Add support for libtirpc

While OpenSolaris libc and glibc both include XDR support, the musl libc
does not in favor of depending on the BSD-licensed libtirpc library.

Adding support is a simple matter of detecting the library, including
the headers and linking against it.  By default libtirpc will be checked
for and if available used.  Otherwise, configure will fall back to using
the xdr implementation provided by libc if available.  The options
--with-tirpc/--without-tirpc can be used to disable this checking.

In addition, the xdr_control() function has been simplied to only
handle ZFSs specific use case.

Original-patch-by: stf <s@ctrlc.hu>
Original-patch-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Signed-off-by: Carlo Landmeter <clandmeter@gmail.com>
Closes openzfs#2254
Closes openzfs#4559

config/user-libtirpc.m4

@@ -0,0 +1,30 @@
+dnl #
+dnl # Check for libtirpc - may be needed for xdr functionality
+dnl #
+AC_DEFUN([ZFS_AC_CONFIG_USER_LIBTIRPC], [
+	AC_ARG_WITH([tirpc],
+	    [AS_HELP_STRING([--with-tirpc],
+	        [use tirpc for xdr encoding @<:@default=check@:>@])],
+	    [],
+	    [with_tirpc=check])
+
+	LIBTIRPC=
+	LIBTIRPC_CFLAGS=
+
+	AS_IF([test "x$with_tirpc" != xno],
+	    [AC_CHECK_LIB([tirpc], [xdrmem_create],
+		[AC_SUBST([LIBTIRPC], [-ltirpc])
+		 AC_SUBST([LIBTIRPC_CFLAGS], [-I/usr/include/tirpc])
+		 AC_DEFINE([HAVE_LIBTIRPC], [1], [Define if you have libtirpc])
+		],
+		[if test "x$with_tirpc" != xcheck; then
+		    AC_MSG_FAILURE(
+			[--with-tirpc was given, but test for tirpc failed])
+		 fi
+		AC_SEARCH_LIBS([xdrmem_create], [tirpc], [], [
+		    AC_MSG_FAILURE([xdrmem_create() requires tirpc or libc])])
+		])],
+	    [AC_SEARCH_LIBS([xdrmem_create], [tirpc], [], [
+		AC_MSG_FAILURE([xdrmem_create() requires libc])])
+	    ])
+])

config/user.m4

@@ -10,6 +10,7 @@ AC_DEFUN([ZFS_AC_CONFIG_USER], [
 	ZFS_AC_CONFIG_USER_ARCH
 	ZFS_AC_CONFIG_USER_ZLIB
 	ZFS_AC_CONFIG_USER_LIBUUID
+	ZFS_AC_CONFIG_USER_LIBTIRPC
 	ZFS_AC_CONFIG_USER_LIBBLKID
 	ZFS_AC_CONFIG_USER_LIBATTR
 	ZFS_AC_CONFIG_USER_LIBUDEV

lib/libnvpair/Makefile.am

@@ -4,7 +4,7 @@ VPATH = \
 	$(top_srcdir)/module/nvpair \
 	$(top_srcdir)/lib/libnvpair
 
-AM_CFLAGS += $(DEBUG_STACKFLAGS) $(FRAME_LARGER_THAN)
+AM_CFLAGS += $(DEBUG_STACKFLAGS) $(FRAME_LARGER_THAN) $(LIBTIRPC_CFLAGS)
 
 DEFAULT_INCLUDES += \
 	-I$(top_srcdir)/include \
@@ -26,8 +26,8 @@ nodist_libnvpair_la_SOURCES = \
 	$(KERNEL_C)
 
 libnvpair_la_LIBADD = \
-        $(top_builddir)/lib/libuutil/libuutil.la
-
+	$(top_builddir)/lib/libuutil/libuutil.la \
+	$(LIBTIRPC)
 libnvpair_la_LDFLAGS = -version-info 1:1:0
 
 EXTRA_DIST = $(USER_C)

lib/libnvpair/nvpair_alloc_system.c

@@ -27,6 +27,7 @@
 
 
 #include <rpc/types.h>
+#include <sys/kmem.h>
 #include <sys/nvpair.h>
 
 static void *

lib/libspl/Makefile.am

@@ -29,7 +29,6 @@ USER_C = \
 	strnlen.c \
 	timestamp.c \
 	zone.c \
-	xdr.c \
 	include/sys/list.h \
 	include/sys/list_impl.h
 

lib/libspl/include/rpc/Makefile.am

@@ -1,4 +1,3 @@
 libspldir = $(includedir)/libspl/rpc
 libspl_HEADERS = \
-	$(top_srcdir)/lib/libspl/include/rpc/types.h \
 	$(top_srcdir)/lib/libspl/include/rpc/xdr.h

lib/libspl/include/rpc/xdr.h

@@ -32,11 +32,20 @@
 #ifndef LIBSPL_RPC_XDR_H
 #define	LIBSPL_RPC_XDR_H
 
-#include_next <rpc/xdr.h>
-
 /*
- * These are XDR control operators
+ * When available prefer libtirpc for xdr functionality.  This library is
+ * mandatory when compiling with musl libc because it does not provide xdr.
  */
+#if defined(HAVE_LIBTIRPC)
+
+#include <tirpc/rpc/xdr.h>
+#ifdef xdr_control
+#undef xdr_control
+#endif
+
+#else
+#include_next <rpc/xdr.h>
+#endif /* HAVE_LIBTIRPC */
 
 #define	XDR_GET_BYTES_AVAIL 1
 
@@ -46,20 +55,20 @@ typedef struct xdr_bytesrec {
 } xdr_bytesrec_t;
 
 /*
- * These are the request arguments to XDR_CONTROL.
- *
- * XDR_PEEK - returns the contents of the next XDR unit on the XDR stream.
- * XDR_SKIPBYTES - skips the next N bytes in the XDR stream.
- * XDR_RDMAGET - for xdr implementation over RDMA, gets private flags from
- *		 the XDR stream being moved over RDMA
- * XDR_RDMANOCHUNK - for xdr implementaion over RDMA, sets private flags in
- *                   the XDR stream moving over RDMA.
+ * This functionality is not required and is disabled in user space.
  */
-#define	XDR_PEEK	2
-#define	XDR_SKIPBYTES	3
-#define	XDR_RDMAGET	4
-#define	XDR_RDMASET	5
+static inline bool_t
+xdr_control(XDR *xdrs, int request, void *info)
+{
+	xdr_bytesrec_t *xptr;
 
-extern bool_t xdr_control(XDR *xdrs, int request, void *info);
+	ASSERT3U(request, ==, XDR_GET_BYTES_AVAIL);
 
-#endif
+	xptr = (xdr_bytesrec_t *)info;
+	xptr->xc_is_last_record = TRUE;
+	xptr->xc_num_avail = xdrs->x_handy;
+
+	return (TRUE);
+}
+
+#endif /* LIBSPL_RPC_XDR_H */