Source of dhcprelay.c - busybox

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/* vi: set sw=4 ts=4: */
/* Port to Busybox Copyright (C) 2006 Jesse Dutton <jessedutton@gmail.com>
 *
 * Licensed under GPL v2, see file LICENSE in this tarball for details.
 *
 * DHCP Relay for 'DHCPv4 Configuration of IPSec Tunnel Mode' support
 * Copyright (C) 2002 Mario Strasser <mast@gmx.net>,
 *                   Zuercher Hochschule Winterthur,
 *                   Netbeat AG
 * Upstream has GPL v2 or later
 */
​
#include "common.h"
#include "options.h"
​
#define SERVER_PORT      67
#define SELECT_TIMEOUT    5 /* select timeout in sec. */
#define MAX_LIFETIME   2*60 /* lifetime of an xid entry in sec. */
​
/* This list holds information about clients. The xid_* functions manipulate this list. */
struct xid_item {
    unsigned timestamp;
    int client;
    uint32_t xid;
    struct sockaddr_in ip;
    struct xid_item *next;
};
​
#define dhcprelay_xid_list (*(struct xid_item*)&bb_common_bufsiz1)
​
static struct xid_item *xid_add(uint32_t xid, struct sockaddr_in *ip, int client)
{
    struct xid_item *item;
​
    /* create new xid entry */
    item = xmalloc(sizeof(struct xid_item));
​
    /* add xid entry */
    item->ip = *ip;
    item->xid = xid;
    item->client = client;
    item->timestamp = monotonic_sec();
    item->next = dhcprelay_xid_list.next;
    dhcprelay_xid_list.next = item;
​
    return item;
}
​
static void xid_expire(void)
{
    struct xid_item *item = dhcprelay_xid_list.next;
    struct xid_item *last = &dhcprelay_xid_list;
    unsigned current_time = monotonic_sec();
​
    while (item != NULL) {
        if ((current_time - item->timestamp) > MAX_LIFETIME) {
            last->next = item->next;
            free(item);
            item = last->next;
        } else {
            last = item;
            item = item->next;
        }
    }
}
​
static struct xid_item *xid_find(uint32_t xid)
{
    struct xid_item *item = dhcprelay_xid_list.next;
    while (item != NULL) {
        if (item->xid == xid) {
            return item;
        }
        item = item->next;
    }
    return NULL;
}
​
static void xid_del(uint32_t xid)
{
    struct xid_item *item = dhcprelay_xid_list.next;
    struct xid_item *last = &dhcprelay_xid_list;
    while (item != NULL) {
        if (item->xid == xid) {
            last->next = item->next;
            free(item);
            item = last->next;
        } else {
            last = item;
            item = item->next;
        }
    }