From d0daebc3d622f95db181601cb0c4a0781f74f758 Mon Sep 17 00:00:00 2001 From: Thomas Graf Date: Tue, 12 Jun 2012 00:44:01 +0000 Subject: ipv4: Add interface option to enable routing of 127.0.0.0/8 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: Thomas Graf Acked-by: Neil Horman Signed-off-by: David S. Miller --- Documentation/networking/ip-sysctl.txt | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'Documentation/networking/ip-sysctl.txt') diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt index 6f896b94abdc..99d0e0504d6e 100644 --- a/Documentation/networking/ip-sysctl.txt +++ b/Documentation/networking/ip-sysctl.txt @@ -862,6 +862,11 @@ accept_local - BOOLEAN local interfaces over the wire and have them accepted properly. default FALSE +route_localnet - BOOLEAN + Do not consider loopback addresses as martian source or destination + while routing. This enables the use of 127/8 for local routing purposes. + default FALSE + rp_filter - INTEGER 0 - No source validation. 1 - Strict mode as defined in RFC3704 Strict Reverse Path -- cgit v1.2.3