attr: Don't shift the 32-bit netmask by 32

attr: Don't shift the 32-bit netmask by 32

This is undefined behavior as per the C99 standard (sentence 1185):

 "If the value of the right operand is negative or is greater or equal
  to the width of the promoted left operand, the behavior is undefined."

Apparently shifts may be done modulo the width on some platforms so
a shift by 32 would not shift at all.