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 --- include/linux/inetdevice.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include/linux/inetdevice.h') diff --git a/include/linux/inetdevice.h b/include/linux/inetdevice.h index 597f4a9f3240..67f9ddacb70c 100644 --- a/include/linux/inetdevice.h +++ b/include/linux/inetdevice.h @@ -38,6 +38,7 @@ enum IPV4_DEVCONF_ACCEPT_LOCAL, IPV4_DEVCONF_SRC_VMARK, IPV4_DEVCONF_PROXY_ARP_PVLAN, + IPV4_DEVCONF_ROUTE_LOCALNET, __IPV4_DEVCONF_MAX }; @@ -131,6 +132,7 @@ static inline void ipv4_devconf_setall(struct in_device *in_dev) #define IN_DEV_PROMOTE_SECONDARIES(in_dev) \ IN_DEV_ORCONF((in_dev), \ PROMOTE_SECONDARIES) +#define IN_DEV_ROUTE_LOCALNET(in_dev) IN_DEV_ORCONF(in_dev, ROUTE_LOCALNET) #define IN_DEV_RX_REDIRECTS(in_dev) \ ((IN_DEV_FORWARD(in_dev) && \ -- cgit