nsim: add packet loss simulation, docs

[vpp.git] / src / plugins / nsim / node.c

diff --git a/src/plugins/nsim/node.c b/src/plugins/nsim/node.c
index d641377..25112ab 100644 (file)
--- a/src/plugins/nsim/node.c
+++ b/src/plugins/nsim/node.c
@@ -25,6 +25,7 @@ typedef struct
   f64 expires;
   u32 tx_sw_if_index;
   int is_drop;
+  int is_lost;
 } nsim_trace_t;
 
 #ifndef CLIB_MARCH_VARIANT
@@ -38,7 +39,8 @@ format_nsim_trace (u8 * s, va_list * args)
   nsim_trace_t *t = va_arg (*args, nsim_trace_t *);
 
   if (t->is_drop)
-    s = format (s, "NSIM: ring drop");
+    s = format (s, "NSIM: dropped, %s", t->is_lost ?
+               "simulated network loss" : "no space in ring");
   else
     s = format (s, "NSIM: tx time %.6f sw_if_index %d",
                t->expires, t->tx_sw_if_index);
@@ -51,7 +53,8 @@ vlib_node_registration_t nsim_node;
 
 #define foreach_nsim_error                              \
 _(BUFFERED, "Packets buffered")                         \
-_(DROPPED, "Packets dropped due to lack of space")
+_(DROPPED, "Packets dropped due to lack of space")     \
+_(LOSS, "Network loss simulation drop packets")
 
 typedef enum
 {
@@ -90,6 +93,7 @@ nsim_inline (vlib_main_t * vm,
   int is_drop0;
   u32 no_error = node->errors[NSIM_ERROR_BUFFERED];
   u32 no_buffer_error = node->errors[NSIM_ERROR_DROPPED];
+  u32 loss_error = node->errors[NSIM_ERROR_LOSS];
   nsim_wheel_entry_t *ep = 0;
 
   ASSERT (wp);
@@ -109,6 +113,19 @@ nsim_inline (vlib_main_t * vm,
       is_drop0 = 0;
       if (PREDICT_TRUE (wp->cursize < wp->wheel_size))
        {
+         if (PREDICT_FALSE (nsm->drop_fraction != 0.0))
+           {
+             /* Get a random number on the closed interval [0,1] */
+             f64 rnd = random_f64 (&nsm->seed);
+             /* Drop the pkt? */
+             if (rnd <= nsm->drop_fraction)
+               {
+                 b[0]->error = loss_error;
+                 is_drop0 = 1;
+                 goto do_trace;
+               }
+           }
+
          ep = wp->entries + wp->tail;
          wp->tail++;
          if (wp->tail == wp->wheel_size)
@@ -130,6 +147,7 @@ nsim_inline (vlib_main_t * vm,
          is_drop0 = 1;
        }
 
+    do_trace:
       if (is_trace)
        {
          if (b[0]->flags & VLIB_BUFFER_IS_TRACED)
@@ -137,6 +155,7 @@ nsim_inline (vlib_main_t * vm,
              nsim_trace_t *t = vlib_add_trace (vm, node, b[0], sizeof (*t));
              t->expires = expires;
              t->is_drop = is_drop0;
+             t->is_lost = b[0]->error == loss_error;
              t->tx_sw_if_index = (is_drop0 == 0) ? ep->tx_sw_if_index : 0;
            }
        }