1 files changed, 56 insertions, 0 deletions
diff --git a/m4/af_alg.m4 b/m4/af_alg.m4
new file mode 100644
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+++ b/m4/af_alg.m4
@@ -0,0 +1,56 @@
+# af_alg.m4 serial 4
+dnl Copyright 2018 Free Software Foundation, Inc.
+dnl This file is free software; the Free Software Foundation
+dnl gives unlimited permission to copy and/or distribute it,
+dnl with or without modifications, as long as this notice is preserved.
+
+dnl From Matteo Croce.
+
+AC_DEFUN_ONCE([gl_AF_ALG],
+[
+  AC_REQUIRE([gl_HEADER_SYS_SOCKET])
+  AC_REQUIRE([AC_C_INLINE])
+
+  dnl Check whether linux/if_alg.h has needed features.
+  AC_CACHE_CHECK([whether linux/if_alg.h has struct sockaddr_alg.],
+    [gl_cv_header_linux_if_alg_salg],
+    [AC_COMPILE_IFELSE(
+       [AC_LANG_PROGRAM([[#include <sys/socket.h>
+                          #include <linux/if_alg.h>
+                          struct sockaddr_alg salg = {
+                            .salg_family = AF_ALG,
+                            .salg_type = "hash",
+                            .salg_name = "sha1",
+                          };]])],
+       [gl_cv_header_linux_if_alg_salg=yes],
+       [gl_cv_header_linux_if_alg_salg=no])])
+  if test "$gl_cv_header_linux_if_alg_salg" = yes; then
+    AC_DEFINE([HAVE_LINUX_IF_ALG_H], [1],
+      [Define to 1 if you have 'struct sockaddr_alg' defined.])
+  fi
+
+  dnl The default is to not use AF_ALG if available,
+  dnl as it's system dependent as to whether the kernel
+  dnl routines are faster than libcrypto for example.
+  use_af_alg=no
+  AC_ARG_WITH([linux-crypto],
+    [AS_HELP_STRING([[--with-linux-crypto]],
+       [use Linux kernel cryptographic API (if available)])],
+    [use_af_alg=$withval],
+    [use_af_alg=no])
+  dnl We cannot use it if it is not available.
+  if test "$gl_cv_header_linux_if_alg_salg" != yes; then
+    if test "$use_af_alg" != no; then
+      AC_MSG_WARN([Linux kernel cryptographic API not found])
+    fi
+    use_af_alg=no
+  fi
+
+  if test "$use_af_alg" != no; then
+    USE_AF_ALG=1
+  else
+    USE_AF_ALG=0
+  fi
+  AC_DEFINE_UNQUOTED([USE_LINUX_CRYPTO_API], [$USE_AF_ALG],
+    [Define to 1 if you want to use the Linux kernel cryptographic API.])
+])