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MEDIUM: quic: Send ACK frames asap

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Due to a erroneous interpretation of the RFC 9000 (quic-transport), ACKs frames
were always sent only after having received two ack-eliciting packets.
This could trigger useless retransmissions for tail packets on the peer side.
For now on, we send as soon as possible ACK frames as soon as we have ACK to send,
in the same packets as the ack-eliciting frame packets, and we also send ACK
frames after having received 2 ack-eliciting packets since the last time we sent
an ACK frame with other ack-eliciting frames.
This commit is contained in:
Frédéric Lécaille
2022-03-29 11:42:03 +02:00
committed by Amaury Denoyelle
parent 205e4f359e
commit b002145e9f
3 changed files with 67 additions and 58 deletions
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115
src/xprt_quic.c
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@@ -174,7 +174,7 @@ DECLARE_STATIC_POOL(pool_head_quic_conn_stream, "qc_stream_desc", sizeof(struct
static struct quic_tx_packet *qc_build_pkt(unsigned char **pos, const unsigned char *buf_end,
struct quic_enc_level *qel, struct list *frms,
struct quic_conn *qc, size_t dglen, int pkt_type,
int padding, int ack, int probe, int cc, int *err);
int padding, int probe, int cc, int *err);
static struct task *quic_conn_app_io_cb(struct task *t, void *context, unsigned int state);
static void qc_idle_timer_rearm(struct quic_conn *qc, int read);
@@ -2636,6 +2636,33 @@ static inline void qc_set_dg(struct cbuf *cbuf,
cb_add(cbuf, dglen + sizeof dglen + sizeof pkt);
}
/* Returns 1 if a packet may be built for <qc> from <qel> encryption level
* with <frms> as ack-eliciting frame list to send, 0 if not.
* <cc> must equal to 1 if an immediate close was asked, 0 if not.
* <probe> must equalt to 1 if a probing packet is required, 0 if not.
*/
static int qc_may_build_pkt(struct quic_conn *qc, struct list *frms,
struct quic_enc_level *qel, int cc, int probe)
{
unsigned int must_ack =
qel->pktns->rx.nb_aepkts_since_last_ack >= QUIC_MAX_RX_AEPKTS_SINCE_LAST_ACK;
/* Do not build any more packet if the TX secrets are not available or
* if there is nothing to send, i.e. if no CONNECTION_CLOSE or ACK are required
* and if there is no more packets to send upon PTO expiration
* and if there is no more ack-eliciting frames to send or in flight
* congestion control limit is reached for prepared data
*/
if (!(qel->tls_ctx.flags & QUIC_FL_TLS_SECRETS_SET) ||
(!cc && !probe && !must_ack &&
(LIST_ISEMPTY(frms) || qc->path->prep_in_flight >= qc->path->cwnd))) {
TRACE_DEVEL("nothing more to do", QUIC_EV_CONN_PHPKTS, qc);
return 0;
}
return 1;
}
/* Prepare as much as possible short packets which are also datagrams into <qr>
* ring buffer for the QUIC connection with <ctx> as I/O handler context from
* <frms> list of prebuilt frames.
