Parameter definition must not depend upon defines

Previously, unless HAVE_TCP_KEEP was defined equally for varnishd
and an API client (vmod), the latter used a wrong struct declaration
and, consequently, struct params members were accessed at a wrong
location. This could have adverse effects from reading bogus
values to overwriting wrong parameters or other memory.

For consistency, we keep uninplemented parameters also in the
cli and rst output with an appropriate description.

Setting them over the cli is not an error, but has no effect.

bin/varnishd/mgt/mgt_param.c

@@ -97,6 +97,10 @@ static const char ONLY_ROOT_TEXT[] =
 	"\n\n"
 	"NB: This parameter only works if varnishd is run as root.";
 
+static const char NOT_IMPLEMENTED_TEXT[] =
+	"This parameter depends on a feature which is not available"
+	" on this platform.";
+
 /*--------------------------------------------------------------------*/
 
 static struct parspec *
@@ -257,19 +261,34 @@ mcf_param_show(struct cli *cli, const char * const *av, void *priv)
 		if (chg && pp->def != NULL && !strcmp(pp->def, VSB_data(vsb)))
 			continue;
 
-		if (lfmt) {
-			VCLI_Out(cli, "%s\n", pp->name);
-			VCLI_Out(cli, "%-*sValue is: ", margin1, " ");
+		if (pp->flags & NOT_IMPLEMENTED) {
+			if (lfmt) {
+				VCLI_Out(cli, "%s\n", pp->name);
+				VCLI_Out(cli, "%-*sNot available", margin1, " ");
+			} else {
+				VCLI_Out(cli, "%-*s-", margin2, pp->name);
+			}
 		} else {
-			VCLI_Out(cli, "%-*s", margin2, pp->name);
+			if (lfmt) {
+				VCLI_Out(cli, "%s\n", pp->name);
+				VCLI_Out(cli, "%-*sValue is: ", margin1, " ");
+			} else {
+				VCLI_Out(cli, "%-*s", margin2, pp->name);
+			}
+
+			VCLI_Out(cli, "%s", VSB_data(vsb));
+			if (pp->units != NULL && *pp->units != '\0')
+				VCLI_Out(cli, " [%s]", pp->units);
+			if (pp->def != NULL && !strcmp(pp->def, VSB_data(vsb)))
+				VCLI_Out(cli, " (default)");
 		}
-		VCLI_Out(cli, "%s", VSB_data(vsb));
-		if (pp->units != NULL && *pp->units != '\0')
-			VCLI_Out(cli, " [%s]", pp->units);
-		if (pp->def != NULL && !strcmp(pp->def, VSB_data(vsb)))
-			VCLI_Out(cli, " (default)");
 		VCLI_Out(cli, "\n");
-		if (lfmt) {
+
+		if (lfmt && pp->flags & NOT_IMPLEMENTED) {
+			VCLI_Out(cli, "\n");
+			mcf_wrap(cli, NOT_IMPLEMENTED_TEXT);
+			VCLI_Out(cli, "\n\n");
+		} else if (lfmt) {
 			if (pp->def != NULL && strcmp(pp->def, VSB_data(vsb)))
 				VCLI_Out(cli, "%-*sDefault is: %s\n",
 				    margin1, "", pp->def);
@@ -466,6 +485,8 @@ MCF_InitParams(struct cli *cli)
 	VTAILQ_FOREACH(pl, &phead, list) {
 		pp = pl->spec;
 
+		if (pp->flags & NOT_IMPLEMENTED)
+			continue;
 		if (pp->min != NULL)
 			mcf_wash_param(cli, pp, &pp->min, "minimum", vsb);
 		if (pp->max != NULL)
@@ -540,6 +561,13 @@ MCF_DumpRstParam(void)
 		for (j = 0; j < strlen(pp->name); j++)
 			printf("~");
 		printf("\n");
+
+		if (pp->flags && pp->flags & NOT_IMPLEMENTED) {
+			printf("\nNot Available: %s\n\n",
+			    NOT_IMPLEMENTED_TEXT);
+			continue;
+		}
+
 		if (pp->units != NULL && *pp->units != '\0')
 			printf("\t* Units: %s\n", pp->units);
 		printf("\t* Default: %s\n", pp->def);
@@ -555,6 +583,9 @@ MCF_DumpRstParam(void)
 		if (pp->flags) {
 			printf("\t* Flags: ");
 			q = "";
+
+			AZ(pp->flags & NOT_IMPLEMENTED);
+
 			if (pp->flags & DELAYED_EFFECT) {
 				printf("%sdelayed", q);
 				q = ", ";

bin/varnishd/mgt/mgt_param.h

@@ -48,6 +48,8 @@ struct parspec {
 #define PROTECTED	(1<<5)
 #define OBJ_STICKY	(1<<6)
 #define ONLY_ROOT	(1<<7)
+#define NOT_IMPLEMENTED	(1<<8)
+
 	const char	*def;
 	const char	*units;
 };

include/tbl/params.h

@@ -1008,6 +1008,11 @@ PARAM(
 )
 
 #if defined(HAVE_TCP_KEEP)
+#define TCP_KEEP_FLAGS	EXPERIMENTAL
+#else
+#define TCP_KEEP_FLAGS	NOT_IMPLEMENTED
+#endif
+
 PARAM(
 	/* name */	tcp_keepalive_intvl,
 	/* typ */	timeout,
@@ -1015,7 +1020,7 @@ PARAM(
 	/* max */	"100",
 	/* default */	"",
 	/* units */	"seconds",
-	/* flags */	EXPERIMENTAL,
+	/* flags */	TCP_KEEP_FLAGS,
 	/* s-text */
 	"The number of seconds between TCP keep-alive probes.",
 	/* l-text */	"",
@@ -1029,7 +1034,7 @@ PARAM(
 	/* max */	"100",
 	/* default */	"",
 	/* units */	"probes",
-	/* flags */	EXPERIMENTAL,
+	/* flags */	TCP_KEEP_FLAGS,
 	/* s-text */
 	"The maximum number of TCP keep-alive probes to send before giving "
 	"up and killing the connection if no response is obtained from the "
@@ -1045,7 +1050,7 @@ PARAM(
 	/* max */	"7200",
 	/* default */	"",
 	/* units */	"seconds",
-	/* flags */	EXPERIMENTAL,
+	/* flags */	TCP_KEEP_FLAGS,
 	/* s-text */
 	"The number of seconds a connection needs to be idle before TCP "
 	"begins sending out keep-alive probes.",
@@ -1053,8 +1058,6 @@ PARAM(
 	/* func */	NULL
 )
 
-#endif /* HAVE_TCP_KEEP */
-
 #if 0
 /* actual location mgt_pool.c */
 PARAM(