Let remove_backend tell if the current dir changed

lib/libvmod_directors/fall_back.c

@@ -123,7 +123,7 @@ vmod_fallback_remove_backend(VRT_CTX,
 {
 	CHECK_OBJ_NOTNULL(ctx, VRT_CTX_MAGIC);
 	CHECK_OBJ_NOTNULL(fb, VMOD_DIRECTORS_FALLBACK_MAGIC);
-	vdir_remove_backend(fb->vd, be);
+	vdir_remove_backend(fb->vd, be, NULL);
 }
 
 VCL_BACKEND __match_proto__()

lib/libvmod_directors/hash.c

@@ -91,7 +91,7 @@ vmod_hash_remove_backend(VRT_CTX,
 
 	CHECK_OBJ_NOTNULL(ctx, VRT_CTX_MAGIC);
 	CHECK_OBJ_NOTNULL(rr, VMOD_DIRECTORS_HASH_MAGIC);
-	vdir_remove_backend(rr->vd, be);
+	vdir_remove_backend(rr->vd, be, NULL);
 }
 
 VCL_BACKEND __match_proto__()

lib/libvmod_directors/random.c

@@ -118,7 +118,7 @@ VCL_VOID vmod_random_remove_backend(VRT_CTX,
 {
 	CHECK_OBJ_NOTNULL(ctx, VRT_CTX_MAGIC);
 	CHECK_OBJ_NOTNULL(rr, VMOD_DIRECTORS_RANDOM_MAGIC);
-	vdir_remove_backend(rr->vd, be);
+	vdir_remove_backend(rr->vd, be, NULL);
 }
 
 VCL_BACKEND __match_proto__()

lib/libvmod_directors/round_robin.c

@@ -127,7 +127,7 @@ vmod_round_robin_remove_backend(VRT_CTX,
 {
 	CHECK_OBJ_NOTNULL(ctx, VRT_CTX_MAGIC);
 	CHECK_OBJ_NOTNULL(rr, VMOD_DIRECTORS_ROUND_ROBIN_MAGIC);
-	vdir_remove_backend(rr->vd, be);
+	vdir_remove_backend(rr->vd, be, NULL);
 }
 
 VCL_BACKEND __match_proto__()

lib/libvmod_directors/vdir.c

@@ -134,7 +134,7 @@ vdir_add_backend(struct vdir *vd, VCL_BACKEND be, double weight)
 }
 
 void
-vdir_remove_backend(struct vdir *vd, VCL_BACKEND be)
+vdir_remove_backend(struct vdir *vd, VCL_BACKEND be, unsigned *cur)
 {
 	unsigned u, n;
 
@@ -155,6 +155,15 @@ vdir_remove_backend(struct vdir *vd, VCL_BACKEND be)
 	memmove(&vd->backend[u], &vd->backend[u+1], n * sizeof(vd->backend[0]));
 	memmove(&vd->weight[u], &vd->weight[u+1], n * sizeof(vd->weight[0]));
 	vd->n_backend--;
+
+	if (cur) {
+		assert(*cur >= 0);
+		assert(*cur <= vd->n_backend);
+		if (u < *cur)
+			(*cur)--;
+		else if (*cur == vd->n_backend)
+			*cur = 0;
+	}
 	vdir_unlock(vd);
 }
 

lib/libvmod_directors/vdir.h

@@ -48,7 +48,7 @@ void vdir_rdlock(struct vdir *vd);
 void vdir_wrlock(struct vdir *vd);
 void vdir_unlock(struct vdir *vd);
 unsigned vdir_add_backend(struct vdir *, VCL_BACKEND be, double weight);
-void vdir_remove_backend(struct vdir *, VCL_BACKEND be);
+void vdir_remove_backend(struct vdir *, VCL_BACKEND be, unsigned *cur);
 unsigned vdir_any_healthy(struct vdir *, const struct busyobj *,
     double *changed);
 VCL_BACKEND vdir_pick_be(struct vdir *, double w, const struct busyobj *);