find_who_change_mtu

问题现象:
修改网卡的mtu之后，发现它隔几秒就会被改回去。
初始值9000：
[root@localhost ~]# ifconfig  eth0  | grep mtu
eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 9000
修改为1500：
[root@localhost ~]# ifconfig  eth0 mtu 1500
隔几秒查，发现被改回去了：
[root@localhost ~]# ifconfig  eth0  | grep mtu
eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 9000

[61051.331107] i40e 0000:0a:00.3 eth0: changing MTU from 9000 to 1500
[61054.861079] i40e 0000:0a:00.3 eth0: changing MTU from 1500 to 9000

编写systamtap脚本，找出修改mtu的进程、父进程、祖父进程......等。
# cat mtu.stp
probe kernel.function("dev_set_mtu")
{
	printf(">>> call stack: \n");
	print_backtrace();

	pp = task_parent(task_current());
	printf("%-8d %-16s \n",pid(), execname());
	printf("<---parent: %-8d %-16s\n", task_pid(pp), task_execname(pp) );

	ppp =  task_parent(pp);
	printf("<---parent: %-8d %-16s\n", task_pid(ppp), task_execname(ppp) );

	p4 =  task_parent(ppp);
	printf("<---parent: %-8d %-16s\n", task_pid(p4), task_execname(p4) );
}

第一次是手工修改mtu：
>>> call stack:
 0xffffffff81528f80 : dev_set_mtu+0x0/0x80 [kernel]
 0xffffffff8154334c : dev_ifsioc+0x24c/0x380 [kernel]
 0xffffffff81543569 : dev_ioctl+0xe9/0x590 [kernel]
 0xffffffff81510755 : sock_do_ioctl+0x45/0x50 [kernel]
 0xffffffff81510e60 : sock_ioctl+0x1f0/0x2c0 [kernel]
 0xffffffff811f3435 : do_vfs_ioctl+0x2e5/0x4c0 [kernel]
 0xffffffff811f36b1 : SyS_ioctl+0xa1/0xc0 [kernel]
 0xffffffff81649309 : system_call_fastpath+0x16/0x1b [kernel]
24280 ifconfig
<---parent: 31121    bash
<---parent: 31021    sshd
<---parent: 4748     sshd

第二次是一个脚本xxxipset.sh做的：
>>> call stack:
 0xffffffff81528f80 : dev_set_mtu+0x0/0x80 [kernel]
 0xffffffff8154334c : dev_ifsioc+0x24c/0x380 [kernel]
 0xffffffff81543569 : dev_ioctl+0xe9/0x590 [kernel]
 0xffffffff81510755 : sock_do_ioctl+0x45/0x50 [kernel]
 0xffffffff81510e60 : sock_ioctl+0x1f0/0x2c0 [kernel]
 0xffffffff811f3435 : do_vfs_ioctl+0x2e5/0x4c0 [kernel]
 0xffffffff811f36b1 : SyS_ioctl+0xa1/0xc0 [kernel]
 0xffffffff81649309 : system_call_fastpath+0x16/0x1b [kernel]
24306 ifconfig
<---parent: 8656     xxxipset.sh
<---parent: 1        systemd
<---parent: 0        swapper/0