Hi,

I have a lot of student that does not use correctly getsockname in case of 
dual stack. 

May be this kind of discussion should be factorized in  sockaddr_storage (the 
historical note particularly).

i suppose the same should be done for getpeername

I think a safe programming example may be given that accept a socket as stdin 
and print information on it. Using socat it could be simple to test. maybe 
forcing ENOTSUPP if *addr > sizeof(sockadd_storage)

Regards

Bastien