interpret.c

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/*
 *   This program 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 Foundation; either version 2 of the License, or
 *   (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program; if not, write to the Free Software
 *   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
 */
 
/**
 * $Id: c2ebfb2f39ec725ca0cf6606f263023ffffba313 $
 *
 * @file unlang/interpret.c
 * @brief Execute compiled unlang structures using an iterative interpret.
 *
 * @copyright 2006-2016 The FreeRADIUS server project
 */
RCSID("$Id: c2ebfb2f39ec725ca0cf6606f263023ffffba313 $")
 
#include <freeradius-devel/unlang/action.h>
#include <freeradius-devel/unlang/interpret.h>
#include <freeradius-devel/util/timer.h>
#include <freeradius-devel/server/base.h>
#include <freeradius-devel/server/modpriv.h>
#include <freeradius-devel/server/rcode.h>
#include <freeradius-devel/unlang/xlat_func.h>
#include <freeradius-devel/unlang/mod_action.h>
 
#include "interpret_priv.h"
#include "unlang_priv.h"
#include "module_priv.h"
 
 
/** The default interpreter instance for this thread
 */
static _Thread_local unlang_interpret_t *intp_thread_default;
 
static fr_table_num_ordered_t const unlang_action_table[] = {
        { L("calculate-result"),        UNLANG_ACTION_CALCULATE_RESULT },
        { L("next"),                    UNLANG_ACTION_EXECUTE_NEXT },
        { L("pushed-child"),            UNLANG_ACTION_PUSHED_CHILD },
        { L("stop"),                    UNLANG_ACTION_STOP_PROCESSING },
        { L("yield"),                   UNLANG_ACTION_YIELD }
};
static size_t unlang_action_table_len = NUM_ELEMENTS(unlang_action_table);
 
static fr_table_num_ordered_t const unlang_frame_action_table[] = {
        { L("pop"),                     UNLANG_FRAME_ACTION_POP         },
        { L("next"),                    UNLANG_FRAME_ACTION_NEXT        },
        { L("yield"),                   UNLANG_FRAME_ACTION_YIELD       }
};
static size_t unlang_frame_action_table_len = NUM_ELEMENTS(unlang_frame_action_table);
 
#ifndef NDEBUG
#include <freeradius-devel/unlang/module_priv.h>
 
typedef enum {
        P_RESULT_LOCATION_UNKNOWN = 0,
        P_RESULT_LOCATION_FRAME,
        P_RESULT_LOCATION_SCRATCH,
        P_RESULT_LOCATION_STATE,
        P_RESULT_LOCATION_MODULE_RCTX,
        P_RESULT_LOCATION_FUNCTION_RCTX
} p_result_location_t;
 
/** Try and figure out where p_result points to
 *
 * If it's somewhere other than these three locations, it's probably wrong.
 */
static int find_p_result_location(p_result_location_t *location, void **chunk, request_t *request, void *ptr)
{
        unlang_stack_t          *stack = request->stack;
        unlang_stack_frame_t    *frame;
        unsigned int            i;
 
        for (i = 0; i <= (unsigned int)stack->depth; i++) {
                frame = &stack->frame[i];
                if (frame->state && (ptr >= (void *)frame->state) &&
                    (ptr < ((void *)((uint8_t *)frame->state + talloc_get_size(frame->state))))) {
                        *location = P_RESULT_LOCATION_STATE;
                        *chunk = frame->state;
                        return i;
                }
 
                if (ptr == &frame->section_result) {
                        *location = P_RESULT_LOCATION_FRAME;
                        *chunk = NULL;
                        return i;
                }
 
                if (ptr == &frame->scratch_result) {
                        *location = P_RESULT_LOCATION_SCRATCH;
                        *chunk = NULL;
                        return i;
                }
 
                if (!frame->instruction) continue;
 
                switch (frame->instruction->type) {
                case UNLANG_TYPE_MODULE:
                {
                        unlang_frame_state_module_t *mod_state = talloc_get_type_abort(frame->state, unlang_frame_state_module_t);
 
                        if (!mod_state->rctx) continue;
 
                        if ((ptr >= (void *)mod_state->rctx) &&
                            (ptr < ((void *)((uint8_t *)mod_state->rctx + talloc_get_size(mod_state->rctx))))) {
                                *location = P_RESULT_LOCATION_MODULE_RCTX;
                                *chunk = mod_state->rctx;
                                return i;
                        }
 
                        /*
                         *      We don't know where the child frame is, so we can't
                         *      determine where the p_result is.
                         */
                }
                        continue;
 
                default:
                        break;
                }
        }
 
        *location = P_RESULT_LOCATION_UNKNOWN;
        *chunk = NULL;
        return -1;
}
 
static fr_table_num_ordered_t const p_result_location_table[] = {
        { L("frame"),           P_RESULT_LOCATION_FRAME },
        { L("module_rctx"),     P_RESULT_LOCATION_MODULE_RCTX },
        { L("scratch"),         P_RESULT_LOCATION_SCRATCH },
        { L("state"),           P_RESULT_LOCATION_STATE },
        { L("unknown"),         P_RESULT_LOCATION_UNKNOWN }
};
static size_t p_result_location_table_len = NUM_ELEMENTS(p_result_location_table);
 
static void instruction_dump(request_t *request, unlang_t const *instruction)
{
        RINDENT();
        if (!instruction) {
                RDEBUG2("instruction    <none>");
                REXDENT();
                return;
        }
 
        RDEBUG2("type           %s", unlang_ops[instruction->type].name);
        RDEBUG2("name           %s", instruction->name);
        RDEBUG2("debug_name     %s", instruction->debug_name);
        REXDENT();
}
 
static void CC_HINT(nonnull) actions_dump(request_t *request, unlang_t const *instruction)
{
        int i;
 
        RDEBUG2("actions");
        RINDENT();
        for (i = 0; i < RLM_MODULE_NUMCODES; i++) {
                RDEBUG2("%s: %s",
                        fr_table_str_by_value(mod_rcode_table, i, "<invalid>"),
                        mod_action_name[instruction->actions.actions[i]]);
        }
        REXDENT();
}
 
static void frame_dump(request_t *request, unlang_stack_frame_t *frame, bool with_actions)
{
        unlang_op_t     *op = NULL;
 
        if (frame->instruction) {
                op = &unlang_ops[frame->instruction->type];
                instruction_dump(request, frame->instruction);
        }
 
        RINDENT();
        if (frame->state) RDEBUG2("state          %s (%p)", talloc_get_name(frame->state), frame->state);
        if (frame->next) {
                RDEBUG2("next           %s", frame->next->debug_name);
        } else {
                RDEBUG2("next           <none>");
        }
 
        fr_assert(MOD_ACTION_VALID(frame->p_result->priority));
 
        if (is_private_result(frame)) {
                int location;
                p_result_location_t type;
                void *chunk;
 
                RDEBUG2("p_rcode        %s", fr_table_str_by_value(mod_rcode_table, frame->p_result->rcode, "<invalid>"));
                RDEBUG2("p_priority     %s", mod_action_name[frame->p_result->priority]);
 
                location = find_p_result_location(&type, &chunk, request, frame->p_result);
                RDEBUG2("p_location     %s [%i] %p (%s)", fr_table_str_by_value(p_result_location_table, type, "<invalid>"),
                        location, frame->p_result, chunk ? talloc_get_name(chunk) : "<none>"
                        );
        } else {
                RDEBUG2("sec_rcode      %s", fr_table_str_by_value(mod_rcode_table, frame->section_result.rcode, "<invalid>"));
                RDEBUG2("sec_priority   %s", mod_action_name[frame->section_result.priority]);
        }
        RDEBUG2("scr_rcode      %s", fr_table_str_by_value(mod_rcode_table, frame->scratch_result.rcode, "<invalid>"));
        RDEBUG2("scr_priority   %s", mod_action_name[frame->scratch_result.priority]);
        RDEBUG2("top_frame      %s", is_top_frame(frame) ? "yes" : "no");
        RDEBUG2("repeat         %s", is_repeatable(frame) ? "yes" : "no");
        RDEBUG2("yielded        %s", is_yielded(frame) ? "yes" : "no");
        RDEBUG2("unwind         %s", is_unwinding(frame) ? "yes" : "no");
 
        if (frame->instruction) {
                RDEBUG2("control        %s%s%s",
                        is_break_point(frame) ? "b" : "-",
                        is_return_point(frame) ? "r" : "-",
                        is_continue_point(frame) ? "c" : "-"
                        );
                if (with_actions) actions_dump(request, frame->instruction);
        }
 
        /*
         *      Call the custom frame dump function
         */
        if (op && op->dump) op->dump(request, frame);
        REXDENT();
}
 
static void stack_dump_body(request_t *request, bool with_actions)
{
        int i;
        unlang_stack_t *stack = request->stack;
 
