ipv4: Add FIB nexthop exceptions.

In a regime where we have subnetted route entries, we need a way to
store persistent storage about destination specific learned values
such as redirects and PMTU values.

This is implemented here via nexthop exceptions.

The initial implementation is a 2048 entry hash table with relaiming
starting at chain length 5.  A more sophisticated scheme can be
devised if that proves necessary.

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

1 files changed, 18 insertions, 0 deletions

diff --git a/include/net/ip_fib.h b/include/net/ip_fib.h
index 5697acefeba3..e9ee1ca07087 100644
--- a/include/net/ip_fib.h
+++ b/include/net/ip_fib.h
@@ -18,6 +18,7 @@
 
 #include <net/flow.h>
 #include <linux/seq_file.h>
+#include <linux/rcupdate.h>
 #include <net/fib_rules.h>
 #include <net/inetpeer.h>
 
@@ -46,6 +47,22 @@ struct fib_config {
 
 struct fib_info;
 
+struct fib_nh_exception {
+        struct fib_nh_exception __rcu   *fnhe_next;
+        __be32                          fnhe_daddr;
+        u32                             fnhe_pmtu;
+        u32                             fnhe_gw;
+        unsigned long                   fnhe_expires;
+        unsigned long                   fnhe_stamp;
+};
+
+struct fnhe_hash_bucket {
+        struct fib_nh_exception __rcu   *chain;
+};
+
+#define FNHE_HASH_SIZE          2048
+#define FNHE_RECLAIM_DEPTH      5
+
 struct fib_nh {
         struct net_device       *nh_dev;
         struct hlist_node       nh_hash;
@@ -63,6 +80,7 @@ struct fib_nh {
         __be32                  nh_gw;
         __be32                  nh_saddr;
         int                     nh_saddr_genid;
+        struct fnhe_hash_bucket *nh_exceptions;
 };
 
 /*