configure: improve FreeBSD DCO check

The libnv check doesn't work as expected on FreeBSD 14.x, because
FreeBSD has namespaced libnv to avoid conflicts with libnvpair.
This means that the naive check generated by AC_CHECK_LIB() fails to
detect libnv even though it's present.

Instead check for the if_ovpn.h header. This is a more accurate check
anyway, as libnv is present on FreeBSD versions prior to 14 (which do
not support DCO).

Signed-off-by: Kristof Provost <kprovost@netgate.com>
Acked-by: Gert Doering <gert@greenie.muc.de>
Message-Id: <20230301091848.80760-1-kprovost@netgate.com>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg26314.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>

diff --git a/configure.ac b/configure.ac
index 4c271464b6bf9167a82de2e95f97e972d5f2ce9c..67f680b28e93b5d8a1566fe2bde8128e0a4c03b2 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -832,9 +832,7 @@ if test "$enable_dco" != "no"; then
                        fi
                        ;;
                *-*-freebsd*)
-                       AC_CHECK_LIB(
-                               [nv],
-                               [nvlist_create],
+                       AC_CHECK_HEADERS([net/if_ovpn.h],
                                [
                                 LIBS="${LIBS} -lnv"
                                 AC_DEFINE(ENABLE_DCO, 1, [Enable data channel offload for FreeBSD])
@@ -842,7 +840,7 @@ if test "$enable_dco" != "no"; then
                                ],
                                [
                                 enable_dco="no"
-                                AC_MSG_WARN([Name/Value pair library not found.])
+                                AC_MSG_WARN([DCO header not found.])
                                ]
                        )
                        if test "$enable_dco" = "no"; then