        RDEBUG2("----- Begin stack debug [depth %i] -----",
                stack->depth);
        for (i = stack->depth; i >= 0; i--) {
                unlang_stack_frame_t *frame = &stack->frame[i];
                RDEBUG2("[%d] Frame contents", i);
                frame_dump(request, frame, with_actions);
        }
        RDEBUG2("----- End stack debug [depth %i] -------", stack->depth);
}
 
void stack_dump(request_t *request)
{
        stack_dump_body(request, false);
}
 
void stack_dump_with_actions(request_t *request)
{
        stack_dump_body(request, true);
}
#define DUMP_STACK if (DEBUG_ENABLED5) stack_dump(request)
#else
#define DUMP_STACK
#endif
 
/** Push a new frame onto the stack
 *
 * @param[in] p_result          Where to write the result of evaluating the section.
 *                              If NULL, results will be written to frame->section_result and will
 *                              be automatically merged with the next highest frame when this one
 *                              is popped.
 * @param[in] request           to push the frame onto.
 * @param[in] instruction       One or more unlang_t nodes describing the operations to execute.
 * @param[in] conf              Configuration for the frame.  If NULL, the following values areused:
 *                              - default result = UNLANG_RESULT_NOT_SET
 *                              - top_frame = UNLANG_SUB_FRAME
 *                              - no_rcode = false
 * @param[in] do_next_sibling   Whether to only execute the first node in the #unlang_t program
 *                              or to execute subsequent nodes.
 * @return
 *      - 0 on success.
 *      - -1 on call stack too deep.
 */
int unlang_interpret_push(unlang_result_t *p_result, request_t *request,
                          unlang_t const *instruction, unlang_frame_conf_t const *conf, bool do_next_sibling)
{
        unlang_stack_t          *stack = request->stack;
        unlang_stack_frame_t    *frame;
 
        static unlang_frame_conf_t default_conf = {
                .default_result = UNLANG_RESULT_NOT_SET,
                .top_frame = UNLANG_SUB_FRAME
        };
 
        if (!conf) conf = &default_conf;
 
        fr_assert(instruction);
 
#ifndef NDEBUG
        if (DEBUG_ENABLED5) RDEBUG3("unlang_interpret_push called with instruction type \"%s\" - args %s %s",
                                    instruction ? instruction->debug_name : "<none>",
                                    do_next_sibling ? "UNLANG_NEXT_SIBLING" : "UNLANG_NEXT_STOP",
                                    conf->top_frame ? "UNLANG_TOP_FRAME" : "UNLANG_SUB_FRAME");
#endif
 
        /*
         *      This is not a cancellation point.
         *
         *      If we cancel here bad things happen inside the interpret.
         */
        if (stack->depth >= (UNLANG_STACK_MAX - 1)) {
                RERROR("Call stack is too deep");
                return - 1;
        }
 
        stack->depth++;
 
        /*
         *      Initialize the next stack frame.
         */
        frame = &stack->frame[stack->depth];
        memset(frame, 0, sizeof(*frame));
 
        frame->instruction = instruction;
 
        if (do_next_sibling && instruction->list) {
                fr_assert(instruction != NULL);
                frame->next = unlang_list_next(instruction->list, instruction);
        }
        /* else frame->next MUST be NULL */
 
        frame->flag = UNLANG_FRAME_FLAG_NONE;
        if (conf->top_frame) top_frame_set(frame);
 
        frame->p_result = p_result ? p_result : &frame->section_result;
        *frame->p_result = conf->default_result;
 
        frame->indent = request->log.indent;
 
        if (!instruction) return 0;
 
        frame_state_init(stack, frame);
 
        return 0;
}
 
typedef struct {
        fr_dict_t const *old_dict;      //!< the previous dictionary for the request
        request_t       *request;       //!< the request
} unlang_variable_ref_t;
 
static int _local_variables_free(unlang_variable_ref_t *ref)
{
        fr_pair_t *vp, *prev;
 
        /*
         *      Local variables are appended to the end of the list.  So we remove them by walking backwards
         *      from the end of the list.
         */
        vp = fr_pair_list_tail(&ref->request->local_pairs);
        while (vp) {
                prev = fr_pair_list_prev(&ref->request->local_pairs, vp);
                if (vp->da->dict != ref->request->local_dict) {
                        break;
                }
 
                (void) fr_pair_delete(&ref->request->local_pairs, vp);
                vp = prev;
        }
 
        ref->request->local_dict = ref->old_dict;
 
        return 0;
}
 
/** Push the children of the current frame onto a new frame onto the stack
 *
 * @param[out] p_result         set to RLM_MOULDE_FAIL if pushing the children fails
 * @param[in] request           to push the frame onto.
 * @param[in] default_rcode     The default result.
 * @param[in] do_next_sibling   Whether to only execute the first node in the #unlang_t program
 *                              or to execute subsequent nodes.
 * @return
 *      - UNLANG_ACTION_PUSHED_CHILD on success.
 *      - UNLANG_ACTION_EXECUTE_NEXT do nothing, but just go to the next sibling instruction
 *      - UNLANG_ACTION_STOP_PROCESSING, fatal error, usually stack overflow.
 */
unlang_action_t unlang_interpret_push_children(unlang_result_t *p_result, request_t *request,
                                               rlm_rcode_t default_rcode, bool do_next_sibling)
{
        unlang_stack_t          *stack = request->stack;
        unlang_stack_frame_t    *frame = &stack->frame[stack->depth];   /* Quiet static analysis */
        unlang_group_t          *g;
        unlang_variable_ref_t   *ref;
 
        fr_assert(has_debug_braces(frame));
 
        g = unlang_generic_to_group(frame->instruction);
 
        /*
         *      The compiler catches most of these, EXCEPT for the
         *      top-level 'recv Access-Request' etc.  Which can exist,
         *      and can be empty.
         */
        if (unlang_list_empty(&g->children)) {
                RDEBUG2("... ignoring empty subsection ...");
                return UNLANG_ACTION_EXECUTE_NEXT;
        }
 
        if (unlang_interpret_push(p_result, request, unlang_list_head(&g->children),
                                  FRAME_CONF(default_rcode, UNLANG_SUB_FRAME), do_next_sibling) < 0) {
                return UNLANG_ACTION_STOP_PROCESSING;
        }
 
        if (!g->variables) return UNLANG_ACTION_PUSHED_CHILD;
 
        /*
         *      Note that we do NOT create the variables, This way we don't have to worry about any
         *      uninitialized values.  If the admin tries to use the variable without initializing it, they
         *      will get a "no such attribute" error.
         */
        if (!frame->state) {
                MEM(ref = talloc(stack, unlang_variable_ref_t));
                frame->state = ref;
        } else {
                MEM(ref = talloc(frame->state, unlang_variable_ref_t));
        }
 
        /*
         *      Set the destructor to clean up local variables.
         */
        ref->request = request;
        ref->old_dict = request->local_dict;
        request->local_dict = g->variables->dict;
        talloc_set_destructor(ref, _local_variables_free);
 
        return UNLANG_ACTION_PUSHED_CHILD;
}
 
static void instruction_retry_handler(UNUSED fr_timer_list_t *tl, UNUSED fr_time_t now, void *ctx);
 
/** Update the current result after each instruction, and after popping each stack frame
 *
 * @note Sets stack->scratch to be the the result of the frame being popped.
 *
 * @param[in] request                   The current request.
 * @param[in] frame                     The current stack frame.
 * @param[in] result                    from the previous action.
 * @return
 *      - UNLANG_FRAME_ACTION_NEXT      evaluate more instructions.
 *      - UNLANG_FRAME_ACTION_POP       the final result has been calculated for this frame.
 */
static inline CC_HINT(always_inline)
unlang_frame_action_t result_calculate(request_t *request, unlang_stack_frame_t *frame, unlang_result_t *result)
{
        unlang_t const  *instruction = frame->instruction;
        unlang_stack_t  *stack = request->stack;
        unlang_result_t *frame_result = frame->p_result;
 
        if (is_unwinding(frame)) {
                RDEBUG4("** [%i] %s - unwinding frame", stack->depth, __FUNCTION__);
                return UNLANG_FRAME_ACTION_POP;
        }
 
        /*
         *      Don't calculate a new return code for the frame, just skip
         *      to the next instruction.
         */
        if (result->rcode == RLM_MODULE_NOT_SET) {
                RDEBUG4("** [%i] %s - skipping frame, no result set",
                        stack->depth, __FUNCTION__);
                return UNLANG_FRAME_ACTION_NEXT;
        }
 
        fr_assert(MOD_ACTION_VALID(frame_result->priority));
        fr_assert(MOD_ACTION_VALID(result->priority));
 
        RDEBUG4("** [%i] %s - have (%s %s) frame or module returned (%s %s)",
                stack->depth, __FUNCTION__,
                fr_table_str_by_value(mod_rcode_table, frame_result->rcode, "<invalid>"),
                mod_action_name[frame_result->priority],
                fr_table_str_by_value(mod_rcode_table, result->rcode, "<invalid>"),
                mod_action_name[result->priority]);
 
