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BUG/MEDIUM: conn-stream: Set back CS to RDY state when the appctx is created

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When an appctx is created on the server side, we now set the corresponding
conn-stream to ready state (CS_ST_RDY). When it happens, the backend
conn-stream is in CS_ST_INI state. It is not consistant to let the
conn-stream in this state because it means it is possible to have a target
installed in CS_ST_INI state, while with a connection, the conn-stream is
switch to CS_ST_RDY or CS_ST_EST state.

It is especially anbiguous because we may be tempted to think there is no
endpoint attached to the conn-stream before the CS_ST_CON state. And it is
indeed the reason for a bug leading to a crash because a cs_detach_endp() is
performed if an abort is detected on the backend conn-stream in CS_ST_INI
state. With a mux or a appctx attached to the conn-stream, "->endp" field is
set to NULL. It is unexpected. The API will be changed to be sure it is not
possible. But it exposes a consistency issue with applets.

So, the conn-stream must not stay in CS_ST_INI state when an appctx is
attached. But there is no reason to set it in CS_ST_REQ. The conn-stream
must be set to CS_ST_RDY to handle applets and connections in the same
way. Note that if only the target is set but no appctx is created, the
backend conn-stream is switched from CS_ST_INI to CS_ST_REQ state to be able
to create the corresponding appctx. This part is unchanged.

This patch depends on the commit "MINOR: backend: Don't allow to change
backend applet".

The ambiguity exists on previous versions. But the issue is
2.6-specific. Thus, no backport is needed.
This commit is contained in:
Christopher Faulet 2022-04-21 11:52:07 +02:00
parent bb5b62ee5c
commit a33ff7a8a7
2 changed files with 23 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

33
src/backend.c
View File

@ -2113,7 +2113,7 @@ abort_connection:
/* This function initiates a server connection request on a conn-stream
* already in CS_ST_REQ state. Upon success, the state goes to CS_ST_ASS for
* a real connection to a server, indicating that a server has been assigned,
* or CS_ST_EST for a successful connection to an applet. It may also return
* or CS_ST_RDY for a successful connection to an applet. It may also return
* CS_ST_QUE, or CS_ST_CLO upon error.
*/
void back_handle_st_req(struct stream *s)
@ -2126,12 +2126,14 @@ void back_handle_st_req(struct stream *s)
DBG_TRACE_ENTER(STRM_EV_STRM_PROC|STRM_EV_CS_ST, s);
if (unlikely(obj_type(s->target) == OBJ_TYPE_APPLET)) {
/* the applet directly goes to the EST state */
struct appctx *appctx = cs_appctx(s->csb);
struct appctx *appctx;
if (!appctx)
/* The target is an applet but the CS is in CS_ST_REQ. Thus it
* means no appctx are attached to the CS. Otherwise, it will be
* in CS_ST_RDY state. So, try to create the appctx now.
*/
BUG_ON(cs_appctx(cs));
appctx = cs_applet_create(cs, objt_applet(s->target));
if (!appctx) {
/* No more memory, let's immediately abort. Force the
* error code to ignore the ERR_LOCAL which is not a
@ -2150,15 +2152,7 @@ void back_handle_st_req(struct stream *s)
goto end;
}
if (tv_iszero(&s->logs.tv_request))
s->logs.tv_request = now;
s->logs.t_queue = tv_ms_elapsed(&s->logs.tv_accept, &now);
cs->state = CS_ST_EST;
s->conn_err_type = STRM_ET_NONE;
be_set_sess_last(s->be);
DBG_TRACE_STATE("applet registered", STRM_EV_STRM_PROC|STRM_EV_CS_ST, s);
/* let back_establish() finish the job */
goto end;
}
@ -2406,6 +2400,19 @@ void back_handle_st_rdy(struct stream *s)
struct channel *rep = &s->res;
DBG_TRACE_ENTER(STRM_EV_STRM_PROC|STRM_EV_CS_ST, s);
if (unlikely(obj_type(s->target) == OBJ_TYPE_APPLET)) {
/* Here the appctx must exists because the CS was set to
* CS_ST_RDY state when the appctx was created.
*/
BUG_ON(!cs_appctx(s->csb));
if (tv_iszero(&s->logs.tv_request))
s->logs.tv_request = now;
s->logs.t_queue = tv_ms_elapsed(&s->logs.tv_accept, &now);
be_set_sess_last(s->be);
}
/* We know the connection at least succeeded, though it could have
* since met an error for any other reason. At least it didn't time out
* even though the timeout might have been reported right after success.

2
src/conn_stream.c
View File

@ -468,6 +468,8 @@ struct appctx *cs_applet_create(struct conn_stream *cs, struct applet *app)
appctx->t->nice = __cs_strm(cs)->task->nice;
cs_cant_get(cs);
appctx_wakeup(appctx);
cs->state = CS_ST_RDY;
return appctx;
}