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authorFlorin Coras <fcoras@cisco.com>2019-09-12 18:36:44 -0700
committerJohn Lo <loj@cisco.com>2019-09-25 14:54:42 +0000
commit36ebcfffbc7ab0e83b4bb8dfaec16bf16cafb954 (patch)
treefe9803af08fd55cf1c9419d6e58f45394e155a7b /src/vnet/tcp/tcp_input.c
parent54c93cfc2556d9c6d2cf472f51d4c2866a556ef6 (diff)
tcp: use sacks for timer based recovery
Type: feature If available, reuse sack scoreboard in timer triggered retransmit to minimize spurious retransmits. Additional changes/refactoring: - limited transmit updates - add sacked rxt count to scoreboard - prr pacing of fast retransmits - startup pacing updates - changed loss window to flight + mss Change-Id: I057de6a9d6401698bd1031d5cf5cfbb62f2bdf61 Signed-off-by: Florin Coras <fcoras@cisco.com>
Diffstat (limited to 'src/vnet/tcp/tcp_input.c')
-rwxr-xr-xsrc/vnet/tcp/tcp_input.c286
1 files changed, 141 insertions, 145 deletions
diff --git a/src/vnet/tcp/tcp_input.c b/src/vnet/tcp/tcp_input.c
index 933f913bc5a..b49b8e8fd77 100755
--- a/src/vnet/tcp/tcp_input.c
+++ b/src/vnet/tcp/tcp_input.c
@@ -508,8 +508,6 @@ tcp_update_rtt (tcp_connection_t * tc, tcp_rate_sample_t * rs, u32 ack)
mrtt = rs->rtt_time * THZ;
goto estimate_rtt;
}
- if (tcp_in_recovery (tc))
- return 0;
goto done;
}
@@ -784,9 +782,17 @@ scoreboard_insert_hole (sack_scoreboard_t * sb, u32 prev_index,
return hole;
}
-#endif /* CLIB_MARCH_VARIANT */
-#ifndef CLIB_MARCH_VARIANT
+always_inline void
+scoreboard_update_sacked_rxt (sack_scoreboard_t * sb, u32 start, u32 end,
+ u8 has_rxt)
+{
+ if (!has_rxt || seq_geq (start, sb->high_rxt))
+ return;
+
+ sb->rxt_sacked +=
+ seq_lt (end, sb->high_rxt) ? (end - start) : (sb->high_rxt - start);
+}
always_inline void
scoreboard_update_bytes (sack_scoreboard_t * sb, u32 ack, u32 snd_mss)
@@ -837,7 +843,7 @@ scoreboard_update_bytes (sack_scoreboard_t * sb, u32 ack, u32 snd_mss)
while (right)
{
sb->lost_bytes += scoreboard_hole_bytes (right);
- sb->last_lost_bytes += right->is_lost ? 0 : right->end - right->start;
+ sb->last_lost_bytes += right->is_lost ? 0 : (right->end - right->start);
right->is_lost = 1;
left = scoreboard_prev_hole (sb, right);
if (!left)
@@ -912,9 +918,8 @@ scoreboard_next_rxt_hole (sack_scoreboard_t * sb,
return hole;
}
-#endif /* CLIB_MARCH_VARIANT */
-static void
+void
scoreboard_init_high_rxt (sack_scoreboard_t * sb, u32 snd_una)
{
sack_scoreboard_hole_t *hole;
@@ -928,7 +933,6 @@ scoreboard_init_high_rxt (sack_scoreboard_t * sb, u32 snd_una)
sb->rescue_rxt = snd_una - 1;
}
-#ifndef CLIB_MARCH_VARIANT
void
scoreboard_init (sack_scoreboard_t * sb)
