/*************************************************************************************** * Linux udhcp client (udhcpc) get IP at anytime * 聲明： * 對於ARM產品，之前在想如何能夠做到像PC機那樣，當網線插入RJ45座的時候，就能自動獲 * 取到IP，這樣就無需另外去設置IP等相關信息，主要考慮到嵌入式產品有時候可能根本沒有圖形 * 界面，如果不能自動連接網絡，只能通過調試口去設置網絡，不合情理，直覺認為可能需要依賴 * udhcpc來做這件事，於是發現了udhcpc命令的-b參數。 * * 2015-10-21 晴 深圳 南山平山村 曾劍鋒 **************************************************************************************/ 一、參考文章： 1. Busybox Command Help http://busybox.net/downloads/BusyBox.html 2. udhcpc 后台運行的方法【總結】 http://www.360doc.com/content/12/0323/09/9106558_196861856.shtml 3. udhcpc running in the background [Summary] http://www.programmershare.com/2365338/ 二、busybox udhcpc help: udhcpc [-Cfbnqtvo] [-c CID] [-V VCLS] [-H HOSTNAME] [-i INTERFACE] [-p pidfile] [-r IP] [-s script] [-O dhcp-option]... -V,--vendorclass=CLASSID Vendor class identifier -i,--interface=INTERFACE Interface to use (default eth0) -H,-h,--hostname=HOSTNAME Client hostname -c,--clientid=CLIENTID Client identifier -C,--clientid-none Suppress default client identifier -p,--pidfile=file Create pidfile -r,--request=IP IP address to request -s,--script=file Run file at DHCP events (default /usr/share/udhcpc/default.script) -t,--retries=N Send up to N request packets -T,--timeout=N Try to get a lease for N seconds (default 3) -A,--tryagain=N Wait N seconds (default 20) after failure -O,--request-option=OPT Request DHCP option OPT (cumulative) -o,--no-default-options Do not request any options (unless -O is also given) -f,--foreground Run in foreground -b,--background Background if lease is not immediately obtained -S,--syslog Log to syslog too -n,--now Exit with failure if lease is not immediately obtained -q,--quit Quit after obtaining lease -R,--release Release IP on quit -a,--arping Use arping to validate offered address 三、udhcpc -b test： root@freescale ~$ ifconfig eth0 Link encap:Ethernet HWaddr 1E:ED:19:27:1A:B3 UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:0 (0.0 B) TX bytes:0 (0.0 B) lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:124 errors:0 dropped:0 overruns:0 frame:0 TX packets:124 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:400286 (390.9 KiB) TX bytes:400286 (390.9 KiB) root@freescale ~$ udhcpc -b （這里我並沒有用udhcpc -b -i eth0 -p /var/run/udhcpc.pid -R &） udhcpc (v1.20.2) started Sending discover... Sending discover... Sending discover... No lease, forking to background root@freescale ~$ PHY: 1:01 - Link is Up - 100/Full root@freescale ~$ ifconfig （插入網線之后，最好等上2-4秒才能獲取到IP） eth0 Link encap:Ethernet HWaddr 1E:ED:19:27:1A:B3 inet addr:10.0.1.52 Bcast:10.0.1.255 Mask:255.255.255.0 UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:4 errors:0 dropped:0 overruns:0 frame:0 TX packets:2 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:1316 (1.2 KiB) TX bytes:656 (656.0 B) lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:124 errors:0 dropped:0 overruns:0 frame:0 TX packets:124 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:400286 (390.9 KiB) TX bytes:400286 (390.9 KiB)