MINOR: global: Add an option to disable the data fast-forward

The new global option "tune.fast-forward" can be set to "off" to disable the
data fast-forward. It is an debug option, thus it is internally marked as
experimental. The directive "expose-experimental-directives" must be set
first to use this one. By default, the data fast-forward is enable.

It could be usefull to force to wake the stream up when data are
received. To be sure, evreything works fine in this case. The data
fast-forward is an optim. It must work without it. But some code may rely on
the fact the stream will not be woken up. With this option, it is possible
to spot some hidden bugs.

doc/configuration.txt

@@ -1123,6 +1123,7 @@ The following keywords are supported in the "global" section :
    - tune.buffers.reserve
    - tune.bufsize
    - tune.comp.maxlevel
+   - tune.fast-forward
    - tune.fd.edge-triggered
    - tune.h2.header-table-size
    - tune.h2.initial-window-size
@@ -2837,6 +2838,17 @@ tune.fail-alloc
   failure) and 100 (no success). This is useful to debug and make sure memory
   failures are handled gracefully.
 
+tune.fast-forward { on | off } [ EXPERIMENTAL ]
+
+  Enabled ('on') or disables ('off') the data fast-forwarding. It is a
+  mechanism to optimize the data forwarding by passing data directly from a
+  side to the other one without waking the stream up. Thanks to this directive,
+  it is possible to disable this optimization. Note it also disable any kernel
+  tcp splicing. This command is not meant for regular use, it will generally
+  only be suggested by developers along complex debugging sessions. For this
+  reason it is internally marked as experimental, meaning that
+  "expose-experimental-directives" must appear on a line before this directive.
+
 tune.fd.edge-triggered { on | off }  [ EXPERIMENTAL ]
   Enables ('on') or disables ('off') the edge-triggered polling mode for FDs
   that support it. This is currently only support with epoll. It may noticeably

include/haproxy/global-t.h

@@ -80,6 +80,7 @@
 #define GTUNE_QUICK_EXIT         (1<<23)
 #define GTUNE_QUIC_SOCK_PER_CONN (1<<24)
 #define GTUNE_NO_QUIC            (1<<25)
+#define GTUNE_NO_FAST_FWD        (1<<26)
 
 /* SSL server verify mode */
 enum {

src/cfgparse-global.c

@@ -36,7 +36,8 @@ static const char *common_kw_list[] = {
 	"tune.idletimer", "tune.rcvbuf.client", "tune.rcvbuf.server",
 	"tune.sndbuf.client", "tune.sndbuf.server", "tune.pipesize",
 	"tune.http.cookielen", "tune.http.logurilen", "tune.http.maxhdr",
-	"tune.comp.maxlevel", "tune.pattern.cache-size", "uid", "gid",
+	"tune.comp.maxlevel", "tune.pattern.cache-size",
+	"tune.fast-forward", "uid", "gid",
 	"external-check", "user", "group", "nbproc", "maxconn",
 	"ssl-server-verify", "maxconnrate", "maxsessrate", "maxsslrate",
 	"maxcomprate", "maxpipes", "maxzlibmem", "maxcompcpuusage", "ulimit-n",
@@ -492,6 +493,34 @@ int cfg_parse_global(const char *file, int linenum, char **args, int kwm)
 			goto out;
 		}
 	}
+	else if (strcmp(args[0], "tune.fast-forward") == 0) {
+		if (!experimental_directives_allowed) {
+			ha_alert("parsing [%s:%d] : '%s' directive is experimental, must be allowed via a global 'expose-experimental-directives'",
+				 file, linenum, args[0]);
+			err_code |= ERR_ALERT | ERR_FATAL;
+			goto out;
+		}
+		mark_tainted(TAINTED_CONFIG_EXP_KW_DECLARED);
+
+		if (alertif_too_many_args(1, file, linenum, args, &err_code))
+			goto out;
+		if (*(args[1]) == 0) {
+			ha_alert("parsing [%s:%d] : '%s' expects either 'on' or 'off' as argument.",
+				 file, linenum, args[0]);
+			err_code |= ERR_ALERT | ERR_FATAL;
+			goto out;
+		}
+		if (strcmp(args[1], "on") == 0)
+			global.tune.options &= ~GTUNE_NO_FAST_FWD;
+		else if (strcmp(args[1], "off") == 0)
+			global.tune.options |= GTUNE_NO_FAST_FWD;
+		else {
+			ha_alert("parsing [%s:%d] : '%s' expects either 'on' or 'off' but got '%s'.",
+				 file, linenum, args[0], args[1]);
+			err_code |= ERR_ALERT | ERR_FATAL;
+			goto out;
+		}
+	}
 	else if (strcmp(args[0], "cluster-secret") == 0) {
 		if (alertif_too_many_args(1, file, linenum, args, &err_code))
 			goto out;