{
@@ -957,6 +961,23 @@ scoreboard_clear (sack_scoreboard_t * sb)
sb->cur_rxt_hole = TCP_INVALID_SACK_HOLE_INDEX;
sb->is_reneging = 0;
}
+
+void
+scoreboard_clear_reneging (sack_scoreboard_t * sb, u32 start, u32 end)
+{
+ sack_scoreboard_hole_t *last_hole;
+
+ clib_warning ("sack reneging");
+
+ scoreboard_clear (sb);
+ last_hole = scoreboard_insert_hole (sb, TCP_INVALID_SACK_HOLE_INDEX,
+ start, end);
+ last_hole->is_lost = 1;
+ sb->tail = scoreboard_hole_index (sb, last_hole);
+ sb->high_sacked = start;
+ scoreboard_init_high_rxt (sb, start);
+}
+
#endif /* CLIB_MARCH_VARIANT */
/**
@@ -983,14 +1004,18 @@ tcp_rcv_sacks (tcp_connection_t * tc, u32 ack)
sack_scoreboard_t *sb = &tc->sack_sb;
sack_block_t *blk, *rcv_sacks;
u32 blk_index = 0, i, j;
+ u8 has_rxt;
sb->last_sacked_bytes = 0;
sb->last_bytes_delivered = 0;
+ sb->rxt_sacked = 0;
if (!tcp_opts_sack (&tc->rcv_opts)
&& sb->head == TCP_INVALID_SACK_HOLE_INDEX)
return;
+ has_rxt = tcp_in_cong_recovery (tc);
+
/* Remove invalid blocks */
blk = tc->rcv_opts.sacks;
while (blk < vec_end (tc->rcv_opts.sacks))
@@ -1121,6 +1146,8 @@ tcp_rcv_sacks (tcp_connection_t * tc, u32 ack)
sb->is_reneging = 0;
}
}
+ scoreboard_update_sacked_rxt (sb, hole->start, hole->end,
+ has_rxt);
scoreboard_remove_hole (sb, hole);
hole = next_hole;
}
@@ -1129,6 +1156,8 @@ tcp_rcv_sacks (tcp_connection_t * tc, u32 ack)
{
if (seq_gt (blk->end, hole->start))
{
+ scoreboard_update_sacked_rxt (sb, hole->start, blk->end,
+ has_rxt);
hole->start = blk->end;
}
blk_index++;
@@ -1145,11 +1174,17 @@ tcp_rcv_sacks (tcp_connection_t * tc, u32 ack)
/* Pool might've moved */
hole = scoreboard_get_hole (sb, hole_index);
hole->end = blk->start;
+
+ scoreboard_update_sacked_rxt (sb, blk->start, blk->end,
+ has_rxt);
+
blk_index++;
ASSERT (hole->next == scoreboard_hole_index (sb, next_hole));
}
else if (seq_lt (blk->start, hole->end))
{
+ scoreboard_update_sacked_rxt (sb, blk->start, hole->end,
+ has_rxt);
hole->end = blk->start;
}
hole = scoreboard_next_hole (sb, hole);
@@ -1166,6 +1201,8 @@ tcp_rcv_sacks (tcp_connection_t * tc, u32 ack)
ASSERT (sb->head == TCP_INVALID_SACK_HOLE_INDEX || tcp_in_recovery (tc)
|| sb->is_reneging || sb->holes[sb->head].start == ack);
ASSERT (sb->last_lost_bytes <= sb->lost_bytes);
+ ASSERT ((ack - tc->snd_una) + sb->last_sacked_bytes
+ - sb->last_bytes_delivered >= sb->rxt_sacked);
TCP_EVT (TCP_EVT_CC_SCOREBOARD, tc);
}
@@ -1209,70 +1246,41 @@ tcp_update_snd_wnd (tcp_connection_t * tc, u32 seq, u32 ack, u32 snd_wnd)
}
}
-#ifndef CLIB_MARCH_VARIANT
/**
* Init loss recovery/fast recovery.
