Laptop wireless network issue

Linux

本本无线网络经常会出现问题，首先需要判断什么问题，是否涉及到需要手动安装驱动。

• sudo rfkill list all
  先列出所有无线设备对应的 phsical id及其 Soft Block，Hard Block 状态：

# List the current state of all available rfkill-using devices(wireless devices), good, all is unblocked!
amy@heizi:~$ rfkill list all
0: phy0: Wireless LAN
	Soft blocked: no
	Hard blocked: no
# but if I type shortkey (Fn+F5) to turn off wifi light, it's soft blocked!
amy@heizi:~$ rfkill list all
0: phy0: Wireless LAN
    Soft blocked: yes
    Hard blocked: no
# so let's use command (rfkill unblock IDENTIFIER where IDENTIFIER is the index no. of an rfkill switch or one of:  <idx> all wifi wlan bluetooth uwb ultrawideband wimax wwan gps fm nfc) to turn up! OOOps, it works!
amy@heizi:~$ rfkill unblock 0
amy@heizi:~$ rfkill list all
0: phy0: Wireless LAN
    Soft blocked: no
    Hard blocked: no
# so if I use wifi hard-buttun under the Laptap to turn off wifi light.
amy@heizi:~$ rfkill list all
0: phy0: Wireless LAN
	Soft blocked: yes
	Hard blocked: yes
amy@heizi:~$ cat /sys/class/rfkill/rfkill0/soft 
1
amy@heizi:~$ cat /sys/class/rfkill/rfkill0/hard
1
#  use cmd (rfkill unblock 0) just unblock soft blocked!!!
amy@heizi:~$ rfkill unblock all
amy@heizi:~$ rfkill list all
0: phy0: Wireless LAN
	Soft blocked: no
	Hard blocked: yes
# 本想通过强制更改hard block状态为0（unblocked），但是发现该文件mode为root:root 444！
amy@heizi:~$ sudo -i echo 0 > /sys/class/rfkill/rfkill0/hard
bash: /sys/class/rfkill/rfkill0/hard: 权限不够
amy@heizi:~$ ll /sys/class/rfkill/rfkill0/hard 
-r--r--r-- 1 root root 4096 11月 20 21:21 /sys/class/rfkill/rfkill0/hard
# 那咱强改文件mode，再试
root@heizi:~# chmod 744 /sys/class/rfkill/rfkill0/hard 
root@heizi:~# sudo -i echo 0 > /sys/class/rfkill/rfkill0/hard 
-bash: 第 0 行: echo: 写错误: 输入/输出错误
# 还是不行啊，所以细心点吧，自己手动把wifi开关打开吧！

• sudo lshw -C net
  能识别到网卡信息的说明网卡驱动是有的，disabled可能是没有正确启用。

amy@heizi:~$ sudo lshw -C net
  *-network               
       description: Ethernet interface
       product: 82566MM Gigabit Network Connection
       vendor: Intel Corporation
       physical id: 19
       logical name: enp0s25
       capacity: 1Gbit/s
......(以太网卡信息略过)......
  *-network
       description: Wireless interface
       product: PRO/Wireless 3945ABG [Golan] Network Connection
       vendor: Intel Corporation
       physical id: 0
       bus info: pci@0000:03:00.0
       logical name: wls3
       version: 02
       serial: 00:1f:3c:c2:f6:fe
       width: 32 bits
       clock: 33MHz
       capabilities: pm msi pciexpress bus_master cap_list ethernet physical wireless
       configuration: broadcast=yes driver=iwl3945 driverversion=4.4.0-98-generic firmware=15.32.2.9 ip=192.168.1.113 latency=0 link=yes multicast=yes wireless=IEEE 802.11abg
       resources: irq:29 memory:dfcff000-dfcfffff
# 记住点网卡逻辑名 wls3, 以及driver名 iwl3945;

OK!!! 我们来看看，打开wifi硬阻塞后，查看lshw -C net情况：

amy@heizi:~$ rfkill list all  #硬阻塞
0: phy0: Wireless LAN
	Soft blocked: yes
	Hard blocked: yes
amy@heizi:~$ rfkill unblock all
amy@heizi:~$ rfkill list all
0: phy0: Wireless LAN
	Soft blocked: no
	Hard blocked: yes
amy@heizi:~$ sudo lshw -C net # 查看网络硬件信息
  *-network DISABLED
       description: Wireless interface
       product: PRO/Wireless 3945ABG [Golan] Network Connection
...
       physical id: 0
       logical name: wls3
...
       configuration: broadcast=yes driver=iwl3945 driverversion=4.4.0-98-generic firmware=15.32.2.9 latency=0 link=no multicast=yes wireless=IEEE 802.11abg
       resources: irq:29 memory:dfcff000-dfcfffff

我的ThinkPad carbon one第一代确实老了, 总是wifi几个小时之后莫名其妙drop 问题。

• lsmod
  

  lsmod is a trivial program which nicely formats the contents of the /proc/modules, showing what kernel modules are currently loaded.

amy@heizi:~$ lsmod
Module                  Size  Used by
ipt_MASQUERADE         16384  1
xfrm_user              32768  1
xfrm_algo              16384  1 xfrm_user
iptable_nat            16384  1
nf_conntrack_ipv4      16384  2
nf_defrag_ipv4         16384  1 nf_conntrack_ipv4
nf_nat_ipv4            16384  1 iptable_nat
iptable_filter         16384  1
ip_tables              24576  2 iptable_filter,iptable_nat
x_tables               36864  5 ip_tables,ipt_MASQUERADE,xt_conntrack,iptable_filter,xt_addrtype
......
bridge                126976  1 br_netfilter
......
kvm                   544768  1 kvm_intel
iwl3945                69632  0

• iwconfig
  该命令用于configure a wireless network interface。
• sudo iwlist wls3 scanning [essid,eg FAST_D16E]
  该命令会列出详细的无线信息，包括iwconfig已经有的和没有的信息。

• lspci | grep -i net

  lspci is a utility for displaying information about PCI buses in the system and devices connected to them.
  Host bridge: <==主板芯片
  VGA compatible controller <==显卡
  Audio device <==音频设备
  PCI bridge <==接口插槽
  USB Controller <==USB控制器
  ISA bridge
  IDE interface
  SMBus
  Ethernet controller <==网卡

• sudo ifconfig wls3 down/up

  Ifconfig is used to configure the kernel-resident network interfaces.
  It is used at boot time to set up interfaces as necessary. After that, it is usually only needed when debugging or when system tuning is needed.

• sudo rmmod -f iwl3945

  rmmod is a trivial program to remove a module (when module unloading support is provided) from the kernel. Most users will want to use modprobe(8) with the -r option instead.

  用 rmmod 命令主要用于卸载正在使用的Linux内核模块，与 modprobe -r 命令相似。

• sudo modprobe iwl3945 11n_disable=1

  modprobe intelligently adds or removes a module from the Linux kernel:
  note that for convenience, there is no difference between _ and - in module names.
  modprobe looks in the module directory /lib/modules/uname -r for all the modules and other files, except for the optional configuration files in the /etc/modprobe.d directory。

• dmesg
  dmesg命令设备故障的诊断是非常重要的。将系统启动信息保存到文件中：
  $ sudo dmesg > messages.txt

  Linux命令dmesg用来显示开机信息，kernel会将开机信息存储在ring buffer中。您若是开机时来不及查看信息，可利用dmesg来查看。开机信息亦保存在/var/log目录中，名称为dmesg的文件里。