        /*
         *      Update request->rcode if the instruction says we should
         *      We don't care about priorities for this.
         *
         *      This is the field that's evaluated in unlang conditions
         *      like `if (ok)`.
         */
        if (is_rcode_set(frame) && (request->rcode != result->rcode)) {
                RDEBUG3("Setting request->rcode to '%s'",
                        fr_table_str_by_value(rcode_table, result->rcode, "<INVALID>"));
                request->rcode = result->rcode;
        }
 
        /*
        *       The array holds a default priority for this return
        *       code.  Grab it in preference to any unset priority.
        */
        if (result->priority == MOD_ACTION_NOT_SET) {
                result->priority = instruction->actions.actions[result->rcode];
 
                fr_assert(MOD_ACTION_VALID(result->priority));
 
                RDEBUG4("** [%i] %s - using default instruction priority for %s, %s",
                        stack->depth, __FUNCTION__,
                        fr_table_str_by_value(mod_rcode_table, result->rcode, "<invalid>"),
                        mod_action_name[result->priority]);
        }
 
        /*
         *      Deal with special priorities which indicate we need
         *      to do something in addition to modifying the frame's
         *      rcode.
         */
        switch (result->priority) {
        /*
         *      The child's prioriy value indicates we
         *      should return from this frame.
         */
        case MOD_ACTION_RETURN:
                RDEBUG4("** [%i] %s - action says to return with (%s %s)",
                        stack->depth, __FUNCTION__,
                        fr_table_str_by_value(mod_rcode_table, result->rcode, "<invalid>"),
                        mod_action_name[result->priority]);
 
                *frame_result = UNLANG_RESULT_RCODE(result->rcode);
                return UNLANG_FRAME_ACTION_POP;
 
        /*
         *      Reject means we should return, but
         *      with a reject rcode.  This allows the
         *      user to change normally positive rcodes
         *      into negative ones.
         *
         *      They could also just check the rcode
         *      after the module returns...
         */
        case MOD_ACTION_REJECT:
                RDEBUG4("** [%i] %s - action says to return with (%s %s)",
                        stack->depth, __FUNCTION__,
                        fr_table_str_by_value(mod_rcode_table, RLM_MODULE_REJECT, "<invalid>"),
                        mod_action_name[result->priority]);
 
                *frame_result = UNLANG_RESULT_RCODE(RLM_MODULE_REJECT);
                return UNLANG_FRAME_ACTION_POP;
 
        case MOD_ACTION_RETRY:
        {
                unlang_retry_t *retry = frame->retry;
 
                RDEBUG4("** [%i] %s - action says to retry with",
                        stack->depth, __FUNCTION__);
 
                /*
                 *      If this is the first time doing the retry,
                 *      then allocate the structure and set the timer.
                 */
                if (!retry) {
                        MEM(frame->retry = retry = talloc_zero(stack, unlang_retry_t));
 
                        retry->request = request;
                        retry->depth = stack->depth;
                        retry->state = FR_RETRY_CONTINUE;
                        retry->count = 1;
 
                        /*
                         *      Set a timer which automatically fires
                         *      if there's a timeout.  And parent it
                         *      from the retry structure, so that the
                         *      timer is automatically freed when the
                         *      frame is cleaned up.
                         */
                        if (fr_time_delta_ispos(instruction->actions.retry.mrd)) {
                                if (fr_timer_in(retry, unlang_interpret_event_list(request)->tl, &retry->ev, instruction->actions.retry.mrd,
                                                false, instruction_retry_handler, request) < 0) {
                                        RPEDEBUG("Failed inserting retry event");
                                        *frame_result = UNLANG_RESULT_RCODE(RLM_MODULE_FAIL);
                                        goto finalize;
                                }
                        }
 
                } else {
                        /*
                         *      We've been told to stop doing retries,
                         *      probably from a timeout.
                         */
                        if (retry->state != FR_RETRY_CONTINUE) goto timeout;
 
                        /*
                         *      Clamp it at the maximum count.
                         */
                        if (instruction->actions.retry.mrc > 0) {
                                retry->count++;
 
                                if (retry->count >= instruction->actions.retry.mrc) {
                                        retry->state = FR_RETRY_MRC;
 
                                        REDEBUG("Retries hit max_rtx_count (%u) - returning 'timeout'", instruction->actions.retry.mrc);
 
                                timeout:
                                        *frame_result = UNLANG_RESULT_RCODE(RLM_MODULE_TIMEOUT);
                                        goto finalize;
                                }
                        }
                }
 
                RINDENT();
                if (instruction->actions.retry.mrc) {
                        RDEBUG("... retrying (%u/%u)", retry->count, instruction->actions.retry.mrc);
                } else {
                        RDEBUG("... retrying");
                }
                REXDENT();
 
                talloc_free(frame->state);
                unlang_frame_perf_cleanup(frame);
                frame_state_init(stack, frame); /* Don't change p_result */
                return UNLANG_FRAME_ACTION_RETRY;
        default:
                break;
        }
        }
 
finalize:
        /*
         *      We're higher or equal to previous priority, remember this
         *      return code and priority.
         */
        if (result->priority >= frame_result->priority) {
                fr_assert(MOD_ACTION_VALID(result->priority));
                fr_assert(MOD_ACTION_VALID(frame_result->priority));
 
                RDEBUG4("** [%i] %s - overwriting existing result (%s %s) with higher priority (%s %s)",
                        stack->depth, __FUNCTION__,
                        fr_table_str_by_value(mod_rcode_table, frame_result->rcode, "<invalid>"),
                        mod_action_name[frame_result->priority],
                        fr_table_str_by_value(mod_rcode_table, result->rcode, "<invalid>"),
                        mod_action_name[result->priority]);
                *frame->p_result = *result;
        }
 
        /*
         *      Determine if we should continue processing siblings
         *      or pop the frame ending the section.
         */
        return frame->next ? UNLANG_FRAME_ACTION_NEXT : UNLANG_FRAME_ACTION_POP;
}
 
/** Function called to merge inter-stack-frame results
 *
 * This function is called whenever a frame is popped from the stack.
 *
 * 'result' is the result from the frame being popped, and 'frame' is the next highest frame in the stack.
 *
 * The logic here is very similar to result_eval(), with two important differences:
 * - The priority of the lower frame is ignored, and the default priority of the higher frame is used.
 *   Unless the higher frame's priority is MOD_ACTION_NOT_SET, in which case the lower frame's priority is used.
 */
static inline CC_HINT(always_inline)
unlang_frame_action_t result_pop(request_t *request, unlang_stack_frame_t *frame, unlang_result_t *result)
{
        unlang_stack_t  *stack = request->stack;
        unlang_result_t our_result = *result;
 
        fr_assert(MOD_ACTION_VALID(result->priority));
 
        /*
         *      When a stack frame is being popped, the priority of the
         *      source (lower) frame is ignored, and the default priority
         *      of the destination (higher) frame is used.
         *
         *      We could (easily) add support for preserving the priority
         *      from the lower frame, if the priority of the higher frame
         *      was MOD_ACTION_NOT_SET, but there are no concrete use
         *      cases for this yet.
         */
        if (result->rcode != RLM_MODULE_NOT_SET) {
                fr_assert(MOD_ACTION_VALID(frame->instruction->actions.actions[result->rcode]));
                our_result.priority = frame->instruction->actions.actions[result->rcode];
        }
 
        RDEBUG4("** [%i] %s - using instruction priority for higher frame (%s, %s)",
                stack->depth, __FUNCTION__,
                fr_table_str_by_value(mod_rcode_table, our_result.rcode, "<invalid>"),
                mod_action_name[our_result.priority]);
 
        return result_calculate(request, frame, &our_result);
}
 
static inline CC_HINT(always_inline) void instruction_done_debug(request_t *request, unlang_stack_frame_t *frame, unlang_t const *instruction)
{
        if (has_debug_braces(instruction)) {
                REXDENT();
 
                /*
                 *      If we're at debug level 1, don't emit the closing
                 *      brace as the opening brace wasn't emitted.
                 *
                 *      Not a typo, we don't want to print the scratch_result
                 *      here, aka the ones the section actually returned,
                 *      vs the section result, which may have just been left
                 *      at defaults.
                 */
                if (RDEBUG_ENABLED && !RDEBUG_ENABLED2) {
                        RDEBUG("# %s %s%s%s", frame->instruction->debug_name,
                                frame->p_result == &frame->section_result ? "(" : "))",
                                fr_table_str_by_value(mod_rcode_table, frame->p_result->rcode, "<invalid>"),
                                frame->p_result == &frame->section_result ? "(" : "))");
                } else {
                        RDEBUG2("} # %s %s%s%s", frame->instruction->debug_name,
                                frame->p_result == &frame->section_result ? "(" : "((",
                                fr_table_str_by_value(mod_rcode_table, frame->p_result->rcode, "<invalid>"),
                                frame->p_result == &frame->section_result ? ")" : "))");
                }
        }
}
 
