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深入剖析ARP协议源码：揭秘网络通信的底层奥秘

2025-01-11 23:28:59

随着信息技术的飞速发展，网络通信已经成为我们日常生活中不可或缺的一部分。而ARP（Address Resolution Protocol，地址解析协议）作为网络通信中的一项基础协议，负责将IP地址解析为物理地址，确保数据包能够在网络中正确传输。本文将深入剖析ARP协议的源码，带您领略网络通信的底层奥秘。

一、ARP协议概述

ARP协议是一种在网络层中实现IP地址到物理地址映射的协议。在以太网、令牌环等局域网中，每个设备都有一个唯一的物理地址（如MAC地址），而IP地址则是网络层的逻辑地址。当一台设备需要与另一台设备通信时，需要通过ARP协议查询目标设备的物理地址，从而实现数据包的发送。

ARP协议的工作过程如下：

1.发送方设备向网络中广播一个ARP请求包，请求包中包含发送方的IP地址和物理地址，以及目标设备的IP地址。

2.网络中的设备接收到ARP请求包后，会检查请求包中的目标IP地址是否与自己的IP地址相同。如果相同，则表示该设备就是目标设备，它会将自己的物理地址封装在ARP响应包中发送给发送方。

3.发送方设备接收到ARP响应包后，会更新自己的ARP缓存，将目标设备的IP地址和物理地址关联起来。

二、ARP协议源码分析

下面以Linux内核中的ARP协议源码为例，分析ARP协议的实现原理。

1.ARP请求与响应

c struct arpreq { struct sockaddr *arp_pa; // 目标IP地址 struct sockaddr *arp_ha; // 目标物理地址 struct sockaddr *arp_pa_src; // 发送方IP地址 struct sockaddr *arp_ha_src; // 发送方物理地址 unsigned int arp_flags; // ARP请求/响应标志 unsigned int arp_op; // ARP操作码 unsigned char arp_data[14]; // ARP数据 };

在ARP请求与响应中，arpreq结构体包含了目标IP地址、目标物理地址、发送方IP地址、发送方物理地址、ARP请求/响应标志和ARP操作码等信息。

2.ARP请求发送

`c static void arp_send(struct arpreq arp) { struct sockaddr src; struct sockaddr dst; struct ethhdr eh; unsigned char pa; unsigned char ha; struct packet_type pt; struct sk_buff skb;

// 获取发送方和目标地址
src = arp->arp_pa_src;
dst = arp->arp_ha_src;
// 创建数据包
skb = alloc_skb(sizeof(struct ethhdr) + ETH_ALEN + ETH_ALEN + 8, GFP_KERNEL);
if (!skb)
    return;
// 设置以太网头部信息
eh = (struct ethhdr *)skb_push(skb, ETH_HLEN);
eh->h_dest = dst->sa_data;
eh->h_source = src->sa_data;
eh->h_proto = htons(ETH_P_ARP);
// 设置ARP头部信息
pa = eh->h_dest + ETH_ALEN;
ha = eh->h_source + ETH_ALEN;
memcpy(pa, src->sa_data, ETH_ALEN);
memcpy(ha, dst->sa_data, ETH_ALEN);
memcpy(pa + ETH_ALEN, arp->arp_ha, ETH_ALEN);
memcpy(ha + ETH_ALEN, arp->arp_pa, ETH_ALEN);
eh->h_proto = htons(ETH_P_ARP);
eh->h_type = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->h_proto = htons(ARPHRD_ETHER);
eh->h_len = ETH_ALEN;
eh->
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