make fakebank use epoll() on platforms where it is available

configure.ac

@@ -88,6 +88,38 @@ AC_MSG_RESULT($enable_expensive)
 AM_CONDITIONAL([HAVE_EXPENSIVE_TESTS], [test "x$enable_expensive" = "xyes"])
 
 
+AC_ARG_ENABLE([[epoll]],
+  [AS_HELP_STRING([[--enable-epoll[=ARG]]], [enable epoll support (yes, no, auto) [auto]])],
+    [enable_epoll=${enableval}],
+    [enable_epoll='auto']
+  )
+
+AS_IF([test "$enable_epoll" != "no"],
+      [AX_HAVE_EPOLL
+       AS_IF([test "${ax_cv_have_epoll}" = "yes"],
+          [AC_DEFINE([[EPOLL_SUPPORT]],[[1]],[Define to 1 to enable epoll support])
+           enable_epoll='yes'],
+       [AS_IF([test "$enable_epoll" = "yes"],
+              AC_MSG_ERROR([[Support for epoll was explicitly requested but cannot be enabled on this platform.]]))
+        enable_epoll='no'])])
+
+AM_CONDITIONAL([MHD_HAVE_EPOLL], [[test "x$enable_epoll" = xyes]])
+
+AS_IF([test "x$enable_epoll" = "xyes"],
+  AC_CACHE_CHECK([for epoll_create1()],
+                 [mhd_cv_have_epoll_create1], [
+    AC_LINK_IFELSE([
+      AC_LANG_PROGRAM([[
+#include <sys/epoll.h>
+        ]], [[
+int fd;
+fd = epoll_create1(EPOLL_CLOEXEC);]])],
+      [mhd_cv_have_epoll_create1=yes],
+      [mhd_cv_have_epoll_create1=no])])
+  AS_IF([test "x$mhd_cv_have_epoll_create1" = "xyes"],[
+    AC_DEFINE([[HAVE_EPOLL_CREATE1]], [[1]], [Define if you have epoll_create1 function.])]))
+
+
 if test "$wallet_only" != yes
 then
 