/** Evaluates all the unlang nodes in a section
 *
 * This function interprets a list of unlang instructions at a given level using the same
 * stack frame, and pushes additional frames onto the stack as needed.
 *
 * This function can be seen as moving horizontally.
 *
 * @param[in] request                   The current request.
 * @param[in] frame                     The current stack frame.
 * @return
 *      - UNLANG_FRAME_ACTION_NEXT      evaluate more instructions in the current stack frame
 *                                      which may not be the same frame as when this function
 *                                      was called.
 *      - UNLANG_FRAME_ACTION_POP       the final result has been calculated for this frame.
 */
static inline CC_HINT(always_inline)
unlang_frame_action_t frame_eval(request_t *request, unlang_stack_frame_t *frame)
{
        unlang_stack_t  *stack = request->stack;
        unlang_result_t *scratch = &frame->scratch_result;
 
        /*
         *      Loop over all the instructions in this list.
         */
        while (frame->instruction) {
                unlang_t const          *instruction = frame->instruction;
                unlang_action_t         ua;
                unlang_frame_action_t   fa;
 
                DUMP_STACK;
 
                fr_assert(instruction->debug_name != NULL); /* if this happens, all bets are off. */
                fr_assert(unlang_ops[instruction->type].interpret != NULL);
                fr_assert(frame->process != NULL);
 
                REQUEST_VERIFY(request);
 
                /*
                 *      We're running this frame, so it can't possibly be yielded.
                 */
                if (is_yielded(frame)) {
                        RDEBUG("%s - Resuming execution", instruction->debug_name);
                        yielded_clear(frame);
                }
 
#ifndef NDEBUG
                /*
                 *      Failure testing!
                 */
                if (request->ins_max) {
                        request->ins_count++;
 
                        if (request->ins_count >= request->ins_max) {
                                RERROR("Failing request due to maximum instruction count %" PRIu64, request->ins_max);
 
                                unlang_interpret_signal(request, FR_SIGNAL_CANCEL);
                        }
                }
#endif
 
                /*
                 *      We're not re-entering this frame, this is the first
                 *      time we're evaluating this instruction, so we should
                 *      print debug braces and indent.
                 */
                if (!is_repeatable(frame)) {
                        if (has_debug_braces(frame)) {
                                RDEBUG2("%s {", instruction->debug_name);
                                RINDENT();
                        }
                /*
                 *      Clear the repeatable flag so this frame
                 *      won't get executed again unless it specifically
                 *      requests it.
                 *
                 *      The flag may still be set again during the
                 *      process function to indicate that the frame
                 *      should be evaluated again.
                 */
                } else {
                        repeatable_clear(frame);
                }
 
                /*
                 *      Execute an operation
                 */
                RDEBUG4("** [%i] %s >> %s", stack->depth, __FUNCTION__,
                        unlang_ops[instruction->type].name);
 
                unlang_frame_perf_resume(frame);
 
                /*
                 *      catch plays games with the frame so we skip
                 *      to the next catch section at a given depth,
                 *      it's not safe to access frame->instruction
                 *      after this point, and the cached instruction
                 *      should be used instead.
                 */
                ua = frame->process(&frame->scratch_result, request, frame);
 
                fr_assert(MOD_ACTION_VALID(scratch->priority));
 
                RDEBUG4("** [%i] %s << %s (%s %s)", stack->depth, __FUNCTION__,
                        fr_table_str_by_value(unlang_action_table, ua, "<INVALID>"),
                        fr_table_str_by_value(mod_rcode_table, scratch->rcode, "<INVALID>"),
                        mod_action_name[scratch->priority]);
 
                /*
                 *      If the frame is cancelled we ignore the
                 *      return code of the process function and
                 *      pop the frame.  We'll keep popping
                 *      frames until we hit a non-cancelled frame
                 *      or the top frame.
                 */
                if (is_unwinding(frame)) goto calculate_result;
 
                switch (ua) {
                case UNLANG_ACTION_STOP_PROCESSING:
                        /*
                         *      This marks all the cancellable
                         *      frames with the unwind flag,
                         *      and starts popping them.
                         */
                        unlang_interpret_signal(request, FR_SIGNAL_CANCEL);
                        return UNLANG_FRAME_ACTION_POP;
 
                /*
                 *      The operation resulted in additional frames
                 *      being pushed onto the stack, execution should
                 *      now continue at the deepest frame.
                 */
                case UNLANG_ACTION_PUSHED_CHILD:
                        fr_assert_msg(&stack->frame[stack->depth] > frame,
                                      "Instruction %s returned UNLANG_ACTION_PUSHED_CHILD, "
                                      "but stack depth was not increased",
                                      instruction->name);
                        unlang_frame_perf_yield(frame);
                        return UNLANG_FRAME_ACTION_NEXT;
 
                /*
                 *      Yield control back to the scheduler, or whatever
                 *      called the interpreter.
                 */
                case UNLANG_ACTION_YIELD:
                        fr_assert_msg(&stack->frame[stack->depth] == frame,
                                      "Instruction %s returned UNLANG_ACTION_YIELD, but pushed additional "
                                      "frames for evaluation.  Instruction should return UNLANG_ACTION_PUSHED_CHILD "
                                      "instead", instruction->name);
                        unlang_frame_perf_yield(frame);
                        yielded_set(frame);
                        RDEBUG4("** [%i] %s - yielding with current (%s %s)", stack->depth, __FUNCTION__,
                                fr_table_str_by_value(mod_rcode_table, scratch->rcode, "<invalid>"),
                                mod_action_name[scratch->priority]);
                        return UNLANG_FRAME_ACTION_YIELD;
 
                /*
                 *      This action is intended to be returned by library
                 *      functions.  It reduces boilerplate.
                 */
                case UNLANG_ACTION_FAIL:
                        /*
                         *      Let unlang_calculate figure out if this is the final result
                         */
                        frame->scratch_result = UNLANG_RESULT_RCODE(RLM_MODULE_FAIL);
                        FALL_THROUGH;
 
                /*
                 *      Instruction finished execution,
                 *      check to see what we need to do next, and update
                 *      the section rcode and priority.
                 */
                case UNLANG_ACTION_CALCULATE_RESULT:
                calculate_result:
                        /*
                         *      Merge in the scratch result _before_ printing
                         *      out the rcode for the frame, so get what we'll
                         *      actually return.
                         */
                        fa = result_calculate(request, frame, &frame->scratch_result);
 
                        instruction_done_debug(request, frame, instruction);
 
                        switch (fa) {
                        case UNLANG_FRAME_ACTION_POP:
                                goto pop;
 
                        case UNLANG_FRAME_ACTION_RETRY:
                                if (has_debug_braces(instruction)) {
                                        REXDENT();
                                        RDEBUG2("} # retrying the same section");
                                }
                                continue; /* with the current instruction */
 
                        default:
                                break;
                        }
                        break;
 
                /*
                 *      Execute the next instruction in this frame
                 */
                case UNLANG_ACTION_EXECUTE_NEXT:
                        if (has_debug_braces(instruction)) {
                                REXDENT();
                                RDEBUG2("}");
                        }
                        break;
                } /* switch over return code from the interpret function */
 
                frame_next(stack, frame);
        }
 
pop:
        fr_assert(MOD_ACTION_VALID(frame->p_result->priority));
 
        RDEBUG4("** [%i] %s - done current subsection with (%s %s), %s",
                stack->depth, __FUNCTION__,
                fr_table_str_by_value(mod_rcode_table, frame->p_result->rcode, "<invalid>"),
                mod_action_name[frame->p_result->priority],
                frame->p_result == &(frame->section_result) ? "will set higher frame rcode" : "will NOT set higher frame rcode (p_result)");
 
        return UNLANG_FRAME_ACTION_POP;
}
 
/** Run the interpreter for a current request
 *
 * This function runs the interpreter for a request.  It deals with popping
 * stack frames, and calaculating the final result for the frame.
 *
 * @param[in] request           to run.  If this is an internal request
 *                              the request may be freed by the interpreter.
 * @param[in] running           Is the interpreter already running.
 * @return The final request rcode.
 */
CC_HINT(hot) rlm_rcode_t unlang_interpret(request_t *request, bool running)
{
        unlang_stack_t          *stack = request->stack;
        unlang_interpret_t      *intp = stack->intp;
        unlang_stack_frame_t    *frame = &stack->frame[stack->depth];
 
        /*
         *      This is needed to ensure that if a frame is marked
         *      for unwinding whilst the request is yielded, we
         *      unwind the cancelled frame correctly, instead of
         *      continuing.
         */
        unlang_frame_action_t   fa = is_unwinding(frame) ? UNLANG_FRAME_ACTION_POP : UNLANG_FRAME_ACTION_NEXT;
 
