Added Samba libreplace implementation for freeifaddrs and getifaddrs

In case if system doesn't provide above functions, don't fail and use
Samba project libreplace implementation.
This allows to run app on embedded systems.

Makefile.am

@@ -8,6 +8,9 @@ openfortivpn_SOURCES = src/config.c src/config.h src/hdlc.c src/hdlc.h \
 		       src/xml.h src/userinput.c src/userinput.h \
 		       src/openssl_hostname_validation.c \
 		       src/openssl_hostname_validation.h
+if LIBREPLACE_REQUIRED
+openfortivpn_SOURCES += src/ifaddrs.c
+endif
 openfortivpn_CFLAGS = -Wall -pedantic
 openfortivpn_CPPFLAGS = -DSYSCONFDIR=\"$(sysconfdir)\" \
 			-DPPP_PATH=\"@PPP_PATH@\" \

configure.ac

@@ -103,8 +103,6 @@ AC_TYPE_UINT8_T
 AC_CHECK_TYPES([struct termios], [], [], [#include <termios.h>])
 
 # Checks for library functions.
-AC_FUNC_MALLOC
-AC_FUNC_REALLOC
 AC_CHECK_FUNCS([ \
 access \
 atoi \
@@ -125,15 +123,13 @@ fputs \
 fread \
 free \
 freeaddrinfo \
-freeifaddrs \
 freopen \
 fwrite \
 gai_strerror \
 getaddrinfo \
 getchar \
 getenv \
 geteuid \
-getifaddrs \
 getopt_long \
 htons \
 index \
@@ -502,6 +498,44 @@ AC_ARG_WITH([resolvconf-config-file],
 	AC_DEFINE_UNQUOTED([RESOLV_CONF_FILE_PATH],["$withval"])
 )
 
+AC_COMPILE_IFELSE([AC_LANG_SOURCE([
+#include <sys/types.h>
+#if STDC_HEADERS
+#include <stdlib.h>
+#include <stddef.h>
+#endif
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <arpa/inet.h>
+#include <ifaddrs.h>
+#include <netdb.h>
+int main(int argc, char **argv){
+	struct ifaddrs *ifp = NULL;
+	int ret = getifaddrs (&ifp);
+	freeifaddrs(ifp);
+}
+])], [
+	libreplace_required=no
+	AC_MSG_NOTICE([HAVE_IFADDRS... 1])
+],[
+	libreplace_required=yes
+	AC_MSG_NOTICE([HAVE_IFADDRS... 0])
+])
+
+AC_ARG_ENABLE([libreplace],
+	[AS_HELP_STRING([--enable-libreplace], [Force to use libreplace ifaddrs implementation])],
+	[enable_libreplace=yes],
+	[enable_libreplace=no])
+AS_CASE(["$enable_libreplace"],
+	[yes], [
+		AC_MSG_NOTICE([Force using libreplace...])
+	],
+	[no], [
+	],
+	[AC_MSG_ERROR([unknown option '$enable_libreplace' for --enable-libreplace])])
+AS_IF([test "x$enable_libreplace" != "xno" -o "x$libreplace_required" != "xno"], [AC_DEFINE([HAVE_IFADDRS],[0])], [AC_DEFINE([HAVE_IFADDRS],[1])])
+AM_CONDITIONAL([LIBREPLACE_REQUIRED], [test "x$enable_libreplace" = "xyes" -o "x$libreplace_required" = "xyes"])
+
 # prepare to get rid of obsolete code (FortiOS 4)
 AC_ARG_ENABLE([obsolete],
 	[AS_HELP_STRING([--disable-obsolete], [disable support for FortiOS 4])],,