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 --- net/ipv4/devinet.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) (limited to 'net/ipv4/devinet.c') diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c index 10e15a144e9..44bf82e3aef 100644 --- a/net/ipv4/devinet.c +++ b/net/ipv4/devinet.c @@ -1500,7 +1500,8 @@ static int devinet_conf_proc(ctl_table *ctl, int write, if (cnf == net->ipv4.devconf_dflt) devinet_copy_dflt_conf(net, i); - if (i == IPV4_DEVCONF_ACCEPT_LOCAL - 1) + if (i == IPV4_DEVCONF_ACCEPT_LOCAL - 1 || + i == IPV4_DEVCONF_ROUTE_LOCALNET - 1) if ((new_value == 0) && (old_value != 0)) rt_cache_flush(net, 0); } @@ -1617,6 +1618,8 @@ static struct devinet_sysctl_table { "force_igmp_version"), DEVINET_SYSCTL_FLUSHING_ENTRY(PROMOTE_SECONDARIES, "promote_secondaries"), + DEVINET_SYSCTL_FLUSHING_ENTRY(ROUTE_LOCALNET, + "route_localnet"), }, }; -- cgit v1.2.3-70-g09d2