Linux编程之PING实现
<p>PING（Packet InterNet Groper）中文名为因特网包探索器，是用来查看网络上另一个主机系统的网络连接是否正常的一个工具。ping命令的工作原理是：向网络上的另一个主机系统发送ICMP报文，如果指定系统得到了报文，它将把回复报文传回给发送者，这有点象潜水艇声纳系统中使用的发声装置。所以，我们想知道我这台主机能不能和另一台进行通信，我们首先需要确认的是我们两台主机间的网络是不是通的，也就是我说的话能不能传到你那里，这是双方进行通信的前提。在Linux下使用指令ping的方法和现象如下：</p>
<p>
<img title="Linux编程之PING实现" alt="Linux编程之PING实现" src="https://zhuji.jb51.net/uploads/img/202305/321dd57e8a9b30b12c074792d43308ca.jpg"></p>
<p>
PING的实现看起来并不复杂，我想自己写代码实现这个功能，需要些什么知识储备？我简单罗列了一下：</p>
<p>
·ICMP协议的理解</p>
<p>
·RAW套接字</p>
<p>
·网络封包和解包技能</p>
<p>
搭建这么一个ping程序的步骤如下：</p>
<p>
1、ICMP包的封装和解封</p>
<p>
2、创建一个线程用于ICMP包的发送</p>
<p>
3、创建一个线程用于ICMP包的接收</p>
<p>
4、原始套接字编程</p>
<p>
PING的流程如下：</p>
<p>
<img title="Linux编程之PING实现" alt="Linux编程之PING实现" src="https://zhuji.jb51.net/uploads/img/202305/2b4c8c7ce0552cbbfff8b585870a5ecd.jpg"></p>
<p>
<strong>一、ICMP包的封装和解封</strong></p>
<p>
（1） ICMP协议理解要进行PING的开发，我们首先需要知道PING的实现是基于ICMP协议来开发的。要进行ICMP包的封装和解封，我们首先需要理解ICMP协议。ICMP位于网络层，允许主机或者路由器报告差错情况和提供有关异常情况的报告。ICMP报文是封装在IP数据报中，作为其中的数据部分。ICMP报文作为IP层数据报的数据，加上数据报头，组成IP数据报发送出去。ICMP报文格式如下：</p>
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<img title="Linux编程之PING实现" alt="Linux编程之PING实现" src="https://zhuji.jb51.net/uploads/img/202305/d628d7c63b8a9c6eff8fd605ca757e36.jpg"></p>
<p>
ICMP报文的种类有两种，即ICMP差错报告报文和ICMP询问报文。PING程序使用的ICMP报文种类为ICMP询问报文。注意一下上面说到的ICMP报文格式中的“类型”字段，我们在组包的时候可以向该字段填写不同的值来标定该ICMP报文的类型。下面列出的是几种常用的ICMP报文类型。</p>
<p>
<img title="Linux编程之PING实现" alt="Linux编程之PING实现" src="https://zhuji.jb51.net/uploads/img/202305/0a87dfd32ca77cedfceab56dedb94477.jpg"></p>
<p>
我们的PING程序需要用到的ICMP的类型是回送请求（8）。<br>
因为ICMP报文的具体格式会因为ICMP报文的类型而各不相同，我们ping包的格式是这样的：</p>
<p>
<img title="Linux编程之PING实现" alt="Linux编程之PING实现" src="https://zhuji.jb51.net/uploads/img/202305/49258b869ff923df3d81f2e48dfedc09.jpg"></p>
<p>
（2） ICMP包的组装</p>
<p>
对照上面的ping包格式，我们封装ping包的代码可以这么写：</p>
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<code class="java keyword">void</code> <code class="java plain">icmp_pack(struct icmp* icmphdr, </code><code class="java keyword">int</code> <code class="java plain">seq, </code><code class="java keyword">int</code> <code class="java plain">length)</code>
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<code class="java spaces"> </code><code class="java keyword">int</code> <code class="java plain">i = </code><code class="java value">0</code><code class="java plain">;</code>
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<code class="java spaces"> </code><code class="java plain">icmphdr->icmp_type = ICMP_ECHO; </code><code class="java comments">//类型填回送请求</code>
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<code class="java spaces"> </code><code class="java plain">icmphdr->icmp_code = </code><code class="java value">0</code><code class="java plain">; </code>
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<code class="java spaces"> </code><code class="java plain">icmphdr->icmp_cksum = </code><code class="java value">0</code><code class="java plain">; </code><code class="java comments">//注意，这里先填写0，很重要！</code>
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<code class="java spaces"> </code><code class="java plain">icmphdr->icmp_seq = seq; </code><code class="java comments">//这里的序列号我们填1,2,3,4....</code>
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<code class="java spaces"> </code><code class="java plain">icmphdr->icmp_id = pid & </code><code class="java value">0xffff</code><code class="java plain">; </code><code class="java comments">//我们使用pid作为icmp_id,icmp_id只是2字节，而pid有4字节</code>
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<code class="java spaces"> </code><code class="java keyword">for</code><code class="java plain">(i=</code><code class="java value">0</code><code class="java plain">;i<length;i++)</code>
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<code class="java spaces"> </code><code class="java plain">icmphdr->icmp_data = i; </code><code class="java comments">//填充数据段，使ICMP报文大于64B</code>
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<code class="java spaces"> </code><code class="java plain">icmphdr->icmp_cksum = cal_chksum((unsigned </code><code class="java keyword">short</code><code class="java plain">*)icmphdr, length); </code><code class="java comments">//校验和计算</code>
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<p>
这里再三提醒一下，<span>icmp_cksum 必须先填写为0</span>再执行校验和算法计算，否则ping时对方主机会因为校验和计算错误而丢弃请求包，导致ping的失败。我一个同事曾经就因为这么一个错误而排查许久，血的教训请铭记。</p>
<p>
这里简单介绍一下checksum（校验和）。</p>
<p>
计算机网络通信时，为了检验在数据传输过程中数据是否发生了错误，通常在传输数据的时候连同校验和一块传输，当接收端接受数据时候会从新计算校验和，如果与原校验和不同就视为出错，丢弃该数据包，并返回icmp报文。</p>
<p>
<strong>算法基本思路：</strong></p>
<p>
IP/ICMP/IGMP/TCP/UDP等协议的校验和算法都是相同的，采用的都是将数据流视为16位整数流进行重复叠加计算。为了计算检验和，首先把检验和字段置为0。然后，对有效数据范围内中每个16位进行二进制反码求和，结果存在检验和字段中，如果数据长度为奇数则补一字节0。当收到数据后，同样对有效数据范围中每个16位数进行二进制反码的求和。由于接收方在计算过程中包含了发送方存在首部中的检验和，因此，如果首部在传输过程中没有发生任何差错，那么接收方计算的结果应该为全0或全1(具体看实现了,本质一样) 。如果结果不是全0或全1，那么表示数据错误。</p>
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<code class="java comments">/*校验和算法*/</code>
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<code class="java plain">unsigned </code><code class="java keyword">short</code> <code class="java plain">cal_chksum(unsigned </code><code class="java keyword">short</code> <code class="java plain">*addr,</code><code class="java keyword">int</code> <code class="java plain">len)</code>
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<code class="java plain">{ </code><code class="java keyword">int</code> <code class="java plain">nleft=len;</code>
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<code class="java spaces"> </code><code class="java keyword">int</code> <code class="java plain">sum=</code><code class="java value">0</code><code class="java plain">;</code>
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<code class="java spaces"> </code><code class="java plain">unsigned </code><code class="java keyword">short</code> <code class="java plain">*w=addr;</code>
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<code class="java spaces"> </code><code class="java plain">unsigned </code><code class="java keyword">short</code> <code class="java plain">answer=</code><code class="java value">0</code><code class="java plain">;</code>
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<code class="java spaces"> </code><code class="java comments">/*把ICMP报头二进制数据以2字节为单位累加起来*/</code>
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<code class="java spaces"> </code><code class="java keyword">while</code><code class="java plain">(nleft></code><code class="java value">1</code><code class="java plain">)</code>
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<code class="java spaces"> </code><code class="java plain">nleft-=</code><code class="java value">2</code><code class="java plain">;</code>
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<code class="java spaces"> </code><code class="java comments">/*若ICMP报头为奇数个字节，会剩下最后一字节。把最后一个字节视为一个2字节数据的高字节，这个2字节数据的低字节为0，继续累加*/</code>
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<code class="java spaces"> </code><code class="java plain">*(unsigned </code><code class="java keyword">char</code> <code class="java plain">*)(&answer)=*(unsigned </code><code class="java keyword">char</code> <code class="java plain">*)w;</code>
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<code class="java spaces"> </code><code class="java plain">sum+=answer;</code>
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<code class="java spaces"> </code><code class="java plain">sum=(sum>></code><code class="java value">16</code><code class="java plain">)+(sum&</code><code class="java value">0xffff</code><code class="java plain">);</code>
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<code class="java spaces"> </code><code class="java plain">sum+=(sum>></code><code class="java value">16</code><code class="java plain">);</code>
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<code class="java spaces"> </code><code class="java plain">answer=~sum;</code>
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<p>
（3） ICMP包的解包</p>
<p>
知道怎么封装包，那解包就也不难了，注意的是，收到一个ICMP包，我们不要就认为这个包就是我们发出去的ICMP回送回答包，我们需要加一层代码来判断该ICMP报文的id和seq字段是否符合我们发送的ICMP报文的设置，来验证ICMP回复包的正确性。</p>
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<code class="java keyword">int</code> <code class="java plain">icmp_unpack(</code><code class="java keyword">char</code><code class="java plain">* buf, </code><code class="java keyword">int</code> <code class="java plain">len)</code>
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<code class="java spaces"> </code><code class="java keyword">int</code> <code class="java plain">iphdr_len;</code>
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<code class="java spaces"> </code><code class="java plain">struct timeval begin_time, recv_time, offset_time;</code>
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<code class="java spaces"> </code><code class="java keyword">int</code> <code class="java plain">rtt; </code><code class="java comments">//round trip time</code>
