drop_in_dir="${unitdir}/70-${iface}.network.d"
mkdir -p "$drop_in_dir"
local -i ruleid=$((device_number+rule_base+100*network_card))
case $family in
4)
if ! subnet_supports_ipv4 $iface; then
return 0
fi
local_addr_key=local-ipv4s
subnet_pd_key=ipv4-prefix
;;
6)
if ! subnet_supports_ipv6 $iface; then
return 0
fi
local_addr_key=ipv6s
subnet_pd_key=ipv6-prefix
;;
*)
error "unable to determine protocol"
return 1
;;
esac
# We'd like to retry here, but we can't distinguish between an
# IMDS failure, a propagation delay, or a legitimately empty
# response.
addrs=$(get_iface_imds ${ether} ${local_addr_key} || true)
# don't fail or retry prefix retrieval. IMDS currently returns an
# error, rather than an empty response, if no prefixes are
# assigned, so we are unable to distinguish between a service
# error and a successful but empty response
prefixes=$(get_iface_imds ${ether} ${subnet_pd_key} 1 || true)
local source
local file="$drop_in_dir/ec2net_policy_${family}.conf"
local work="${file}.new"
touch "$work"
for source in $addrs $prefixes; do
cat <<EOF >> "$work"
[RoutingPolicyRule]
From=${source}
Priority=${ruleid}
Table=${ruleid}
EOF
done
_install_and_reload "$work" "$file"
}
create_if_overrides() {
local iface="$1"; test -n "$iface" || { echo "Invalid iface at $LINENO" >&2 ; exit 1; }
local -i device_number="$2"; test -n "$device_number" || { echo "Invalid device_number at $LINENO" >&2 ; exit 1; }
local -i network_card="$3"; test -n "$network_card" || { echo "Invalid network_card at $LINENO" >&2 ; exit 1; }
local ether="$4"; test -n "$ether" || { echo "Invalid ether at $LINENO" >&2 ; exit 1; }
local cfgfile="$5"; test -n "$cfgfile" || { echo "Invalid cfgfile at $LINENO" >&2 ; exit 1; }
local cfgdir="${cfgfile}.d"
local dropin="${cfgdir}/eni.conf"
local -i metric=$((metric_base+100*network_card+device_number))
local -i tableid=$((rule_base+100*network_card+device_number))
mkdir -p "$cfgdir"
cat <<EOF > "${dropin}.tmp"
# Configuration for ${iface} generated by policy-routes@${iface}.service
[Match]
MACAddress=${ether}
[Network]
DHCP=yes
[DHCPv4]
RouteMetric=${metric}
UseRoutes=true
UseGateway=true
[IPv6AcceptRA]
RouteMetric=${metric}
UseGateway=true
EOF
cat <<EOF >> "${dropin}.tmp"
[Route]
Table=${tableid}
Gateway=_ipv6ra
EOF
if ! ipv6_disabled; then
for dest in $(subnet_prefixroutes "$ether" ipv6); do
cat <<EOF >> "${dropin}.tmp"
[Route]
Table=${tableid}
Destination=${dest}
EOF
done
fi
if subnet_supports_ipv4 "$iface"; then
# if not in a v6-only network, add IPv4 routes to the private table
cat <<EOF >> "${dropin}.tmp"
[Route]
Gateway=_dhcp4
Table=${tableid}
EOF
local dest
for dest in $(subnet_prefixroutes "$ether" ipv4); do
cat <<EOF >> "${dropin}.tmp"
[Route]
Table=${tableid}
Destination=${dest}
EOF
done
fi
mv "${dropin}.tmp" "$dropin"
echo 1
}
add_altnames() {
local iface=$1
local ether=$2
local device_number=$3
local network_card=$4
local eni_id
eni_id=$(get_iface_imds "$ether" interface-id)
