Re: One AF_* constant for each of sockaddr_{hci,l2cap,rfcomm}?

["Maksim Yevmenkin" <maksim_(_dot_)_yevmenkin_(_at_)_gmail_(_dot_)_com>]

On 8/30/07, Eugene M. Kim <freebsd_(_dot_)_org_(_at_)_ab_(_dot_)_ote_(_dot_)_we_(_dot_)_lv> wrote:
> Hello,
>
> It seems that AF_BLUETOOTH ambiguously identifies three different types
> of socket—HCI, L2CAP and RFCOMM—each with its own sockaddr_* type.  This
> deviates from the standard practice where there is a 1:1 mapping between
> an AF_* constant and a corresponding sockaddr_* type, and this may, in
> turn, break usage of system calls such as getsockname(2) and
> getpeername(2): These calls return a struct sockaddr whose sa_family
> should uniquely and unambiguously identify the real sockaddr_* struct to
> which the returned sockaddr should be type-cast; if sa_family ==
> AF_BLUETOOTH, there are three possibilities and an application that
> calls get{sock,peer}name(2) cannot choose one of them without extra
> information (namely, the third argument to the socket() call that
> created the socket).

the application probably can use sa_len field to figure out which
sockaddr_ structure it is. it is somewhat a hack but it should work.

> In this light, shouldn't a unique AF_* constant be allocated for each
> Bluetooth socket type, such as AF_BTHCI, AF_BTL2CAP and AF_BTRFCOMM,
> instead of just one AF_BLUETOOTH?

i'd rather not to it. may be it is better to add sa_proto field to
bluetooth sockaddr_ structures and have union data field for each
protocol?

thanks,
max
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