十一、 ss - 网络相关信息 ss命令用来显示网络套接字信息，它允许显示类似netstat一样的信息。关于ss和netstat使用，可参考下列资源。 相关链接： ss: Display Linux TCP / UDP Network and Socket Information
The ss command is used to show socket statistics. It can display stats for PACKET sockets, TCP sockets, UDP sockets, DCCP sockets, RAW sockets, Unix domain sockets, and much more. It allows showing information similar to netstat command. It can display more TCP and state information than other tools. It is a new, incredibly useful and faster (as compare to netstat) tool for tracking TCP connections and sockets. SS can provide information about: . All TCP sockets. . All UDP sockets. . All established ssh / ftp / http / https connections. . All local processes connected to X server. . Filtering by state (such as connected, synchronized, SYN-RECV, SYN-SENT,TIME-WAIT), addresses and ports. . All the tcp sockets in state FIN-WAIT-1 and much more.
Most Linux distributions are shipped with ss and many monitoring tools. Being familiar with this tool helps enhance your understand of what's going on in the system sockets and helps you find the possible causes of a performance problem.
Task: Display Sockets Summary List currently established, closed, orphaned and waiting TCP sockets, enter: # ss -s
Type the following to see process named using open socket:
查看使用端口的进程 # ss -pl
Find out who is responsible for opening socket / port # 4949: 查看端口对应进程的状态信息 # ss -lp | grep 4949
Sample output: 0 0 *:4949 *:* users:(("munin-node",3772,5)) munin-node (PID # 3772) is responsible for opening port # 4949. You can get more information about this process (like memory used, users, current working directory and so on) visiting /proc/3772 directory: # cd /proc/3772 # ls -l
Task: Display All TCP Sockets # ss -t -a
Task: Display All UDP Sockets # ss -u -a
Task: Display All Established SMTP Connections # ss -o state established '( dport = :smtp or sport = :smtp )'
Task: Display All Established HTTP Connections # ss -o state established '( dport = :http or sport = :http )'
Task: Find All Local Processes Connected To X Server # ss -x src /tmp/.X11-unix/*
Task: List All The Tcp Sockets in State FIN-WAIT-1 List all the TCP sockets in state -FIN-WAIT-1 for our httpd to network 202.54.1/24 and look at their timers: # ss -o state fin-wait-1 '( sport = :http or sport = :https )' dst 202.54.1/24
How Do I Filter Sockets Using TCP States? 如何过滤TCP socket的状态 The syntax is as follows: ## tcp ipv4 ## ss -4 state FILTER-NAME-HERE ## tcp ipv6 ## ss -6 state FILTER-NAME-HERE Where FILTER-NAME-HERE can be any one of the following: established syn-sent syn-recv fin-wait-1 fin-wait-2 time-wait closed close-wait last-ack listen closing all : All of the above states connected : All the states except for listen and closed synchronized : All the connected states except for syn-sent bucket : Show states, which are maintained as minisockets, i.e. time-wait and syn-recv. big : Opposite to bucket state.
Examples Type the following command to see closing sockets: $ ss -4 state closing Recv-Q Send-Q Local Address:Port Peer Address:Port 1 11094 75.126.153.214:http 175.44.24.85:4669
How Do I Matches Remote Address And Port Numbers? 查看访问远程地址的本机端口 Use the following syntax: ss dst ADDRESS_PATTERN ## Show all ports connected from remote 192.168.1.5## ss dst 192.168.1.5 ## show all ports connected from remote 192.168.1.5:http port## ss dst 192.168.1.5:http ss dst 192.168.1.5:smtp ss dst 192.168.1.5:443 Find out connection made by remote 123.1.2.100:http to our local virtual servers: # ss dst 123.1.2.100:http
Sample outputs: State Recv-Q Send-Q Local Address:Port Peer Address:Port ESTAB 0 0 75.126.153.206:http 123.1.2.100:35710 ESTAB 0 0 75.126.153.206:http 123.1.2.100:35758
How Do I Matches Local Address And Port Numbers? 查看本机使用某个地址的匹配的端口 ss src ADDRESS_PATTERN ### find out all ips connected to nixcraft.com ip address 75.126.153.214 ### ## Show all ports connected to local 75.126.153.214## ss src 75.126.153.214 ## http (80) port only ## ss src 75.126.153.214:http ss src 75.126.153.214:80 ## smtp (25) port only ## ss src 75.126.153.214:smtp ss src 75.126.153.214:25
How Do I Compare Local and/or Remote Port To A Number? 端口的数字化比较查询: Use the following syntax: ## Compares remote port to a number ## ss dport OP PORT ## Compares local port to a number ## sport OP PORT
Where OP can be one of the following: <= or le : Less than or equal to port >= or ge : Greater than or equal to port == or eq : Equal to port != or ne : Not equal to port < or gt : Less than to port > or lt : Greater than to port Note: le, gt, eq, ne etc. are use in unix shell and are accepted as well. Examples ################################################################################### ### Do not forget to escape special characters when typing them in command line ### ################################################################################### ss sport = :http ss dport = :http ss dport \> :1024 ss sport \> :1024 ss sport \< :32000 ss sport eq :22 ss dport != :22 ss state connected sport = :http ss \( sport = :http or sport = :https \) ss -o state fin-wait-1 \( sport = :http or sport = :https \) dst 192.168.1/24 ss vs netstat Speed Use the time command to run both programs and summarize system resource usage. Type the netstat command as follows: # time netstat -at
Sample outputs: real 2m52.254s user 0m0.178s sys 0m0.170s
Now, try the ss command: # time Sample outputs: real 2m11.102s user 0m0.124s sys 0m0.068s Note: Both outputs are taken from reverse proxy acceleration server running on RHEL 6.x amd64.
