6 files changed, 17 insertions, 4 deletions

diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index 989f5538b8dd..006b39dec87d 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 eecfa559bfb4..699e85c01a4d 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 1e4743ee6831..9f047d73a216 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 b6e7aaea4604..f1d676e4b368 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 c100709d6ddf..e3126612fcbb 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 3b373a8b0473..3323168ee52d 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