@@ -2670,28 +2697,17 @@ static int qc_prep_app_pkts(struct quic_conn *qc, struct qring *qr,
*/
end_buf = pos + cb_contig_space(cbuf) - sizeof(uint16_t);
while (end_buf - pos >= (int)qc->path->mtu + dg_headlen) {
int err, probe, ack, cc;
int err, probe, cc;
TRACE_POINT(QUIC_EV_CONN_PHPKTS, qc, qel);
probe = ack = 0;
probe = 0;
cc = qc->flags & QUIC_FL_CONN_IMMEDIATE_CLOSE;
if (!cc) {
/* We do not probe if an immediate close was asked */
if (!cc)
probe = qel->pktns->tx.pto_probe;
ack = qel->pktns->flags & QUIC_FL_PKTNS_ACK_REQUIRED;
}
/* Do not build any more packet if the TX secrets are not available or
* if there is nothing to send, i.e. if no CONNECTION_CLOSE or ACK are required
* and if there is no more packets to send upon PTO expiration
* and if there is no more CRYPTO data available or in flight
* congestion control limit is reached for prepared data
*/
if (!(qel->tls_ctx.flags & QUIC_FL_TLS_SECRETS_SET) ||
(!cc && !ack && !probe &&
(LIST_ISEMPTY(frms) ||
qc->path->prep_in_flight >= qc->path->cwnd))) {
TRACE_DEVEL("nothing more to do", QUIC_EV_CONN_PHPKTS, qc);
if (!qc_may_build_pkt(qc, frms, qel, cc, probe))
break;
}
/* Leave room for the datagram header */
pos += dg_headlen;
@@ -2703,7 +2719,7 @@ static int qc_prep_app_pkts(struct quic_conn *qc, struct qring *qr,
}
pkt = qc_build_pkt(&pos, end, qel, frms, qc, 0, 0,
QUIC_PACKET_TYPE_SHORT, ack, probe, cc, &err);
QUIC_PACKET_TYPE_SHORT, probe, cc, &err);
switch (err) {
case -2:
goto err;
@@ -2783,30 +2799,17 @@ static int qc_prep_pkts(struct quic_conn *qc, struct qring *qr,
end_buf = pos + cb_contig_space(cbuf) - sizeof dglen;
first_pkt = prv_pkt = NULL;
while (end_buf - pos >= (int)qc->path->mtu + dg_headlen || prv_pkt) {
int err, probe, ack, cc;
int err, probe, cc;
enum quic_pkt_type pkt_type;
TRACE_POINT(QUIC_EV_CONN_PHPKTS, qc, qel);
probe = ack = 0;
probe = 0;
cc = qc->flags & QUIC_FL_CONN_IMMEDIATE_CLOSE;
if (!cc) {
/* We do not probe if an immediate close was asked */
if (!cc)
probe = qel->pktns->tx.pto_probe;
ack = qel->pktns->flags & QUIC_FL_PKTNS_ACK_REQUIRED;
}
/* Do not build any more packet if the TX secrets are not available or
* if there is nothing to send, i.e. if no CONNECTION_CLOSE or ACK are required
* and if there is no more packets to send upon PTO expiration
* and if there is no more CRYPTO data available or in flight
* congestion control limit is reached for prepared data
*/
if (!(qel->tls_ctx.flags & QUIC_FL_TLS_SECRETS_SET) ||
(!cc && !ack && !probe &&
(LIST_ISEMPTY(&qel->pktns->tx.frms) ||
qc->path->prep_in_flight >= qc->path->cwnd))) {
TRACE_DEVEL("nothing more to do", QUIC_EV_CONN_PHPKTS, qc);
/* Set the current datagram as prepared into <cbuf> if
* the was already a correct packet which was previously written.
*/
if (!qc_may_build_pkt(qc, &qel->pktns->tx.frms, qel, cc, probe)) {
if (prv_pkt)
qc_set_dg(cbuf, dglen, first_pkt);
/* Let's select the next encryption level */
@@ -2833,7 +2836,7 @@ static int qc_prep_pkts(struct quic_conn *qc, struct qring *qr,
}
cur_pkt = qc_build_pkt(&pos, end, qel, &qel->pktns->tx.frms,
qc, dglen, padding, pkt_type, ack, probe, cc, &err);
qc, dglen, padding, pkt_type, probe, cc, &err);
switch (err) {
case -2:
goto err;
@@ -3382,9 +3385,9 @@ int qc_treat_rx_pkts(struct quic_enc_level *cur_el, struct quic_enc_level *next_
else {
struct quic_arng ar = { .first = pkt->pn, .last = pkt->pn };
if (pkt->flags & QUIC_FL_RX_PACKET_ACK_ELICITING) {
if (!(++qc->rx.nb_ack_eliciting & 1) || force_ack)
qel->pktns->flags |= QUIC_FL_PKTNS_ACK_REQUIRED;
if (pkt->flags & QUIC_FL_RX_PACKET_ACK_ELICITING || force_ack) {
qel->pktns->flags |= QUIC_FL_PKTNS_ACK_REQUIRED;
qel->pktns->rx.nb_aepkts_since_last_ack++;
qc_idle_timer_rearm(qc, 1);
}
if (pkt->pn > largest_pn)
@@ -3920,7 +3923,6 @@ static struct quic_conn *qc_new_conn(unsigned int version, int ipv4,
qc->tx.bytes = 0;
/* RX part. */
qc->rx.bytes = 0;
qc->rx.nb_ack_eliciting = 0;
qc->rx.buf = b_make(buf_area, QUIC_CONN_RX_BUFSZ, 0, 0);
LIST_INIT(&qc->rx.pkt_list);
if (!quic_tls_ku_init(qc)) {
@@ -5179,7 +5181,7 @@ static inline int qc_build_frms(struct list *outlist, struct list *inlist,
static int qc_do_build_pkt(unsigned char *pos, const unsigned char *end,
size_t dglen, struct quic_tx_packet *pkt,
int64_t pn, size_t *pn_len, unsigned char **buf_pn,
int ack, int padding, int cc, int probe,
int padding, int cc, int probe,
struct quic_enc_level *qel, struct quic_conn *qc,
struct list *frms)
{
@@ -5197,14 +5199,11 @@ static int qc_do_build_pkt(unsigned char *pos, const unsigned char *end,
/* Length field value with CRYPTO frames if present. */
len_frms = 0;
beg = pos;
/* When not probing and not acking, and no immediate close is required,
* reduce the size of this buffer to respect
* the congestion controller window. So, we do not limit the size of this
* packet if we have an ACK frame to send because an ACK frame is not
* ack-eliciting. This size will be limited if we have ack-eliciting
* frames to send from <frms>.
