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iwd
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frame-xchg: Add facility to keep retransmitting after ACK 

In some cases a P2P peer will ACK our frame but not reply on the first
attempt, and other implementations seem to handle this by going back to
retransmitting the frame at a high rate until it gets ACKed again, at
which point they will again give the peer a longer time to tx the
response frame.  Implement the same logic here by adding a
retries_on_ack parameter that takes the number of additional times we
want to restart the normal retransmit counter after we received no
response frame on the first attempt.  So passing 0 maintains the
current behaviour, 1 for 1 extra attempt, etc.

In effect we may retransmit a frame about 15 * (retry_on_ack + 1) *
<in-kernel retransmit limit> times.  The kernel/driver retransmits a
frame a number of times if there's no ACK (I've seen about 20 normally)
at a high frequency, if that fails we retry the whole process 15 times
inside frame-xchg.c and if we still get no ACK at any point, we give up.
If we do get an ACK, we wait for a response frame and if we don't get
that we will optionally reset the retry counter and restart the whole
thing retry_on_ack times.
This commit is contained in:
Andrew Zaborowski 2020-03-19 22:12:10 +01:00 committed by Denis Kenzior
parent e7a9a43410
commit e6de4b10ad
2 changed files with 45 additions and 21 deletions
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62
src/frame-xchg.c
View File