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<code class="java spaces"> </code><code class="java plain">struct ip* ip_hdr = (struct ip *)buf;</code>
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<code class="java spaces"> </code><code class="java plain">iphdr_len = ip_hdr->ip_hl*</code><code class="java value">4</code><code class="java plain">;</code>
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<code class="java spaces"> </code><code class="java plain">struct icmp* icmp = (struct icmp*)(buf+iphdr_len); </code><code class="java comments">//使指针跳过IP头指向ICMP头</code>
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<code class="java spaces"> </code><code class="java plain">len-=iphdr_len; </code><code class="java comments">//icmp包长度</code>
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<code class="java spaces"> </code><code class="java keyword">if</code><code class="java plain">(len < </code><code class="java value">8</code><code class="java plain">) </code><code class="java comments">//判断长度是否为ICMP包长度</code>
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<code class="java spaces"> </code><code class="java plain">{</code>
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<code class="java spaces"> </code><code class="java plain">fprintf(stderr, </code><code class="java string">"Invalid icmp packet.Its length is less than 8\n"</code><code class="java plain">);</code>
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<code class="java spaces"> </code><code class="java keyword">return</code> <code class="java plain">-</code><code class="java value">1</code><code class="java plain">;</code>
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<code class="java spaces"> </code><code class="java comments">//判断该包是ICMP回送回答包且该包是我们发出去的</code>
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<code class="java spaces"> </code><code class="java keyword">if</code><code class="java plain">((icmp->icmp_type == ICMP_ECHOREPLY) && (icmp->icmp_id == pid)) </code>
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<code class="java spaces"> </code><code class="java plain">{</code>
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<code class="java spaces"> </code><code class="java keyword">if</code><code class="java plain">((icmp->icmp_seq < </code><code class="java value">0</code><code class="java plain">) || (icmp->icmp_seq > PACKET_SEND_MAX_NUM))</code>
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<code class="java spaces"> </code><code class="java plain">{</code>
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<div class="line number22 index21 alt1">
<code class="java spaces"> </code><code class="java plain">fprintf(stderr, </code><code class="java string">"icmp packet seq is out of range!\n"</code><code class="java plain">);</code>
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<code class="java spaces"> </code><code class="java keyword">return</code> <code class="java plain">-</code><code class="java value">1</code><code class="java plain">;</code>
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<code class="java spaces"> </code><code class="java plain">}</code>
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<code class="java spaces"> </code><code class="java plain">ping_packet.flag = </code><code class="java value">0</code><code class="java plain">;</code>
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<div class="line number27 index26 alt2">
<code class="java spaces"> </code><code class="java plain">begin_time = ping_packet.begin_time; </code><code class="java comments">//去除该包的发出时间</code>
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<div class="line number28 index27 alt1">
<code class="java spaces"> </code><code class="java plain">gettimeofday(&recv_time, NULL);</code>
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<div class="line number29 index28 alt2">
</div>
<div class="line number30 index29 alt1">
<code class="java spaces"> </code><code class="java plain">offset_time = cal_time_offset(begin_time, recv_time);</code>
</div>
<div class="line number31 index30 alt2">
<code class="java spaces"> </code><code class="java plain">rtt = offset_time.tv_sec*</code><code class="java value">1000</code> <code class="java plain">+ offset_time.tv_usec/</code><code class="java value">1000</code><code class="java plain">; </code><code class="java comments">//毫秒为单位</code>
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<div class="line number32 index31 alt1">
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<code class="java spaces"> </code><code class="java plain">printf(</code><code class="java string">"%d byte from %s: icmp_seq=%u ttl=%d rtt=%d ms\n"</code><code class="java plain">,</code>
</div>
<div class="line number34 index33 alt1">
<code class="java spaces"> </code><code class="java plain">len, inet_ntoa(ip_hdr->ip_src), icmp->icmp_seq, ip_hdr->ip_ttl, rtt); </code>
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<code class="java spaces"> </code><code class="java plain">}</code>
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<code class="java spaces"> </code><code class="java keyword">else</code>
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<code class="java spaces"> </code><code class="java plain">{</code>
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<div class="line number39 index38 alt2">
<code class="java spaces"> </code><code class="java plain">fprintf(stderr, </code><code class="java string">"Invalid ICMP packet! Its id is not matched!\n"</code><code class="java plain">);</code>
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<div class="line number40 index39 alt1">
<code class="java spaces"> </code><code class="java keyword">return</code> <code class="java plain">-</code><code class="java value">1</code><code class="java plain">;</code>
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<div class="line number41 index40 alt2">
<code class="java spaces"> </code><code class="java plain">}</code>
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<code class="java spaces"> </code><code class="java keyword">return</code> <code class="java value">0</code><code class="java plain">;</code>
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<code class="java plain">}</code>
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<textarea></textarea>
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<p>
<strong>二、发包线程的搭建</strong></p>
<p>
根据PING程序的框架，我们需要建立一个线程用于ping包的发送，我的想法是这样的：使用sendto进行发包，发包速率我们维持在1秒1发，我们需要用一个全局变量记录第一个ping包发出的时间，除此之外，我们还需要一个全局变量来记录我们发出的ping包到底有几个，这两个变量用于后来收到ping包回复后的数据计算。</p>
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<code class="java keyword">void</code> <code class="java plain">ping_send()</code>
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<div class="line number2 index1 alt1">
<code class="java plain">{</code>
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<div class="line number3 index2 alt2">
<code class="java spaces"> </code><code class="java keyword">char</code> <code class="java plain">send_buf[</code><code class="java value">128</code><code class="java plain">];</code>
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<div class="line number4 index3 alt1">
<code class="java spaces"> </code><code class="java plain">memset(send_buf, </code><code class="java value">0</code><code class="java plain">, sizeof(send_buf));</code>
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<code class="java spaces"> </code><code class="java plain">gettimeofday(&start_time, NULL); </code><code class="java comments">//记录第一个ping包发出的时间</code>
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<div class="line number6 index5 alt1">
<code class="java spaces"> </code><code class="java keyword">while</code><code class="java plain">(alive)</code>
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<code class="java spaces"> </code><code class="java plain">{</code>
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<code class="java spaces"> </code><code class="java keyword">int</code> <code class="java plain">size = </code><code class="java value">0</code><code class="java plain">;</code>
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<div class="line number9 index8 alt2">
<code class="java spaces"> </code><code class="java plain">gettimeofday(&(ping_packet.begin_time), NULL);</code>
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<div class="line number10 index9 alt1">
<code class="java spaces"> </code><code class="java plain">ping_packet.flag = </code><code class="java value">1</code><code class="java plain">; </code><code class="java comments">//将该标记为设置为该包已发送</code>
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<div class="line number11 index10 alt2">
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<div class="line number12 index11 alt1">
<code class="java spaces"> </code><code class="java plain">icmp_pack((struct icmp*)send_buf, send_count, </code><code class="java value">64</code><code class="java plain">); </code><code class="java comments">//封装icmp包</code>