#ifndef NDEBUG
        if (DEBUG_ENABLED5) DEBUG("###### unlang_interpret is starting");
        DUMP_STACK;
#endif
 
        fr_assert(!unlang_request_is_scheduled(request)); /* if we're running it, it can't be scheduled */
        fr_assert_msg(intp, "request has no interpreter associated");
 
        RDEBUG4("** [%i] %s - interpret entered", stack->depth, __FUNCTION__);
        if (!running) intp->funcs.resume(request, intp->uctx);
 
        for (;;) {
                fr_assert(stack->depth > 0);
                fr_assert(stack->depth < UNLANG_STACK_MAX);
 
                RDEBUG4("** [%i] %s - frame action %s", stack->depth, __FUNCTION__,
                        fr_table_str_by_value(unlang_frame_action_table, fa, "<INVALID>"));
                switch (fa) {
                next:
                        RDEBUG4("** [%i] %s - frame action next", stack->depth, __FUNCTION__);
                        FALL_THROUGH;
 
                case UNLANG_FRAME_ACTION_NEXT:  /* Evaluate the current frame */
                        frame = &stack->frame[stack->depth];
                        fa = frame_eval(request, frame);
                        if (fa != UNLANG_FRAME_ACTION_POP) continue;
 
                        RDEBUG4("** [%i] %s - frame action %s", stack->depth, __FUNCTION__,
                                fr_table_str_by_value(unlang_frame_action_table, fa, "<INVALID>"));
                        FALL_THROUGH;
 
                case UNLANG_FRAME_ACTION_POP:                           /* Pop this frame and check the one beneath it */
                {
                        bool top_frame = is_top_frame(frame);
                        bool private_result = is_private_result(frame);
 
                        unlang_result_t section_result = frame->section_result; /* record the result of the frame before we pop it*/
 
                        DUMP_STACK;
 
                        /*
                         *      Triggers can run modules which pop, and then the stack is empty.
                         */
                        if (unlikely(stack->depth == 0)) {
                                break;
                        }
 
                        /*
                         *      Head on back up the stack
                         */
                        frame_pop(request, stack);
                        RDEBUG4("** [%i] %s - frame popped", stack->depth + 1, __FUNCTION__);
 
                        /*
                         *      Update the stack frame
                         */
                        frame = &stack->frame[stack->depth];
                        DUMP_STACK;
 
                        /*
                         *      Transition back to the C stack
                         *
                         *      We still need to merge in the previous frame's result,
                         *      but we don't care about the action, as we're returning.
                         */
                        if (top_frame) {
                                if (!private_result) result_calculate(request, frame, &section_result);
                                break;  /* stop */
                        }
 
                        /*
                         *      Don't process the section result for a frame if
                         *      the result is being consumed by a module.
                         */
                        if (private_result) {
                                fa = is_unwinding(frame) ? UNLANG_FRAME_ACTION_POP : UNLANG_FRAME_ACTION_NEXT;
                        /*
                         *      Merge lower frame into higher frame.
                         *
                         *      this _MUST_ be done, even on resume, because the
                         *      section result needs to be updated for the frame
                         *      being resumed, in case it cares about the rcode
                         *      like transaction sections.
                         */
                        } else {
                                fa = result_pop(request, frame, &section_result);
                        }
 
                        /*
                         *      Resume a "foreach" loop, or a "load-balance" section
                         *      or anything else that needs to be checked on the way
                         *      back on up the stack.  Here we just resume evaluating
                         *      the frame, we don't advance the instruction.
                         */
                        if (!is_unwinding(frame) && is_repeatable(frame)) goto next;
 
                        /*
                         *      Close out the section we entered earlier
                         */
                        instruction_done_debug(request, frame, frame->instruction);
 
                        fr_assert(MOD_ACTION_VALID(frame->section_result.priority));
 
                        /*
                         *      If we're continuing after popping a frame
                         *      then we advance the instruction else we
                         *      end up executing the same code over and over...
                         */
                        switch (fa) {
                        case UNLANG_FRAME_ACTION_NEXT:
                                DEBUG4("** [%i] %s - continuing after subsection with (%s %s)",
                                        stack->depth, __FUNCTION__,
                                        fr_table_str_by_value(mod_rcode_table, frame->section_result.rcode, "<invalid>"),
                                        mod_action_name[frame->section_result.priority]);
                                frame_next(stack, frame);
                                goto next;
 
                        /*
                         *      Else if we're really done with this frame
                         *      print some helpful debug...
                         */
                        default:
                                RDEBUG4("** [%i] %s - done current subsection with (%s %s)",
                                        stack->depth, __FUNCTION__,
                                        fr_table_str_by_value(mod_rcode_table, frame->section_result.rcode, "<invalid>"),
                                        mod_action_name[frame->section_result.priority]);
                                continue;
                        }
 
                }
 
                case UNLANG_FRAME_ACTION_YIELD:
                        /* Cannot yield from a nested call to unlang_interpret */
                        fr_assert(!running);
 
                        RDEBUG4("** [%i] %s - interpret yielding", stack->depth, __FUNCTION__);
                        intp->funcs.yield(request, intp->uctx);
                        return RLM_MODULE_NOT_SET;
 
                case UNLANG_FRAME_ACTION_RETRY: /* retry the current frame */
                        goto next;
                }
                break;
        }
 
        fr_assert(stack->depth >= 0);
 
        /*
         *      We're at the top frame, return the result from the
         *      stack, and get rid of the top frame.
         */
        RDEBUG4("** [%i] %s - interpret exiting, returning (%s)", stack->depth, __FUNCTION__,
                fr_table_str_by_value(mod_rcode_table, frame->section_result.rcode, "<invalid>"));
 
        DUMP_STACK;
 
        {
                rlm_rcode_t             rcode;
                /*
                 *      Record this now as the done functions may free
                 *      the request.
                 *
                 *      Note: We use p_result here, as that's where the
                 *      result of evaluating the frame was written.
                 *      We don't use the section_result, as that may have
                 *      been left as its default value which may be 0
                 *      (reject).
                 */
                rcode = frame->p_result->rcode;
 
                /*
                 *      This usually means the request is complete in its
                 *      entirety.
                 */
                if ((stack->depth == 0) && !running) unlang_interpret_request_done(request);
 
                return rcode;
        }
}
 
static unlang_group_t empty_group = {
        .self = {
                .type = UNLANG_TYPE_GROUP,
                .debug_name = "empty-group",
                .actions = {
                        .actions = {
                                MOD_ACTION_RETURN,
                                MOD_ACTION_RETURN,
                                MOD_ACTION_RETURN,
                                MOD_ACTION_RETURN,
                                MOD_ACTION_RETURN,
                                MOD_ACTION_RETURN,
                                MOD_ACTION_RETURN,
                                MOD_ACTION_RETURN,
                                MOD_ACTION_RETURN
                        },
                        .retry = RETRY_INIT,
                },
        },
};
 
/** Push a configuration section onto the request stack for later interpretation.
 *
 */
int unlang_interpret_push_section(unlang_result_t *p_result, request_t *request, CONF_SECTION *cs, unlang_frame_conf_t const *conf)
{
        unlang_t        *instruction = NULL;
 
        /*
         *      Interpretable unlang instructions are stored as CONF_DATA
         *      associated with sections.
         */
        if (cs) {
                instruction = (unlang_t *)cf_data_value(cf_data_find(cs, unlang_group_t, NULL));
                if (!instruction) {
                        REDEBUG("Failed to find pre-compiled unlang for section %s %s { ... }",
                                cf_section_name1(cs), cf_section_name2(cs));
                        return -1;
                }
        }
 
        return unlang_interpret_push_instruction(p_result, request, instruction, conf);
}
 
/** Push an instruction onto the request stack for later interpretation.
 *
 */
int unlang_interpret_push_instruction(unlang_result_t *p_result, request_t *request, void *instruction, unlang_frame_conf_t const *conf)
{
        unlang_stack_t  *stack = request->stack;
 
        if (!instruction) {
                instruction = unlang_group_to_generic(&empty_group);
        }
 
        /*
         *      Push the default action, and the instruction which has
         *      no action.
         */
        if (unlang_interpret_push(p_result, request, instruction, conf, UNLANG_NEXT_SIBLING) < 0) {
                return -1;
        }
 
        RDEBUG4("** [%i] %s - substack begins", stack->depth, __FUNCTION__);
 
        return 0;
}
 
/** Allocate a new unlang stack
 *
 * @param[in] ctx       to allocate stack in.
 * @return
 *      - A new stack on success.
 *      - NULL on OOM.
 */
void *unlang_interpret_stack_alloc(TALLOC_CTX *ctx)
{
        /*
         *      Should never be evaluated, is just here to reduce
         *      branches, so we don't need to check for frame->instruction.
         */
        static unlang_t unlang_instruction = {
                .debug_name = "top",
                .actions = DEFAULT_MOD_ACTIONS,
        };
 
        unlang_stack_t *stack;
 