m4/ax_have_epoll.m4

@@ -0,0 +1,104 @@
+# ===========================================================================
+#      https://www.gnu.org/software/autoconf-archive/ax_have_epoll.html
+# ===========================================================================
+#
+# SYNOPSIS
+#
+#   AX_HAVE_EPOLL([ACTION-IF-FOUND], [ACTION-IF-NOT-FOUND])
+#   AX_HAVE_EPOLL_PWAIT([ACTION-IF-FOUND], [ACTION-IF-NOT-FOUND])
+#
+# DESCRIPTION
+#
+#   This macro determines whether the system supports the epoll I/O event
+#   interface. A neat usage example would be:
+#
+#     AX_HAVE_EPOLL(
+#       [AX_CONFIG_FEATURE_ENABLE(epoll)],
+#       [AX_CONFIG_FEATURE_DISABLE(epoll)])
+#     AX_CONFIG_FEATURE(
+#       [epoll], [This platform supports epoll(7)],
+#       [HAVE_EPOLL], [This platform supports epoll(7).])
+#
+#   The epoll interface was added to the Linux kernel in version 2.5.45, and
+#   the macro verifies that a kernel newer than this is installed. This
+#   check is somewhat unreliable if <linux/version.h> doesn't match the
+#   running kernel, but it is necessary regardless, because glibc comes with
+#   stubs for the epoll_create(), epoll_wait(), etc. that allow programs to
+#   compile and link even if the kernel is too old; the problem would then
+#   be detected only at runtime.
+#
+#   Linux kernel version 2.6.19 adds the epoll_pwait() call in addition to
+#   epoll_wait(). The availability of that function can be tested with the
+#   second macro. Generally speaking, it is safe to assume that
+#   AX_HAVE_EPOLL would succeed if AX_HAVE_EPOLL_PWAIT has, but not the
+#   other way round.
+#
+# LICENSE
+#
+#   Copyright (c) 2008 Peter Simons <simons@cryp.to>
+#
+#   Copying and distribution of this file, with or without modification, are
+#   permitted in any medium without royalty provided the copyright notice
+#   and this notice are preserved. This file is offered as-is, without any
+#   warranty.
+
+#serial 11
+
+AC_DEFUN([AX_HAVE_EPOLL], [dnl
+  ax_have_epoll_cppflags="${CPPFLAGS}"
+  AC_CHECK_HEADER([linux/version.h], [CPPFLAGS="${CPPFLAGS} -DHAVE_LINUX_VERSION_H"])
+  AC_MSG_CHECKING([for Linux epoll(7) interface])
+  AC_CACHE_VAL([ax_cv_have_epoll], [dnl
+    AC_LINK_IFELSE([dnl
+      AC_LANG_PROGRAM([dnl
+#include <sys/epoll.h>
+#ifdef HAVE_LINUX_VERSION_H
+#  include <linux/version.h>
+#  if LINUX_VERSION_CODE < KERNEL_VERSION(2,5,45)
+#    error linux kernel version is too old to have epoll
+#  endif
+#endif
+], [dnl
+int fd, rc;
+struct epoll_event ev;
+fd = epoll_create(128);
+rc = epoll_wait(fd, &ev, 1, 0);])],
+      [ax_cv_have_epoll=yes],
+      [ax_cv_have_epoll=no])])
+  CPPFLAGS="${ax_have_epoll_cppflags}"
+  AS_IF([test "${ax_cv_have_epoll}" = "yes"],
+    [AC_MSG_RESULT([yes])
+$1],[AC_MSG_RESULT([no])
+$2])
+])dnl
+
+AC_DEFUN([AX_HAVE_EPOLL_PWAIT], [dnl
+  ax_have_epoll_cppflags="${CPPFLAGS}"
+  AC_CHECK_HEADER([linux/version.h],
+    [CPPFLAGS="${CPPFLAGS} -DHAVE_LINUX_VERSION_H"])
+  AC_MSG_CHECKING([for Linux epoll(7) interface with signals extension])
+  AC_CACHE_VAL([ax_cv_have_epoll_pwait], [dnl
+    AC_LINK_IFELSE([dnl
+      AC_LANG_PROGRAM([dnl
+#ifdef HAVE_LINUX_VERSION_H
+#  include <linux/version.h>
+#  if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,19)
+#    error linux kernel version is too old to have epoll_pwait
+#  endif
+#endif
+#include <sys/epoll.h>
+#include <signal.h>
+], [dnl
+int fd, rc;
+struct epoll_event ev;
+fd = epoll_create(128);
+rc = epoll_wait(fd, &ev, 1, 0);
+rc = epoll_pwait(fd, &ev, 1, 0, (sigset_t const *)(0));])],
+      [ax_cv_have_epoll_pwait=yes],
+      [ax_cv_have_epoll_pwait=no])])
+  CPPFLAGS="${ax_have_epoll_cppflags}"
+  AS_IF([test "${ax_cv_have_epoll_pwait}" = "yes"],
+    [AC_MSG_RESULT([yes])
+$1],[AC_MSG_RESULT([no])
+$2])
+])dnl

src/bank-lib/fakebank.c

@@ -1,6 +1,6 @@
 /*
   This file is part of TALER
-  (C) 2016, 2017 Inria and GNUnet e.V.
+  (C) 2016, 2017, 2018 Inria and GNUnet e.V.
 
