fix($code): --20211120 fix a small bug in attack.c

[Jacob953]

Describe the bug

• It does not automatically add '\0' to the end of character arrays in C language.
• To generate random hostnames, it just lacks one unit for length of array name, which should be 6 rather than 5.

a small bug, which has mentioned in the Tasks book :)

What I'd done

• I just expanded array length on lines between 56 and 62.
• And I'm sorry that the code style is changed by my VS Code auto-formatting plug-in when saving. (

@kevin-w-du

[kevin-w-du]

Can you please use a plain-text editor to make the change. It is very hard for us to see exactly what changes you have made due to the style change. I feel very uncomfortable to commit the changes. This will also destroy the contribution made by the other people in the past. Thanks for your help.