        /*
         *      If we have talloc_pooled_object allocate the
         *      stack as a combined chunk/pool, with memory
         *      to hold at mutable data for at least a quarter
         *      of the maximum number of stack frames.
         *
         *      Having a dedicated pool for mutable stack data
         *      means we don't have memory fragmentations issues
         *      as we would if request were used as the pool.
         *
         *      This number is pretty arbitrary, but it seems
         *      like too low level to make into a tuneable.
         */
        MEM(stack = talloc_zero_pooled_object(ctx, unlang_stack_t, UNLANG_STACK_MAX, 128));     /* 128 bytes per state */
        stack->frame[0].p_result = &stack->frame[0].section_result;
        stack->frame[0].scratch_result = UNLANG_RESULT_NOT_SET;
        stack->frame[0].section_result = UNLANG_RESULT_NOT_SET;
        stack->frame[0].instruction = &unlang_instruction;      /* The top frame has no instruction, so we use a dummy one */
 
        return stack;
}
 
/** Indicate to the caller of the interpreter that this request is complete
 *
 */
void unlang_interpret_request_done(request_t *request)
{
        unlang_stack_t          *stack = request->stack;
        unlang_interpret_t      *intp;
 
        if (!fr_cond_assert(stack != NULL)) return;
 
        intp = stack->intp;
 
        request->master_state = REQUEST_DONE;
        switch (request->type) {
        case REQUEST_TYPE_EXTERNAL:
                intp->funcs.done_external(request, frame_current(request)->section_result.rcode, intp->uctx);
                break;
 
        case REQUEST_TYPE_INTERNAL:
                intp->funcs.done_internal(request, frame_current(request)->section_result.rcode, intp->uctx);
                break;
 
        case REQUEST_TYPE_DETACHED:
                intp->funcs.done_detached(request, frame_current(request)->section_result.rcode, intp->uctx);   /* Callback will usually free the request */
                break;
        }
}
 
/** Tell the interpreter to detach the request
 *
 * This function should not be called directly use unlang_interpret_signal(request, FR_SIGNAL_DETACH) instead.
 * This will ensure all frames on the request's stack receive the detach signal.
 */
static inline CC_HINT(always_inline)
void unlang_interpret_request_detach(request_t *request)
{
        unlang_stack_t          *stack = request->stack;
        unlang_interpret_t      *intp;
 
        if (!fr_cond_assert(stack != NULL)) return;
 
        if (!request_is_detachable(request)) return;
 
        intp = stack->intp;
 
        intp->funcs.detach(request, intp->uctx);
}
 
void unlang_interpret_request_prioritise(request_t *request, uint32_t priority)
{
        unlang_stack_t          *stack = request->stack;
        unlang_interpret_t      *intp;
 
        if (!fr_cond_assert(stack != NULL)) return;
 
        intp = stack->intp;
 
        request->priority = priority;
 
        if (intp->funcs.prioritise) intp->funcs.prioritise(request, intp->uctx);
}
 
/** Delivers a frame to one or more frames in the stack
 *
 * This is typically called via an "async" action, i.e. an action outside
 * of the normal processing of the request.
 *
 * For FR_SIGNAL_CANCEL all frames are marked up for cancellation, but the
 * cancellation is handled by the interpret.
 *
 * Other signal types are delivered immediately, inrrespecitve of whether
 * the request is currently being processed or not.
 *
 * Signaling stops at the "limit" frame.  This is so that keywords
 * such as "timeout" and "limit" can signal frames *lower* than theirs
 * to stop, but then continue with their own work.
 *
 * @note It's better (clearer) to use one of the unwind_* functions
 *      unless the entire request is being cancelled.
 *
 * @param[in] request           The current request.
 * @param[in] action            to signal.
 * @param[in] limit             the frame at which to stop signaling.
 */
void unlang_stack_signal(request_t *request, fr_signal_t action, int limit)
{
        unlang_stack_frame_t    *frame;
        unlang_stack_t          *stack = request->stack;
        int                     i, depth = stack->depth;
 
        (void)talloc_get_type_abort(request, request_t);        /* Check the request hasn't already been freed */
 
        fr_assert(stack->depth >= 1);
 
        /*
         *      Does not complete the unwinding here, just marks
         *      up the frames for unwinding.  The request must
         *      be marked as runnable to complete the cancellation.
         */
        if (action == FR_SIGNAL_CANCEL) unwind_to_depth(stack, limit);
 
        /*
         *      Walk back up the stack, calling signal handlers
         *      to cancel any pending operations and free/release
         *      any resources.
         *
         *      There may be multiple resumption points in the
         *      stack, as modules can push xlats and function
         *      calls.
         *
         *      Note: Slightly confusingly, a cancellation signal
         *      can still be delivered to a frame that is not
         *      cancellable, but the frame won't be automatically
         *      unwound.
         */
        for (i = depth; i >= limit; i--) {
                frame = &stack->frame[i];
                if (frame->signal) {
                        frame->signal(request, frame, action);
 
                        /*
                         *      Once the cancellation function has been
                         *      called, the frame is no longer in a state
                         *      where it can accept further signals.
                         */
                        if (action == FR_SIGNAL_CANCEL) frame->signal = NULL;
                }
        }
}
 
/** Send a signal (usually stop) to a request
 *
 * This is typically called via an "async" action, i.e. an action
 * outside of the normal processing of the request.
 *
 * @note This does NOT immediately stop the request, it just deliveres
 *       signals, and in the case of a cancel, marks up frames for unwinding
 *       and adds it to the runnable queue if it's yielded.
 *
 * @note This function should be safe to call anywhere.
 *
 * @param[in] request           The current request.
 * @param[in] action            to signal.
 */
void unlang_interpret_signal(request_t *request, fr_signal_t action)
{
        unlang_stack_t          *stack = request->stack;
 
        switch (action) {
        case FR_SIGNAL_DETACH:
                /*
                 *      Ensure the request is able to be detached
                 *      else don't signal.
                 */
                if (!fr_cond_assert(request_is_detachable(request))) return;
                break;
 
        default:
                break;
        }
 
        /*
         *      Requests that haven't been run through the interpreter
         *      yet should have a stack depth of zero, so we don't
         *      need to do anything.
         */
        if (!stack || stack->depth == 0) return;
 
        unlang_stack_signal(request, action, 1);
 
        switch (action) {
        case FR_SIGNAL_CANCEL:
        {
                unlang_stack_frame_t *frame = &stack->frame[stack->depth];
                /*
                 *      Let anything that cares, know that the
                 *      request was forcefully stopped.
                 */
                request->master_state = REQUEST_STOP_PROCESSING;
 
                /*
                 *      Give cancelled requests the highest priority
                 *      to get them to release resources ASAP.
                 */
                unlang_interpret_request_prioritise(request, UINT32_MAX);
 
                /*
                 *      If the request is yielded, mark it as runnable
                 *
                 *      If the request was _not_ cancelled, it means
                 *      it's not cancellable, and we need to let the
                 *      request progress normally.
                 *
                 *      A concrete example of this, is the parent of
                 *      subrequests, which must not continue until
                 *      the subrequest is done.
                 */
                if (stack && is_yielded(frame) && is_unwinding(frame) && !unlang_request_is_scheduled(request)) {
                        unlang_interpret_mark_runnable(request);
                }
        }
                break;
 
        case FR_SIGNAL_DETACH:
                /*
                 *      Cleanup any cross-request pointers, and mark the
                 *      request as detached.  When the request completes it
                 *      should by automatically freed.
                 */
                unlang_interpret_request_detach(request);
                break;
 
        default:
                break;
        }
}
 
static void instruction_retry_handler(UNUSED fr_timer_list_t *tl, UNUSED fr_time_t now, void *ctx)
{
        unlang_retry_t                  *retry = talloc_get_type_abort(ctx, unlang_retry_t);
        request_t                       *request = talloc_get_type_abort(retry->request, request_t);
 
        RDEBUG("retry timeout reached, signalling interpreter to cancel.");
 
        /*
         *      Signal all lower frames to exit.
         */
        unlang_stack_signal(request, FR_SIGNAL_CANCEL, retry->depth);
 
        retry->state = FR_RETRY_MRD;
        unlang_interpret_mark_runnable(request);
}
 
static void instruction_timeout_handler(UNUSED fr_timer_list_t *tl, UNUSED fr_time_t now, void *ctx)
{
        request_t                       *request = talloc_get_type_abort(ctx, request_t);
 
        RDEBUG("Maximum timeout reached, signalling interpreter to stop the request.");
 
        /*
         *      Stop the entire request.
         */
        unlang_interpret_signal(request, FR_SIGNAL_CANCEL);
}
 
