+ u32 offset, n_segs = 0, n_written, bi;
+ vlib_main_t *vm = wrk->vm;
+ vlib_buffer_t *b = 0;
+
+ tc->snd_nxt = tc->snd_una_max;
+ offset = tc->snd_una_max - tc->snd_una;
+ while (n_segs < burst_size)
+ {
+ n_written = tcp_prepare_segment (wrk, tc, offset, tc->snd_mss, &b);
+ if (!n_written)
+ goto done;
+
+ bi = vlib_get_buffer_index (vm, b);
+ tcp_enqueue_to_output (wrk, b, bi, tc->c_is_ip4);
+ offset += n_written;
+ n_segs += 1;
+ }
+
+done:
+ return n_segs;
+}
+
+#define scoreboard_rescue_rxt_valid(_sb, _tc) \
+ (seq_geq (_sb->rescue_rxt, _tc->snd_una) \
+ && seq_leq (_sb->rescue_rxt, _tc->snd_congestion))
+
+/**
+ * Do fast retransmit with SACKs
+ */
+int
+tcp_fast_retransmit_sack (tcp_worker_ctx_t * wrk, tcp_connection_t * tc,
+ u32 burst_size)
+{
+ u32 n_written = 0, offset, max_bytes, n_segs = 0, n_segs_now;
+ sack_scoreboard_hole_t *hole;
+ vlib_main_t *vm = wrk->vm;
+ vlib_buffer_t *b = 0;
+ sack_scoreboard_t *sb;
+ u32 bi, old_snd_nxt;
+ int snd_space;
+ u32 max_deq;
+ u8 snd_limited = 0, can_rescue = 0;
+
+ ASSERT (tcp_in_fastrecovery (tc));
+
+ snd_space = tcp_available_cc_snd_space (tc);
+ if (snd_space < tc->snd_mss)
+ {
+ tcp_program_fastretransmit (wrk, tc);
+ return 0;
+ }
+
+ TCP_EVT_DBG (TCP_EVT_CC_EVT, tc, 0);
+ old_snd_nxt = tc->snd_nxt;
+ sb = &tc->sack_sb;
+ hole = scoreboard_get_hole (sb, sb->cur_rxt_hole);
+
+ max_deq = session_tx_fifo_max_dequeue (&tc->connection);
+ max_deq -= tc->snd_una_max - tc->snd_una;
+
+ while (snd_space > 0 && n_segs < burst_size)
+ {
+ hole = scoreboard_next_rxt_hole (sb, hole, max_deq, &can_rescue,
+ &snd_limited);
+ if (!hole)
+ {
+ if (max_deq)
+ {
+ snd_space = clib_min (max_deq, snd_space);
+ burst_size = clib_min (burst_size - n_segs,
+ snd_space / tc->snd_mss);
+ n_segs_now = tcp_fast_retransmit_unsent (wrk, tc, burst_size);
+ if (max_deq > n_segs_now * tc->snd_mss)
+ tcp_program_fastretransmit (wrk, tc);
+ n_segs += n_segs_now;
+ goto done;
+ }
+
+ if (!can_rescue || scoreboard_rescue_rxt_valid (sb, tc))
+ break;
+
+ /* If rescue rxt undefined or less than snd_una then one segment of
+ * up to SMSS octets that MUST include the highest outstanding
+ * unSACKed sequence number SHOULD be returned, and RescueRxt set to
+ * RecoveryPoint. HighRxt MUST NOT be updated.
+ */
+ max_bytes = clib_min (tc->snd_mss,
+ tc->snd_congestion - tc->snd_una);
+ max_bytes = clib_min (max_bytes, snd_space);
+ offset = tc->snd_congestion - tc->snd_una - max_bytes;
+ sb->rescue_rxt = tc->snd_congestion;
+ tc->snd_nxt = tc->snd_una + offset;
+ n_written = tcp_prepare_retransmit_segment (wrk, tc, offset,
+ max_bytes, &b);
+ if (!n_written)
+ goto done;
+
+ bi = vlib_get_buffer_index (vm, b);
+ tcp_enqueue_to_output (wrk, b, bi, tc->c_is_ip4);
+ n_segs += 1;
+ break;
+ }
+
+ max_bytes = clib_min (hole->end - sb->high_rxt, snd_space);
+ max_bytes = snd_limited ? clib_min (max_bytes, tc->snd_mss) : max_bytes;
+ if (max_bytes == 0)
+ break;
+
+ offset = sb->high_rxt - tc->snd_una;
+ tc->snd_nxt = sb->high_rxt;
+ n_written = tcp_prepare_retransmit_segment (wrk, tc, offset, max_bytes,
+ &b);
+ ASSERT (n_written <= snd_space);
+
+ /* Nothing left to retransmit */
+ if (n_written == 0)
+ break;
+
+ bi = vlib_get_buffer_index (vm, b);
+ tcp_enqueue_to_output (wrk, b, bi, tc->c_is_ip4);
+
+ sb->high_rxt += n_written;
+ snd_space -= n_written;
+ n_segs += 1;
+ }
+
+ if (hole)
+ tcp_program_fastretransmit (wrk, tc);
+
+done:
+ /* If window allows, send 1 SMSS of new data */
+ tc->snd_nxt = old_snd_nxt;
+ return n_segs;
+}
+
+/**
+ * Fast retransmit without SACK info
+ */
+int
+tcp_fast_retransmit_no_sack (tcp_worker_ctx_t * wrk, tcp_connection_t * tc,
+ u32 burst_size)
+{
+ u32 n_written = 0, offset = 0, bi, old_snd_nxt, max_deq, n_segs_now;
+ vlib_main_t *vm = wrk->vm;
+ int snd_space, n_segs = 0;