src/http_ana.c

@@ -941,7 +941,7 @@ int http_request_forward_body(struct stream *s, struct channel *req, int an_bit)
 	}
 	else {
 		c_adv(req, htx->data - co_data(req));
-		if (msg->flags & HTTP_MSGF_XFER_LEN)
+		if (!(global.tune.options & GTUNE_NO_FAST_FWD) && (msg->flags & HTTP_MSGF_XFER_LEN))
 			channel_htx_forward_forever(req, htx);
 	}
 
@@ -2044,7 +2044,7 @@ int http_response_forward_body(struct stream *s, struct channel *res, int an_bit
 	}
 	else {
 		c_adv(res, htx->data - co_data(res));
-		if (msg->flags & HTTP_MSGF_XFER_LEN)
+		if (!(global.tune.options & GTUNE_NO_FAST_FWD) && (msg->flags & HTTP_MSGF_XFER_LEN))
 			channel_htx_forward_forever(res, htx);
 	}
 

src/stream.c

@@ -2258,7 +2258,7 @@ struct task *process_stream(struct task *t, void *context, unsigned int state)
 			 * to the consumer.
 			 */
 			co_set_data(req, htx->data);
-			if (!(req->flags & (CF_SHUTR|CF_SHUTW_NOW)))
+			if (!(global.tune.options & GTUNE_NO_FAST_FWD) && !(req->flags & (CF_SHUTR|CF_SHUTW_NOW)))
 				channel_htx_forward_forever(req, htx);
 		}
 		else {
@@ -2266,7 +2266,7 @@ struct task *process_stream(struct task *t, void *context, unsigned int state)
 			 * to the consumer (which might possibly not be connected yet).
 			 */
 			c_adv(req, ci_data(req));
-			if (!(req->flags & (CF_SHUTR|CF_SHUTW_NOW)))
+			if (!(global.tune.options & GTUNE_NO_FAST_FWD) && !(req->flags & (CF_SHUTR|CF_SHUTW_NOW)))
 				channel_forward_forever(req);
 		}
 	}
@@ -2429,7 +2429,7 @@ struct task *process_stream(struct task *t, void *context, unsigned int state)
 			 * to the consumer.
 			 */
 			co_set_data(res, htx->data);
-			if (!(res->flags & (CF_SHUTR|CF_SHUTW_NOW)))
+			if (!(global.tune.options & GTUNE_NO_FAST_FWD) && !(res->flags & (CF_SHUTR|CF_SHUTW_NOW)))
 				channel_htx_forward_forever(res, htx);
 		}
 		else {
@@ -2437,7 +2437,7 @@ struct task *process_stream(struct task *t, void *context, unsigned int state)
 			 * to the consumer.
 			 */
 			c_adv(res, ci_data(res));
-			if (!(res->flags & (CF_SHUTR|CF_SHUTW_NOW)))
+			if (!(global.tune.options & GTUNE_NO_FAST_FWD) && !(res->flags & (CF_SHUTR|CF_SHUTW_NOW)))
 				channel_forward_forever(res);
 		}