   TALER is free software; you can redistribute it and/or modify it under the
   terms of the GNU General Public License as published by the Free Software
@@ -19,7 +19,6 @@
  * @brief library that fakes being a Taler bank for testcases
  * @author Christian Grothoff <christian@grothoff.org>
  */
-
 #include "platform.h"
 #include "taler_fakebank_lib.h"
 #include "taler_bank_service.h"
@@ -125,6 +124,18 @@ struct TALER_FAKEBANK_Handle
    * Number of transactions.
    */
   uint64_t serial_counter;
+
+#if EPOLL_SUPPORT
+  /**
+   * Boxed @e mhd_fd.
+   */
+  struct GNUNET_NETWORK_Handle *mhd_rfd;
+  
+  /**
+   * File descriptor to use to wait for MHD.
+   */
+  int mhd_fd;
+#endif
 };
 
 
@@ -328,6 +339,9 @@ TALER_FAKEBANK_stop (struct TALER_FAKEBANK_Handle *h)
     GNUNET_SCHEDULER_cancel (h->mhd_task);
     h->mhd_task = NULL;
   }
+#if EPOLL_SUPPORT
+  GNUNET_NETWORK_socket_free_memory_only_ (h->mhd_rfd);
+#endif
   if (NULL != h->mhd_bank)
   {
     MHD_stop_daemon (h->mhd_bank);
@@ -976,10 +990,42 @@ static void
 run_mhd (void *cls);
 
 
+#if EPOLL_SUPPORT
 /**
  * Schedule MHD.  This function should be called initially when an
  * MHD is first getting its client socket, and will then automatically
  * always be called later whenever there is work to be done.
+ *
+ * @param h fakebank handle to schedule MHD for
+ */
+static void
+schedule_httpd (struct TALER_FAKEBANK_Handle *h)
+{
+  int haveto;
+  MHD_UNSIGNED_LONG_LONG timeout;
+  struct GNUNET_TIME_Relative tv;
+
+  haveto = MHD_get_timeout (h->mhd_bank,
+			    &timeout);
+  if (MHD_YES == haveto)
+    tv.rel_value_us = (uint64_t) timeout * 1000LL;
+  else
+    tv = GNUNET_TIME_UNIT_FOREVER_REL;
+  if (NULL != h->mhd_task)
+    GNUNET_SCHEDULER_cancel (h->mhd_task);
+  h->mhd_task =
+    GNUNET_SCHEDULER_add_read_net (tv,
+				   h->mhd_rfd,
+				   &run_mhd,
+				   h);
+}
+#else
+/**
+ * Schedule MHD.  This function should be called initially when an
+ * MHD is first getting its client socket, and will then automatically
+ * always be called later whenever there is work to be done.
+ *
+ * @param h fakebank handle to schedule MHD for
  */
 static void
 schedule_httpd (struct TALER_FAKEBANK_Handle *h)
@@ -1033,6 +1079,7 @@ schedule_httpd (struct TALER_FAKEBANK_Handle *h)
   if (NULL != wws)
     GNUNET_NETWORK_fdset_destroy (wws);
 }
+#endif
 
 
 /**
@@ -1063,7 +1110,11 @@ TALER_FAKEBANK_start (uint16_t port)
   struct TALER_FAKEBANK_Handle *h;
 
   h = GNUNET_new (struct TALER_FAKEBANK_Handle);
-  h->mhd_bank = MHD_start_daemon (MHD_USE_DEBUG | MHD_USE_DUAL_STACK,
+  h->mhd_bank = MHD_start_daemon (MHD_USE_DEBUG
+#if EPOLL_SUPPORT
+				  | MHD_USE_EPOLL
+#endif
+				  | MHD_USE_DUAL_STACK,
                                   port,
                                   NULL, NULL,
                                   &handle_mhd_request, h,
@@ -1075,6 +1126,11 @@ TALER_FAKEBANK_start (uint16_t port)
     GNUNET_free (h);
     return NULL;
   }
+#if EPOLL_SUPPORT
+  h->mhd_fd = MHD_get_daemon_info (h->mhd_bank,
+				   MHD_DAEMON_INFO_EPOLL_FD)->epoll_fd;
+  h->mhd_rfd = GNUNET_NETWORK_socket_box_native (h->mhd_fd);
+#endif
   schedule_httpd (h);
   return h;
 }