• Jeff Dike's avatar
    [PATCH] uml: assign random MACs to interfaces if necessary · f3e7ed2b
    Jeff Dike authored
    Assign a random MAC to an ethernet interface if one was not provided on the
    command line.  This became pressing when distros started bringing interfaces
    up before assigning IPs to them.  The previous pattern of assigning an IP then
    bringing it up allowed the MAC to be generated from the first IP assigned.
    However, once the thing is up, it's probably a bad idea to change the MAC, so
    the MAC stayed initialized to fe:fd:0:0:0:0.
    
    Now, if there is no MAC from the command line, one is generated.  We use the
    microseconds from gettimeofday (20 bits), plus the low 12 bits of the pid to
    seed the random number generator.  random() is called twice, with 16 bits of
    each result used.  I didn't want to have to try to fill in 32 bits optimally
    given an arbitrary RAND_MAX, so I just assume that it is greater than 65536
    and use 16 bits of each random() return.
    
    There is also a bit of reformatting and whitespace cleanup here.
    Signed-off-by: default avatarJeff Dike <jdike@addtoit.com>
    Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
    f3e7ed2b
net_user.h 1.65 KB