ipv4 05/05: add sysctl to accept packets with local source addresses

Patrick McHardy
2009-12-03T11:25:52Z

commit 8ec1e0ebe26087bfc5c0394ada5feb5758014fc8
Author: Patrick McHardy <kaber@trash.net>
Date: Thu Dec 3 12:16:35 2009 +0100

ipv4: add sysctl to accept packets with local source addresses

Change fib_validate_source() to accept packets with a local source address when
the "accept_local" sysctl is set for the incoming inet device. Combined with the
previous patches, this allows to communicate between multiple local interfaces
over the wire.

Signed-off-by: Patrick McHardy <kaber@trash.net>

diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index 989f553..006b39d 100644
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -731,6 +731,12 @@ accept_source_route - BOOLEAN
default TRUE (router)
FALSE (host)

+accept_local - BOOLEAN
+ Accept packets with local source addresses. In combination with
+ suitable routing, this can be used to direct packets between two
+ local interfaces over the wire and have them accepted properly.
+ 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 eecfa55..699e85c 100644
--- a/include/linux/inetdevice.h
+++ b/include/linux/inetdevice.h
@@ -83,6 +83,7 @@ static inline void ipv4_devconf_setall(struct in_device *in_dev)
#define IN_DEV_RPFILTER(in_dev) IN_DEV_MAXCONF((in_dev), RP_FILTER)
#define IN_DEV_SOURCE_ROUTE(in_dev) IN_DEV_ANDCONF((in_dev), \
ACCEPT_SOURCE_ROUTE)
+#define IN_DEV_ACCEPT_LOCAL(in_dev) IN_DEV_ORCONF((in_dev), ACCEPT_LOCAL)
#define IN_DEV_BOOTP_RELAY(in_dev) IN_DEV_ANDCONF((in_dev), BOOTP_RELAY)

#define IN_DEV_LOG_MARTIANS(in_dev) IN_DEV_ORCONF((in_dev), LOG_MARTIANS)
diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index 1e4743e..9f047d7 100644
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -490,6 +490,7 @@ enum
NET_IPV4_CONF_PROMOTE_SECONDARIES=20,
NET_IPV4_CONF_ARP_ACCEPT=21,
NET_IPV4_CONF_ARP_NOTIFY=22,
+ NET_IPV4_CONF_ACCEPT_LOCAL=23,
__NET_IPV4_CONF_MAX
};

diff --git a/kernel/sysctl_check.c b/kernel/sysctl_check.c
index b6e7aae..f1d676e 100644
--- a/kernel/sysctl_check.c
+++ b/kernel/sysctl_check.c
@@ -220,6 +220,7 @@ static const struct trans_ctl_table trans_net_ipv4_conf_vars_table[] = {
{ NET_IPV4_CONF_PROMOTE_SECONDARIES, "promote_secondaries" },
{ NET_IPV4_CONF_ARP_ACCEPT, "arp_accept" },
{ NET_IPV4_CONF_ARP_NOTIFY, "arp_notify" },
+ { NET_IPV4_CONF_ACCEPT_LOCAL, "accept_local" },
{}
};

diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
index c100709..e312661 100644
--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c
@@ -1468,6 +1468,7 @@ static struct devinet_sysctl_table {
DEVINET_SYSCTL_RW_ENTRY(SEND_REDIRECTS, "send_redirects"),
DEVINET_SYSCTL_RW_ENTRY(ACCEPT_SOURCE_ROUTE,
"accept_source_route"),
+ DEVINET_SYSCTL_RW_ENTRY(ACCEPT_LOCAL, "accept_local"),
DEVINET_SYSCTL_RW_ENTRY(PROXY_ARP, "proxy_arp"),
DEVINET_SYSCTL_RW_ENTRY(MEDIUM_ID, "medium_id"),
DEVINET_SYSCTL_RW_ENTRY(BOOTP_RELAY, "bootp_relay"),
diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c
index 3b373a8..3323168 100644
--- a/net/ipv4/fib_frontend.c
+++ b/net/ipv4/fib_frontend.c
@@ -241,16 +241,17 @@ int fib_validate_source(__be32 src, __be32 dst, u8 tos, int oif,
.iif = oif };

struct fib_result res;
- int no_addr, rpf;
+ int no_addr, rpf, accept_local;
int ret;
struct net *net;

- no_addr = rpf = 0;
+ no_addr = rpf = accept_local = 0;
rcu_read_lock();
in_dev = __in_dev_get_rcu(dev);
if (in_dev) {
no_addr = in_dev->ifa_list == NULL;
rpf = IN_DEV_RPFILTER(in_dev);
+ accept_local = IN_DEV_ACCEPT_LOCAL(in_dev);
}
rcu_read_unlock();

@@ -260,8 +261,10 @@ int fib_validate_source(__be32 src, __be32 dst, u8 tos, int oif,
net = dev_net(dev);
if (fib_lookup(net, &fl, &res))
goto last_resort;
- if (res.type != RTN_UNICAST)
- goto e_inval_res;
+ if (res.type != RTN_UNICAST) {
+ if (res.type != RTN_LOCAL || !accept_local)
+ goto e_inval_res;
+ }
*spec_dst = FIB_RES_PREFSRC(res);
fib_combine_itag(itag, &res);
#ifdef CONFIG_IP_ROUTE_MULTIPATH