regress: add a knob to disable test_ipv6_addr

at least on the CI is failing with "can't connect to ::1:10965:
Address not available" which suggests IPv6 is broken there.

.cirrus.yml

@@ -1,14 +1,17 @@
 # gcc' -Werror=use-after-free gets tripped by vis.c: it sees a use
 # after free where it's not possible and breaks the CI.
 
+# seems that inside the CI it's not currently possible to bind to ::1
+# so set HAVE_IPV6=no.
+
 linux_amd64_task:
   container:
     image: alpine:latest
   test_script:
     - apk add alpine-sdk linux-headers bison libretls-dev libevent-dev
     - ./configure CFLAGS='-O2 -pipe -Wno-deprecated-declarations -Wno-use-after-free' -Werror
     - make
-    - make regress REGRESS_HOST="*"
+    - make regress REGRESS_HOST="*" HAVE_IPV6=no
 
 linux_arm_task:
   arm_container:
@@ -17,7 +20,7 @@ linux_arm_task:
     - apk add alpine-sdk linux-headers bison libretls-dev libevent-dev
     - ./configure CFLAGS='-O2 -pipe -Wno-deprecated-declarations -Wno-use-after-free' -Werror
     - make
-    - make regress REGRESS_HOST="*"
+    - make regress REGRESS_HOST="*" HAVE_IPV6=no
 
 freebsd_14_task:
   freebsd_instance:
@@ -26,7 +29,7 @@ freebsd_14_task:
   script:
     - ./configure CFLAGS='-O2 -pipe -Wno-deprecated-declarations' -Werror
     - make
-    - make regress
+    - make regress HAVE_IPV6=no
 
 #
 # There are some issues with imsg fd passing on macos at the moment that

regress/Makefile

@@ -7,6 +7,9 @@ GENCERT_FLAGS=
 # host to bind to during regress
 REGRESS_HOST =	localhost
 
+# set to no if don't have IPv6 working (need to listen on ::1)
+HAVE_IPV6 =	yes
+
 DISTFILES =	Makefile \
 		env \
 		err \
@@ -39,7 +42,7 @@ IRI_OBJS =	${IRI_SRCS:.c=.o} ${REG_COMPATS}
 .PHONY: all data clean dist
 
 all: data puny-test iri_test fcgi-test
-	env REGRESS_HOST="${REGRESS_HOST}" ./regress ${TESTS}
+	env HAVE_IPV6="${HAVE_IPV6}" REGRESS_HOST="${REGRESS_HOST}" ./regress ${TESTS}
 
 data: testdata localhost.pem testca.pem valid.crt invalid.pem
 

regress/lib.sh

@@ -26,7 +26,10 @@ run_test() {
 
 	rm -f reg.conf
 
-	if ! $1; then
+	if [ "$2" = "need_ipv6" -a "$HAVE_IPV6" != "yes" ]; then
+		echo "$1 skipped (needs HAVE_IPV6='yes')"
+		return
+	elif ! $1; then
 		echo "$1 failed"
 		failed="$failed $1"
 		failed_no=$((failed_no + 1))