 
/** Set a timeout for a request.
 *
 *  The timeout is associated with the current stack frame.
 *
 */
int unlang_interpret_set_timeout(request_t *request, fr_time_delta_t timeout)
{
        unlang_stack_t                  *stack = request->stack;
        unlang_stack_frame_t            *frame = &stack->frame[stack->depth];
        unlang_retry_t                  *retry;
        TALLOC_CTX                      *frame_ctx;
 
        fr_assert(!frame->retry);
        fr_assert(fr_time_delta_ispos(timeout));
 
        frame_ctx = frame->state;
        if (!frame_ctx) frame_ctx = stack;
 
        frame->retry = retry = talloc_zero(frame_ctx, unlang_retry_t);
        if (!frame->retry) return -1;
 
        retry->request = request;
        retry->depth = stack->depth;
        retry->state = FR_RETRY_CONTINUE;
        retry->count = 1;
 
        return fr_timer_in(retry, unlang_interpret_event_list(request)->tl, &retry->ev, timeout,
                           false, instruction_timeout_handler, request);
}
 
 
/** Return the depth of the request's stack
 *
 */
int unlang_interpret_stack_depth(request_t *request)
{
        unlang_stack_t  *stack = request->stack;
 
        return stack->depth;
}
 
/** Get the last instruction result OR the last frame that was popped
 *
 * @param[in] request   The current request.
 * @return the current rcode for the frame.
 */
rlm_rcode_t unlang_interpret_rcode(request_t *request)
{
        return frame_current(request)->p_result->rcode;
}
 
/** Get the last instruction priority OR the last frame that was popped
 *
 * @param[in] request   The current request.
 * @return the current rcode for the frame.
 */
unlang_mod_action_t unlang_interpret_priority(request_t *request)
{
        return frame_current(request)->p_result->priority;
}
 
/** Get the last instruction result OR the last frame that was popped
 *
 * @param[in] request   The current request.
 * @return the current result for the frame.
 */
unlang_result_t *unlang_interpret_result(request_t *request)
{
        return frame_current(request)->p_result;
}
 
/** Return whether a request is currently scheduled
 *
 */
bool unlang_request_is_scheduled(request_t const *request)
{
        unlang_stack_t          *stack = request->stack;
        unlang_interpret_t      *intp = stack->intp;
 
        return intp->funcs.scheduled(request, intp->uctx);
}
 
/** Return whether a request has been cancelled
 */
bool unlang_request_is_cancelled(request_t const *request)
{
        return (request->master_state == REQUEST_STOP_PROCESSING);
}
 
/** Return whether a request has been marked done
 */
bool unlang_request_is_done(request_t const *request)
{
        return (request->master_state == REQUEST_DONE);
}
 
/** Check if a request as resumable.
 *
 * @param[in] request           The current request.
 * @return
 *      - true if the request is resumable (i.e. has yielded)
 *      - false if the request is not resumable (i.e. has not yielded)
 */
bool unlang_interpret_is_resumable(request_t *request)
{
        unlang_stack_t                  *stack = request->stack;
        unlang_stack_frame_t            *frame = &stack->frame[stack->depth];
 
        return is_yielded(frame);
}
 
/** Mark a request as resumable.
 *
 * It's not called "unlang_interpret", because it doesn't actually
 * resume the request, it just schedules it for resumption.
 *
 * @note that this schedules the request for resumption.  It does not immediately
 *      start running the request.
 *
 * @param[in] request           The current request.
 */
void unlang_interpret_mark_runnable(request_t *request)
{
        unlang_stack_t                  *stack = request->stack;
        unlang_interpret_t              *intp = stack->intp;
        unlang_stack_frame_t            *frame = &stack->frame[stack->depth];
 
        bool                            scheduled = unlang_request_is_scheduled(request);
 
        /*
         *      The request hasn't yielded, OR it's already been
         *      marked as runnable.  Don't do anything.
         *
         *      The IO code, or children have no idea where they're
         *      being called from.  They just ask to mark the parent
         *      resumable when they're done.  So we have to check here
         *      if this request is resumable.
         *
         *      If the parent called the child directly, then the
         *      parent hasn't yielded, so it isn't resumable.  When
         *      the child is done, the parent will automatically
         *      continue running.  We therefore don't need to insert
         *      the parent into the backlog.
         *
         *      Multiple child request may also mark a parent request
         *      runnable, before the parent request starts running.
         */
        if (!is_yielded(frame) || scheduled) {
                RDEBUG3("Not marking request %s as runnable due to%s%s",
                        request->name,
                        !is_yielded(frame) ?
                        " it not being yielded " : "", scheduled ? " it already being scheduled" : "");
                return;
        }
 
        RDEBUG3("Interpreter - Request marked as runnable");
 
        intp->funcs.mark_runnable(request, intp->uctx);
}
 
/** Get a talloc_ctx which is valid only for this frame
 *
 * @param[in] request           The current request.
 * @return
 *      - a TALLOC_CTX which is valid only for this stack frame
 */
TALLOC_CTX *unlang_interpret_frame_talloc_ctx(request_t *request)
{
        unlang_stack_t                  *stack = request->stack;
        unlang_stack_frame_t            *frame = &stack->frame[stack->depth];
 
        if (frame->state) return (TALLOC_CTX *)frame->state;
 
        /*
         *      If the frame doesn't ordinarily have a
         *      state, assume the caller knows what it's
         *      doing and allocate one.
         */
        return (TALLOC_CTX *)(frame->state = talloc_new(request));
}
 
static xlat_arg_parser_t const unlang_cancel_xlat_args[] = {
        { .required = false, .single = true, .type = FR_TYPE_TIME_DELTA },
        XLAT_ARG_PARSER_TERMINATOR
};
 
static xlat_action_t unlang_cancel_xlat(TALLOC_CTX *ctx, fr_dcursor_t *out,
                                        UNUSED xlat_ctx_t const *xctx,
                                        request_t *request, fr_value_box_list_t *args);
 
/** Signal the request to stop executing
 *
 * The request can't be running at this point because we're in the event
 * loop.  This means the request is always in a consistent state when
 * the timeout event fires, even if that's state is waiting on I/O.
 */
static void unlang_cancel_event(UNUSED fr_timer_list_t *tl, UNUSED fr_time_t now, void *uctx)
{
        request_t *request = talloc_get_type_abort(uctx, request_t);
 
        RDEBUG2("Request canceled by dynamic timeout");
        /*
         *      Cleans up the memory allocated to hold
         *      the pointer, not the event itself.
         */
        talloc_free(request_data_get(request, (void *)unlang_cancel_xlat, 0));
 
        unlang_interpret_signal(request, FR_SIGNAL_CANCEL);
}
 
/** Allows a request to dynamically alter its own lifetime
 *
 * %cancel(<timeout>)
 *
 * If timeout is 0, then the request is immediately cancelled.
 */
static xlat_action_t unlang_cancel_xlat(TALLOC_CTX *ctx, fr_dcursor_t *out,
                                        UNUSED xlat_ctx_t const *xctx,
                                        request_t *request, fr_value_box_list_t *args)
{
        fr_value_box_t          *timeout;
        fr_event_list_t         *el = unlang_interpret_event_list(request);
        fr_timer_t              **ev_p, **ev_p_og;
        fr_value_box_t          *vb;
        fr_time_t               when = fr_time_from_sec(0); /* Invalid clang complaints if we don't set this */
 
        XLAT_ARGS(args, &timeout);
 
        /*
         *      No timeout means cancel immediately, so yield allowing
         *      the interpreter to run the event we added to cancel
         *      the request.
         *
         *      We call unlang_xlat_yield to keep the interpreter happy
         *      as it expects to see a resume function set.
         */
        if (!timeout || fr_time_delta_eq(timeout->vb_time_delta, fr_time_delta_from_sec(0))) {
                unlang_interpret_signal(request, FR_SIGNAL_CANCEL);
                return XLAT_ACTION_DONE;
        }
 
        /*
         *      First see if we already have a timeout event
         *      that was previously added by this xlat.
         */
        ev_p = ev_p_og = request_data_get(request, (void *)unlang_cancel_xlat, 0);
        if (ev_p) {
                if (*ev_p) when = fr_timer_when(*ev_p); /* *ev_p should never be NULL, really... */
        } else {
                /*
                 *      Must not be parented from the request
                 *      as this is freed by request data.
                 */
                MEM(ev_p = talloc_zero(NULL, fr_timer_t *));
        }
 
        if (unlikely(fr_timer_in(ev_p, el->tl, ev_p,
                      timeout ? timeout->vb_time_delta : fr_time_delta_from_sec(0),
              false, unlang_cancel_event, request) < 0)) {
                RPERROR("Failed inserting cancellation event");
                talloc_free(ev_p);
                return XLAT_ACTION_FAIL;
        }
        if (unlikely(request_data_add(request, (void *)unlang_cancel_xlat, 0,
                                      UNCONST(fr_timer_t **, ev_p), true, true, false) < 0)) {
                RPERROR("Failed associating cancellation event with request");
                talloc_free(ev_p);
                return XLAT_ACTION_FAIL;
        }
 
        if (ev_p_og) {
                MEM(vb = fr_value_box_alloc(ctx, FR_TYPE_TIME_DELTA, NULL));
 