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<div class="line number13 index12 alt2">
<code class="java spaces"> </code><code class="java plain">size = sendto(rawsock, send_buf, </code><code class="java value">64</code><code class="java plain">, </code><code class="java value">0</code><code class="java plain">, (struct sockaddr*)&dest, sizeof(dest));</code>
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<div class="line number14 index13 alt1">
<code class="java spaces"> </code><code class="java plain">send_count++; </code><code class="java comments">//记录发出ping包的数量</code>
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<div class="line number15 index14 alt2">
<code class="java spaces"> </code><code class="java keyword">if</code><code class="java plain">(size < </code><code class="java value">0</code><code class="java plain">)</code>
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<div class="line number16 index15 alt1">
<code class="java spaces"> </code><code class="java plain">{</code>
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<div class="line number17 index16 alt2">
<code class="java spaces"> </code><code class="java plain">fprintf(stderr, </code><code class="java string">"send icmp packet fail!\n"</code><code class="java plain">);</code>
</div>
<div class="line number18 index17 alt1">
<code class="java spaces"> </code><code class="java keyword">continue</code><code class="java plain">;</code>
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<code class="java spaces"> </code><code class="java plain">}</code>
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<div class="line number21 index20 alt2">
<code class="java spaces"> </code><code class="java plain">sleep(</code><code class="java value">1</code><code class="java plain">);</code>
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<div class="line number22 index21 alt1">
<code class="java spaces"> </code><code class="java plain">}</code>
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<div class="line number23 index22 alt2">
<code class="java plain">}</code>
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<p>
<strong>三、收包线程的搭建</strong><br>
我们同样建立一个接收包的线程，这里我们采用select函数进行收包，并为select函数设置超时时间为200us，若发生超时，则进行下一个循环。同样地，我们也需要一个全局变量来记录成功接收到的ping回复包的数量。</p>
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<code class="java keyword">void</code> <code class="java plain">ping_recv()</code>
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<div class="line number2 index1 alt1">
<code class="java plain">{</code>
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<code class="java spaces"> </code><code class="java plain">struct timeval tv;</code>
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<div class="line number4 index3 alt1">
<code class="java spaces"> </code><code class="java plain">tv.tv_usec = </code><code class="java value">200</code><code class="java plain">; </code><code class="java comments">//设置select函数的超时时间为200us</code>
</div>
<div class="line number5 index4 alt2">
<code class="java spaces"> </code><code class="java plain">tv.tv_sec = </code><code class="java value">0</code><code class="java plain">;</code>
</div>
<div class="line number6 index5 alt1">
<code class="java spaces"> </code><code class="java plain">fd_set read_fd;</code>
</div>
<div class="line number7 index6 alt2">
<code class="java spaces"> </code><code class="java keyword">char</code> <code class="java plain">recv_buf[</code><code class="java value">512</code><code class="java plain">];</code>
</div>
<div class="line number8 index7 alt1">
<code class="java spaces"> </code><code class="java plain">memset(recv_buf, </code><code class="java value">0</code> <code class="java plain">,sizeof(recv_buf));</code>
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<div class="line number9 index8 alt2">
<code class="java spaces"> </code><code class="java keyword">while</code><code class="java plain">(alive)</code>
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<code class="java spaces"> </code><code class="java plain">{</code>
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<code class="java spaces"> </code><code class="java keyword">int</code> <code class="java plain">ret = </code><code class="java value">0</code><code class="java plain">;</code>
</div>
<div class="line number12 index11 alt1">
<code class="java spaces"> </code><code class="java plain">FD_ZERO(&read_fd);</code>
</div>
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<code class="java spaces"> </code><code class="java plain">FD_SET(rawsock, &read_fd);</code>
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<div class="line number14 index13 alt1">
<code class="java spaces"> </code><code class="java plain">ret = select(rawsock+</code><code class="java value">1</code><code class="java plain">, &read_fd, NULL, NULL, &tv);</code>
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<code class="java spaces"> </code><code class="java keyword">switch</code><code class="java plain">(ret)</code>
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<code class="java spaces"> </code><code class="java plain">{</code>
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<code class="java spaces"> </code><code class="java keyword">case</code> <code class="java plain">-</code><code class="java value">1</code><code class="java plain">:</code>
</div>
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<code class="java spaces"> </code><code class="java plain">fprintf(stderr,</code><code class="java string">"fail to select!\n"</code><code class="java plain">);</code>
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<code class="java spaces"> </code><code class="java keyword">break</code><code class="java plain">;</code>
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<code class="java spaces"> </code><code class="java keyword">case</code> <code class="java value">0</code><code class="java plain">:</code>
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<code class="java spaces"> </code><code class="java keyword">break</code><code class="java plain">;</code>
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<code class="java spaces"> </code><code class="java keyword">default</code><code class="java plain">:</code>
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<code class="java spaces"> </code><code class="java plain">{</code>
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<code class="java spaces"> </code><code class="java keyword">int</code> <code class="java plain">size = recv(rawsock, recv_buf, sizeof(recv_buf), </code><code class="java value">0</code><code class="java plain">);</code>
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<code class="java spaces"> </code><code class="java keyword">if</code><code class="java plain">(size < </code><code class="java value">0</code><code class="java plain">)</code>
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<code class="java spaces"> </code><code class="java plain">{</code>
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<code class="java spaces"> </code><code class="java plain">fprintf(stderr,</code><code class="java string">"recv data fail!\n"</code><code class="java plain">);</code>
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<code class="java spaces"> </code><code class="java keyword">continue</code><code class="java plain">;</code>
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<code class="java spaces"> </code><code class="java plain">}</code>
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<code class="java spaces"> </code><code class="java plain">ret = icmp_unpack(recv_buf, size); </code><code class="java comments">//对接收的包进行解封</code>
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<code class="java spaces"> </code><code class="java keyword">if</code><code class="java plain">(ret == -</code><code class="java value">1</code><code class="java plain">) </code><code class="java comments">//不是属于自己的icmp包，丢弃不处理</code>
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<code class="java spaces"> </code><code class="java plain">{</code>
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<code class="java spaces"> </code><code class="java keyword">continue</code><code class="java plain">;</code>
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<code class="java spaces"> </code><code class="java plain">}</code>
</div>
<div class="line number36 index35 alt1">
<code class="java spaces"> </code><code class="java plain">recv_count++; </code><code class="java comments">//接收包计数</code>
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<code class="java spaces"> </code><code class="java plain">}</code>
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<code class="java spaces"> </code><code class="java keyword">break</code><code class="java plain">;</code>
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<code class="java spaces"> </code><code class="java plain">}</code>
