From: Phil Sutter <phil@nwl.cc>
Date: Thu, 29 Jan 2026 18:35:24 +0000 (+0100)
Subject: configure: Auto-detect libz unless explicitly requested
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=758cfe51968a1fbd78cc7a6041c467e64f090d3a;p=thirdparty%2Fiptables.git

configure: Auto-detect libz unless explicitly requested

If user did not pass --with-zlib and it is not available, simply turn
off rule compat expression compression. It is not strictly necessary and
users may not care.

While at it, drop the conditional AC_DEFINE() call: In fact,
AC_CHECK_LIB() does that already.

Fixes: ff5f6a208efcc ("nft-ruleparse: Fallback to compat expressions in userdata")
Signed-off-by: Phil Sutter <phil@nwl.cc>
---

diff --git a/configure.ac b/configure.ac
index d42588c8..2a8abf21 100644
--- a/configure.ac
+++ b/configure.ac
@@ -79,11 +79,12 @@ AC_ARG_ENABLE([profiling],
 	[enable_profiling="$enableval"], [enable_profiling="no"])
 AC_ARG_WITH([zlib], [AS_HELP_STRING([--without-zlib],
 	    [Disable payload compression of rule compat expressions])],
-           [], [with_zlib=yes])
+           [], [with_zlib=check])
 AS_IF([test "x$with_zlib" != xno], [
        AC_CHECK_LIB([z], [compress], ,
-		    AC_MSG_ERROR([No suitable version of zlib found]))
-       AC_DEFINE([HAVE_ZLIB], [1], [Define if you have zlib])
+		    [if test "x$with_zlib" != xcheck; then
+			AC_MSG_ERROR([No suitable version of zlib found])
+		     fi; with_zlib=no])
 ])
 
 AC_MSG_CHECKING([whether $LD knows -Wl,--no-undefined])
@@ -297,7 +298,7 @@ Iptables Configuration:
   nftables support:			${enable_nftables}
   connlabel support:			${enable_connlabel}
   profiling support:			${enable_profiling}
-  compress rule compat expressions:	${with_zlib}
+  compress rule compat expressions:	${with_zlib/check/yes}
 
 Build parameters:
   Put plugins into executable (static):	${enable_static}
diff --git a/iptables/nft-compat.c b/iptables/nft-compat.c
index 632733ca..dfcc05b8 100644
--- a/iptables/nft-compat.c
+++ b/iptables/nft-compat.c
@@ -16,7 +16,7 @@
 #include <string.h>
 #include <xtables.h>
 
-#ifdef HAVE_ZLIB
+#ifdef HAVE_LIBZ
 #include <zlib.h>
 #endif
 
@@ -64,7 +64,7 @@ pack_rule_udata_ext_data(struct rule_udata_ext *rue,
 			 const void *data, size_t datalen)
 {
 	size_t datalen_out = datalen;
-#ifdef HAVE_ZLIB
+#ifdef HAVE_LIBZ
 	compress(rue->data, &datalen_out, data, datalen);
 	rue->flags |= RUE_FLAG_ZIP;
 #else
@@ -144,7 +144,7 @@ __nftnl_expr_from_udata_ext(struct rule_udata_ext *rue, const void *data)
 static struct nftnl_expr *
 nftnl_expr_from_zipped_udata_ext(struct rule_udata_ext *rue)
 {
-#ifdef HAVE_ZLIB
+#ifdef HAVE_LIBZ
 	uLongf datalen = rue->orig_size;
 	struct nftnl_expr *expr = NULL;
 	void *data;