ipv4: Add FLOWI_FLAG_KNOWN_NH

[ Upstream commit c92b96553a80c1dbe2ebe128bbe37c8f98f148bf ]

Add flag to request that output route should be
returned with known rt_gateway, in case we want to use
it as nexthop for neighbour resolving.

	The returned route can be cached as follows:

- in NH exception: because the cached routes are not shared
	with other destinations
- in FIB NH: when using gateway because all destinations for
	NH share same gateway

	As last option, to return rt_gateway!=0 we have to
set DST_NOCACHE.

Signed-off-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/include/net/flow.h b/include/net/flow.h
index e1dd5082ec7e43605e66ae0c48789ed1b4e68e35..628e11b98c580d7f66ace375f5a4e0598d03b471 100644 (file)
--- a/include/net/flow.h
+++ b/include/net/flow.h
@@ -21,6 +21,7 @@ struct flowi_common {
        __u8    flowic_flags;
 #define FLOWI_FLAG_ANYSRC              0x01
 #define FLOWI_FLAG_CAN_SLEEP           0x02
+#define FLOWI_FLAG_KNOWN_NH            0x04
        __u32   flowic_secid;
 };
 

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 308d9639a885ccaa9f1b35169e6772db70af86e6..2a1383c10fb28bff4ba867c30db4a2f4b3f12d13 100644 (file)
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -1762,6 +1762,7 @@ static struct rtable *__mkroute_output(const struct fib_result *res,
        struct in_device *in_dev;
        u16 type = res->type;
        struct rtable *rth;
+       bool do_cache;
 
        in_dev = __in_dev_get_rcu(dev_out);
        if (!in_dev)
@@ -1798,24 +1799,36 @@ static struct rtable *__mkroute_output(const struct fib_result *res,
        }
 
        fnhe = NULL;
+       do_cache = fi != NULL;
        if (fi) {
                struct rtable __rcu **prth;
+               struct fib_nh *nh = &FIB_RES_NH(*res);
 
-               fnhe = find_exception(&FIB_RES_NH(*res), fl4->daddr);
+               fnhe = find_exception(nh, fl4->daddr);
                if (fnhe)
                        prth = &fnhe->fnhe_rth;
-               else
-                       prth = __this_cpu_ptr(FIB_RES_NH(*res).nh_pcpu_rth_output);
+               else {
+                       if (unlikely(fl4->flowi4_flags &
+                                    FLOWI_FLAG_KNOWN_NH &&
+                                    !(nh->nh_gw &&
+                                      nh->nh_scope == RT_SCOPE_LINK))) {
+                               do_cache = false;
+                               goto add;
+                       }
+                       prth = __this_cpu_ptr(nh->nh_pcpu_rth_output);
+               }
                rth = rcu_dereference(*prth);
                if (rt_cache_valid(rth)) {
                        dst_hold(&rth->dst);
                        return rth;
                }
        }
+
+add:
        rth = rt_dst_alloc(dev_out,
                           IN_DEV_CONF_GET(in_dev, NOPOLICY),
                           IN_DEV_CONF_GET(in_dev, NOXFRM),
-                          fi);
+                          do_cache);
        if (!rth)
                return ERR_PTR(-ENOBUFS);