// SPDX-License-Identifier: MIT
/*
Copyright (c) 2007, 2008 by Juliusz Chroboczek
*/

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <sys/time.h>
#include <time.h>
#include <string.h>
#include <stdlib.h>

#include <zebra.h>
#include "if.h"

#include "babel_main.h"
#include "babeld.h"
#include "util.h"
#include "neighbour.h"
#include "resend.h"
#include "message.h"
#include "babel_interface.h"

struct timeval resend_time = {0, 0};
struct resend *to_resend = NULL;

static int
resend_match(struct resend *resend,
             int kind, const unsigned char *prefix, unsigned char plen)
{
    return (resend->kind == kind &&
            resend->plen == plen && memcmp(resend->prefix, prefix, 16) == 0);
}

/* This is called by neigh.c when a neighbour is flushed */

void
flush_resends(struct neighbour *neigh)
{
    /* Nothing for now */
}

static struct resend *
find_resend(int kind, const unsigned char *prefix, unsigned char plen,
             struct resend **previous_return)
{
    struct resend *current, *previous;

    previous = NULL;
    current = to_resend;
    while(current) {
        if(resend_match(current, kind, prefix, plen)) {
            if(previous_return)
                *previous_return = previous;
            return current;
        }
        previous = current;
        current = current->next;
    }

    return NULL;
}

struct resend *
find_request(const unsigned char *prefix, unsigned char plen,
             struct resend **previous_return)
{
    return find_resend(RESEND_REQUEST, prefix, plen, previous_return);
}

int
record_resend(int kind, const unsigned char *prefix, unsigned char plen,
              unsigned short seqno, const unsigned char *id,
              struct interface *ifp, int delay)
{
    struct resend *resend;
    unsigned int ifindex = ifp ? ifp->ifindex : 0;

    if((kind == RESEND_REQUEST &&
        input_filter(NULL, prefix, plen, NULL, ifindex) >= INFINITY) ||
       (kind == RESEND_UPDATE &&
        output_filter(NULL, prefix, plen, ifindex) >= INFINITY))
        return 0;

    if(delay >= 0xFFFF)
        delay = 0xFFFF;

    resend = find_resend(kind, prefix, plen, NULL);
    if(resend) {
        if(resend->delay && delay)
            resend->delay = MIN(resend->delay, delay);
        else if(delay)
            resend->delay = delay;
        resend->time = babel_now;
        resend->max = RESEND_MAX;
        if(id && memcmp(resend->id, id, 8) == 0 &&
           seqno_compare(resend->seqno, seqno) > 0) {
            return 0;
        }
        if(id)
            memcpy(resend->id, id, 8);
        else
            memset(resend->id, 0, 8);
        resend->seqno = seqno;
        if(resend->ifp != ifp)
            resend->ifp = NULL;
    } else {
        resend = malloc(sizeof(struct resend));
        if(resend == NULL)
            return -1;
        resend->kind = kind;
        resend->max = RESEND_MAX;
        resend->delay = delay;
        memcpy(resend->prefix, prefix, 16);
        resend->plen = plen;
        resend->seqno = seqno;
        if(id)
            memcpy(resend->id, id, 8);
        else
            memset(resend->id, 0, 8);
        resend->ifp = ifp;
        resend->time = babel_now;
        resend->next = to_resend;
        to_resend = resend;
    }

    if(resend->delay) {
        struct timeval timeout;
        timeval_add_msec(&timeout, &resend->time, resend->delay);
        timeval_min(&resend_time, &timeout);
    }
    return 1;
}

static int
resend_expired(struct resend *resend)
{
    switch(resend->kind) {
    case RESEND_REQUEST:
        return timeval_minus_msec(&babel_now, &resend->time) >= REQUEST_TIMEOUT;
    default:
        return resend->max <= 0;
    }
}

int
unsatisfied_request(const unsigned char *prefix, unsigned char plen,
                    unsigned short seqno, const unsigned char *id)
{
    struct resend *request;

    request = find_request(prefix, plen, NULL);
    if(request == NULL || resend_expired(request))
        return 0;

    if(memcmp(request->id, id, 8) != 0 ||
       seqno_compare(request->seqno, seqno) <= 0)
        return 1;

    return 0;
}

/* Determine whether a given request should be forwarded. */
int
request_redundant(struct interface *ifp,
                  const unsigned char *prefix, unsigned char plen,
                  unsigned short seqno, const unsigned char *id)
{
    struct resend *request;

    request = find_request(prefix, plen, NULL);
    if(request == NULL || resend_expired(request))
        return 0;

    if(memcmp(request->id, id, 8) == 0 &&
       seqno_compare(request->seqno, seqno) > 0)
        return 0;

    if(request->ifp != NULL && request->ifp != ifp)
        return 0;

    if(request->max > 0)
        /* Will be resent. */
        return 1;

    if(timeval_minus_msec(&babel_now, &request->time) <
       (ifp ? MIN(babel_get_if_nfo(ifp)->hello_interval, 1000) : 1000))
        /* Fairly recent. */
        return 1;

    return 0;
}

int
satisfy_request(const unsigned char *prefix, unsigned char plen,
                unsigned short seqno, const unsigned char *id,
                struct interface *ifp)
{
    struct resend *request, *previous;

    request = find_request(prefix, plen, &previous);
    if(request == NULL)
        return 0;

    if(ifp != NULL && request->ifp != ifp)
        return 0;

    if(memcmp(request->id, id, 8) != 0 ||
       seqno_compare(request->seqno, seqno) <= 0) {
        /* We cannot remove the request, as we may be walking the list right
           now.  Mark it as expired, so that expire_resend will remove it. */
        request->max = 0;
        request->time.tv_sec = 0;
        recompute_resend_time();
        return 1;
    }

    return 0;
}

void
expire_resend(void)
{
    struct resend *current, *previous;
    int recompute = 0;

    previous = NULL;
    current = to_resend;
    while(current) {
        if(resend_expired(current)) {
            if(previous == NULL) {
                to_resend = current->next;
                free(current);
                current = to_resend;
            } else {
                previous->next = current->next;
                free(current);
                current = previous->next;
            }
            recompute = 1;
        } else {
            previous = current;
            current = current->next;
        }
    }
    if(recompute)
        recompute_resend_time();
}

void
recompute_resend_time(void)
{
    struct resend *request;
    struct timeval resend = {0, 0};

    request = to_resend;
    while(request) {
        if(!resend_expired(request) && request->delay > 0 && request->max > 0) {
            struct timeval timeout;
            timeval_add_msec(&timeout, &request->time, request->delay);
            timeval_min(&resend, &timeout);
        }
        request = request->next;
    }

    resend_time = resend;
}

void
do_resend(void)
{
    struct resend *resend;

    resend = to_resend;
    while(resend) {
        if(!resend_expired(resend) && resend->delay > 0 && resend->max > 0) {
            struct timeval timeout;
            timeval_add_msec(&timeout, &resend->time, resend->delay);
            if(timeval_compare(&babel_now, &timeout) >= 0) {
                switch(resend->kind) {
                case RESEND_REQUEST:
                    send_multihop_request(resend->ifp,
                                          resend->prefix, resend->plen,
                                          resend->seqno, resend->id, 127);
                    break;
                case RESEND_UPDATE:
                    send_update(resend->ifp, 1,
                                resend->prefix, resend->plen);
                    break;
                default: abort();
                }
                resend->delay = MIN(0xFFFF, resend->delay * 2);
                resend->max--;
            }
        }
        resend = resend->next;
    }
    recompute_resend_time();
}