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authorFlorin Coras <fcoras@cisco.com>2019-09-27 08:16:40 -0700
committerAndrew Yourtchenko <ayourtch@gmail.com>2019-10-27 10:02:16 +0000
commit7b135c639e7d8144859258700700112d0c61f8c1 (patch)
treee1043d3c21e560c0d0cf9b9b321278e22b7dc959 /src/vnet/tcp/tcp_output.c
parent31c31c25e92435b24b321615266b8ad9d5d2d1aa (diff)
tcp: retry lost retransmits
Add heuristic that detects lost retransmitted segments and retries sending them. Type: feature Change-Id: I34d1bb16799e1993779222eb2bfad4b40704159e Signed-off-by: Florin Coras <fcoras@cisco.com> (cherry picked from commit be237bf02382854118986e8ea84c7544e42023f2)
Diffstat (limited to 'src/vnet/tcp/tcp_output.c')
-rw-r--r--src/vnet/tcp/tcp_output.c44
1 files changed, 39 insertions, 5 deletions
diff --git a/src/vnet/tcp/tcp_output.c b/src/vnet/tcp/tcp_output.c
index a7b0e398d36..79866aff03a 100644
--- a/src/vnet/tcp/tcp_output.c
+++ b/src/vnet/tcp/tcp_output.c
@@ -1599,7 +1599,7 @@ tcp_timer_retransmit_handler (u32 tc_index)
}
if (tcp_opts_sack_permitted (&tc->rcv_opts))
- scoreboard_init_high_rxt (&tc->sack_sb, tc->snd_una + tc->snd_mss);
+ scoreboard_init_rxt (&tc->sack_sb, tc->snd_una + n_bytes);
tcp_program_retransmit (tc);
}
@@ -1858,7 +1858,7 @@ done:
/**
* Estimate send space using proportional rate reduction (RFC6937)
*/
-static int
+int
tcp_fastrecovery_prr_snd_space (tcp_connection_t * tc)
{
u32 pipe, prr_out;
@@ -1874,13 +1874,24 @@ tcp_fastrecovery_prr_snd_space (tcp_connection_t * tc)
}
else
{
- int limit = tc->prr_delivered - prr_out + tc->snd_mss;
+ int limit;
+ limit = clib_max ((int) (tc->prr_delivered - prr_out), 0) + tc->snd_mss;
space = clib_min (tc->ssthresh - pipe, limit);
}
space = clib_max (space, prr_out ? 0 : tc->snd_mss);
return space;
}
+static inline u8
+tcp_retransmit_should_retry_head (tcp_connection_t * tc,
+ sack_scoreboard_t * sb)
+{
+ u32 tx_adv_sack = sb->high_sacked - tc->snd_congestion;
+ f64 rr = (f64) tc->ssthresh / tc->prev_cwnd;
+
+ return (tx_adv_sack > (tc->snd_una - tc->prr_start) * rr);
+}
+
#define scoreboard_rescue_rxt_valid(_sb, _tc) \
(seq_geq (_sb->rescue_rxt, _tc->snd_una) \
&& seq_leq (_sb->rescue_rxt, _tc->snd_congestion))
@@ -1917,8 +1928,31 @@ tcp_retransmit_sack (tcp_worker_ctx_t * wrk, tcp_connection_t * tc,
return 0;
}
- TCP_EVT (TCP_EVT_CC_EVT, tc, 0);
sb = &tc->sack_sb;
+
+ /* Check if snd_una is a lost retransmit */
+ if (seq_gt (sb->high_sacked, tc->snd_congestion)
+ && tc->rxt_head != tc->snd_una
+ && tcp_retransmit_should_retry_head (tc, sb))
+ {
+ n_written = tcp_prepare_retransmit_segment (wrk, tc, 0, tc->snd_mss,
+ &b);
+ if (!n_written)
+ {
+ tcp_program_retransmit (tc);
+ goto done;
+ }
+ bi = vlib_get_buffer_index (vm, b);
+ tcp_enqueue_to_output (wrk, b, bi, tc->c_is_ip4);
+ n_segs = 1;
+
+ tc->rxt_head = tc->snd_una;
+ tc->rxt_delivered += n_written;
+ tc->prr_delivered += n_written;
+ ASSERT (tc->rxt_delivered <= tc->snd_rxt_bytes);
+ }
+
+ TCP_EVT (TCP_EVT_CC_EVT, tc, 0);
hole = scoreboard_get_hole (sb, sb->cur_rxt_hole);
max_deq = transport_max_tx_dequeue (&tc->connection);
@@ -1931,7 +1965,7 @@ tcp_retransmit_sack (tcp_worker_ctx_t * wrk, tcp_connection_t * tc,
if (!hole)
{
/* We are out of lost holes to retransmit so send some new data. */
- if (max_deq)
+ if (max_deq > tc->snd_mss)
{
u32 n_segs_new, av_window;
av_window = tc->snd_wnd - (tc->snd_nxt - tc->snd_una);