Implement a dbg acceptor as a VEXT

it actually just uses the TCP acceptor code, but tests plugging via an extension

bin/varnishtest/tests/x00001.vtc

@@ -0,0 +1,27 @@
+varnishtest "Minimal acceptor VEXT test"
+
+shell -err -expect {Error: Acceptor foo not found} {
+	varnishd -b None -a %foo,socket -n ${tmpdir}
+}
+
+shell -err -expect {Error: Acceptor bar not found} {
+	varnishd -b None -a name=%bar,socket -n ${tmpdir}
+}
+
+varnish v1 \
+    -arg "-E ${topbuild}/vmod/.libs/libvmod_vext_debug.so" \
+    -arg "-a dbg=%dbg,${listen_addr}" \
+    -vcl {
+
+	backend none none;
+
+	sub vcl_recv {
+		return (synth(200));
+	}
+} -start
+
+#client c1 -repeat 10 {
+client c1 {
+	txreq
+	rxresp
+} -run

vmod/Makefile.am

@@ -31,6 +31,7 @@ include $(srcdir)/automake_boilerplate_blob.am
 include $(srcdir)/automake_boilerplate_h2.am
 include $(srcdir)/automake_boilerplate_cookie.am
 include $(srcdir)/automake_boilerplate_debug.am
+include $(srcdir)/automake_boilerplate_vext_debug.am
 include $(srcdir)/automake_boilerplate_directors.am
 include $(srcdir)/automake_boilerplate_proxy.am
 include $(srcdir)/automake_boilerplate_purge.am
@@ -55,6 +56,8 @@ vmod_debug_symbols_regex = 'Vmod_.*_Data'
 # not --strict
 vmodtoolargs_debug = --boilerplate -o vcc_debug_if
 
-dist_noinst_DATA = $(srcdir)/vmod_debug.vcc
+dist_noinst_DATA = \
+	$(srcdir)/vmod_debug.vcc \
+	$(srcdir)/vmod_vext_debug.vcc
 
 dist_vcc_DATA = $(vmod_vcc_files)

vmod/automake_boilerplate_vext_debug.am

@@ -0,0 +1,43 @@
+## Generated by vmodtool.py --boilerplate.
+
+vmod_vext_debug_vcc ?= $(srcdir)/vmod_vext_debug.vcc
+
+vmod_vcc_files += $(vmod_vext_debug_vcc)
+
+vmod_LTLIBRARIES += libvmod_vext_debug.la
+
+libvmod_vext_debug_la_SOURCES = \
+	vmod_vext_debug.c \
+	vmod_vext_debug_acceptor.c
+
+libvmod_vext_debug_la_CFLAGS =
+
+vmodtoolargs_vext_debug ?= --strict --boilerplate -o vcc_vext_debug_if
+vmod_vext_debug_symbols_regex ?= Vmod_vext_debug_Data
+
+libvmod_vext_debug_la_LDFLAGS = \
+	-export-symbols-regex $(vmod_vext_debug_symbols_regex) \
+	$(AM_LDFLAGS) \
+	$(VMOD_LDFLAGS)
+
+nodist_libvmod_vext_debug_la_SOURCES = vcc_vext_debug_if.c vcc_vext_debug_if.h
+
+EXTRA_libvmod_vext_debug_la_DEPENDENCIES = $(nodist_libvmod_vext_debug_la_SOURCES)
+
+EXTRA_DIST += automake_boilerplate_vext_debug.am
+
+$(libvmod_vext_debug_la_OBJECTS): vcc_vext_debug_if.h
+
+vcc_vext_debug_if.h vmod_vext_debug.rst vmod_vext_debug.man.rst: vcc_vext_debug_if.c
+
+# A doc-change will not update mtime on the .h and .c files, so a
+# touch(1) is necessary to signal that vmodtool was in fact run.
+vcc_vext_debug_if.c: $(VMODTOOL) $(srcdir)/vmod_vext_debug.vcc
+	@PYTHON@ $(VMODTOOL) $(vmodtoolargs_vext_debug) $(srcdir)/vmod_vext_debug.vcc
+	touch vcc_vext_debug_if.c
+
+clean-local: clean-vmod-vext_debug
+
+clean-vmod-vext_debug:
+	rm -f $(nodist_libvmod_vext_debug_la_SOURCES)
+	rm -f vmod_vext_debug.rst vmod_vext_debug.man.rst

