# 樹莓派Wifi基地台

****目的:使用樹莓派將實體乙太網路打造成wifi ap分享器****

**準備材料:**
1. 樹莓派3 x1
2. 網路線 x1
3. PL2303(usb to uart)
4. SD x1(8g以上)

**操作環境:**
ubuntu 18.04.2 LTS

## 格式化SD卡
**使用fdisk指令**
>1. fdisk /dev/sdX
**X是SD卡裝置**
> 2. 之後使用**d**刪除分割區以及使用**n**建立你想要的切割區

## 燒錄作業系統raspbian到SD卡上

燒錄檔版本: 2020-02-13-raspbian-buster
**問題1：** 在'sudo apt-get update -y'的時候可能會遇到更新網址過期問題可用以下指令解決
>sudo apt-get -y update --allow-releaseinfo-change

**問題2：** 出現以下訊息需注意電源線和電源是否供電足夠
>>Voltage normalised (0x00000000)

1. 從觀網上下載raspbian的映像擋
2. 使用命令**dd**將映像擋燒錄到SD卡上
> dd status=progress bs=4M conv=sync if=$place_to_image/raspbian.img of=/dev/sdX
3. 成功之後將SD卡拔掉重新插入之後系統如果顯示**boot**和**rootfs**兩個資料夾則表示燒錄成功

## 藉由uart連接電腦和樹莓派
1. 須修改**boot**資料夾裡面的**cmdline.txt**和**config.txt**兩個檔案
cmdline.txt: 刪除檔案裡面的quiet字體
config.txt:加入以下三行
>dtoverlay=pi3-miniuart-bt
core_freq=250
enable_uart=1
2. 硬體部份會使用PL2303連接樹莓派和電腦
> **樹莓派腳位**
> **PL2303**

> PL2303使用上有四條片分別是
> 1. 5v電源(紅色)
> 2. GND(黑色)
> 3. TX(綠色)
> 4. RX(白色)

3. 腳位連接
**PL2303---樹莓派**
3.1 GND(黑色)---pin6,pin9,pin14,pin20,pin25,pin30,pin34,pin34
3.2 TX(綠色)---RX(pin10)
3.3 RX(白色)---TX(pin8)

4. 通訊軟體接
使用putty連接,設定參數如下:

之後上電之後putty會開始跑出開機訊息,最後要輸入預設的帳號密碼

> 帳號:pi
> 密碼:raspberry
## 打造樹莓派wifi分享器
****連接內部wifi網路(wlan0)和外部網路(eth0)的橋接器(樹莓派)****

1. 設定乙太網路
1.1 接上網路線
2.1 設定/etc/network/interfaces
> auto eth0
iface eth0 inet static
address 192.168.188.40
network 255.255.255.0
broadcast 192.168.188.255
gateway 192.168.188.254
dns-nameservers 192.168.188.254 168.95.192.1 168.95.1.1

>auto wlan0
iface wlan0 inet static
address 192.168.2.1
netmask 255.255.255.0

2.2 使用ifconfig和ifup指令來設定eth0界面
> ifup eth0
ifconfig eth0 down
ifconfig eth0 up

2.3 使用ifconfig 來看IP是否設定成功
> ifconfig eth0
>
2.4 重啟網路服務:
> /etc/init.d/networking restart.

3. DHCP 伺服器
在內部的wifi網路裡面需要一個DHCP伺服器來動態分配IP

3.1 下載一個DHCP 伺服器-isc-dhcp-server
> apt-get install isc-dhcp-server
>
3.2 修改/etc/dhcp/dhcpd.conf,以下是我修改後的檔案

# dhcpd.conf                                                                    
#                                                                               
# Sample configuration file for ISC dhcpd                                       
#                                                                               
                                                                                
# option definitions common to all supported networks...                        
#option domain-name "example.org";                                              
#option domain-name-servers ns1.example.org, ns2.example.org;                   
                                                                                
default-lease-time 600;                                                         
max-lease-time 7200;                                                            
                                                                                
# The ddns-updates-style parameter controls whether or not the server will      
# attempt to do a DNS update when a lease is confirmed. We default to the       
# behavior of the version 2 packages ('none', since DHCP v2 didn't              
# have support for DDNS.)                                                       
ddns-update-style none;                                                         
                                                                                
