ip: reassembly - pacing reassembly timeouts

[vpp.git] / src / vnet / ip / reass / ip4_full_reass.c

diff --git a/src/vnet/ip/reass/ip4_full_reass.c b/src/vnet/ip/reass/ip4_full_reass.c
index b5ea027..1ac2261 100644 (file)
--- a/src/vnet/ip/reass/ip4_full_reass.c
+++ b/src/vnet/ip/reass/ip4_full_reass.c
@@ -29,8 +29,12 @@
 #include <stddef.h>
 
 #define MSEC_PER_SEC 1000
-#define IP4_REASS_TIMEOUT_DEFAULT_MS             100
-#define IP4_REASS_EXPIRE_WALK_INTERVAL_DEFAULT_MS 10000        // 10 seconds default
+#define IP4_REASS_TIMEOUT_DEFAULT_MS 200
+
+/* As there are only 1024 reass context per thread, either the DDOS attacks
+ * or fractions of real timeouts, would consume these contexts quickly and
+ * running out context space and unable to perform reassembly */
+#define IP4_REASS_EXPIRE_WALK_INTERVAL_DEFAULT_MS 50 // 50 ms default
 #define IP4_REASS_MAX_REASSEMBLIES_DEFAULT 1024
 #define IP4_REASS_MAX_REASSEMBLY_LENGTH_DEFAULT          3
 #define IP4_REASS_HT_LOAD_FACTOR (0.75)
@@ -155,6 +159,8 @@ typedef struct
   ip4_full_reass_t *pool;
   u32 reass_n;
   u32 id_counter;
+  // for pacing the main thread timeouts
+  u32 last_id;
   clib_spinlock_t lock;
 } ip4_full_reass_per_thread_t;
 
@@ -1699,14 +1705,33 @@ ip4_full_reass_walk_expired (vlib_main_t *vm, vlib_node_runtime_t *node,
 
          vec_reset_length (pool_indexes_to_free);
 
-         pool_foreach_index (index, rt->pool)
+         /* Pace the number of timeouts handled per thread,to avoid barrier
+          * sync issues in real world scenarios */
+
+         u32 beg = rt->last_id;
+         /* to ensure we walk at least once per sec per context */
+         u32 end =
+           beg + (IP4_REASS_MAX_REASSEMBLIES_DEFAULT *
+                    IP4_REASS_EXPIRE_WALK_INTERVAL_DEFAULT_MS / MSEC_PER_SEC +
+                  1);
+         if (end > vec_len (rt->pool))
+           {
+             end = vec_len (rt->pool);
+             rt->last_id = 0;
+           }
+         else
            {
+             rt->last_id = end;
+           }
+
+         pool_foreach_stepping_index (
+           index, beg, end, rt->pool, ({
              reass = pool_elt_at_index (rt->pool, index);
              if (now > reass->last_heard + rm->timeout)
                {
                  vec_add1 (pool_indexes_to_free, index);
                }
-           }
+           }));
 
          if (vec_len (pool_indexes_to_free))
            vlib_node_increment_counter (vm, node->node_index,