# Interface altnames can also be added using systemd .link files.
# However, in order to use them, we need to wait until a
# systemd-networkd reload operation completes and then trigger a
# udev "move" event. We avoid that overhead by adding the
# altnames directly using ip(8).
if [ -n "$eni_id" ] &&
! ip link show dev "$iface" | grep -q -E "altname\s+${eni_id}"; then
ip link property add dev "$iface" altname "$eni_id" || true
fi
local device_number_alt="device-number-${device_number}"
if [ -n "$network_card" ]; then
# On instance types that don't support a network-card key, we
# won't append a value here. A value of zero would be
# appropriate, but would be a visible change to the interface
# configuration on these instance types and could disrupt
# existing automation.
device_number_alt="${device_number_alt}.${network_card}"
fi
if [ -n "$device_number" ] &&
! ip link show dev "$device_number_alt" > /dev/null 2>&1; then
ip link property add dev "$iface" altname "${device_number_alt}" || true
fi
}
create_interface_config() {
local iface=$1
local device_number=$2
local network_card=$3
local ether=$4
local libdir=/usr/lib/systemd/network
local defconfig="${libdir}/80-ec2.network"
local -i retval=0
local cfgfile="${unitdir}/70-${iface}.network"
if [ -e "$cfgfile" ] &&
[ ! -v EC2_IF_INITIAL_SETUP ]; then
debug "Using existing cfgfile ${cfgfile}"
echo $retval
return
fi
debug "Linking $cfgfile to $defconfig"
mkdir -p "$unitdir"
ln -sf "$defconfig" "$cfgfile"
retval+=$(create_if_overrides "$iface" "$device_number" "$network_card" "$ether" "$cfgfile")
add_altnames "$iface" "$ether" "$device_number" "$network_card"
echo $retval
}
# The primary interface is defined as the interface whose MAC address
# is in the top-level `mac` key. It will always have device-number 0
# and network-card 0. It gets unique treatment in a few areas.
_is_primary_interface() {
local ether default_mac
ether="$1"
default_mac=$(get_imds mac)
[ "$ether" = "$default_mac" ]
}
# device-number, which represents the DeviceIndex field in an EC2
# NetworkInterfaceAttachment object, is not guaranteed to have
# propagated to IMDS by the time a hot-plugged interface is visible to
# the instance. Further complicating things, IMDS returns 0 for the
# device-number before propagation is complete, which is a valid value
# and represents the instance's primary interface. We cope with this
# by ensuring that the only interface for which we return 0 as the
# device-number is the one whose MAC address matches the instance's
# top-level "mac" field, which is static and guaranteed to be
# available as soon as the instance launches.
_get_device_number() {
local iface ether network_card_index
iface="$1"
ether="$2"
network_card_index=${3:-0}
if _is_primary_interface "$ether"; then
echo 0 ; return 0
fi
local -i maxtries=60 ntries=0
for (( ntries = 0; ntries < maxtries; ntries++ )); do
device_number=$(get_iface_imds "$ether" device-number 1)
# if either the device number or the card index are nonzero,
# then we treat the value returned as valid. Zero values for
# both is only valid for the primary interface, which we've
# already concluded is not this one.
if [ $device_number -ne 0 ] || [ $network_card_index -ne 0 ]; then
echo "$device_number"
return 0
else
sleep 0.1
fi
done
error "Unable to identify device-number for $iface after $ntries attempts"
echo -1
return 1
}
# print the network-card IMDS value for the given interface
# NOTE: On many instance types, this value is not defined. This
# function will print the empty string on those instances. On
# instances where it is defined, it will be a numeric value.
_get_network_card() {
local iface ether network_card
iface="$1"
ether="$2"
if _is_primary_interface "$ether"; then
echo 0 ; return 0
fi
network_card=$(get_iface_imds "$ether" network-card)
echo ${network_card}
}
# Interfaces get configured with addresses and routes from
# DHCP. Routes are inserted in the main table with metrics based on
# their physical location (slot ID) to ensure deterministic route
# ordering. Interfaces also get policy routing rules based on source
# address matching and ensuring that all egress traffic with one of
# the interface's IPs (primary or secondary, IPv4 or IPv6, including
# addresses from delegated prefixes) will be routing according to an
# interface-specific routing table.
setup_interface() {
local iface ether
local -i device_number network_card rc
iface=$1
ether=$2
network_card=$(_get_network_card "$iface" "$ether")
device_number=$(_get_device_number "$iface" "$ether" "$network_card")
rc=$?
