load_balance.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: edef045877585838f2d2a214e9382de77f25a457 $
 *
 * @file unlang/load_balance.c
 * @brief Implementation of the unlang "load-balance" keyword.
 *
 * @copyright 2006-2019 The FreeRADIUS server project
 */
#include <freeradius-devel/util/hash.h>
#include <freeradius-devel/util/rand.h>
 
#include "load_balance_priv.h"
#include "module_priv.h"
 
#define unlang_redundant_load_balance unlang_load_balance
 
static unlang_action_t unlang_load_balance_next(rlm_rcode_t *p_result, request_t *request,
                                                unlang_stack_frame_t *frame)
{
        unlang_frame_state_redundant_t  *redundant = talloc_get_type_abort(frame->state, unlang_frame_state_redundant_t);
        unlang_group_t                  *g = unlang_generic_to_group(frame->instruction);
 
#ifdef STATIC_ANALYZER
        if (!redundant->found) {
                *p_result = RLM_MODULE_FAIL;
                return UNLANG_ACTION_CALCULATE_RESULT;
        }
#endif
        /*
         *      Set up the first round versus subsequent ones.
         */
        if (!redundant->child) {
                redundant->child = redundant->found;
 
        } else {
                /*
                 *      child is NULL on the first pass.  But if it's
                 *      back to the found one, then we're done.
                 */
                if (redundant->child == redundant->found) {
                        /* DON'T change p_result, as it is taken from the child */
                        return UNLANG_ACTION_CALCULATE_RESULT;
                }
 
                RDEBUG4("%s resuming", frame->instruction->debug_name);
 
                /*
                 *      We are in a resumed frame.  The module we
                 *      chose failed, so we have to go through the
                 *      process again.
                 */
 
                fr_assert(frame->instruction->type != UNLANG_TYPE_LOAD_BALANCE); /* this is never called again */
 
                /*
                 *      If the current child says "return", then do
                 *      so.
                 */
                if (redundant->child->actions.actions[*p_result] == MOD_ACTION_RETURN) {
                        /* DON'T change p_result, as it is taken from the child */
                        return UNLANG_ACTION_CALCULATE_RESULT;
                }
        }
 
        /*
         *      Push the child, and yield for a later return.
         */
        if (unlang_interpret_push(request, redundant->child, frame->result, UNLANG_NEXT_STOP, UNLANG_SUB_FRAME) < 0) {
                *p_result = RLM_MODULE_FAIL;
                return UNLANG_ACTION_STOP_PROCESSING;
        }
 
        /*
         *      Now that we've pushed this child, make the next call
         *      use the next child, wrapping around to the beginning.
         *
         *      @todo - track the one we chose, and if it fails, do
         *      the load-balancing again, except this time skipping
         *      the failed module.  AND, keep track of multiple failed
         *      modules in the unlang_frame_state_redundant_t
         *      structure.
         */
        redundant->child = redundant->child->next;
        if (!redundant->child) redundant->child = g->children;
 
        repeatable_set(frame);
 
        return UNLANG_ACTION_PUSHED_CHILD;
}
 
static unlang_action_t unlang_load_balance(rlm_rcode_t *p_result, request_t *request, unlang_stack_frame_t *frame)
{
        unlang_frame_state_redundant_t  *redundant;
        unlang_group_t                  *g = unlang_generic_to_group(frame->instruction);
        unlang_load_balance_t           *gext = NULL;
 
        uint32_t count = 0;
 
        if (!g->num_children) {
                *p_result = RLM_MODULE_NOOP;
                return UNLANG_ACTION_CALCULATE_RESULT;
        }
 
        gext = unlang_group_to_load_balance(g);
 
        RDEBUG4("%s setting up", frame->instruction->debug_name);
 
        redundant = talloc_get_type_abort(frame->state,
                                          unlang_frame_state_redundant_t);
 
        if (gext && gext->vpt) {
                uint32_t hash, start;
                ssize_t slen;
                char const *p = NULL;
                char buffer[1024];
 
                /*
                 *      Integer data types let the admin
                 *      select which frame is being used.
                 */
                if (tmpl_is_attr(gext->vpt) &&
                    ((tmpl_attr_tail_da(gext->vpt)->type == FR_TYPE_UINT8) ||
                     (tmpl_attr_tail_da(gext->vpt)->type == FR_TYPE_UINT16) ||
                     (tmpl_attr_tail_da(gext->vpt)->type == FR_TYPE_UINT32) ||
                     (tmpl_attr_tail_da(gext->vpt)->type == FR_TYPE_UINT64))) {
                        fr_pair_t *vp;
 