@ -107,6 +107,7 @@ struct frame_xchg_data {
unsigned int retry_cnt;
unsigned int retry_interval;
unsigned int resp_timeout;
unsigned int retries_on_ack;
bool in_frame_cb : 1;
bool stale : 1;
};
@ -726,6 +727,9 @@ static bool frame_watch_remove_by_handler(uint64_t wdev_id, uint32_t group_id,
}
static void frame_xchg_tx_retry(struct frame_xchg_data *fx);
static bool frame_xchg_resp_handle(const struct mmpdu_header *mpdu,
const void *body, size_t body_len,
int rssi, void *user_data);
static void frame_xchg_resp_cb(const struct mmpdu_header *mpdu,
const void *body, size_t body_len,
int rssi, void *user_data);
@ -805,12 +809,20 @@ static void frame_xchg_timeout_cb(struct l_timeout *timeout,
frame_xchg_tx_retry(fx);
}
static void frame_xchg_resp_timeout_cb(struct l_timeout *timeout,
static void frame_xchg_listen_end_cb(struct l_timeout *timeout,
void *user_data)
{
struct frame_xchg_data *fx = user_data;
frame_xchg_done(fx, 0);
if (!fx->retries_on_ack) {
frame_xchg_done(fx, 0);
return;
}
l_timeout_remove(fx->timeout);
fx->retries_on_ack--;
fx->retry_cnt = 0;
frame_xchg_tx_retry(fx);
}
static void frame_xchg_tx_status(struct frame_xchg_data *fx, bool acked)
@ -850,17 +862,20 @@ static void frame_xchg_tx_status(struct frame_xchg_data *fx, bool acked)
fx->have_cookie = false;
l_debug("Processing an early frame");
frame_xchg_resp_cb(fx->early_frame.mpdu, fx->early_frame.body,
fx->early_frame.body_len,
fx->early_frame.rssi, fx);
frame_xchg_done(fx, 0);
if (frame_xchg_resp_handle(fx->early_frame.mpdu,
fx->early_frame.body,
fx->early_frame.body_len,
fx->early_frame.rssi, fx))
return;
frame_xchg_listen_end_cb(NULL, fx);
return;
}
/* Txed frame ACKed, listen for response frames */
fx->timeout = l_timeout_create_ms(fx->resp_timeout,
frame_xchg_resp_timeout_cb, fx,
frame_xchg_listen_end_cb, fx,
frame_xchg_timeout_destroy);
}
@ -946,9 +961,9 @@ static void frame_xchg_tx_retry(struct frame_xchg_data *fx)
fx->retry_cnt++;
}
static void frame_xchg_resp_cb(const struct mmpdu_header *mpdu,
const void *body, size_t body_len,
int rssi, void *user_data)
static bool frame_xchg_resp_handle(const struct mmpdu_header *mpdu,
const void *body, size_t body_len,
int rssi, void *user_data)
{
struct frame_xchg_data *fx = user_data;
const struct l_queue_entry *entry;
@ -957,10 +972,10 @@ static void frame_xchg_resp_cb(const struct mmpdu_header *mpdu,
l_debug("");
if (memcmp(mpdu->address_1, fx->tx_mpdu->address_2, 6))
return;
return false;
if (memcmp(mpdu->address_2, fx->tx_mpdu->address_1, 6))
return;
return false;
/*
* Is the received frame's BSSID same as the transmitted frame's
@ -970,7 +985,7 @@ static void frame_xchg_resp_cb(const struct mmpdu_header *mpdu,
*/
if (memcmp(mpdu->address_3, fx->tx_mpdu->address_3, 6) &&
!util_mem_is_zero(mpdu->address_3, 6))
return;
return false;
for (entry = l_queue_get_entries(fx->rx_watches);
entry; entry = entry->next) {
@ -994,18 +1009,18 @@ static void frame_xchg_resp_cb(const struct mmpdu_header *mpdu,
* to just exit without touching anything.
*/
if (!fx->in_frame_cb)
return;
return true;
fx->in_frame_cb = false;
if (done || fx->stale) {
fx->cb = NULL;
frame_xchg_done(fx, 0);
return;
return true;
}
}
return;
return false;
early_frame:
/*
@ -1016,13 +1031,21 @@ early_frame:
* Save the response frame to be processed in the Tx done callback.
*/
if (fx->early_frame.mpdu)
return;
return false;
hdr_len = (const uint8_t *) body - (const uint8_t *) mpdu;
fx->early_frame.mpdu = l_memdup(mpdu, body_len + hdr_len);
fx->early_frame.body = (const uint8_t *) fx->early_frame.mpdu + hdr_len;
fx->early_frame.body_len = body_len;
fx->early_frame.rssi = rssi;
return false;
}
static void frame_xchg_resp_cb(const struct mmpdu_header *mpdu,
const void *body, size_t body_len,
int rssi, void *user_data)
{
frame_xchg_resp_handle(mpdu, body, body_len, rssi, user_data);
}
static bool frame_xchg_match(const void *a, const void *b)
@ -1050,8 +1073,8 @@ static bool frame_xchg_match(const void *a, const void *b)
*/
void frame_xchg_startv(uint64_t wdev_id, struct iovec *frame, uint32_t freq,
unsigned int retry_interval, unsigned int resp_timeout,
uint32_t group_id, frame_xchg_cb_t cb, void *user_data,
va_list resp_args)
unsigned int retries_on_ack, uint32_t group_id,
frame_xchg_cb_t cb, void *user_data, va_list resp_args)
{
struct frame_xchg_data *fx;
size_t frame_len;
@ -1095,6 +1118,7 @@ void frame_xchg_startv(uint64_t wdev_id, struct iovec *frame, uint32_t freq,
fx->freq = freq;
fx->retry_interval = retry_interval;
fx->resp_timeout = resp_timeout;
fx->retries_on_ack = retries_on_ack;
fx->cb = cb;
fx->user_data = user_data;
fx->group_id = group_id;

4
src/frame-xchg.h
View File

@ -45,6 +45,6 @@ bool frame_watch_wdev_remove(uint64_t wdev_id);
void frame_xchg_startv(uint64_t wdev_id, struct iovec *frame, uint32_t freq,
unsigned int retry_interval, unsigned int resp_timeout,
uint32_t group_id, frame_xchg_cb_t cb, void *user_data,
va_list resp_args);
unsigned int retries_on_ack, uint32_t group_id,
frame_xchg_cb_t cb, void *user_data, va_list resp_args);
void frame_xchg_stop(uint64_t wdev_id);