sockaddr, sockaddr_in, sockaddr_in6, sockaddr_un

typedef __kernel_sa_family_t sa_family_t;

struct sockaddr {
sa_family_t sa_family; /* address family, AF_xxx*/
char sa_data[14];/* 14 bytes of protocol address*/
};

---16个字节长度


struct in_addr {
__be32 s_addr;
};
#define __SOCK_SIZE__ 16/* sizeof(struct sockaddr)*/
struct sockaddr_in {
  __kernel_sa_family_t sin_family;/* Address family*/
  __be16 sin_port;/* Port number*/
  struct in_addr sin_addr;/* Internet address*/

  /* Pad to size of `struct sockaddr'. 补充到16个字节长度 */
  unsigned char __pad[__SOCK_SIZE__ - sizeof(short int) -
sizeof(unsigned short int) - sizeof(struct in_addr)];
};


struct in6_addr {
union {
__u8 u6_addr8[16];
__be16 u6_addr16[8];
__be32 u6_addr32[4];
} in6_u;
#define s6_addr in6_u.u6_addr8
#define s6_addr16 in6_u.u6_addr16
#define s6_addr32 in6_u.u6_addr32
};
struct sockaddr_in6 {
unsigned short intsin6_family;    /* AF_INET6 */
__be16 sin6_port;      /* Transport layer port # */
__be32 sin6_flowinfo;  /* IPv6 flow information */
struct in6_addrsin6_addr;      /* IPv6 address */ 
__u32 sin6_scope_id;  /* scope id (new in RFC2553) */
};


typedef unsigned short __kernel_sa_family_t;
#define UNIX_PATH_MAX 108
struct sockaddr_un {
__kernel_sa_family_t sun_family; /* AF_UNIX */
char sun_path[UNIX_PATH_MAX];/* pathname */
};

char *get_ip_str(const struct sockaddr *sa, char *s, size_t maxlen)
{
    switch(sa->sa_family) {
        case AF_INET:
            inet_ntop(AF_INET, &(((struct sockaddr_in *)sa)->sin_addr),
                    s, maxlen);
            break;


        case AF_INET6:
            inet_ntop(AF_INET6, &(((struct sockaddr_in6 *)sa)->sin6_addr),
                    s, maxlen);
            break;


        default:
            strncpy(s, "Unknown AF", maxlen);
            return NULL;
    }


    return s;
}