• Thomas Graf's avatar
    ipv4: Add interface option to enable routing of 127.0.0.0/8 · d0daebc3
    Thomas Graf authored
    Routing of 127/8 is tradtionally forbidden, we consider
    packets from that address block martian when routing and do
    not process corresponding ARP requests.
    
    This is a sane default but renders a huge address space
    practically unuseable.
    
    The RFC states that no address within the 127/8 block should
    ever appear on any network anywhere but it does not forbid
    the use of such addresses outside of the loopback device in
    particular. For example to address a pool of virtual guests
    behind a load balancer.
    
    This patch adds a new interface option 'route_localnet'
    enabling routing of the 127/8 address block and processing
    of ARP requests on a specific interface.
    
    Note that for the feature to work, the default local route
    covering 127/8 dev lo needs to be removed.
    
    Example:
      $ sysctl -w net.ipv4.conf.eth0.route_localnet=1
      $ ip route del 127.0.0.0/8 dev lo table local
      $ ip addr add 127.1.0.1/16 dev eth0
      $ ip route flush cache
    
    V2: Fix invalid check to auto flush cache (thanks davem)
    Signed-off-by: default avatarThomas Graf <tgraf@suug.ch>
    Acked-by: Neil Horman (CI test user)'s avatarNeil Horman <nhorman@tuxdriver.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    d0daebc3
ip-sysctl.txt 54.2 KB