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Message-ID: <20120608101859.GH32152@canuck.infradead.org>
Date: Fri, 8 Jun 2012 06:18:59 -0400
From: Thomas Graf <tgraf@...g.ch>
To: davem@...emloft.net
Cc: netdev@...r.kernel.org
Subject: [PATCH net-next] 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
Signed-off-by: Thomas Graf <tgraf@...g.ch>
---
Documentation/networking/ip-sysctl.txt | 5 +++++
include/linux/inetdevice.h | 2 ++
net/ipv4/arp.c | 3 ++-
net/ipv4/devinet.c | 5 ++++-
net/ipv4/route.c | 30 +++++++++++++++++++++---------
5 files changed, 34 insertions(+), 11 deletions(-)
diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index 6f896b9..99d0e05 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
diff --git a/include/linux/inetdevice.h b/include/linux/inetdevice.h
index 597f4a9..67f9dda 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) && \
diff --git a/net/ipv4/arp.c b/net/ipv4/arp.c
index cda37be..2e560f0 100644
--- a/net/ipv4/arp.c
+++ b/net/ipv4/arp.c
@@ -790,7 +790,8 @@ static int arp_process(struct sk_buff *skb)
* Check for bad requests for 127.x.x.x and requests for multicast
* addresses. If this is one such, delete it.
*/
- if (ipv4_is_loopback(tip) || ipv4_is_multicast(tip))
+ if (ipv4_is_multicast(tip) ||
+ (!IN_DEV_ROUTE_LOCALNET(in_dev) && ipv4_is_loopback(tip)))
goto out;
/*
diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
index 10e15a1..378c28b 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)
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"),
},
};
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 98b30d0..7509acc 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -2023,9 +2023,13 @@ static int ip_route_input_mc(struct sk_buff *skb, __be32 daddr, __be32 saddr,
return -EINVAL;
if (ipv4_is_multicast(saddr) || ipv4_is_lbcast(saddr) ||
- ipv4_is_loopback(saddr) || skb->protocol != htons(ETH_P_IP))
+ skb->protocol != htons(ETH_P_IP))
goto e_inval;
+ if (likely(!IN_DEV_ROUTE_LOCALNET(in_dev)))
+ if (ipv4_is_loopback(saddr))
+ goto e_inval;
+
if (ipv4_is_zeronet(saddr)) {
if (!ipv4_is_local_multicast(daddr))
goto e_inval;
@@ -2266,8 +2270,7 @@ static int ip_route_input_slow(struct sk_buff *skb, __be32 daddr, __be32 saddr,
by fib_lookup.
*/
- if (ipv4_is_multicast(saddr) || ipv4_is_lbcast(saddr) ||
- ipv4_is_loopback(saddr))
+ if (ipv4_is_multicast(saddr) || ipv4_is_lbcast(saddr))
goto martian_source;
if (ipv4_is_lbcast(daddr) || (saddr == 0 && daddr == 0))
@@ -2279,9 +2282,17 @@ static int ip_route_input_slow(struct sk_buff *skb, __be32 daddr, __be32 saddr,
if (ipv4_is_zeronet(saddr))
goto martian_source;
- if (ipv4_is_zeronet(daddr) || ipv4_is_loopback(daddr))
+ if (ipv4_is_zeronet(daddr))
goto martian_destination;
+ if (likely(!IN_DEV_ROUTE_LOCALNET(in_dev))) {
+ if (ipv4_is_loopback(daddr))
+ goto martian_destination;
+
+ if (ipv4_is_loopback(saddr))
+ goto martian_source;
+ }
+
/*
* Now we are ready to route packet.
*/
@@ -2520,9 +2531,14 @@ static struct rtable *__mkroute_output(const struct fib_result *res,
u16 type = res->type;
struct rtable *rth;
- if (ipv4_is_loopback(fl4->saddr) && !(dev_out->flags & IFF_LOOPBACK))
+ in_dev = __in_dev_get_rcu(dev_out);
+ if (!in_dev)
return ERR_PTR(-EINVAL);
+ if (likely(!IN_DEV_ROUTE_LOCALNET(in_dev)))
+ if (ipv4_is_loopback(fl4->saddr) && !(dev_out->flags & IFF_LOOPBACK))
+ return ERR_PTR(-EINVAL);
+
if (ipv4_is_lbcast(fl4->daddr))
type = RTN_BROADCAST;
else if (ipv4_is_multicast(fl4->daddr))
@@ -2533,10 +2549,6 @@ static struct rtable *__mkroute_output(const struct fib_result *res,
if (dev_out->flags & IFF_LOOPBACK)
flags |= RTCF_LOCAL;
- in_dev = __in_dev_get_rcu(dev_out);
- if (!in_dev)
- return ERR_PTR(-EINVAL);
-
if (type == RTN_BROADCAST) {
flags |= RTCF_BROADCAST | RTCF_LOCAL;
fi = NULL;
--
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