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<code class="java spaces"> </code><code class="java plain">}</code>
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<code class="java plain">}<strong></code>
</div>
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<code class="java plain"></strong></code>
</div>
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<p>
</p>
<p>
<strong>四、中断处理</strong></p>
<p>
我们规定了一次ping发送的包的最大值为64个，若超出该数值就停止发送。作为PING的使用者，我们一般只会发送若干个包，若有这几个包顺利返回，我们就crtl+c中断ping。这里的代码主要是为中断信号写一个中断处理函数，将alive这个全局变量设置为0，进而使发送ping包的循环停止而结束程序。</p>
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<code class="java keyword">void</code> <code class="java plain">icmp_sigint(</code><code class="java keyword">int</code> <code class="java plain">signo)</code>
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<code class="java plain">{</code>
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<code class="java spaces"> </code><code class="java plain">alive = </code><code class="java value">0</code><code class="java plain">;</code>
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<code class="java spaces"> </code><code class="java plain">gettimeofday(&end_time, NULL);</code>
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<code class="java spaces"> </code><code class="java plain">time_interval = cal_time_offset(start_time, end_time);</code>
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<code class="java plain">}</code>
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<code class="java plain">signal(SIGINT, icmp_sigint);</code>
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<p>
<strong>五、总体实现</strong></p>
<p>
各模块介绍完了，现在贴出完整代码。</p>
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</td>
<td class="code">
<div class="container">
<div class="line number1 index0 alt2">
<code class="cpp preprocessor">#include <stdio.h></code>
</div>
<div class="line number2 index1 alt1">
<code class="cpp preprocessor">#include <netinet/in.h></code>
</div>
<div class="line number3 index2 alt2">
<code class="cpp preprocessor">#include <netinet/ip.h></code>
</div>
<div class="line number4 index3 alt1">
<code class="cpp preprocessor">#include <netinet/ip_icmp.h></code>
</div>
<div class="line number5 index4 alt2">
<code class="cpp preprocessor">#include <unistd.h></code>
</div>
<div class="line number6 index5 alt1">
<code class="cpp preprocessor">#include <signal.h></code>
</div>
<div class="line number7 index6 alt2">
<code class="cpp preprocessor">#include <arpa/inet.h></code>
</div>
<div class="line number8 index7 alt1">
<code class="cpp preprocessor">#include <errno.h></code>
</div>
<div class="line number9 index8 alt2">
<code class="cpp preprocessor">#include <sys/time.h></code>
</div>
<div class="line number10 index9 alt1">
<code class="cpp preprocessor">#include <string.h></code>
</div>
<div class="line number11 index10 alt2">
<code class="cpp preprocessor">#include <netdb.h></code>
</div>
<div class="line number12 index11 alt1">
<code class="cpp preprocessor">#include <pthread.h></code>
</div>
<div class="line number13 index12 alt2">
</div>
<div class="line number14 index13 alt1">
</div>
<div class="line number15 index14 alt2">
<code class="cpp preprocessor">#define PACKET_SEND_MAX_NUM 64</code>
</div>
<div class="line number16 index15 alt1">
</div>
<div class="line number17 index16 alt2">
<code class="cpp keyword bold">typedef</code> <code class="cpp keyword bold">struct</code> <code class="cpp plain">ping_packet_status</code>
</div>
<div class="line number18 index17 alt1">
<code class="cpp plain">{</code>
</div>
<div class="line number19 index18 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">struct</code> <code class="cpp plain">timeval begin_time;</code>
</div>
<div class="line number20 index19 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">struct</code> <code class="cpp plain">timeval end_time;</code>
</div>
<div class="line number21 index20 alt2">
<code class="cpp spaces"> </code><code class="cpp color1 bold">int</code> <code class="cpp plain">flag; </code><code class="cpp comments">//发送标志,1为已发送</code>
</div>
<div class="line number22 index21 alt1">
<code class="cpp spaces"> </code><code class="cpp color1 bold">int</code> <code class="cpp plain">seq; </code><code class="cpp comments">//包的序列号</code>
</div>
<div class="line number23 index22 alt2">
<code class="cpp plain">}ping_packet_status;</code>
</div>
<div class="line number24 index23 alt1">
</div>
<div class="line number25 index24 alt2">
</div>
<div class="line number26 index25 alt1">
</div>
<div class="line number27 index26 alt2">
<code class="cpp plain">ping_packet_status ping_packet;</code>
</div>
<div class="line number28 index27 alt1">
</div>
<div class="line number29 index28 alt2">
<code class="cpp color1 bold">int</code> <code class="cpp plain">alive;</code>
</div>
<div class="line number30 index29 alt1">
<code class="cpp color1 bold">int</code> <code class="cpp plain">rawsock;</code>
</div>
<div class="line number31 index30 alt2">
<code class="cpp color1 bold">int</code> <code class="cpp plain">send_count;</code>
</div>
<div class="line number32 index31 alt1">
<code class="cpp color1 bold">int</code> <code class="cpp plain">recv_count;</code>
</div>
<div class="line number33 index32 alt2">
<code class="cpp plain">pid_t pid;</code>
</div>
<div class="line number34 index33 alt1">
<code class="cpp keyword bold">struct</code> <code class="cpp plain">sockaddr_in dest;</code>
</div>
<div class="line number35 index34 alt2">
<code class="cpp keyword bold">struct</code> <code class="cpp plain">timeval start_time;</code>
</div>
<div class="line number36 index35 alt1">
<code class="cpp keyword bold">struct</code> <code class="cpp plain">timeval end_time;</code>
</div>
<div class="line number37 index36 alt2">
<code class="cpp keyword bold">struct</code> <code class="cpp plain">timeval time_interval;</code>
</div>
<div class="line number38 index37 alt1">
</div>
<div class="line number39 index38 alt2">
<code class="cpp comments">/*校验和算法*/</code>
</div>
<div class="line number40 index39 alt1">
<code class="cpp plain">unsigned </code><code class="cpp color1 bold">short</code> <code class="cpp plain">cal_chksum(unsigned </code><code class="cpp color1 bold">short</code> <code class="cpp plain">*addr,</code><code class="cpp color1 bold">int</code> <code class="cpp plain">len)</code>
</div>
<div class="line number41 index40 alt2">
<code class="cpp plain">{ </code><code class="cpp color1 bold">int</code> <code class="cpp plain">nleft=len;</code>
</div>
<div class="line number42 index41 alt1">
<code class="cpp spaces"> </code><code class="cpp color1 bold">int</code> <code class="cpp plain">sum=0;</code>
</div>
<div class="line number43 index42 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">unsigned </code><code class="cpp color1 bold">short</code> <code class="cpp plain">*w=addr;</code>
</div>
<div class="line number44 index43 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">unsigned </code><code class="cpp color1 bold">short</code> <code class="cpp plain">answer=0;</code>
</div>
<div class="line number45 index44 alt2">
</div>
<div class="line number46 index45 alt1">
<code class="cpp spaces"> </code><code class="cpp comments">/*把ICMP报头二进制数据以2字节为单位累加起来*/</code>
</div>
<div class="line number47 index46 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">while</code><code class="cpp plain">(nleft>1)</code>
</div>
<div class="line number48 index47 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">{ </code>
</div>
<div class="line number49 index48 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">sum+=*w++;</code>
</div>
<div class="line number50 index49 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">nleft-=2;</code>
</div>
<div class="line number51 index50 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">}</code>
</div>
<div class="line number52 index51 alt1">
<code class="cpp spaces"> </code><code class="cpp comments">/*若ICMP报头为奇数个字节，会剩下最后一字节。把最后一个字节视为一个2字节数据的高字节，这个2字节数据的低字节为0，继续累加*/</code>
</div>
<div class="line number53 index52 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">if</code><code class="cpp plain">( nleft==1)</code>
</div>
<div class="line number54 index53 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">{ </code>
</div>
<div class="line number55 index54 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">*(unsigned </code><code class="cpp color1 bold">char</code> <code class="cpp plain">*)(&answer)=*(unsigned </code><code class="cpp color1 bold">char</code> <code class="cpp plain">*)w;</code>
</div>
<div class="line number56 index55 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">sum+=answer;</code>
</div>
<div class="line number57 index56 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">}</code>
</div>
<div class="line number58 index57 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">sum=(sum>>16)+(sum&0xffff);</code>
</div>
<div class="line number59 index58 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">sum+=(sum>>16);</code>
</div>
