VRF in Linux using namespaces

vrf1.sh

#!/bin/sh

# 2017-feb-13

NSNAME="vrf1"
LINK1="${NSNAME}_10"  # ..my link to VRF
LINK2="${NSNAME}_11"  # ..VRF link to me
  IP1="10.20.30.10"
  IP2="10.20.30.11"
 MASK="24"
 GATE="10.20.30.1"
EXT_IFACE="eth0"
RTABLE="123"

VrfExec() { ip netns exec "$NSNAME" ip "$@"; }

VrfCreate() {
     ip netns add      "$NSNAME"
     ip link  add name "$LINK1" type veth peer name "$LINK2"
     ip link  set dev  "$LINK2" netns "$NSNAME"
     ip link  set dev  "$LINK1" up
VrfExec link  set dev  "$LINK2" up
VrfExec link  set dev   lo      up
     ip addr  add "$IP1/32"    dev "$LINK1"
     ip route add "$IP2/32"    dev "$LINK1"
VrfExec addr  add "$IP2/$MASK" dev "$LINK2"
VrfExec route add default via "$GATE"

     ip rule  add iif  "$LINK1"       table "$RTABLE"
     ip route add default via "$GATE" table "$RTABLE"

     sysctl "net.ipv4.conf.$EXT_IFACE.proxy_arp"=1
     sysctl "net.ipv4.conf.$LINK1.proxy_arp"=1
}

VrfDelete() {
     ip netns delete "$NSNAME"
     ip route delete default via "$GATE" table "$RTABLE"
     ip rule  delete iif  "$LINK1"       table "$RTABLE"
     ip link  delete      "$LINK1"

     sysctl "net.ipv4.conf.$EXT_IFACE.proxy_arp"=0
}

case "$1" in
    create|add ) VrfCreate ;;
    delete|del ) VrfDelete ;;
    exec|run|r ) shift; ip netns exec "$NSNAME" "$@" ;;
    test       )        ip netns exec "$NSNAME" ping 8.8.8.8 ;;
    * ) echo "Usage: ${0##*/} cmd ..cmd = create, delete, run" ;;
esac

## END ##

vrfinit.sh

#!/bin/sh -e

 EXT_IFACE="$(ip route get 1.2.3.4 | awk '$4 == "dev" {print $5}')"
EXT_IPADDR="$(ip route get 1.2.3.4 | awk '$6 == "src" {print $7}')"

VRF_NET="10.250"

test -n "$1" && VRFNUM="$1" || VRFNUM="1"
VRF="vrf$VRFNUM"

VrfExec() { ip netns exec "${VRF}" ip "$@"; }

     ip netns add      "${VRF}"
     ip link  add name "${VRF}a" type veth peer name "${VRF}b"
     ip link  set dev  "${VRF}b" netns "${VRF}"
     ip link  set dev  "${VRF}a" up
VrfExec link  set dev  "${VRF}b" up
VrfExec link  set dev   lo       up
     ip addr  add "$VRF_NET.$VRFNUM.1/30" dev "${VRF}a"
VrfExec addr  add "$VRF_NET.$VRFNUM.2/30" dev "${VRF}b"
VrfExec route add default via "$VRF_NET.${VRFNUM}.1"

iptables-save | grep -q -- "-A POSTROUTING -s $VRF_NET.${VRFNUM}.2 -o $EXT_IFACE -j SNAT --to-source $EXT_IPADDR" ||
            iptables -t nat -A POSTROUTING -s "$VRF_NET.${VRFNUM}.2" -o "$EXT_IFACE" -j SNAT --to-source "$EXT_IPADDR"

sysctl net.ipv4.ip_forward=1

## END ##