vmod/vmod_vext_debug.c

@@ -0,0 +1,10 @@
+#include "config.h"
+#include "vdef.h"
+#include "vrt.h"
+#include "vcc_vext_debug_if.h"
+
+VCL_VOID
+dbgvext_dummy(VRT_CTX)
+{
+	(void) ctx;
+}

vmod/vmod_vext_debug.vcc

@@ -0,0 +1,40 @@
+# Copyright 2024 UPLEX - Nils Goroll Systemoptimierung
+# All rights reserved.
+#
+# Author: Nils Goroll <[email protected]>
+#
+# SPDX-License-Identifier: BSD-2-Clause
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions
+# are met:
+# 1. Redistributions of source code must retain the above copyright
+#    notice, this list of conditions and the following disclaimer.
+# 2. Redistributions in binary form must reproduce the above copyright
+#    notice, this list of conditions and the following disclaimer in the
+#    documentation and/or other materials provided with the distribution.
+#
+# THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+# ARE DISCLAIMED.  IN NO EVENT SHALL AUTHOR OR CONTRIBUTORS BE LIABLE
+# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+# OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+# SUCH DAMAGE.
+
+$ABI strict
+$Prefix dbgvext
+$Module vext_debug 3 "Varnish Extension development, test and debug"
+$Synopsis auto
+DESCRIPTION
+===========
+
+At this point, this vmod does not expose any interface to VCL.
+
+It implements the "dbg" acceptor, which simply wraps the "tcp" acceptor.
+
+$Function VOID dummy()

vmod/vmod_vext_debug_acceptor.c

@@ -0,0 +1,86 @@
+/*-
+ * Copyright 2024 UPLEX - Nils Goroll Systemoptimierung
+ * All rights reserved.
+ *
+ * Author: Nils Goroll <[email protected]>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include "config.h"
+
+#include <stdio.h>
+
+#include "cache/cache_varnishd.h"
+#include "acceptor/cache_acceptor.h"
+#include "acceptor/mgt_acceptor.h"
+
+struct acceptor DBG_acceptor;
+
+// these callbacks are all noops, because we initialize our dbg acceptor as a
+// tcp acceptor, which keeps a list of its instances, so the respective
+// functions get already called through the tcp acceptor
+
+static int
+acc_dbg_reopen(void)
+{
+	return (0);
+}
+
+static void
+acc_dbg_start(struct cli *cli)
+{
+	(void) cli;
+}
+
+static void
+acc_dbg_accept(struct pool * pp)
+{
+	(void) pp;
+}
+
+static void
+acc_dbg_update(pthread_mutex_t * shut_mtx)
+{
+	(void) shut_mtx;
+}
+
+static void
+acc_dbg_shutdown(void)
+{
+}
+
+static void __attribute__((constructor))
+init_register_acceptor(void) {
+    fprintf(stderr, "HELLO from dbg acceptor VEXT\n");
+    DBG_acceptor = TCP_acceptor;
+    DBG_acceptor.name = "dbg";
+    DBG_acceptor.reopen = acc_dbg_reopen;
+    DBG_acceptor.start = acc_dbg_start;
+    DBG_acceptor.accept = acc_dbg_accept;
+    DBG_acceptor.update = acc_dbg_update;
+    DBG_acceptor.shutdown = acc_dbg_shutdown;
+
+    VCA_Add(&DBG_acceptor);
+}