<div class="line number60 index59 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">answer=~sum;</code>
</div>
<div class="line number61 index60 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">return</code> <code class="cpp plain">answer;</code>
</div>
<div class="line number62 index61 alt1">
<code class="cpp plain">}</code>
</div>
<div class="line number63 index62 alt2">
</div>
<div class="line number64 index63 alt1">
<code class="cpp keyword bold">struct</code> <code class="cpp plain">timeval cal_time_offset(</code><code class="cpp keyword bold">struct</code> <code class="cpp plain">timeval begin, </code><code class="cpp keyword bold">struct</code> <code class="cpp plain">timeval end)</code>
</div>
<div class="line number65 index64 alt2">
<code class="cpp plain">{</code>
</div>
<div class="line number66 index65 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">struct</code> <code class="cpp plain">timeval ans;</code>
</div>
<div class="line number67 index66 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">ans.tv_sec = end.tv_sec - begin.tv_sec;</code>
</div>
<div class="line number68 index67 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">ans.tv_usec = end.tv_usec - begin.tv_usec;</code>
</div>
<div class="line number69 index68 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">if</code><code class="cpp plain">(ans.tv_usec < 0) </code><code class="cpp comments">//如果接收时间的usec小于发送时间的usec，则向sec域借位</code>
</div>
<div class="line number70 index69 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">{</code>
</div>
<div class="line number71 index70 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">ans.tv_sec--;</code>
</div>
<div class="line number72 index71 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">ans.tv_usec+=1000000;</code>
</div>
<div class="line number73 index72 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">}</code>
</div>
<div class="line number74 index73 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">return</code> <code class="cpp plain">ans;</code>
</div>
<div class="line number75 index74 alt2">
<code class="cpp plain">}</code>
</div>
<div class="line number76 index75 alt1">
</div>
<div class="line number77 index76 alt2">
<code class="cpp keyword bold">void</code> <code class="cpp plain">icmp_pack(</code><code class="cpp keyword bold">struct</code> <code class="cpp plain">icmp* icmphdr, </code><code class="cpp color1 bold">int</code> <code class="cpp plain">seq, </code><code class="cpp color1 bold">int</code> <code class="cpp plain">length)</code>
</div>
<div class="line number78 index77 alt1">
<code class="cpp plain">{</code>
</div>
<div class="line number79 index78 alt2">
<code class="cpp spaces"> </code><code class="cpp color1 bold">int</code> <code class="cpp plain">i = 0;</code>
</div>
<div class="line number80 index79 alt1">
</div>
<div class="line number81 index80 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">icmphdr->icmp_type = ICMP_ECHO;</code>
</div>
<div class="line number82 index81 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">icmphdr->icmp_code = 0;</code>
</div>
<div class="line number83 index82 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">icmphdr->icmp_cksum = 0;</code>
</div>
<div class="line number84 index83 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">icmphdr->icmp_seq = seq;</code>
</div>
<div class="line number85 index84 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">icmphdr->icmp_id = pid & 0xffff;</code>
</div>
<div class="line number86 index85 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">for</code><code class="cpp plain">(i=0;i<length;i++)</code>
</div>
<div class="line number87 index86 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">{</code>
</div>
<div class="line number88 index87 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">icmphdr->icmp_data = i;</code>
</div>
<div class="line number89 index88 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">}</code>
</div>
<div class="line number90 index89 alt1">
</div>
<div class="line number91 index90 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">icmphdr->icmp_cksum = cal_chksum((unsigned </code><code class="cpp color1 bold">short</code><code class="cpp plain">*)icmphdr, length);</code>
</div>
<div class="line number92 index91 alt1">
<code class="cpp plain">}</code>
</div>
<div class="line number93 index92 alt2">
</div>
<div class="line number94 index93 alt1">
<code class="cpp color1 bold">int</code> <code class="cpp plain">icmp_unpack(</code><code class="cpp color1 bold">char</code><code class="cpp plain">* buf, </code><code class="cpp color1 bold">int</code> <code class="cpp plain">len)</code>
</div>
<div class="line number95 index94 alt2">
<code class="cpp plain">{</code>
</div>
<div class="line number96 index95 alt1">
<code class="cpp spaces"> </code><code class="cpp color1 bold">int</code> <code class="cpp plain">iphdr_len;</code>
</div>
<div class="line number97 index96 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">struct</code> <code class="cpp plain">timeval begin_time, recv_time, offset_time;</code>
</div>
<div class="line number98 index97 alt1">
<code class="cpp spaces"> </code><code class="cpp color1 bold">int</code> <code class="cpp plain">rtt; </code><code class="cpp comments">//round trip time</code>
</div>
<div class="line number99 index98 alt2">
</div>
<div class="line number100 index99 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">struct</code> <code class="cpp plain">ip* ip_hdr = (</code><code class="cpp keyword bold">struct</code> <code class="cpp plain">ip *)buf;</code>
</div>
<div class="line number101 index100 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">iphdr_len = ip_hdr->ip_hl*4;</code>
</div>
<div class="line number102 index101 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">struct</code> <code class="cpp plain">icmp* icmp = (</code><code class="cpp keyword bold">struct</code> <code class="cpp plain">icmp*)(buf+iphdr_len);</code>
</div>
<div class="line number103 index102 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">len-=iphdr_len; </code><code class="cpp comments">//icmp包长度</code>
</div>
<div class="line number104 index103 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">if</code><code class="cpp plain">(len < 8) </code><code class="cpp comments">//判断长度是否为ICMP包长度</code>
</div>
<div class="line number105 index104 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">{</code>
</div>
<div class="line number106 index105 alt1">
<code class="cpp spaces"> </code><code class="cpp functions bold">fprintf</code><code class="cpp plain">(stderr, </code><code class="cpp string">"Invalid icmp packet.Its length is less than 8\n"</code><code class="cpp plain">);</code>
</div>
<div class="line number107 index106 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">return</code> <code class="cpp plain">-1;</code>
</div>
<div class="line number108 index107 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">}</code>
</div>
<div class="line number109 index108 alt2">
</div>
<div class="line number110 index109 alt1">
<code class="cpp spaces"> </code><code class="cpp comments">//判断该包是ICMP回送回答包且该包是我们发出去的</code>
</div>
<div class="line number111 index110 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">if</code><code class="cpp plain">((icmp->icmp_type == ICMP_ECHOREPLY) && (icmp->icmp_id == pid)) </code>
</div>
<div class="line number112 index111 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">{</code>
</div>
<div class="line number113 index112 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">if</code><code class="cpp plain">((icmp->icmp_seq < 0) || (icmp->icmp_seq > PACKET_SEND_MAX_NUM))</code>
</div>
<div class="line number114 index113 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">{</code>
</div>
<div class="line number115 index114 alt2">
<code class="cpp spaces"> </code><code class="cpp functions bold">fprintf</code><code class="cpp plain">(stderr, </code><code class="cpp string">"icmp packet seq is out of range!\n"</code><code class="cpp plain">);</code>
</div>
<div class="line number116 index115 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">return</code> <code class="cpp plain">-1;</code>
</div>
<div class="line number117 index116 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">}</code>
</div>
<div class="line number118 index117 alt1">
</div>
<div class="line number119 index118 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">ping_packet.flag = 0;</code>
</div>
<div class="line number120 index119 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">begin_time = ping_packet.begin_time;</code>
</div>
<div class="line number121 index120 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">gettimeofday(&recv_time, NULL);</code>
</div>
<div class="line number122 index121 alt1">
</div>
<div class="line number123 index122 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">offset_time = cal_time_offset(begin_time, recv_time);</code>
</div>
