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avdtp: fix race condition when starting a stream

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The AVDTP spec allows for a race condition between remote and local
device when issuing an AVDTP_START cmd on a stream in the OPEN state.

However, the internal state must continue to be consistent. For example,
suppose that avdtp_start() has been called while in the OPEN state and
a AVDTP_START cmd is sent.  Now before we have received a response (and
thus entered the STREAMING state), we *receive* a START cmd. Prior to
this fix, since the sep is still in the OPEN state, we would accept
the new START cmd. This will leads us to send both a Start_Ind and
Start_Cfm - not good.

Now, we track this transitional state (starting == TRUE).

NB - 'starting' is only in a valid state while the sep is in the
OPEN state. 'starting' is reset when we return to the OPEN state.
This commit is contained in:
Peter Hurley 2011-07-07 10:51:34 -04:00 committed by Johan Hedberg
parent 13568564b1
commit 5d88d8d690
1 changed files with 25 additions and 4 deletions
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29
audio/avdtp.c
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@ -378,6 +378,7 @@ struct avdtp_stream {
guint idle_timer;
gboolean delay_reporting;
uint16_t delay; /* AVDTP 1.3 Delay Reporting feature */
gboolean starting; /* only valid while sep state == OPEN */
};
/* Structure describing an AVDTP connection between two devices */
@ -1065,6 +1066,7 @@ static void avdtp_sep_set_state(struct avdtp *session,
avdtp_delay_report(session, stream, stream->delay);
break;
case AVDTP_STATE_OPEN:
stream->starting = FALSE;
if (old_state > AVDTP_STATE_OPEN && session->auto_dc)
stream->idle_timer = g_timeout_add_seconds(STREAM_TIMEOUT,
stream_timeout,
@ -1708,10 +1710,13 @@ static gboolean avdtp_start_cmd(struct avdtp *session, uint8_t transaction,
stream = sep->stream;
if (sep->state != AVDTP_STATE_OPEN) {
/* Also reject start cmd if we already initiated start */
if (sep->state != AVDTP_STATE_OPEN ||
stream->starting == TRUE) {
err = AVDTP_BAD_STATE;
goto failed;
}
stream->starting = TRUE;
if (sep->ind && sep->ind->start) {
if (!sep->ind->start(session, sep, stream, &err,
@ -1726,6 +1731,7 @@ static gboolean avdtp_start_cmd(struct avdtp *session, uint8_t transaction,
AVDTP_START, NULL, 0);
failed:
DBG("Rejecting (%d)", err);
memset(&rej, 0, sizeof(rej));
rej.acp_seid = failed_seid;
rej.error = err;
@ -2580,9 +2586,12 @@ static int cancel_request(struct avdtp *session, int err)
break;
case AVDTP_START:
error("Start: %s (%d)", strerror(err), err);
if (lsep && lsep->cfm && lsep->cfm->start)
if (lsep && lsep->cfm && lsep->cfm->start) {
lsep->cfm->start(session, lsep, stream, &averr,
lsep->user_data);
if (stream)
stream->starting = FALSE;
}
break;
case AVDTP_SUSPEND:
error("Suspend: %s (%d)", strerror(err), err);
@ -3087,9 +3096,11 @@ static gboolean avdtp_parse_rej(struct avdtp *session,
return FALSE;
error("START request rejected: %s (%d)",
avdtp_strerror(&err), err.err.error_code);
if (sep && sep->cfm && sep->cfm->start)
if (sep && sep->cfm && sep->cfm->start) {
sep->cfm->start(session, sep, stream, &err,
sep->user_data);
stream->starting = FALSE;
}
return TRUE;
case AVDTP_SUSPEND:
if (!stream_rej_to_err(buf, size, &err, &acp_seid))
@ -3547,6 +3558,7 @@ int avdtp_open(struct avdtp *session, struct avdtp_stream *stream)
int avdtp_start(struct avdtp *session, struct avdtp_stream *stream)
{
struct start_req req;
int ret;
if (!g_slist_find(session->streams, stream))
return -EINVAL;
@ -3559,11 +3571,20 @@ int avdtp_start(struct avdtp *session, struct avdtp_stream *stream)
return -EINVAL;
}
if (stream->starting == TRUE) {
DBG("stream already started");
return -EINVAL;
}
memset(&req, 0, sizeof(req));
req.first_seid.seid = stream->rseid;
return send_request(session, FALSE, stream, AVDTP_START,
ret = send_request(session, FALSE, stream, AVDTP_START,
&req, sizeof(req));
if (ret == 0)
stream->starting = TRUE;
return ret;
}
int avdtp_close(struct avdtp *session, struct avdtp_stream *stream,