busybox: using ip instead of ifconfig for ifup/ifdown
There is an issue for requesting dynamic IP with ifup/ifdown command
when using dhclient.
Steps to reproduce:
1. Build a full-cmdline image and install dhcp-client as the default DHCP client.
2. Configure a static IP for eth0 in /etc/networking/interfaces and reboot.
$ ifconfig eth0
eth0 inet addr:192.168.1.2 Bcast:192.168.1.255 Mask:255.255.255.0
$ ifdown eth0
3. Modify /etc/networking/interfaces to configure a dynamic IP for eth0
$ ifup eth0
$ ifconfig eth0
eth0 inet addr:192.168.1.2 Bcast:192.168.1.255 Mask:255.255.255.0
You could see the eth0 still has a static IP. But actually it also has a
dynamic IP:
$ ip addr show eth0
eth0:
inet 192.168.1.2/24 brd 192.168.1.255 scope global eth0
inet 128.224.162.173/23 brd 128.224.163.255 scope global eth0
The root cause is the ifdown invokes "ifconfig" to down the eth0 but
doesn't remove its IP. The dhclient would invoke "ip" to configure the
interface. It can not remove an IP from down interface with "ip addr
flush" and "ip addr add" command can set multiple IPs on one interface.
To fix this issue, we should use the "ip" command to implement
ifup/ifdown, rather than using the older "ifconfig". It will flush the
IP before down the interface.
Signed-off-by: Yi Zhao <yi.zhao@windriver.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