<div class="line number124 index123 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">rtt = offset_time.tv_sec*1000 + offset_time.tv_usec/1000; </code><code class="cpp comments">//毫秒为单位</code>
</div>
<div class="line number125 index124 alt2">
</div>
<div class="line number126 index125 alt1">
<code class="cpp spaces"> </code><code class="cpp functions bold">printf</code><code class="cpp plain">(</code><code class="cpp string">"%d byte from %s: icmp_seq=%u ttl=%d rtt=%d ms\n"</code><code class="cpp plain">,</code>
</div>
<div class="line number127 index126 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">len, inet_ntoa(ip_hdr->ip_src), icmp->icmp_seq, ip_hdr->ip_ttl, rtt); </code>
</div>
<div class="line number128 index127 alt1">
</div>
<div class="line number129 index128 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">}</code>
</div>
<div class="line number130 index129 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">else</code>
</div>
<div class="line number131 index130 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">{</code>
</div>
<div class="line number132 index131 alt1">
<code class="cpp spaces"> </code><code class="cpp functions bold">fprintf</code><code class="cpp plain">(stderr, </code><code class="cpp string">"Invalid ICMP packet! Its id is not matched!\n"</code><code class="cpp plain">);</code>
</div>
<div class="line number133 index132 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">return</code> <code class="cpp plain">-1;</code>
</div>
<div class="line number134 index133 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">}</code>
</div>
<div class="line number135 index134 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">return</code> <code class="cpp plain">0;</code>
</div>
<div class="line number136 index135 alt1">
<code class="cpp plain">}</code>
</div>
<div class="line number137 index136 alt2">
</div>
<div class="line number138 index137 alt1">
<code class="cpp keyword bold">void</code> <code class="cpp plain">ping_send()</code>
</div>
<div class="line number139 index138 alt2">
<code class="cpp plain">{</code>
</div>
<div class="line number140 index139 alt1">
<code class="cpp spaces"> </code><code class="cpp color1 bold">char</code> <code class="cpp plain">send_buf;</code>
</div>
<div class="line number141 index140 alt2">
<code class="cpp spaces"> </code><code class="cpp functions bold">memset</code><code class="cpp plain">(send_buf, 0, </code><code class="cpp keyword bold">sizeof</code><code class="cpp plain">(send_buf));</code>
</div>
<div class="line number142 index141 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">gettimeofday(&start_time, NULL); </code><code class="cpp comments">//记录第一个ping包发出的时间</code>
</div>
<div class="line number143 index142 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">while</code><code class="cpp plain">(alive)</code>
</div>
<div class="line number144 index143 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">{</code>
</div>
<div class="line number145 index144 alt2">
<code class="cpp spaces"> </code><code class="cpp color1 bold">int</code> <code class="cpp plain">size = 0;</code>
</div>
<div class="line number146 index145 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">gettimeofday(&(ping_packet.begin_time), NULL);</code>
</div>
<div class="line number147 index146 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">ping_packet.flag = 1; </code><code class="cpp comments">//将该标记为设置为该包已发送</code>
</div>
<div class="line number148 index147 alt1">
</div>
<div class="line number149 index148 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">icmp_pack((</code><code class="cpp keyword bold">struct</code> <code class="cpp plain">icmp*)send_buf, send_count, 64); </code><code class="cpp comments">//封装icmp包</code>
</div>
<div class="line number150 index149 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">size = sendto(rawsock, send_buf, 64, 0, (</code><code class="cpp keyword bold">struct</code> <code class="cpp plain">sockaddr*)&dest, </code><code class="cpp keyword bold">sizeof</code><code class="cpp plain">(dest));</code>
</div>
<div class="line number151 index150 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">send_count++; </code><code class="cpp comments">//记录发出ping包的数量</code>
</div>
<div class="line number152 index151 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">if</code><code class="cpp plain">(size < 0)</code>
</div>
<div class="line number153 index152 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">{</code>
</div>
<div class="line number154 index153 alt1">
<code class="cpp spaces"> </code><code class="cpp functions bold">fprintf</code><code class="cpp plain">(stderr, </code><code class="cpp string">"send icmp packet fail!\n"</code><code class="cpp plain">);</code>
</div>
<div class="line number155 index154 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">continue</code><code class="cpp plain">;</code>
</div>
<div class="line number156 index155 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">}</code>
</div>
<div class="line number157 index156 alt2">
</div>
<div class="line number158 index157 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">sleep(1);</code>
</div>
<div class="line number159 index158 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">}</code>
</div>
<div class="line number160 index159 alt1">
<code class="cpp plain">}</code>
</div>
<div class="line number161 index160 alt2">
</div>
<div class="line number162 index161 alt1">
<code class="cpp keyword bold">void</code> <code class="cpp plain">ping_recv()</code>
</div>
<div class="line number163 index162 alt2">
<code class="cpp plain">{</code>
</div>
<div class="line number164 index163 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">struct</code> <code class="cpp plain">timeval tv;</code>
</div>
<div class="line number165 index164 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">tv.tv_usec = 200; </code><code class="cpp comments">//设置select函数的超时时间为200us</code>
</div>
<div class="line number166 index165 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">tv.tv_sec = 0;</code>
</div>
<div class="line number167 index166 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">fd_set read_fd;</code>
</div>
<div class="line number168 index167 alt1">
<code class="cpp spaces"> </code><code class="cpp color1 bold">char</code> <code class="cpp plain">recv_buf;</code>
</div>
<div class="line number169 index168 alt2">
<code class="cpp spaces"> </code><code class="cpp functions bold">memset</code><code class="cpp plain">(recv_buf, 0 ,</code><code class="cpp keyword bold">sizeof</code><code class="cpp plain">(recv_buf));</code>
</div>
<div class="line number170 index169 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">while</code><code class="cpp plain">(alive)</code>
</div>
<div class="line number171 index170 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">{</code>
</div>
<div class="line number172 index171 alt1">
<code class="cpp spaces"> </code><code class="cpp color1 bold">int</code> <code class="cpp plain">ret = 0;</code>
</div>
<div class="line number173 index172 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">FD_ZERO(&read_fd);</code>
</div>
<div class="line number174 index173 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">FD_SET(rawsock, &read_fd);</code>
</div>
<div class="line number175 index174 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">ret = select(rawsock+1, &read_fd, NULL, NULL, &tv);</code>
</div>
<div class="line number176 index175 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">switch</code><code class="cpp plain">(ret)</code>
</div>
<div class="line number177 index176 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">{</code>
</div>
<div class="line number178 index177 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">case</code> <code class="cpp plain">-1:</code>
</div>
<div class="line number179 index178 alt2">
<code class="cpp spaces"> </code><code class="cpp functions bold">fprintf</code><code class="cpp plain">(stderr,</code><code class="cpp string">"fail to select!\n"</code><code class="cpp plain">);</code>
</div>
<div class="line number180 index179 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">break</code><code class="cpp plain">;</code>
</div>
<div class="line number181 index180 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">case</code> <code class="cpp plain">0:</code>
</div>
<div class="line number182 index181 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">break</code><code class="cpp plain">;</code>
</div>
<div class="line number183 index182 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">default</code><code class="cpp plain">:</code>
</div>
<div class="line number184 index183 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">{</code>
</div>
<div class="line number185 index184 alt2">
<code class="cpp spaces"> </code><code class="cpp color1 bold">int</code> <code class="cpp plain">size = recv(rawsock, recv_buf, </code><code class="cpp keyword bold">sizeof</code><code class="cpp plain">(recv_buf), 0);</code>
</div>
