ipv4: tcp: dont cache output dst for syncookies

Don't cache output dst for syncookies, as this adds pressure on IP route
cache and rcu subsystem for no gain.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Hans Schillstrom <hans.schillstrom@ericsson.com>
Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 1 deletions

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index a91f6d33804c..8d62d85e68dc 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -1156,7 +1156,7 @@ restart:
         candp = NULL;
         now = jiffies;
 
-        if (!rt_caching(dev_net(rt->dst.dev))) {
+        if (!rt_caching(dev_net(rt->dst.dev)) || (rt->dst.flags & DST_NOCACHE)) {
                 /*
                  * If we're not caching, just tell the caller we
                  * were successful and don't touch the route.  The
@@ -2582,6 +2582,9 @@ static struct rtable *__mkroute_output(const struct fib_result *res,
 
         rt_set_nexthop(rth, fl4, res, fi, type, 0);
 
+        if (fl4->flowi4_flags & FLOWI_FLAG_RT_NOCACHE)
+                rth->dst.flags |= DST_NOCACHE;
+
         return rth;
 }