Get address family from socket. Linux

Question

I want to write a C++ wrapper for the Linux Socket API. In the socket() ctor the adress family (AF) is requested. I dont want to require the AF in the connect() signature again, becuase it has been already given in the constructor of socket. So how do I get the AF from an existing socket?

Answer 1

Damn. Searched about half an hour. Now after posting this question I found immiediately the answer.

getsockopt([...]) with option SO_DOMAIN (see socket options)

Answer 2

POSIX-standard getsockname will help:

int getsockname(int socket, struct sockaddr *restrict address,
       socklen_t *restrict address_len);

it will fill in given struct sockaddr (upon success):

struct sockaddr {
    unsigned short    sa_family;  // <- that's what you looking for
    char              sa_data[14];  
}