TCP/IP 详解 卷1 ch7 Ping

1. ping 命令，新版默认不回显，要加-s

 

/home/a/j/nomad2:ping -s x4100.unix-center.net PING x4100.unix-center.net: 56 data bytes 64 bytes from x4100.unix-center.net (192.168.1.10): icmp_seq=0. time=0.0960 ms 64 bytes from x4100.unix-center.net (192.168.1.10): icmp_seq=1. time=0.0910 ms 64 bytes from x4100.unix-center.net (192.168.1.10): icmp_seq=2. time=0.0560 ms 64 bytes from x4100.unix-center.net (192.168.1.10): icmp_seq=3. time=0.0660 ms 64 bytes from x4100.unix-center.net (192.168.1.10): icmp_seq=4. time=0.0590 ms 64 bytes from x4100.unix-center.net (192.168.1.10): icmp_seq=5. time=0.0560 ms 64 bytes from x4100.unix-center.net (192.168.1.10): icmp_seq=6. time=0.0620 ms 64 bytes from x4100.unix-center.net (192.168.1.10): icmp_seq=7. time=0.0560 ms 64 bytes from x4100.unix-center.net (192.168.1.10): icmp_seq=8. time=0.0650 ms 64 bytes from x4100.unix-center.net (192.168.1.10): icmp_seq=9. time=0.0560 ms 64 bytes from x4100.unix-center.net (192.168.1.10): icmp_seq=10. time=0.0700 ms

第一个往返时间大，可能由于ARP。

 

2. ping WAN, youkuaiyun.com for example,

 

/home/a/j/nomad2:ping -s 117.79.93.195 PING 117.79.93.195: 56 data bytes 64 bytes from 117.79.93.195: icmp_seq=0. time=88.5 ms 64 bytes from 117.79.93.195: icmp_seq=1. time=0.872 ms 64 bytes from 117.79.93.195: icmp_seq=2. time=0.841 ms 64 bytes from 117.79.93.195: icmp_seq=3. time=0.998 ms 64 bytes from 117.79.93.195: icmp_seq=4. time=1.03 ms 64 bytes from 117.79.93.195: icmp_seq=5. time=0.595 ms 64 bytes from 117.79.93.195: icmp_seq=6. time=0.875 ms 64 bytes from 117.79.93.195: icmp_seq=7. time=0.782 ms 64 bytes from 117.79.93.195: icmp_seq=8. time=0.878 ms 64 bytes from 117.79.93.195: icmp_seq=9. time=0.829 ms 64 bytes from 117.79.93.195: icmp_seq=10. time=1.06 ms

 

有可能会丢包

 

3. IP Record Route Option

 

ping -R

 

4. ping is implemented in kernel, refer to http://lxr.linux.no/#linux+v2.6.36/net/ipv4/icmp.c

 

815/* 816 * Handle ICMP_ECHO ("ping") requests. 817 * 818 * RFC 1122: 3.2.2.6 MUST have an echo server that answers ICMP echo 819 * requests. 820 * RFC 1122: 3.2.2.6 Data received in the ICMP_ECHO request MUST be 821 * included in the reply. 822 * RFC 1812: 4.3.3.6 SHOULD have a config option for silently ignoring 823 * echo requests, MUST have default=NOT. 824 * See also WRT handling of options once they are done and working. 825 */ 826 827static void icmp_echo(struct sk_buff *skb) 828{ 829 struct net *net; 830 831 net = dev_net(skb_dst(skb)->dev); 832 if (!net->ipv4.sysctl_icmp_echo_ignore_all) { 833 struct icmp_bxm icmp_param; 834 835 icmp_param.data.icmph = *icmp_hdr(skb); 836 icmp_param.data.icmph.type = ICMP_ECHOREPLY; 837 icmp_param.skb = skb; 838 icmp_param.offset = 0; 839 icmp_param.data_len = skb->len; 840 icmp_param.head_len = sizeof(struct icmphdr); 841 icmp_reply(&icmp_param, skb); 842 } 843}

 

5. 一些应用

 

注意：ping本机IP(127.0.0.1 and 221.3.24.40)使用wireshark抓不到包。

 

0) 使用ipconfig /all观察本地网络设置是否正确；

1) ping 127.0.0.1   检查本机TCP/IP协议栈是否正常，失败则重装TCP/IP协议

2) ping 本机IP地址   检查网卡是否工作正常，失败则检查网线是否插上、网卡驱动是否正常

3) ping 网关IP地址   检查网关、网线及网络设置是否正常

4) ping 远端主机      检查本机与外部网络的连接是否正常

5) ping DNS服务器地址 检查本机是否能正常连接到DNS，更合适的检查DNS是否可用的方法是利用nslookup命令来测试