+
+static void
+tcp46_listen_trace_frame (vlib_main_t *vm, vlib_node_runtime_t *node,
+ u32 *to_next, u32 n_bufs)
+{
+ tcp_connection_t *tc = 0;
+ tcp_rx_trace_t *t;
+ vlib_buffer_t *b;
+ int i;
+
+ for (i = 0; i < n_bufs; i++)
+ {
+ b = vlib_get_buffer (vm, to_next[i]);
+ if (!(b->flags & VLIB_BUFFER_IS_TRACED))
+ continue;
+ if (vnet_buffer (b)->tcp.flags == TCP_STATE_LISTEN)
+ tc = tcp_listener_get (vnet_buffer (b)->tcp.connection_index);
+ t = vlib_add_trace (vm, node, b, sizeof (*t));
+ tcp_set_rx_trace_data (t, tc, tcp_buffer_hdr (b), b, 1);
+ }
+}
+
+/**
+ * SYN received in TIME-WAIT state.
+ *
+ * RFC 1122:
+ * "When a connection is [...] on TIME-WAIT state [...]
+ * [a TCP] MAY accept a new SYN from the remote TCP to
+ * reopen the connection directly, if it:
+ *
+ * (1) assigns its initial sequence number for the new
+ * connection to be larger than the largest sequence
+ * number it used on the previous connection incarnation,
+ * and
+ *
+ * (2) returns to TIME-WAIT state if the SYN turns out
+ * to be an old duplicate".
+ *
+ * The function returns true if the syn can be accepted during
+ * connection time-wait (port reuse). In this case the function
+ * also calculates what the iss should be for the new connection.
+ */
+always_inline int
+syn_during_timewait (tcp_connection_t *tc, vlib_buffer_t *b, u32 *iss)
+{
+ int paws_reject = tcp_segment_check_paws (tc);
+ u32 tw_iss;
+
+ *iss = 0;
+ /* Check that the SYN arrived out of window. We accept it */
+ if (!paws_reject &&
+ (seq_geq (vnet_buffer (b)->tcp.seq_number, tc->rcv_nxt) ||
+ (tcp_opts_tstamp (&tc->rcv_opts) &&
+ timestamp_lt (tc->tsval_recent, tc->rcv_opts.tsval))))
+ {
+ /* Set the iss of the new connection to be the largest sequence number
+ * the old peer would have accepted and add some random number
+ */
+ tw_iss = tc->snd_nxt + tcp_available_snd_wnd (tc) +
+ (uword) (tcp_time_now_us (tc->c_thread_index) * 1e6) % 65535;
+ if (tw_iss == 0)
+ tw_iss++;
+ *iss = tw_iss;
+
+ return 1;
+ }
+ else
+ {
+ TCP_DBG (
+ "ERROR not accepting SYN in timewait,paws_reject=%d, seq_num =%ld, "
+ "rcv_nxt=%ld, tstamp_present=%d, tsval_recent = %d, tsval = %d\n",
+ paws_reject, vnet_buffer (b)->tcp.seq_number, tc->rcv_nxt,
+ tcp_opts_tstamp (&tc->rcv_opts), tc->tsval_recent, tc->rcv_opts.tsval);
+ return 0;
+ }
+}