                        slen = tmpl_find_vp(&vp, request, gext->vpt);
                        if (slen < 0) {
                                REDEBUG("Failed finding attribute %s", gext->vpt->name);
                                goto randomly_choose;
                        }
 
                        switch (tmpl_attr_tail_da(gext->vpt)->type) {
                        case FR_TYPE_UINT8:
                                start = ((uint32_t) vp->vp_uint8) % g->num_children;
                                break;
 
                        case FR_TYPE_UINT16:
                                start = ((uint32_t) vp->vp_uint16) % g->num_children;
                                break;
 
                        case FR_TYPE_UINT32:
                                start = vp->vp_uint32 % g->num_children;
                                break;
 
                        case FR_TYPE_UINT64:
                                start = (uint32_t) (vp->vp_uint64 % ((uint64_t) g->num_children));
                                break;
 
                        default:
                                goto randomly_choose;
                        }
 
                } else {
                        slen = tmpl_expand(&p, buffer, sizeof(buffer), request, gext->vpt, NULL, NULL);
                        if (slen < 0) {
                                REDEBUG("Failed expanding template");
                                goto randomly_choose;
                        }
 
                        hash = fr_hash(p, slen);
 
                        start = hash % g->num_children;
                }
 
                RDEBUG3("load-balance starting at child %d", (int) start);
 
                count = 0;
                for (redundant->child = redundant->found = g->children;
                     redundant->child != NULL;
                     redundant->child = redundant->child->next) {
                        count++;
                        if (count == start) {
                                redundant->found = redundant->child;
                                break;
                        }
                }
 
        } else {
        randomly_choose:
                count = 0;
 
                /*
                 *      Choose a child at random.
                 *
                 *      @todo - leverage the "power of 2", as per
                 *      lib/io/network.c.  This is good enough for
                 *      most purposes.  However, in order to do this,
                 *      we need to track active callers across
                 *      *either* multiple modules in one thread, *or*
                 *      across multiple threads.
                 *
                 *      We don't have thread-specific instance data
                 *      for this load-balance section.  So for now,
                 *      just pick a random child.
                 */
                for (redundant->child = redundant->found = g->children;
                     redundant->child != NULL;
                     redundant->child = redundant->child->next) {
                        count++;
 
                        if ((count * (fr_rand() & 0xffffff)) < (uint32_t) 0x1000000) {
                                redundant->found = redundant->child;
                        }
                }
        }
 
        /*
         *      Plain "load-balance".  Just do one child.
         */
        if (frame->instruction->type == UNLANG_TYPE_LOAD_BALANCE) {
                if (unlang_interpret_push(request, redundant->found,
                                          frame->result, UNLANG_NEXT_STOP, UNLANG_SUB_FRAME) < 0) {
                        *p_result = RLM_MODULE_FAIL;
                        return UNLANG_ACTION_STOP_PROCESSING;
                }
                return UNLANG_ACTION_PUSHED_CHILD;
        }
 
        /*
         *      "redundant" and "redundant-load-balance" starts at
         *      "found", but we need to indicate that we're at the
         *      first child.
         */
        redundant->child = NULL;
 
        frame->process = unlang_load_balance_next;
        return unlang_load_balance_next(p_result, request, frame);
}
 
void unlang_load_balance_init(void)
{
        unlang_register(UNLANG_TYPE_LOAD_BALANCE,
                           &(unlang_op_t){
                                .name = "load-balance group",
                                .interpret = unlang_load_balance,
                                .debug_braces = true,
                                .frame_state_size = sizeof(unlang_frame_state_redundant_t),
                                .frame_state_type = "unlang_frame_state_redundant_t",
                           });
 
        unlang_register(UNLANG_TYPE_REDUNDANT_LOAD_BALANCE,
                           &(unlang_op_t){
                                .name = "redundant-load-balance group",
                                .interpret = unlang_redundant_load_balance,
                                .debug_braces = true,
                                .frame_state_size = sizeof(unlang_frame_state_redundant_t),
                                .frame_state_type = "unlang_frame_state_redundant_t",
                           });
}