                /*
                 *      Return how long before the previous
                 *      cancel event would have fired.
                 *
                 *      This can be useful for doing stacked
                 *      cancellations in policy.
                 */
                vb->vb_time_delta = fr_time_sub(when, unlang_interpret_event_list(request)->tl->time());
                fr_dcursor_insert(out, vb);
        }
 
        /*
         *      No value if this is the first cleanup event
         */
        return XLAT_ACTION_DONE;
}
 
static xlat_arg_parser_t const unlang_interpret_xlat_args[] = {
        { .required = true, .single = true, .type = FR_TYPE_STRING },
        XLAT_ARG_PARSER_TERMINATOR
};
 
/** Get information about the interpreter state
 *
 * @ingroup xlat_functions
 */
static xlat_action_t unlang_interpret_xlat(TALLOC_CTX *ctx, fr_dcursor_t *out,
                                           UNUSED xlat_ctx_t const *xctx,
                                           request_t *request, fr_value_box_list_t *in)
{
        unlang_stack_t          *stack = request->stack;
        int                     depth = stack->depth;
        unlang_stack_frame_t    *frame;
        unlang_t const          *instruction;
        fr_value_box_t          *arg = fr_value_box_list_head(in);
        char const              *fmt = arg->vb_strvalue;
        fr_value_box_t          *vb;
 
        MEM(vb = fr_value_box_alloc_null(ctx));
 
        /*
         *      Find the correct stack frame.
         */
        while (*fmt == '.') {
                if (depth <= 1) {
                        if (fr_value_box_bstrndup(vb, vb, NULL, "<underflow>", 11, false) < 0) {
                        error:
                                talloc_free(vb);
                                return XLAT_ACTION_FAIL;
                        }
                        goto finish;
                }
 
                fmt++;
                depth--;
        }
 
        /*
         *      Get the current instruction.
         */
        frame = &stack->frame[depth];
        instruction = frame->instruction;
 
        /*
         *      Nothing there...
         */
        if (!instruction) {
                talloc_free(vb);
                return XLAT_ACTION_DONE;
        }
 
        /*
         *      How deep the current stack is.
         */
        if (strcmp(fmt, "depth") == 0) {
                fr_value_box_int32(vb, NULL, depth, false);
                goto finish;
        }
 
        /*
         *      The current module
         */
        if (strcmp(fmt, "module") == 0) {
                if (fr_value_box_strdup(vb, vb, NULL, request->module, false) < 0) goto error;
 
                goto finish;
        }
 
        /*
         *      Name of the instruction.
         */
        if (strcmp(fmt, "name") == 0) {
                if (fr_value_box_bstrndup(vb, vb, NULL, instruction->name,
                                          strlen(instruction->name), false) < 0) goto error;
                goto finish;
        }
 
        /*
         *      The request processing stage.
         */
        if (strcmp(fmt, "processing_stage") == 0) {
                if (fr_value_box_strdup(vb, vb, NULL, request->component, false) < 0) goto error;
 
                goto finish;
        }
 
        /*
         *      The current return code.
         */
        if (strcmp(fmt, "rcode") == 0) {
                if (fr_value_box_strdup(vb, vb, NULL, fr_table_str_by_value(rcode_table, request->rcode, "<INVALID>"), false) < 0) goto error;
 
                goto finish;
        }
 
        /*
         *      The virtual server handling the request
         */
        if (strcmp(fmt, "server") == 0) {
                if (!unlang_call_current(request)) goto finish;
 
                if (fr_value_box_strdup(vb, vb, NULL, cf_section_name2(unlang_call_current(request)), false) < 0) goto error;
 
                goto finish;
        }
 
        /*
         *      Unlang instruction type.
         */
        if (strcmp(fmt, "type") == 0) {
                if (fr_value_box_bstrndup(vb, vb, NULL, unlang_ops[instruction->type].name,
                                          strlen(unlang_ops[instruction->type].name), false) < 0) goto error;
 
                goto finish;
        }
 
        /*
         *      All of the remaining things need a CONF_ITEM.
         */
        if (!instruction->ci) {
                if (fr_value_box_bstrndup(vb, vb, NULL, "<INVALID>", 3, false) < 0) goto error;
 
                goto finish;
        }
 
        /*
         *      Line number of the current section.
         */
        if (strcmp(fmt, "line") == 0) {
                fr_value_box_int32(vb, NULL, cf_lineno(instruction->ci), false);
 
                goto finish;
        }
 
        /*
         *      Filename of the current section.
         */
        if (strcmp(fmt, "filename") == 0) {
                if (fr_value_box_strdup(vb, vb, NULL, cf_filename(instruction->ci), false) < 0) goto error;
 
                goto finish;
        }
 
finish:
        if (vb->type != FR_TYPE_NULL) {
                fr_dcursor_append(out, vb);
        } else {
                talloc_free(vb);
        }
 
        return XLAT_ACTION_DONE;
}
 
/** Initialize a unlang compiler / interpret.
 *
 * @param[in] ctx       to bind lifetime of the interpret to.
 *                      Shouldn't be any free order issues here as
 *                      the interpret itself has no state.
 *                      But event loop should be stopped before
 *                      freeing the interpret.
 * @param[in] el        for any timer or I/O events.
 * @param[in] funcs     Callbacks to used to communicate request
 *                      state to our owner.
 * @param[in] uctx      Data to pass to callbacks.
 */
unlang_interpret_t *unlang_interpret_init(TALLOC_CTX *ctx,
                                          fr_event_list_t *el, unlang_request_func_t *funcs, void *uctx)
{
        unlang_interpret_t *intp;
 
        fr_assert(funcs->init_internal);
 
        fr_assert(funcs->done_internal);
        fr_assert(funcs->done_detached);
        fr_assert(funcs->done_external);
 
        fr_assert(funcs->detach);
        fr_assert(funcs->yield);
        fr_assert(funcs->resume);
        fr_assert(funcs->mark_runnable);
        fr_assert(funcs->scheduled);
 
        MEM(intp = talloc(ctx, unlang_interpret_t));
        *intp = (unlang_interpret_t){
                .el = el,
                .funcs = *funcs,
                .uctx = uctx
        };
 
        return intp;
}
 
/** Discard the bottom most frame on the request's stack
 *
 * This is used for cleaning up after errors. i.e. the caller
 * uses a push function, and experiences an error and needs to
 * remove the frame that was just pushed.
 */
void unlang_interpet_frame_discard(request_t *request)
{
        frame_pop(request, request->stack);
}
 
/** Set a specific interpreter for a request
 *
 */
void unlang_interpret_set(request_t *request, unlang_interpret_t *intp)
{
        unlang_stack_t  *stack = request->stack;
        stack->intp = intp;
}
 
/** Get the interpreter set for a request
 *
 */
unlang_interpret_t *unlang_interpret_get(request_t *request)
{
        unlang_stack_t  *stack = request->stack;
 
        return stack->intp;
}
 
/** Get the event list for the current interpreter
 *
 */
fr_event_list_t *unlang_interpret_event_list(request_t *request)
{
        unlang_stack_t  *stack = request->stack;
 
        if (!stack->intp) return NULL;
 
        return stack->intp->el;
}
 
/** Set the default interpreter for this thread
 *
 */
void unlang_interpret_set_thread_default(unlang_interpret_t *intp)
{
        if (intp) (void)talloc_get_type_abort(intp, unlang_interpret_t);
 
        intp_thread_default = intp;
}
 
/** Get the default interpreter for this thread
 *
 * This allows detached requests to be executed asynchronously
 */
unlang_interpret_t *unlang_interpret_get_thread_default(void)
{
        if (!intp_thread_default) return NULL;
 
        return talloc_get_type_abort(intp_thread_default, unlang_interpret_t);
}
 
int unlang_interpret_init_global(TALLOC_CTX *ctx)
{
        xlat_t  *xlat;
        /*
         *  Should be void, but someone decided not to register multiple xlats
         *  breaking the convention we use everywhere else in the server...
         */
        if (unlikely((xlat = xlat_func_register(ctx, "interpreter", unlang_interpret_xlat, FR_TYPE_VOID)) == NULL)) return -1;
        xlat_func_args_set(xlat, unlang_interpret_xlat_args);
 
        if (unlikely((xlat = xlat_func_register(ctx, "cancel", unlang_cancel_xlat, FR_TYPE_VOID)) == NULL)) return -1;
        xlat_func_args_set(xlat, unlang_cancel_xlat_args);
 
        return 0;
}