<div class="line number186 index185 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">if</code><code class="cpp plain">(size < 0)</code>
</div>
<div class="line number187 index186 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">{</code>
</div>
<div class="line number188 index187 alt1">
<code class="cpp spaces"> </code><code class="cpp functions bold">fprintf</code><code class="cpp plain">(stderr,</code><code class="cpp string">"recv data fail!\n"</code><code class="cpp plain">);</code>
</div>
<div class="line number189 index188 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">continue</code><code class="cpp plain">;</code>
</div>
<div class="line number190 index189 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">}</code>
</div>
<div class="line number191 index190 alt2">
</div>
<div class="line number192 index191 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">ret = icmp_unpack(recv_buf, size); </code><code class="cpp comments">//对接收的包进行解封</code>
</div>
<div class="line number193 index192 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">if</code><code class="cpp plain">(ret == -1) </code><code class="cpp comments">//不是属于自己的icmp包，丢弃不处理</code>
</div>
<div class="line number194 index193 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">{</code>
</div>
<div class="line number195 index194 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">continue</code><code class="cpp plain">;</code>
</div>
<div class="line number196 index195 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">}</code>
</div>
<div class="line number197 index196 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">recv_count++; </code><code class="cpp comments">//接收包计数</code>
</div>
<div class="line number198 index197 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">}</code>
</div>
<div class="line number199 index198 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">break</code><code class="cpp plain">;</code>
</div>
<div class="line number200 index199 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">}</code>
</div>
<div class="line number201 index200 alt2">
</div>
<div class="line number202 index201 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">}</code>
</div>
<div class="line number203 index202 alt2">
<code class="cpp plain">}</code>
</div>
<div class="line number204 index203 alt1">
</div>
<div class="line number205 index204 alt2">
<code class="cpp keyword bold">void</code> <code class="cpp plain">icmp_sigint(</code><code class="cpp color1 bold">int</code> <code class="cpp plain">signo)</code>
</div>
<div class="line number206 index205 alt1">
<code class="cpp plain">{</code>
</div>
<div class="line number207 index206 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">alive = 0;</code>
</div>
<div class="line number208 index207 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">gettimeofday(&end_time, NULL);</code>
</div>
<div class="line number209 index208 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">time_interval = cal_time_offset(start_time, end_time);</code>
</div>
<div class="line number210 index209 alt1">
<code class="cpp plain">}</code>
</div>
<div class="line number211 index210 alt2">
</div>
<div class="line number212 index211 alt1">
<code class="cpp keyword bold">void</code> <code class="cpp plain">ping_stats_show()</code>
</div>
<div class="line number213 index212 alt2">
<code class="cpp plain">{</code>
</div>
<div class="line number214 index213 alt1">
<code class="cpp spaces"> </code><code class="cpp color1 bold">long</code> <code class="cpp functions bold">time</code> <code class="cpp plain">= time_interval.tv_sec*1000+time_interval.tv_usec/1000;</code>
</div>
<div class="line number215 index214 alt2">
<code class="cpp spaces"> </code><code class="cpp comments">/*注意除数不能为零，这里send_count有可能为零，所以运行时提示错误*/</code>
</div>
<div class="line number216 index215 alt1">
<code class="cpp spaces"> </code><code class="cpp functions bold">printf</code><code class="cpp plain">(</code><code class="cpp string">"%d packets transmitted, %d recieved, %d%c packet loss, time %ldms\n"</code><code class="cpp plain">,</code>
</div>
<div class="line number217 index216 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">send_count, recv_count, (send_count-recv_count)*100/send_count, </code><code class="cpp string">'%'</code><code class="cpp plain">, </code><code class="cpp functions bold">time</code><code class="cpp plain">);</code>
</div>
<div class="line number218 index217 alt1">
<code class="cpp plain">}</code>
</div>
<div class="line number219 index218 alt2">
</div>
<div class="line number220 index219 alt1">
</div>
<div class="line number221 index220 alt2">
<code class="cpp color1 bold">int</code> <code class="cpp plain">main(</code><code class="cpp color1 bold">int</code> <code class="cpp plain">argc, </code><code class="cpp color1 bold">char</code><code class="cpp plain">* argv[])</code>
</div>
<div class="line number222 index221 alt1">
<code class="cpp plain">{</code>
</div>
<div class="line number223 index222 alt2">
<code class="cpp spaces"> </code><code class="cpp color1 bold">int</code> <code class="cpp plain">size = 128*1024;</code><code class="cpp comments">//128k</code>
</div>
<div class="line number224 index223 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">struct</code> <code class="cpp plain">protoent* protocol = NULL;</code>
</div>
<div class="line number225 index224 alt2">
<code class="cpp spaces"> </code><code class="cpp color1 bold">char</code> <code class="cpp plain">dest_addr_str;</code>
</div>
<div class="line number226 index225 alt1">
<code class="cpp spaces"> </code><code class="cpp functions bold">memset</code><code class="cpp plain">(dest_addr_str, 0, 80);</code>
</div>
<div class="line number227 index226 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">unsigned </code><code class="cpp color1 bold">int</code> <code class="cpp plain">inaddr = 1;</code>
</div>
<div class="line number228 index227 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">struct</code> <code class="cpp plain">hostent* host = NULL;</code>
</div>
<div class="line number229 index228 alt2">
</div>
<div class="line number230 index229 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">pthread_t send_id,recv_id;</code>
</div>
<div class="line number231 index230 alt2">
</div>
<div class="line number232 index231 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">if</code><code class="cpp plain">(argc < 2)</code>
</div>
<div class="line number233 index232 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">{</code>
</div>
<div class="line number234 index233 alt1">
<code class="cpp spaces"> </code><code class="cpp functions bold">printf</code><code class="cpp plain">(</code><code class="cpp string">"Invalid IP ADDRESS!\n"</code><code class="cpp plain">);</code>
</div>
<div class="line number235 index234 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">return</code> <code class="cpp plain">-1;</code>
</div>
<div class="line number236 index235 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">}</code>
</div>
<div class="line number237 index236 alt2">
</div>
<div class="line number238 index237 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">protocol = getprotobyname(</code><code class="cpp string">"icmp"</code><code class="cpp plain">); </code><code class="cpp comments">//获取协议类型ICMP</code>
</div>
<div class="line number239 index238 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">if</code><code class="cpp plain">(protocol == NULL)</code>
</div>
<div class="line number240 index239 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">{</code>
</div>
<div class="line number241 index240 alt2">
<code class="cpp spaces"> </code><code class="cpp functions bold">printf</code><code class="cpp plain">(</code><code class="cpp string">"Fail to getprotobyname!\n"</code><code class="cpp plain">);</code>
</div>
<div class="line number242 index241 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">return</code> <code class="cpp plain">-1;</code>
</div>
<div class="line number243 index242 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">}</code>
</div>
<div class="line number244 index243 alt1">
</div>
<div class="line number245 index244 alt2">
<code class="cpp spaces"> </code><code class="cpp functions bold">memcpy</code><code class="cpp plain">(dest_addr_str, argv, </code><code class="cpp functions bold">strlen</code><code class="cpp plain">(argv)+1);</code>
</div>
<div class="line number246 index245 alt1">
</div>
<div class="line number247 index246 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">rawsock = socket(AF_INET,SOCK_RAW,protocol->p_proto);</code>
</div>
<div class="line number248 index247 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">if</code><code class="cpp plain">(rawsock < 0)</code>
</div>
<div class="line number249 index248 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">{</code>
</div>
<div class="line number250 index249 alt1">
