fix backend.list x.y when labels are in use

labels are struct vcl objects for which most members are empty/null, with the
label member pointing to the labeled vcl.

As such, label vcl objects also have no vdire struct. Hence, when iterating over
VCLs to find backends, labels need to be skipped.

Author: nigoroll

bin/varnishd/cache/cache_vcl.c

@@ -530,6 +530,8 @@ vcl_iterdir(struct cli *cli, const char *pat, const struct vcl *vcl,
 	int i, found = 0;
 	struct vcldir *vdir;
 
+	AN(vcl->vdire);	// no labels
+
 	Lck_AssertHeld(&vcl_mtx);
 	VTAILQ_FOREACH(vdir, &vcl->vdire->directors, directors_list) {
 		CHECK_OBJ(vdir, VCLDIR_MAGIC);
@@ -575,6 +577,9 @@ VCL_IterDirector(struct cli *cli, const char *pat,
 	} else {
 		Lck_Lock(&vcl_mtx);
 		VTAILQ_FOREACH(vcl, &vcl_head, list) {
+			// skip labels
+			if (! vcl->vdire)
+				continue;
 			i = vcl_iterdir(cli, VSB_data(vsb), vcl, func, priv);
 			if (i < 0) {
 				found = i;

bin/varnishtest/tests/c00077.vtc

@@ -15,6 +15,7 @@ varnish v1 -clierr 106 "vcl.label vcl.A vcl1"
 varnish v1 -cliok "vcl.label vclA vcl1"
 # labeling twice #2834
 varnish v1 -cliok "vcl.label vclA vcl1"
+varnish v1 -cliok "backend.list vcl1.*"
 
 varnish v1 -vcl+backend {
 	sub vcl_recv {