# If this DHCP server is the official DHCP server for the local                 
# network, the authoritative directive should be uncommented.                   
authoritative;                                                                  
                                                                                
# Use this to send dhcp log messages to a different log file (you also          
# have to hack syslog.conf to complete the redirection).                        
#log-facility local7;                                                           
                                                                                
# No service will be given on this subnet, but declaring it helps the           
# DHCP server to understand the network topology.                               
                                                                                
#subnet 10.152.187.0 netmask 255.255.255.0 {                                    
#}                                                                              
                                                                                
# This is a very basic subnet declaration.                                      
                                                                                
#subnet 10.254.239.0 netmask 255.255.255.224 {                                  
#  range 10.254.239.10 10.254.239.20;                                           
#  option routers rtr-239-0-1.example.org, rtr-239-0-2.example.org;             
#}                                                                              
                                                                                
# This declaration allows BOOTP clients to get dynamic addresses,               
# which we don't really recommend.                                              
                                                                                
#subnet 10.254.239.32 netmask 255.255.255.224 {                                 
#  range dynamic-bootp 10.254.239.40 10.254.239.60;                             
#  option broadcast-address 10.254.239.31;                                      
#  option routers rtr-239-32-1.example.org;                                     
#}                                                                              
                                                                                
# A slightly different configuration for an internal subnet.                    
#subnet 10.5.5.0 netmask 255.255.255.224 {                                      
#  range 10.5.5.26 10.5.5.30;                                                   
#  option domain-name-servers ns1.internal.example.org;                         
#  option domain-name "internal.example.org";                                   
#  option routers 10.5.5.1;                                                     
#  option broadcast-address 10.5.5.31;                                          
#  default-lease-time 600;                                                      
#  max-lease-time 7200;                                                         
#}                                                                              
                                                                                
subnet 192.168.2.0 netmask 255.255.255.0 {                                      
  range 192.168.2.10 192.168.2.50;                                              
  option domain-name-servers 168.95.192.1, 168.95.1.1 ;                                     
  option domain-name "local";                                                   
  option routers 192.168.2.1;                                                   
  option broadcast-address 192.168.188.255;                                     
  default-lease-time 600;                                                       
  max-lease-time 7200;                                                          
}                                                                               
                                                                                
# Hosts which require special configuration options can be listed in            
# host statements.   If no address is specified, the address will be            
# allocated dynamically (if possible), but the host-specific information        
# will still come from the host declaration.                                    
                                                                                
#host passacaglia {                                                             
#  hardware ethernet 0:0:c0:5d:bd:95;                                           
#  filename "vmunix.passacaglia";                                               
#  server-name "toccata.example.com";                                           
#}                                                                              
                                                                                
# Fixed IP addresses can also be specified for hosts.   These addresses         
# should not also be listed as being available for dynamic assignment.          
# Hosts for which fixed IP addresses have been specified can boot using         
# BOOTP or DHCP.   Hosts for which no fixed address is specified can only       
# be booted with DHCP, unless there is an address range on the subnet           
# to which a BOOTP client is connected which has the dynamic-bootp flag         
# set.                                                                          
#host fantasia {                                                                
#  hardware ethernet 08:00:07:26:c0:a5;                                         
#  fixed-address fantasia.example.com;                                          
#}                                                                              
                                                                                
# You can declare a class of clients and then do address allocation             
# based on that.   The example below shows a case where all clients             
# in a certain class get addresses on the 10.17.224/24 subnet, and all          
# other clients get addresses on the 10.0.29/24 subnet.                         
                                                                                
#class "foo" {                                                                  
#  match if substring (option vendor-class-identifier, 0, 4) = "SUNW";          
#}                                                                              
                                                                                
#shared-network 224-29 {                                                        
#  subnet 10.17.224.0 netmask 255.255.255.0 {                                   
#    option routers rtr-224.example.org;                                        
#  }                                                                            
#  subnet 10.0.29.0 netmask 255.255.255.0 {                                     
#    option routers rtr-29.example.org;                                         
#  }                                                                            
#  pool {                                                                       
#    allow members of "foo";                                                    
#    range 10.17.224.10 10.17.224.250;                                          
#  }                                                                            
#  pool {                                                                       
#    deny members of "foo";                                                     
#    range 10.0.29.10 10.0.29.230;                                              
#  }                                                                            
#}               