<code class="cpp spaces"> </code><code class="cpp functions bold">printf</code><code class="cpp plain">(</code><code class="cpp string">"Fail to create socket!\n"</code><code class="cpp plain">);</code>
</div>
<div class="line number251 index250 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">return</code> <code class="cpp plain">-1;</code>
</div>
<div class="line number252 index251 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">}</code>
</div>
<div class="line number253 index252 alt2">
</div>
<div class="line number254 index253 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">pid = getpid();</code>
</div>
<div class="line number255 index254 alt2">
</div>
<div class="line number256 index255 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">setsockopt(rawsock, SOL_SOCKET, SO_RCVBUF, &size, </code><code class="cpp keyword bold">sizeof</code><code class="cpp plain">(size)); </code><code class="cpp comments">//增大接收缓冲区至128K</code>
</div>
<div class="line number257 index256 alt2">
</div>
<div class="line number258 index257 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">bzero(&dest,</code><code class="cpp keyword bold">sizeof</code><code class="cpp plain">(dest));</code>
</div>
<div class="line number259 index258 alt2">
</div>
<div class="line number260 index259 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">dest.sin_family = AF_INET;</code>
</div>
<div class="line number261 index260 alt2">
</div>
<div class="line number262 index261 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">inaddr = inet_addr(argv);</code>
</div>
<div class="line number263 index262 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">if</code><code class="cpp plain">(inaddr == INADDR_NONE) </code><code class="cpp comments">//判断用户输入的是否为IP地址还是域名</code>
</div>
<div class="line number264 index263 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">{</code>
</div>
<div class="line number265 index264 alt2">
<code class="cpp spaces"> </code><code class="cpp comments">//输入的是域名地址</code>
</div>
<div class="line number266 index265 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">host = gethostbyname(argv);</code>
</div>
<div class="line number267 index266 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">if</code><code class="cpp plain">(host == NULL)</code>
</div>
<div class="line number268 index267 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">{</code>
</div>
<div class="line number269 index268 alt2">
<code class="cpp spaces"> </code><code class="cpp functions bold">printf</code><code class="cpp plain">(</code><code class="cpp string">"Fail to gethostbyname!\n"</code><code class="cpp plain">);</code>
</div>
<div class="line number270 index269 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">return</code> <code class="cpp plain">-1;</code>
</div>
<div class="line number271 index270 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">}</code>
</div>
<div class="line number272 index271 alt1">
</div>
<div class="line number273 index272 alt2">
<code class="cpp spaces"> </code><code class="cpp functions bold">memcpy</code><code class="cpp plain">((</code><code class="cpp color1 bold">char</code><code class="cpp plain">*)&dest.sin_addr, host->h_addr, host->h_length);</code>
</div>
<div class="line number274 index273 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">}</code>
</div>
<div class="line number275 index274 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">else</code>
</div>
<div class="line number276 index275 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">{</code>
</div>
<div class="line number277 index276 alt2">
<code class="cpp spaces"> </code><code class="cpp functions bold">memcpy</code><code class="cpp plain">((</code><code class="cpp color1 bold">char</code><code class="cpp plain">*)&dest.sin_addr, &inaddr, </code><code class="cpp keyword bold">sizeof</code><code class="cpp plain">(inaddr));</code><code class="cpp comments">//输入的是IP地址</code>
</div>
<div class="line number278 index277 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">}</code>
</div>
<div class="line number279 index278 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">inaddr = dest.sin_addr.s_addr;</code>
</div>
<div class="line number280 index279 alt1">
<code class="cpp spaces"> </code><code class="cpp functions bold">printf</code><code class="cpp plain">(</code><code class="cpp string">"PING %s, (%d.%d.%d.%d) 56(84) bytes of data.\n"</code><code class="cpp plain">,dest_addr_str,</code>
</div>
<div class="line number281 index280 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">(inaddr&0x000000ff), (inaddr&0x0000ff00)>>8, </code>
</div>
<div class="line number282 index281 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">(inaddr&0x00ff0000)>>16, (inaddr&0xff000000)>>24);</code>
</div>
<div class="line number283 index282 alt2">
</div>
<div class="line number284 index283 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">alive = 1; </code><code class="cpp comments">//控制ping的发送和接收</code>
</div>
<div class="line number285 index284 alt2">
</div>
<div class="line number286 index285 alt1">
<code class="cpp spaces"> </code><code class="cpp functions bold">signal</code><code class="cpp plain">(SIGINT, icmp_sigint);</code>
</div>
<div class="line number287 index286 alt2">
</div>
<div class="line number288 index287 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">if</code><code class="cpp plain">(pthread_create(&send_id, NULL, (</code><code class="cpp keyword bold">void</code><code class="cpp plain">*)ping_send, NULL))</code>
</div>
<div class="line number289 index288 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">{</code>
</div>
<div class="line number290 index289 alt1">
<code class="cpp spaces"> </code><code class="cpp functions bold">printf</code><code class="cpp plain">(</code><code class="cpp string">"Fail to create ping send thread!\n"</code><code class="cpp plain">);</code>
</div>
<div class="line number291 index290 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">return</code> <code class="cpp plain">-1;</code>
</div>
<div class="line number292 index291 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">}</code>
</div>
<div class="line number293 index292 alt2">
</div>
<div class="line number294 index293 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">if</code><code class="cpp plain">(pthread_create(&recv_id, NULL, (</code><code class="cpp keyword bold">void</code><code class="cpp plain">*)ping_recv, NULL))</code>
</div>
<div class="line number295 index294 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">{</code>
</div>
<div class="line number296 index295 alt1">
<code class="cpp spaces"> </code><code class="cpp functions bold">printf</code><code class="cpp plain">(</code><code class="cpp string">"Fail to create ping recv thread!\n"</code><code class="cpp plain">);</code>
</div>
<div class="line number297 index296 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">return</code> <code class="cpp plain">-1;</code>
</div>
<div class="line number298 index297 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">}</code>
</div>
<div class="line number299 index298 alt2">
</div>
<div class="line number300 index299 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">pthread_join(send_id, NULL);</code><code class="cpp comments">//等待send ping线程结束后进程再结束</code>
</div>
<div class="line number301 index300 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">pthread_join(recv_id, NULL);</code><code class="cpp comments">//等待recv ping线程结束后进程再结束</code>
</div>
<div class="line number302 index301 alt1">
</div>
<div class="line number303 index302 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">ping_stats_show();</code>
</div>
<div class="line number304 index303 alt1">
</div>
<div class="line number305 index304 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">close(rawsock);</code>
</div>
<div class="line number306 index305 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">return</code> <code class="cpp plain">0;</code>
</div>
<div class="line number307 index306 alt2">
</div>
<div class="line number308 index307 alt1">
<code class="cpp plain">}</code>
</div>
</div>
</td>
</tr></tbody></table>
</div>
</div>
<div class="codetool" id="codetool">
<div class="code_n">
<textarea></textarea>
</div>
</div>
</div>
<p>
编译以及实验现象如下：<br>
我的实验环境是两台服务器，发起ping的主机是172.0.5.183，被ping的主机是172.0.5.182，以下是我的两次实验现象（ping IP和ping 域名）。</p>
<p>
<span><strong>特别注意：</strong></span></p>
<p>
只有root用户才能利用socket()函数生成原始套接字，要让Linux的一般用户能执行以上程序，需进行如下的特别操作：用root登陆，编译以上程序gcc -lpthread -o ping ping.c</p>
<p>
<img title="Linux编程之PING实现" alt="Linux编程之PING实现" src="https://zhuji.jb51.net/uploads/img/202305/d7db0ff2a4bf6c460a3868e5223c8770.jpg"></p>
<p>
实验现象可以看出，PING是成功的，表明两主机间的网络是通的，发出的所有ping包都收到了回复。</p>
<p>
下面是Linux系统自带的PING程序，我们可以对比一下我们设计的PING程序跟系统自带的PING程序有何不同。</p>
<p>
<img title="Linux编程之PING实现" alt="Linux编程之PING实现" src="https://zhuji.jb51.net/uploads/img/202305/0173f8be96e5e96cdc8f2556a2d46bf1.jpg"></p>
<p>
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。</p>
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