Merge remote-tracking branch 'dgoulet/ticket12541_032_02'

  o Major feature (scheduler, channel):

    - Introducing the KIST scheduler which stands for Kernel Informed Socket

      Transport. It is only available on Linux systems. This comes from a

      researched and published paper you can find here:

      http://www.robgjansen.com/publications/kist-sec2014.pdf

      https://arxiv.org/abs/1709.01044

      This is also a major refactoring of the entire scheduler subsystem in

      order for it to be more modular and thus much more easier to add more

      scheduler type later. The current scheduler has been named "Vanilla" but

      we favor KIST if available in this version.

      A new torrc option has been added and named "Schedulers type1,type2,..."

      which allows a user to select which scheduler type it wants tor to use.

      It is also possible to change it at runtime. It is an ordered list by

      priority. KIST might not be available on all platforms so there is a

      fallback to "KISTLite" that uses the same mechanisms but without the

      kernel support.

      The current default values are: Schedulers KIST,KISTLite,Vanilla.

      Closes ticket 12541.

[#include <openssl/ssl.h>

])

dnl Define the set of checks for KIST scheduler support.

AC_DEFUN([CHECK_KIST_SUPPORT],[

  dnl KIST needs struct tcp_info and for certain members to exist.

  AC_CHECK_MEMBERS(

    [struct tcp_info.tcpi_unacked, struct tcp_info.tcpi_snd_mss],

    , ,[[#include <netinet/tcp.h>]])

  dnl KIST needs SIOCOUTQNSD to exist for an ioctl call.

  AC_COMPILE_IFELSE([AC_LANG_PROGRAM([], [

                     #include <linux/sockios.h>

                     #ifndef SIOCOUTQNSD

                     #error

                     #endif

                     ])], have_siocoutqnsd=yes, have_siocoutqnsd=no)

  if test "x$have_siocoutqnsd" = "xyes"; then

    if test "x$ac_cv_member_struct_tcp_info_tcpi_unacked" = "xyes"; then

      if test "x$ac_cv_member_struct_tcp_info_tcpi_snd_mss" = "xyes"; then

        have_kist_support=yes

      fi

    fi

  fi

])

dnl Now, trigger the check.

CHECK_KIST_SUPPORT

AS_IF([test "x$have_kist_support" = "xyes"],

      [AC_DEFINE(HAVE_KIST_SUPPORT, 1, [Defined if KIST scheduler is supported

                                        on this system])],

      [AC_MSG_NOTICE([KIST scheduler can't be used. Missing support.])])

LIBS="$save_LIBS"

LDFLAGS="$save_LDFLAGS"

CPPFLAGS="$save_CPPFLAGS"

    option has been set to 1, it cannot be set back to 0 without

    restarting Tor. (Default: 0)

[[Schedulers]] **Schedulers** **KIST**|**KISTLite**|**Vanilla**::

    Specify the scheduler type that tor should use to handle outbound data on

    channels. This is an ordered list by priority which means that the first

    value will be tried first and if unavailable, the second one is tried and

    so on. It is possible to change thse values at runtime.

    (Default: KIST,KISTLite,Vanilla)

 +

    The possible scheduler types are:

+

    KIST: Kernel Informed Socket Transport. Tor will use the kernel tcp

    information stack per-socket to make an informed decision on if it should

    send or not the data. (Only available on Linux)

+

    KISTLite: Same as KIST but without kernel support which means that tor

    will use all the same mecanics as KIST but without the TCP information the

    kernel can provide.

+

    Vanilla: The scheduler that tor has always used that is do as much as

    possible or AMAP.

[[KISTSchedRunInterval]] **KISTSchedRunInterval** __NUM__ **msec**::

    If KIST or KISTLite is used in Schedulers option, this control at which

    interval the scheduler tick is. If the value is 0 msec, the value is taken

    from the consensus if possible else it will fallback to the default 10

    msec. Maximum possible value is 100 msec. (Default: 0 msec)

[[KISTSockBufSizeFactor]] **KISTSockBufSizeFactor** __NUM__::

    If KIST is used in Schedulers, this is a multiplier of the per-socket

    limit calculation of the KIST algorithm. (Default: 1.0)

CLIENT OPTIONS

--------------

  return 0;

}

#ifdef HAVE_KIST_SUPPORT

#include <linux/sockios.h>

static int

sb_ioctl(scmp_filter_ctx ctx, sandbox_cfg_t *filter)

{

  int rc;

  (void) filter;

  rc = seccomp_rule_add_1(ctx, SCMP_ACT_ALLOW, SCMP_SYS(ioctl),

                          SCMP_CMP(1, SCMP_CMP_EQ, SIOCOUTQNSD));

  if (rc)

    return rc;

  return 0;

}

#endif /* HAVE_KIST_SUPPORT */

/**

 * Function responsible for setting up the setsockopt syscall for

 * the seccomp filter sandbox.

    return rc;

#endif

#ifdef HAVE_KIST_SUPPORT

#include <netinet/tcp.h>

  rc = seccomp_rule_add_2(ctx, SCMP_ACT_ALLOW, SCMP_SYS(getsockopt),

      SCMP_CMP(1, SCMP_CMP_EQ, SOL_TCP),

      SCMP_CMP(2, SCMP_CMP_EQ, TCP_INFO));

  if (rc)

    return rc;

#endif

  return 0;

}

    sb_socket,

    sb_setsockopt,

    sb_getsockopt,

    sb_socketpair

    sb_socketpair,

#ifdef HAVE_KIST_SUPPORT

    sb_ioctl,

#endif

};

const char *

#define HT_CLEAR(name, head)         name##_HT_CLEAR(head)

#define HT_INIT(name, head)          name##_HT_INIT(head)

#define HT_REP_IS_BAD_(name, head)    name##_HT_REP_IS_BAD_(head)

#define HT_FOREACH_FN(name, head, fn, data) \

   name##_HT_FOREACH_FN((head), (fn), (data))

/* Helper: */

static inline unsigned

ht_improve_hash(unsigned h)