Add --enable-zstd to our configure script.

This patch adds support for enabling support for Zstandard to our configure
script. By default, the --enable-zstd option is set to "auto" which means if
libzstd is available we'll build Tor with Zstandard support.

See: https://bugs.torproject.org/21662

Makefile.am

@@ -16,7 +16,7 @@ noinst_PROGRAMS=
 DISTCLEANFILES=
 bin_SCRIPTS=
 AM_CPPFLAGS=
-AM_CFLAGS=@TOR_SYSTEMD_CFLAGS@ @CFLAGS_BUGTRAP@ @TOR_LZMA_CFLAGS@
+AM_CFLAGS=@TOR_SYSTEMD_CFLAGS@ @CFLAGS_BUGTRAP@ @TOR_LZMA_CFLAGS@ @TOR_ZSTD_CFLAGS@
 SHELL=@SHELL@
 
 if COVERAGE_ENABLED

configure.ac

@@ -764,6 +764,38 @@ fi
 AC_SUBST(TOR_LZMA_CFLAGS)
 AC_SUBST(TOR_LZMA_LIBS)
 
+dnl ------------------------------------------------------
+dnl Where we do we find zstd?
+
+AC_ARG_ENABLE(zstd,
+      AS_HELP_STRING(--enable-zstd, [enable support for the Zstandard compression scheme.]),
+      [case "${enableval}" in
+        "yes") zstd=true ;;
+        "no")  zstd=false ;;
+        * ) AC_MSG_ERROR(bad value for --enable-zstd) ;;
+      esac], [zstd=auto])
+
+if test "x$enable_zstd" = "xno"; then
+    have_zstd=no;
+else
+    PKG_CHECK_MODULES([ZSTD],
+                      [libzstd],
+                      have_zstd=yes,
+                      have_zstd=no)
+
+    if test "x$have_zstd" = "xno" ; then
+        AC_MSG_WARN([Unable to find libzstd.])
+    fi
+fi
+
+if test "x$have_zstd" = "xyes"; then
+    AC_DEFINE(HAVE_ZSTD,1,[Have Zstd])
+    TOR_ZSTD_CFLAGS="${ZSTD_CFLAGS}"
+    TOR_ZSTD_LIBS="${ZSTD_LIBS}"
+fi
+AC_SUBST(TOR_ZSTD_CFLAGS)
+AC_SUBST(TOR_ZSTD_LIBS)
+
 dnl ----------------------------------------------------------------------
 dnl Check if libcap is available for capabilities.
 

src/or/include.am

@@ -121,7 +121,7 @@ src_or_tor_LDADD = src/or/libtor.a src/common/libor.a src/common/libor-ctime.a \
 	src/common/libor-event.a src/trunnel/libor-trunnel.a \
 	@TOR_ZLIB_LIBS@ @TOR_LIB_MATH@ @TOR_LIBEVENT_LIBS@ @TOR_OPENSSL_LIBS@ \
 	@TOR_LIB_WS32@ @TOR_LIB_GDI@ @CURVE25519_LIBS@ @TOR_SYSTEMD_LIBS@ \
-	@TOR_LZMA_LIBS@
+	@TOR_LZMA_LIBS@ @TOR_ZSTD_LIBS@
 
 if COVERAGE_ENABLED
 src_or_tor_cov_SOURCES = src/or/tor_main.c
@@ -134,7 +134,7 @@ src_or_tor_cov_LDADD = src/or/libtor-testing.a src/common/libor-testing.a \
 	src/common/libor-event-testing.a src/trunnel/libor-trunnel-testing.a \
 	@TOR_ZLIB_LIBS@ @TOR_LIB_MATH@ @TOR_LIBEVENT_LIBS@ @TOR_OPENSSL_LIBS@ \
 	@TOR_LIB_WS32@ @TOR_LIB_GDI@ @CURVE25519_LIBS@ @TOR_SYSTEMD_LIBS@ \
-	@TOR_LZMA_LIBS@
+	@TOR_LZMA_LIBS@ @TOR_ZSTD_LIBS@
 endif
 