*
* Triggered by dup acks as opposed to timer timeout. Note that cwnd is
* updated in @ref tcp_cc_handle_event after fast retransmit
*/
-void
+static void
tcp_cc_init_congestion (tcp_connection_t * tc)
{
tcp_fastrecovery_on (tc);
tc->snd_congestion = tc->snd_nxt;
tc->cwnd_acc_bytes = 0;
tc->snd_rxt_bytes = 0;
+ tc->rxt_delivered = 0;
+ tc->prr_delivered = 0;
tc->prev_ssthresh = tc->ssthresh;
tc->prev_cwnd = tc->cwnd;
- tc->cc_algo->congestion (tc);
- tc->fr_occurences += 1;
- TCP_EVT (TCP_EVT_CC_EVT, tc, 4);
-}
-#endif /* CLIB_MARCH_VARIANT */
-static void
-tcp_cc_recovery_exit (tcp_connection_t * tc)
-{
- tc->rto_boff = 0;
- tcp_update_rto (tc);
- tc->snd_rxt_ts = 0;
- tc->rtt_ts = 0;
- tcp_recovery_off (tc);
- TCP_EVT (TCP_EVT_CC_EVT, tc, 3);
-}
+ tcp_cc_congestion (tc);
-#ifndef CLIB_MARCH_VARIANT
-void
-tcp_cc_fastrecovery_clear (tcp_connection_t * tc)
-{
- tc->snd_rxt_bytes = 0;
- tc->rcv_dupacks = 0;
- tc->rtt_ts = 0;
+ /* Post retransmit update cwnd to ssthresh and account for the
+ * three segments that have left the network and should've been
+ * buffered at the receiver XXX */
+ if (!tcp_opts_sack_permitted (&tc->rcv_opts))
+ tc->cwnd += 3 * tc->snd_mss;
- tcp_fastrecovery_off (tc);
- tcp_fastrecovery_first_off (tc);
- tc->flags &= ~TCP_CONN_FRXT_PENDING;
-
- TCP_EVT (TCP_EVT_CC_EVT, tc, 3);
+ tc->fr_occurences += 1;
+ TCP_EVT (TCP_EVT_CC_EVT, tc, 4);
}
-#endif /* CLIB_MARCH_VARIANT */
static void
tcp_cc_congestion_undo (tcp_connection_t * tc)
{
tc->cwnd = tc->prev_cwnd;
tc->ssthresh = tc->prev_ssthresh;
- tc->rcv_dupacks = 0;
- if (tcp_in_recovery (tc))
- {
- tcp_cc_recovery_exit (tc);
- tc->snd_nxt = seq_max (tc->snd_nxt, tc->snd_congestion);
- }
- else if (tcp_in_fastrecovery (tc))
- {
- tcp_cc_fastrecovery_clear (tc);
- }
tcp_cc_undo_recovery (tc);
ASSERT (tc->rto_boff == 0);
TCP_EVT (TCP_EVT_CC_EVT, tc, 5);
@@ -1288,48 +1296,74 @@ tcp_cc_is_spurious_timeout_rxt (tcp_connection_t * tc)
}
static inline u8
-tcp_cc_is_spurious_fast_rxt (tcp_connection_t * tc)
+tcp_cc_is_spurious_retransmit (tcp_connection_t * tc)
{
- return (tcp_in_fastrecovery (tc)
- && tc->cwnd > tc->ssthresh + 3 * tc->snd_mss);
+ return (tcp_cc_is_spurious_timeout_rxt (tc));
}
-static u8
-tcp_cc_is_spurious_retransmit (tcp_connection_t * tc)
+static inline u8
+tcp_should_fastrecover_sack (tcp_connection_t * tc)
+{
+ return (tc->sack_sb.lost_bytes
+ || ((TCP_DUPACK_THRESHOLD - 1) * tc->snd_mss
+ < tc->sack_sb.sacked_bytes));
+}
+
+static inline u8
+tcp_should_fastrecover (tcp_connection_t * tc)
{
- return (tcp_cc_is_spurious_timeout_rxt (tc)
- || tcp_cc_is_spurious_fast_rxt (tc));
+ return ((tc->rcv_dupacks == TCP_DUPACK_THRESHOLD)
+ || tcp_should_fastrecover_sack (tc));
}
static int
tcp_cc_recover (tcp_connection_t * tc)
{
sack_scoreboard_hole_t *hole;
+ u8 is_spurious = 0;
ASSERT (tcp_in_cong_recovery (tc));
- hole = scoreboard_first_hole (&tc->sack_sb);
- if (hole && hole->start == tc->snd_una && hole->end == tc->snd_nxt)
- scoreboard_clear (&tc->sack_sb);
-
if (tcp_cc_is_spurious_retransmit (tc))
{
tcp_cc_congestion_undo (tc);
- return 1;
+ is_spurious = 1;
}
- if (tcp_in_recovery (tc))
- tcp_cc_recovery_exit (tc);
- else if (tcp_in_fastrecovery (tc))
