linux netdb header that defines addrinfo struct

netdb.h

struct addrinfo
{
  int ai_flags;     /* Input flags.  */
  int ai_family;    /* Protocol family for socket.  */
  int ai_socktype;    /* Socket type.  */
  int ai_protocol;    /* Protocol for socket.  */
  socklen_t ai_addrlen;   /* Length of socket address.  */
  struct sockaddr *ai_addr; /* Socket address for socket.  */
  char *ai_canonname;   /* Canonical name for service location.  */  
  struct addrinfo *ai_next; /* Pointer to next in list.  */
};