Recommended readings: See ss command help page.
十二、netstat - 网络相关信息 netstat可以显示网络链接、路由表信息、接口统计信息、伪装链接和多播成员(multicast memberships), ? Get Detailed Information About Particular IP address Connections Using netstat Command
netstat command and shell pipe feature can be used to dig out more information about particular IP address connection. You can find out total established connections, closing connection, SYN and FIN bits and much more. You can also display summary statistics for each protocol using netstat.
This is useful to find out if your server is under attack or not. You can also list abusive IP address using this method. 查看服务器是否受到攻击，并找出攻击的IP # netstat -nat | awk '{print $6}' | sort | uniq -c | sort -n
Dig out more information about a specific ip address: 找出更多的信息: # netstat -nat |grep {IP-address} | awk '{print $6}' | sort | uniq -c | sort -n 2 LAST_ACK 2 LISTEN 4 FIN_WAIT1 14 ESTABLISHED 91 TIME_WAIT 130 FIN_WAIT2
Busy server can give out more information: # netstat -nat |grep 202.54.1.10 | awk '{print $6}' | sort | uniq -c | sort -n Output:
15 CLOSE_WAIT 37 LAST_ACK 64 FIN_WAIT_1 65 FIN_WAIT_2 1251 TIME_WAIT 3597 SYN_SENT 5124 ESTABLISHED Get List Of All Unique IP Address
To print list of all unique IP address connected to server, enter: # netstat -nat | awk '{ print $5}' | cut -d: -f1 | sed -e '/^$/d' | uniq
To print total of all unique IP address, enter: # netstat -nat | awk '{ print $5}' | cut -d: -f1 | sed -e '/^$/d' | uniq | wc -l
Output: 449
Find Out If Box is Under DoS Attack or Not If you think your Linux box is under attack, print out a list of open connections on your box and sorts them by according to IP address, enter: # netstat -atun | awk '{print $5}' | cut -d: -f1 | sed -e '/^$/d' |sort | uniq -c | sort -n
You can simply block all abusive IPs using iptables or just null route them. 使用iptables来做限制
Get Live View of TCP Connections You can use tcptrack command to display the status of TCP connections that it sees on a given network interface. tcptrack monitors their state and displays information such as state, source/destination addresses and bandwidth usage in a sorted, updated list very much like the top command.
Display Summary Statistics for Each Protocol Simply use netstat -s: # netstat -s | less # netstat -t -s | less # netstat -u -s | less # netstat -w -s | less # netstat -s
Output: Ip: 88354557 total packets received 0 forwarded 0 incoming packets discarded 88104061 incoming packets delivered 96037391 requests sent out 13 outgoing packets dropped 66 fragments dropped after timeout 295 reassemblies required 106 packets reassembled ok 66 packet reassembles failed 34 fragments failed Icmp: 18108 ICMP messages received 58 input ICMP message failed. ICMP input histogram: destination unreachable: 7173 timeout in transit: 472 redirects: 353 echo requests: 10096 28977 ICMP messages sent 0 ICMP messages failed ICMP output histogram: destination unreachable: 18881 echo replies: 10096 Tcp: 1202226 active connections openings 2706802 passive connection openings 7394 failed connection attempts 47018 connection resets received 23 connections established 87975383 segments received 95235730 segments send out 681174 segments retransmited 2044 bad segments received. 80805 resets sent Udp: 92689 packets received 14611 packets to unknown port received. 0 packet receive errors 96755 packets sent TcpExt: 48452 invalid SYN cookies received 7357 resets received for embryonic SYN_RECV sockets 43 ICMP packets dropped because they were out-of-window 5 ICMP packets dropped because socket was locked 2672073 TCP sockets finished time wait in fast timer 441 time wait sockets recycled by time stamp 368562 delayed acks sent 430 delayed acks further delayed because of locked socket Quick ack mode was activated 36127 times 32318597 packets directly queued to recvmsg prequeue. 741479256 packets directly received from backlog 1502338990 packets directly received from prequeue 18343750 packets header predicted 10220683 packets header predicted and directly queued to user 17516622 acknowledgments not containing data received 36549771 predicted acknowledgments 102672 times recovered from packet loss due to fast retransmit Detected reordering 1596 times using reno fast retransmit Detected reordering 1 times using time stamp 8 congestion windows fully recovered 32 congestion windows partially recovered using Hoe heuristic 19 congestion windows recovered after partial ack 0 TCP data loss events 39951 timeouts after reno fast retransmit 29653 timeouts in loss state 197005 fast retransmits 186937 retransmits in slow start 131433 other TCP timeouts TCPRenoRecoveryFail: 20217 147 times receiver scheduled too late for direct processing 29010 connections reset due to unexpected data 365 connections reset due to early user close 6979 connections aborted due to timeout Display Interface Table
You can easily display dropped and total transmitted packets with netstat for eth0: # netstat --interfaces eth0
十七、Cacti - 基于Web的监控工具 Cacti是一套完成的网络图形化解决方案，基于RRDTool的资料存储和图形化功能。 Cacti提供一个快速的轮询器、进阶的图形化模板、多种 数据采集方法和用户管理功能。 All of this is wrapped in an intuitive, easy to use interface that makes sense for LAN-sized installations up to complex networks with hundreds of devices. 它提供关于网络、CPU、内存、已登录用户、Apache、DNS等信息。 关于怎样在CentOS / RHEL安装配置Cacti， 详见: monitoring-rrd-software/
