tcp: avoid spurious asserts while discarding bytes

Found by hst in ci, probably because of af_packet interfaces with
gso/gro on. Only applies to chained buffers.

Type: fix

Change-Id: I8d223a526bbdf88a2a7b60a0028e79ce14015a37
Signed-off-by: Florin Coras <[email protected]>

diff --git a/src/vnet/tcp/tcp_input.c b/src/vnet/tcp/tcp_input.c
index 3abfc95..f1b3429 100644 (file)
--- a/src/vnet/tcp/tcp_input.c
+++ b/src/vnet/tcp/tcp_input.c
@@ -1173,27 +1173,37 @@ tcp_session_enqueue_ooo (tcp_connection_t * tc, vlib_buffer_t * b,
 static int
 tcp_buffer_discard_bytes (vlib_buffer_t * b, u32 n_bytes_to_drop)
 {
-  u32 discard, first = b->current_length;
-  vlib_main_t *vm = vlib_get_main ();
-
   /* Handle multi-buffer segments */
   if (n_bytes_to_drop > b->current_length)
     {
+      u32 n_to_drop, first = b->current_length;
+      vlib_main_t *vm = vlib_get_main ();
+
       if (!(b->flags & VLIB_BUFFER_NEXT_PRESENT) ||
          (first + b->total_length_not_including_first_buffer <
           n_bytes_to_drop))
        return -1;
       b->total_length_not_including_first_buffer -= n_bytes_to_drop - first;
+      n_to_drop = n_bytes_to_drop;
       do
        {
-         discard = clib_min (n_bytes_to_drop, b->current_length);
-         vlib_buffer_advance (b, discard);
+         /* Not calling vlib_buffer_advance to avoid min chain seg size
+          * asserts that are not relevant for chained buffers that are about
+          * to be freed */
+         if (n_to_drop <= b->current_length)
+           {
+             b->current_length -= n_to_drop;
+             b->current_data += n_to_drop;
+             break;
+           }
+         n_to_drop -= b->current_length;
+         b->current_data += b->current_length;
+         b->current_length = 0;
          b = vlib_get_buffer (vm, b->next_buffer);
-         n_bytes_to_drop -= discard;
-         if (!b && n_bytes_to_drop)
+         if (!b)
            return -1;
        }
-      while (n_bytes_to_drop);
+      while (n_to_drop);
     }
   else
     vlib_buffer_advance (b, n_bytes_to_drop);