+ tc->prr_delivered = 0;
+ tc->rxt_delivered = 0;
+ tc->snd_rxt_bytes = 0;
+ tc->snd_rxt_ts = 0;
+ tc->rtt_ts = 0;
+ tc->flags &= ~TCP_CONN_RXT_PENDING;
+
+ /* Previous recovery left us congested. Continue sending as part
+ * of the current recovery event with an updated snd_congestion */
+ if (tc->sack_sb.sacked_bytes)
{
- tcp_cc_recovered (tc);
- tcp_cc_fastrecovery_clear (tc);
+ tc->snd_congestion = tc->snd_nxt;
+ if (tcp_opts_sack_permitted (&tc->rcv_opts))
+ scoreboard_init_high_rxt (&tc->sack_sb, tc->snd_una);
+ tcp_program_retransmit (tc);
+ return is_spurious;
}
+ hole = scoreboard_first_hole (&tc->sack_sb);
+ if (hole && hole->start == tc->snd_una && hole->end == tc->snd_nxt)
+ scoreboard_clear (&tc->sack_sb);
+
+ if (!tcp_in_recovery (tc) && !is_spurious)
+ tcp_cc_recovered (tc);
+
+ tcp_fastrecovery_off (tc);
+ tcp_fastrecovery_first_off (tc);
+ tcp_recovery_off (tc);
+ TCP_EVT (TCP_EVT_CC_EVT, tc, 3);
+
ASSERT (tc->rto_boff == 0);
ASSERT (!tcp_in_cong_recovery (tc));
ASSERT (tcp_scoreboard_is_sane_post_recovery (tc));
- return 0;
+ return is_spurious;
}
static void
@@ -1353,17 +1387,28 @@ tcp_cc_update (tcp_connection_t * tc, tcp_rate_sample_t * rs)
tc->snd_congestion = tc->snd_una - 1;
}
-static u8
-tcp_should_fastrecover_sack (tcp_connection_t * tc)
+static void
+tcp_update_delivered (tcp_connection_t * tc, u8 is_dack, u8 has_sack)
{
- return (TCP_DUPACK_THRESHOLD - 1) * tc->snd_mss < tc->sack_sb.sacked_bytes;
-}
+ if (has_sack)
+ {
+ ASSERT (tc->bytes_acked >= tc->sack_sb.last_bytes_delivered
+ || (tc->flags & TCP_CONN_FINSNT));
-static u8
-tcp_should_fastrecover (tcp_connection_t * tc)
-{
- return (tc->rcv_dupacks == TCP_DUPACK_THRESHOLD
- || tcp_should_fastrecover_sack (tc));
+ tc->rxt_delivered += tc->sack_sb.rxt_sacked;
+ tc->prr_delivered += tc->bytes_acked + tc->sack_sb.last_sacked_bytes
+ - tc->sack_sb.last_bytes_delivered;
+ }
+ else
+ {
+ tcp_fastrecovery_first_on (tc);
+ tc->rxt_delivered = clib_max (tc->rxt_delivered + tc->bytes_acked,
+ tc->snd_rxt_bytes);
+ if (is_dack)
+ tc->prr_delivered += is_dack;
+ else
+ tc->prr_delivered += tc->bytes_acked - tc->snd_mss * tc->rcv_dupacks;
+ }
}
/**
@@ -1380,29 +1425,21 @@ tcp_cc_handle_event (tcp_connection_t * tc, tcp_rate_sample_t * rs,
* and accounting for segments that have left the network are done
* lower.
*/
- if (tcp_in_fastrecovery (tc))
+ if (tcp_in_cong_recovery (tc))
{
if (!has_sack)
- tc->rcv_dupacks++;
+ tc->rcv_dupacks += is_dack;
if (!tc->bytes_acked)
{
- tcp_program_fastretransmit (tc);
+ tcp_update_delivered (tc, is_dack, has_sack);
+ tcp_program_retransmit (tc);
if (!has_sack)
tcp_cc_rcv_cong_ack (tc, TCP_CC_DUPACK, rs);
return;
}
}
/*
- * In timer triggered recovery
- */
- else if (tcp_in_recovery (tc))
- {
- /* No fast recovery entry at this point */
- if (!tc->bytes_acked)
- return;
- }
- /*
* Duplicate ACK. Check if we should enter fast recovery
*/
else if (is_dack)
@@ -1410,33 +1447,24 @@ tcp_cc_handle_event (tcp_connection_t * tc, tcp_rate_sample_t * rs,
TCP_EVT (TCP_EVT_DUPACK_RCVD, tc, 1);
ASSERT (tc->snd_una != tc->snd_nxt || tc->sack_sb.last_sacked_bytes);
+ /* Heuristic to catch potential late dupacks */
+ if (!tc->sack_sb.sacked_bytes && tc->snd_una == tc->snd_congestion