3.3 修改/etc/default/isc-dhcp-server,以下是我修改後的檔案

# Defaults for isc-dhcp-server (sourced by /etc/init.d/isc-dhcp-server)

# Path to dhcpd's config file (default: /etc/dhcp/dhcpd.conf).
#DHCPDv4_CONF=/etc/dhcp/dhcpd.conf
#DHCPDv6_CONF=/etc/dhcp/dhcpd6.conf

# Path to dhcpd's PID file (default: /var/run/dhcpd.pid).
#DHCPDv4_PID=/var/run/dhcpd.pid
#DHCPDv6_PID=/var/run/dhcpd6.pid

# Additional options to start dhcpd with.
#       Don't use options -cf or -pf here; use DHCPD_CONF/ DHCPD_PID instead
#OPTIONS=""

# On what interfaces should the DHCP server (dhcpd) serve DHCP requests?
#       Separate multiple interfaces with spaces, e.g. "eth0 eth1".
INTERFACESv4="wlan0"
INTERFACESv6="wlan0"

3.4 重新啟動DHCP服務
>service isc-dhcp-server restart

4. 封包轉送
****將內部網路(wlan0)的封包外部網路(eth0)之間轉送****

4.1 修改/etc/sysctl.conf裡的net.ipv4.ip_forward
>net.ipv4.ip_forward=1

4.2 使用下列指令是封包轉送馬上生效
>sh -c "echo 1 > /proc/sys/net/ipv4/ip_forward"

4.3 設定 NAT,下以下指令
>iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE

>iptables -A FORWARD -i eth0 -o wlan0 -m state --state RELATED,ESTABLISHED -j ACCEPT

>iptables -A FORWARD -i wlan0 -o eth0 -j ACCEPT
>
4.4 為了讓NAT在每次啟動時候都可以自動執行須下以下指令
>sh -c "iptables-save > /etc/iptables.ipv4.nat"

以及在/etc/network/interfaces，加入：
>up iptables-restore < /etc/iptables.ipv4.nat

5. hostapd 服務

****需透過hostapd這個軟體將樹莓派本身的無線網卡設定成一個AP(access point)****

5.1 下載hostapd
> apt-get install hostapd

5.2 參考/usr/share/doc/hostapd/examples/hostapd.conf.gz 建立/etc/hostapd/hostapd.conf 設定檔
修改部份可以參考****參考資料1****

5.3 修改/etc/default/hostapd設定檔使 DAEMON_CONF 指向 /etc/hostapd/hostapd.conf
> DAEMON_CONF="/etc/hostapd/hostapd.conf"

5.4 測試hostapd
> hostapd /etc/hostapd/hostapd.conf
>
5.5 /etc/rc.local

#!/bin/sh -e
#
# rc.local
#
# This script is executed at the end of each multiuser runlevel.
# Make sure that the script will "exit 0" on success or any other
# value on error.
#
# In order to enable or disable this script just change the execution
# bits.
#
# By default this script does nothing.

# Print the IP address
_IP=$(hostname -I) || true
if [ "$_IP" ]; then
  printf "My IP address is %s\n" "$_IP"
fi
sudo hostapd /etc/hostapd/hostapd.conf &
exit 0

****參考資料:****
[1. 樹莓派 Raspberry Pi 設定無線網路 WiFi AP，打造無線 IP 分享器](https://blog.gtwang.org/iot/setup-raspberry-pi-as-wireless-access-point/)
[2. 兩部主機兩點溝通： ping](http://linux.vbird.org/linux_server/0140networkcommand.php#ping)
[3. NAT 伺服器的設定](http://linux.vbird.org/linux_server/0250simple_firewall.php#nat)
[4. GNU / Linux 各種壓縮與解壓縮指令](http://note.drx.tw/2008/04/command.html)
[5. Linux下使用hostapd 建立 WiFi訪問熱點](https://b8807053.pixnet.net/blog/post/349831267-linux%E4%B8%8B%E4%BD%BF%E7%94%A8hostapd-%E5%BB%BA%E7%AB%8B-wifi%E8%A8%AA%E5%95%8F%E7%86%B1%E9%BB%9E)
###### tags: `raspberry pi` `wifi 基地台`