ipv4: Elide fib_validate_source() completely when possible.

If rpfilter is off (or the SKB has an IPSEC path) and there are not
tclassid users, we don't have to do anything at all when
fib_validate_source() is invoked besides setting the itag to zero.

We monitor tclassid uses with a counter (modified only under RTNL and
marked __read_mostly) and we protect the fib_validate_source() real
work with a test against this counter and whether rpfilter is to be
done.

Having a way to know whether we need no tclassid processing or not
also opens the door for future optimized rpfilter algorithms that do
not perform full FIB lookups.

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 10 insertions, 0 deletions

diff --git a/net/ipv4/fib_semantics.c b/net/ipv4/fib_semantics.c
index 415f8230fc88..c46c20b6b0b6 100644
--- a/net/ipv4/fib_semantics.c
+++ b/net/ipv4/fib_semantics.c
@@ -163,6 +163,12 @@ void free_fib_info(struct fib_info *fi)
                 return;
         }
         fib_info_cnt--;
+#ifdef CONFIG_IP_ROUTE_CLASSID
+        change_nexthops(fi) {
+                if (nexthop_nh->nh_tclassid)
+                        fib_num_tclassid_users--;
+        } endfor_nexthops(fi);
+#endif
         call_rcu(&fi->rcu, free_fib_info_rcu);
 }
 
@@ -421,6 +427,8 @@ static int fib_get_nhs(struct fib_info *fi, struct rtnexthop *rtnh,
 #ifdef CONFIG_IP_ROUTE_CLASSID
                         nla = nla_find(attrs, attrlen, RTA_FLOW);
                         nexthop_nh->nh_tclassid = nla ? nla_get_u32(nla) : 0;
+                        if (nexthop_nh->nh_tclassid)
+                                fib_num_tclassid_users++;
 #endif
                 }
 
@@ -815,6 +823,8 @@ struct fib_info *fib_create_info(struct fib_config *cfg)
                 nh->nh_flags = cfg->fc_flags;
 #ifdef CONFIG_IP_ROUTE_CLASSID
                 nh->nh_tclassid = cfg->fc_flow;
+                if (nh->nh_tclassid)
+                        fib_num_tclassid_users++;
 #endif
 #ifdef CONFIG_IP_ROUTE_MULTIPATH
                 nh->nh_weight = 1;