+ && timestamp_leq (tc->rcv_opts.tsecr, tc->tsecr_last_ack))
+ return;
+
tc->rcv_dupacks++;
if (tcp_should_fastrecover (tc))
{
- u32 pacer_wnd;
-
ASSERT (!tcp_in_fastrecovery (tc));
- /* Heuristic to catch potential late dupacks
- * after fast retransmit exits */
- if (is_dack && tc->snd_una == tc->snd_congestion
- && timestamp_leq (tc->rcv_opts.tsecr, tc->tsecr_last_ack))
- {
- tc->rcv_dupacks = 0;
- return;
- }
-
tcp_cc_init_congestion (tc);
if (has_sack)
scoreboard_init_high_rxt (&tc->sack_sb, tc->snd_una);
- /* Constrain rate until we get a partial ack */
- pacer_wnd = clib_max (0.1 * tc->cwnd, 2 * tc->snd_mss);
- tcp_connection_tx_pacer_reset (tc, pacer_wnd,
- 0 /* start bucket */ );
- tcp_program_fastretransmit (tc);
+ tcp_connection_tx_pacer_reset (tc, tc->cwnd, 0 /* start bucket */ );
+ tcp_program_retransmit (tc);
return;
}
else
@@ -1475,6 +1503,10 @@ tcp_cc_handle_event (tcp_connection_t * tc, tcp_rate_sample_t * rs,
* Legitimate ACK. 1) See if we can exit recovery
*/
+ /* RFC6675: If the incoming ACK is a cumulative acknowledgment,
+ * reset dupacks to 0. Also needed if in congestion recovery */
+ tc->rcv_dupacks = 0;
+
if (seq_geq (tc->snd_una, tc->snd_congestion))
{
/* If spurious return, we've already updated everything */
@@ -1493,55 +1525,18 @@ tcp_cc_handle_event (tcp_connection_t * tc, tcp_rate_sample_t * rs,
* Legitimate ACK. 2) If PARTIAL ACK try to retransmit
*/
- /* RFC6675: If the incoming ACK is a cumulative acknowledgment,
- * reset dupacks to 0. Also needed if in congestion recovery */
- tc->rcv_dupacks = 0;
-
- /* Post RTO timeout don't try anything fancy */
- if (tcp_in_recovery (tc))
- {
- tcp_cc_rcv_ack (tc, rs);
- transport_add_tx_event (&tc->connection);
- return;
- }
-
/* Remove retransmitted bytes that have been delivered */
- if (has_sack)
- {
- ASSERT (tc->bytes_acked >= tc->sack_sb.last_bytes_delivered
- || (tc->flags & TCP_CONN_FINSNT));
+ tcp_update_delivered (tc, is_dack, has_sack);
- /* If we have sacks and we haven't gotten an ack beyond high_rxt,
- * remove sacked bytes delivered */
- if (seq_lt (tc->snd_una, tc->sack_sb.high_rxt))
- {
- u32 rxt_delivered;
- rxt_delivered = tc->bytes_acked - tc->sack_sb.last_bytes_delivered;
- ASSERT (tc->snd_rxt_bytes >= rxt_delivered);
- tc->snd_rxt_bytes -= rxt_delivered;
- }
- else
- {
- /* Apparently all retransmitted holes have been acked */
- tc->snd_rxt_bytes = 0;
- tc->sack_sb.high_rxt = tc->snd_una;
- }
- }
+ if (tcp_in_recovery (tc))
+ tcp_cc_rcv_ack (tc, rs);
else
- {
- tcp_fastrecovery_first_on (tc);
- if (tc->snd_rxt_bytes > tc->bytes_acked)
- tc->snd_rxt_bytes -= tc->bytes_acked;
- else
- tc->snd_rxt_bytes = 0;
- }
-
- tcp_cc_rcv_cong_ack (tc, TCP_CC_PARTIALACK, rs);
+ tcp_cc_rcv_cong_ack (tc, TCP_CC_PARTIALACK, rs);
/*
* Since this was a partial ack, try to retransmit some more data
*/
- tcp_program_fastretransmit (tc);
+ tcp_program_retransmit (tc);
}
/**
@@ -2767,6 +2762,7 @@ tcp46_rcv_process_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
/* Update rtt and rto */
tcp_estimate_initial_rtt (tc0);
+ tcp_connection_tx_pacer_update (tc0);
/* Switch state to ESTABLISHED */
tc0->state = TCP_STATE_ESTABLISHED;