/* When not probing, and no immediate close is required, reduce the size of this
* buffer to respect the congestion controller window.
* This size will be limited if we have ack-eliciting frames to send from <frms>.
*/
if (!probe && !ack && !cc) {
if (!probe && !LIST_ISEMPTY(frms) && !cc) {
size_t path_room;
path_room = quic_path_prep_data(qc->path);
@@ -5236,7 +5235,8 @@ static int qc_do_build_pkt(unsigned char *pos, const unsigned char *end,
head_len = pos - beg;
/* Build an ACK frame if required. */
ack_frm_len = 0;
if (!cc && ack && !eb_is_empty(&qel->pktns->rx.arngs.root)) {
if ((qel->pktns->flags & QUIC_FL_PKTNS_ACK_REQUIRED)) {
BUG_ON(eb_is_empty(&qel->pktns->rx.arngs.root));
ack_frm.tx_ack.ack_delay = 0;
ack_frm.tx_ack.arngs = &qel->pktns->rx.arngs;
/* XXX BE CAREFUL XXX : here we reserved at least one byte for the
@@ -5326,6 +5326,7 @@ static int qc_do_build_pkt(unsigned char *pos, const unsigned char *end,
goto no_room;
pkt->largest_acked_pn = quic_pktns_get_largest_acked_pn(qel->pktns);
pkt->flags |= QUIC_FL_TX_PACKET_ACK;
}
/* Ack-eliciting frames */
@@ -5421,7 +5422,7 @@ static struct quic_tx_packet *qc_build_pkt(unsigned char **pos,
const unsigned char *buf_end,
struct quic_enc_level *qel, struct list *frms,
struct quic_conn *qc, size_t dglen, int padding,
int pkt_type, int ack, int probe, int cc, int *err)
int pkt_type, int probe, int cc, int *err)
{
/* The pointer to the packet number field. */
unsigned char *buf_pn;
@@ -5447,7 +5448,7 @@ static struct quic_tx_packet *qc_build_pkt(unsigned char **pos,
pn = qel->pktns->tx.next_pn + 1;
if (!qc_do_build_pkt(*pos, buf_end, dglen, pkt, pn, &pn_len, &buf_pn,
ack, padding, cc, probe, qel, qc, frms)) {
padding, cc, probe, qel, qc, frms)) {
*err = -1;
goto err;
}
@@ -5486,8 +5487,10 @@ static struct quic_tx_packet *qc_build_pkt(unsigned char **pos,
pkt->in_flight_len = pkt->len;
qc->path->prep_in_flight += pkt->len;
}
/* Always reset these flags */
qel->pktns->flags &= ~QUIC_FL_PKTNS_ACK_REQUIRED;
if (pkt->flags & QUIC_FL_TX_PACKET_ACK) {
qel->pktns->flags &= ~QUIC_FL_PKTNS_ACK_REQUIRED;
qel->pktns->rx.nb_aepkts_since_last_ack = 0;
}
pkt->pktns = qel->pktns;
TRACE_LEAVE(QUIC_EV_CONN_HPKT, qc, pkt);