linux网络工具应用详解之二

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
http://www.cyberciti.biz/tips/linux-investigate-sockets-network-connections.html

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

Sample Output:
Total: 734 (kernel 904)
TCP:   1415 (estab 112, closed 1259, orphaned 11, synrecv 0, timewait 1258/0), ports 566
Transport Total     IP        IPv6
*  904       -         -
RAW  0         0         0
UDP  15        12        3
TCP  156       134       22
INET  171       146       25
FRAG  0         0         0  

Task: Display All Open Network Ports
​显示所有打开的网络端口
# ss -l

Sample Output:
ss -l
Recv-Q Send-Q           Local Address:Port                                                      Peer Address:Port
0      0                127.0.0.1:smux                                                                 *:*
0      0                127.0.0.1:10024                                                                *:*
0      0                127.0.0.1:10025                                                                *:*
0      0                        *:3306                                                                 *:*
0      0                         :http                                                                 *:*
0      0                        *:4949                                                                 *:*
0      0                        *:domain                                                               *:*
0      0                        *:ssh                                                                  *:*
0      0                        *:smtp                                                                 *:*
0      0                127.0.0.1:rndc                                                                 *:*
0      0                127.0.0.1:6010                                                                 *:*
0      0                        *:https                                                                *:*
0      0                        :::34571                                                               :::*
0      0                        :::34572                                                               :::*
0      0                        :::34573                                                               :::*
0      0                       ::1:rndc                                                                :::*       


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
http://www.cyberciti.biz/tips/netstat-command-tutorial-examples.html

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


Output:
      1 CLOSE_WAIT
      1 established)
      1 Foreign
      3 FIN_WAIT1
      3 LAST_ACK
     13 ESTABLISHED
     17 LISTEN
    154 FIN_WAIT2
    327 TIME_WAIT


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

Output:

    1 10.0.77.52
      2 10.1.11.3
      4 12.109.42.21
      6 12.191.136.3
.....
...
....
    13 202.155.209.202
     18 208.67.222.222
     28 0.0.0.0
    233 127.0.0.1

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

Output:
Kernel Interface table
Iface       MTU Met    RX-OK RX-ERR RX-DRP RX-OVR    TX-OK TX-ERR TX-DRP TX-OVR Flg
eth0       1500   0  2040929      0      0      0  3850539      0      0      0 BMRU


十三、 iptraf - 网络实时信息
iptraf是一个可交互式的IP网络监控工具。它可以生成多种网络统计信息包括：
TCP信息、UDP数量、ICMP和OSPF信息、以太网负载信息、节点状态、IP校验错误等。
有下面几种信息格式：
• 不同网络TCP链接传输量
• 不同网络接口IP传输量
• 不同协议网络传输量
• 不同TCP/UDP端口和不同包大小网络传输量
• 不同第二层地址网络传输量
 
图02：一般接口信息：不同网络接口IP传输量
 


图03：不同网络TCP链接传输量


十三、tcpdump：详细的网络流量分析
tcpdump是一个简单网络流量转储工具，然而要使用好需要对TCP/IP协议非常熟悉。

例如要显示关于DNS的网络流量，输入：
# tcpdump -i eth1 'udp port 53' 


显示所有进出80端口IPv4 HTTP包，也就是只打印包含数据的包。例如：SYN、FIN包和ACK-only包输入：
# tcpdump 'tcp port 80 and (((ip[2:2] - ((ip[0]&0xf)<<2)) - ((tcp[12]&0xf0)>>2)) != 0)'

显示所有到的FTP会话，输入：
# tcpdump -i eth1 'dst 202.54.1.5 and (port 21 or 20' 

显示所有到192.168.1.5的HTTP会话
# tcpdump -ni eth0 'dst 192.168.1.5 and tcp and port http'

用wireshark浏览转储文件中的详细信息，输入：
# tcpdump -n -i eth1 -s 0 -w output.txt src or dst port 80 

十四、strace - 系统调用
追踪系统调用和型号，这对于调试Web服务器和其他服务器非常有用。了解怎样追踪进程和他功能。

十五、/proc文件系统 - 各种内核信息
/proc目录下文件提供了很多不同硬件设备和内核的详细信息。更多详情参见Linux kernel /proc。一般/proc例如：
# cat /proc/cpuinfo
# cat /proc/meminfo
# cat /proc/zoneinfo
# cat /proc/mounts 


十六、Nagios - 服务器及网络监控
Nagios 是一款非常流行的系统及网络监控软件。
你可以轻松监控所有的主机、网络设备及服务。它能在发生故障和重新恢复后发送警讯。
FAN是"Fully Automated Nagios"的缩写。
FAN的目标就是由Nagios社群提供Nagios的安装。
为了使安装Nagios服务器更加容易，FAN提供一个标准ISO格 式的光盘镜像。
此发行版中还会包含一组增强用户使用体验的工具。
​
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:http://www.cyberciti.biz/faq/fedora-rhel-install-cacti- monitoring-rrd-software/