Add ASan support

Dockerfile

@@ -7,6 +7,7 @@ RUN apt-get update && apt-get install -y \
 	build-essential \
 	libtool \
 	automake \
+	autoconf-archive \
 	python3-docutils
 
 WORKDIR /

README.md

@@ -76,6 +76,22 @@ Fork, code, and PR! See build instructions above.
 
 I'm happy to review any PRs. Any bug reports are also welcome.
 
+### Debugging
+
+The module can also be built with [`AddressSanitizer`](https://github.com/google/sanitizers/wiki/AddressSanitizer) support.
+
+It is recommended that when developing on the module, you build with `AddressSanitizer` support enabled in order to help identify any memory issues with the VMOD.
+
+In order to build the module with this enabled, run the `bootstrap` script with `--enable-asan`. 
+
+```
+./bootstrap --enable-asan
+```
+
+There are also some scripts in the `debug` directory to assist. Navigate to the `debug` directory and run `docker compose up --build` in order to build the module with ASan support as well as with a backend `nginx` to field example requests.
+
+_Note_: Do not use the module built with ASan support in production. This is meant for development purposes only.
+
 ## Acknowledgements
 
 - The NY Times [`libvmod-queryfilter` VMOD](https://github.com/nytimes/libvmod-queryfilter/) for insipiration.

configure.ac

@@ -18,6 +18,23 @@ AC_ARG_WITH([rst2man],
 	[RST2MAN="$withval"],
 	[AC_CHECK_PROGS(RST2MAN, [rst2man rst2man.py], [])])
 
+AC_ARG_ENABLE([asan],
+	AS_HELP_STRING([--enable-asan],
+		[enable address sanitizer (default is NO)]),
+	[
+		ASAN_FLAGS="-fsanitize-recover=address"
+		AC_DEFINE([ENABLE_ASAN], [1],
+			[Define to 1 if ASAN sanitizer is enabled.])
+	], [])
+
+if test -n "$ASAN_FLAGS"; then
+	AX_CHECK_COMPILE_FLAG([$ASAN_FLAGS -fsanitize-address-use-after-scope],
+		[ASAN_FLAGS="$ASAN_FLAGS -fsanitize-address-use-after-scope"],
+		[])
+fi
+
+CFLAGS="$CFLAGS $ASAN_FLAGS"
+LDFLAGS="$LDFLAGS $ASAN_FLAGS"
 VARNISH_PREREQ([7.0.0])
 VARNISH_VMODS([querymodifier])
 

debug/Dockerfile

@@ -0,0 +1,20 @@
+FROM varnish:7.6.1
+
+USER root
+
+RUN apt-get update && \
+    apt-get install --yes \
+    build-essential \
+    libtool \
+    automake \
+    python3-docutils \
+    autoconf-archive \
+    libasan8
+
+WORKDIR /
+
+COPY . /libvmod-querymodifier
+RUN cd /libvmod-querymodifier \
+	&& ./bootstrap --enable-asan \
+	&& make \
+	&& make install

debug/default.conf

@@ -0,0 +1,5 @@
+server {
+    location / {
+        return 200 'OK';
+    }
+}

debug/default.vcl

@@ -0,0 +1,14 @@
+vcl 4.1;
+
+import querymodifier;
+import std;
+
+backend default {
+	.host = "nginx";
+	.port = "80";
+}
+
+sub vcl_recv {
+	std.syslog(180, "RECV: " + req.http.host + req.url);
+	set req.url = querymodifier.modifyparams(req.url, "ts,v,cacheFix,date", true);
+}

debug/docker-compose.yml

@@ -0,0 +1,19 @@
+services:
+  varnish:
+    build:
+      context: ../
+      dockerfile: ./debug/Dockerfile
+    command: /entrypoint.sh
+    ports:
+      - 8080:80
+    environment:
+      - VARNISH_SIZE=200M
+    volumes:
+      - ./default.vcl:/etc/varnish/default.vcl
+      - ./entrypoint.sh:/entrypoint.sh
+  nginx:
+    image: nginx:1.27-alpine
+    ports:
+      - 8081:80
+    volumes:
+      - ./default.conf:/etc/nginx/conf.d/default.conf

debug/entrypoint.sh

@@ -0,0 +1,12 @@
+#!/bin/sh
+
+export LD_PRELOAD=/usr/lib/aarch64-linux-gnu/libasan.so.8
+export ASAN_OPTIONS=halt_on_error=0:detect_leaks=1
+
+varnishd \
+	-F \
+	-f /etc/varnish/default.vcl \
+	-a http=:"${VARNISH_HTTP_PORT:-80}",HTTP \
+	-a proxy=:"${VARNISH_PROXY_PORT:-8443}",PROXY \
+	-p feature=+http2 \
+	-s malloc,"$VARNISH_SIZE"