 ORHEADERS = \

src/test/fuzz/include.am

@@ -19,7 +19,8 @@ FUZZING_LIBS = \
 	@TOR_LIBEVENT_LIBS@ \
 	@TOR_OPENSSL_LIBS@ @TOR_LIB_WS32@ @TOR_LIB_GDI@ @CURVE25519_LIBS@ \
 	@TOR_SYSTEMD_LIBS@ \
-	@TOR_LZMA_LIBS@
+	@TOR_LZMA_LIBS@ \
+	@TOR_ZSTD_LIBS@
 
 oss-fuzz-prereqs: \
 	src/or/libtor-testing.a \

src/test/include.am

@@ -180,7 +180,7 @@ src_test_test_switch_id_LDADD = \
 	src/common/libor-testing.a \
 	src/common/libor-ctime-testing.a \
 	@TOR_ZLIB_LIBS@ @TOR_LIB_MATH@ \
-	@TOR_LZMA_LIBS@
+	@TOR_LZMA_LIBS@ @TOR_ZSTD_LIBS@
 
 src_test_test_LDFLAGS = @TOR_LDFLAGS_zlib@ @TOR_LDFLAGS_openssl@ \
         @TOR_LDFLAGS_libevent@
@@ -194,7 +194,7 @@ src_test_test_LDADD = src/or/libtor-testing.a \
 	src/trunnel/libor-trunnel-testing.a \
 	@TOR_ZLIB_LIBS@ @TOR_LIB_MATH@ @TOR_LIBEVENT_LIBS@ \
 	@TOR_OPENSSL_LIBS@ @TOR_LIB_WS32@ @TOR_LIB_GDI@ @CURVE25519_LIBS@ \
-	@TOR_SYSTEMD_LIBS@ @TOR_LZMA_LIBS@
+	@TOR_SYSTEMD_LIBS@ @TOR_LZMA_LIBS@ @TOR_ZSTD_LIBS@
 
 src_test_test_slow_CPPFLAGS = $(src_test_test_CPPFLAGS)
 src_test_test_slow_CFLAGS = $(src_test_test_CFLAGS)
@@ -217,7 +217,7 @@ src_test_bench_LDADD = src/or/libtor.a src/common/libor.a \
 	src/common/libor-event.a src/trunnel/libor-trunnel.a \
 	@TOR_ZLIB_LIBS@ @TOR_LIB_MATH@ @TOR_LIBEVENT_LIBS@ \
 	@TOR_OPENSSL_LIBS@ @TOR_LIB_WS32@ @TOR_LIB_GDI@ @CURVE25519_LIBS@ \
-	@TOR_SYSTEMD_LIBS@ @TOR_LZMA_LIBS@
+	@TOR_SYSTEMD_LIBS@ @TOR_LZMA_LIBS@ @TOR_ZSTD_LIBS@
 
 src_test_test_workqueue_LDFLAGS = @TOR_LDFLAGS_zlib@ @TOR_LDFLAGS_openssl@ \
         @TOR_LDFLAGS_libevent@
@@ -228,7 +228,7 @@ src_test_test_workqueue_LDADD = src/or/libtor-testing.a \
 	src/common/libor-event-testing.a \
 	@TOR_ZLIB_LIBS@ @TOR_LIB_MATH@ @TOR_LIBEVENT_LIBS@ \
 	@TOR_OPENSSL_LIBS@ @TOR_LIB_WS32@ @TOR_LIB_GDI@ @CURVE25519_LIBS@ \
-	@TOR_LZMA_LIBS@
+	@TOR_LZMA_LIBS@ @TOR_ZSTD_LIBS@
 
 src_test_test_timers_CPPFLAGS = $(src_test_test_CPPFLAGS)
 src_test_test_timers_CFLAGS = $(src_test_test_CFLAGS)