if [ $rc -ne 0 ]; then
error "Unable to identify device-number for $iface in IMDS"
exit 1
fi
# Newly provisioned resources (new ENI attachments) take some
# time to be fully reflected in IMDS. In that case, we poll
# for a period of time to ensure we've captured all the
# sources needed for policy routing. When refreshing an
# existing ENI attachment's configuration, we skip the
# polling.
local -i deadline
deadline=$(date -d "now+30 seconds" +%s)
while [ "$(date +%s)" -lt $deadline ]; do
local -i changes=0
changes+=$(create_interface_config "$iface" "$device_number" "$network_card" "$ether")
for family in 4 6; do
if ! _is_primary_interface "$ether"; then
# We only create rules for secondary interfaces so
# external tools that modify the main route table can
# still communicate with the host's primary IPs. For
# example, considering a host with address 10.1.2.3 on
# ens5 (device-number-0) and a container communicating
# on a docker0 bridge interface, the expectation is
# that the container can communicate with 10.1.2.3 in
# both directions. If we install policy rules,
# they'll redirect the return traffic out ens5 rather
# than docker0, effectively blackholing it.
# https://github.com/amazonlinux/amazon-ec2-net-utils/issues/97
changes+=$(create_rules "$iface" "$device_number" "$network_card" $family)
fi
done
changes+=$(create_ipv4_aliases $iface $ether)
if [ ! -v EC2_IF_INITIAL_SETUP ] ||
[ "$changes" -gt 0 ]; then
break
fi
done
echo $changes
}
# All instances of this process that may reconfigure networkd register
# themselves as such. When exiting, they'll reload networkd only if
# they're the registered process running.
maybe_reload_networkd() {
rm -f "${lockdir}/${iface}"
if rmdir "$lockdir" 2> /dev/null; then
if [ -e "$reload_flag" ]; then
rm -f "$reload_flag" 2> /dev/null
networkctl reload
info "Reloaded networkd"
else
debug "No networkd reload needed"
fi
else
debug "Deferring networkd reload to another process"
fi
}
register_networkd_reloader() {
local -i registered=1 cnt=0
local -i max=10000
local -r lockfile="${lockdir}/${iface}"
local old_opts=$-
# Disable -o errexit in the following block so we can capture
# nonzero exit codes from a redirect without considering them
# fatal errors
set +e
while [ $cnt -lt $max ]; do
cnt+=1
mkdir -p "$lockdir"
trap 'debug "Called trap" ; maybe_reload_networkd' EXIT
# If the redirect fails, most likely because the target file
# already exists and -o noclobber is in effect, $? will be set
# nonzero. If it succeeds, it is set to 0
echo $$ > "${lockfile}"
# shellcheck disable=SC2320
registered=$?
[ $registered -eq 0 ] && break
sleep 0.1
if (( $cnt % 100 == 0 )); then
warn "Unable to lock ${iface} after ${cnt} tries."
fi
done
# re-enable -o errexit if it had originally been set
[[ $old_opts = *e* ]] && set -e
# If registered is still nonzero when we get here, we have failed
# to create the lock. Log this and exit.
if [ $registered -ne 0 ]; then
local msg="Unable to lock configuration for ${iface}."
error "$(printf "%s Check pid %d", "$msg", "$(cat "${lockfile}")")"
exit 1
fi
}
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