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GETADDRINFO(3)	       FreeBSD Library Functions Manual		GETADDRINFO(3)

NAME
     getaddrinfo freeaddrinfo, gai_strerror -- nodename-to-address translation
     in	protocol-independent manner

SYNOPSIS
     #include <sys/socket.h>
     #include <netdb.h>

     int
     getaddrinfo(const char *nodename, const char *servname,
	 const struct addrinfo *hints, struct addrinfo **res);

     void
     freeaddrinfo(struct addrinfo *ai);

     char *
     gai_strerror(int ecode);

DESCRIPTION
     The getaddrinfo() function	is defined for protocol-independent nodename-
     to-address	translation.  It performs functionality	of gethostbyname(3)
     and getservbyname(3), in more sophisticated manner.

     The addrinfo structure is defined as a result of including	the <netdb.h>
     header:

     struct addrinfo {							*
	  int	  ai_flags;	/* AI_PASSIVE, AI_CANONNAME, AI_NUMERICHOST */
	  int	  ai_family;	/* PF_xxx */
	  int	  ai_socktype;	/* SOCK_xxx */
	  int	  ai_protocol;	/* 0 or	IPPROTO_xxx for	IPv4 and IPv6 */
	  size_t  ai_addrlen;	/* length of ai_addr */
	  char	 *ai_canonname;	/* canonical name for nodename */
	  struct sockaddr  *ai_addr; /*	binary address */
	  struct addrinfo  *ai_next; /*	next structure in linked list */
     };

     The nodename and servname arguments are pointers to null-terminated
     strings or	NULL.  One or both of these two	arguments must be a non-NULL
     pointer.  In the normal client scenario, both the nodename	and servname
     are specified.  In	the normal server scenario, only the servname is spec-
     ified.  A non-NULL	nodename string	can be either a	node name or a numeric
     host address string (i.e.,	a dotted-decimal IPv4 address or an IPv6 hex
     address).	A non-NULL servname string can be either a service name	or a
     decimal port number.

     The caller	can optionally pass an addrinfo	structure, pointed to by the
     third argument, to	provide	hints concerning the type of socket that the
     caller supports.  In this hints structure all members other than
     ai_flags, ai_family, ai_socktype, and ai_protocol must be zero or a NULL
     pointer.  A value of PF_UNSPEC for	ai_family means	the caller will	accept
     any protocol family.  A value of 0	for ai_socktype	means the caller will
     accept any	socket type.  A	value of 0 for ai_protocol means the caller
     will accept any protocol.	For example, if	the caller handles only	TCP
     and not UDP, then the ai_socktype member of the hints structure should be
     set to SOCK_STREAM	when getaddrinfo() is called.  If the caller handles
     only IPv4 and not IPv6, then the ai_family	member of the hints structure
     should be set to PF_INET when getaddrinfo() is called.  If	the third ar-
     gument to getaddrinfo() is	a NULL pointer,	this is	the same as if the
     caller had	filled in an addrinfo structure	initialized to zero with
     ai_family set to PF_UNSPEC.

     Upon successful return a pointer to a linked list of one or more addrinfo
     structures	is returned through the	final argument.	 The caller can
     process each addrinfo structure in	this list by following the ai_next
     pointer, until a NULL pointer is encountered.  In each returned addrinfo
     structure the three members ai_family, ai_socktype, and ai_protocol are
     the corresponding arguments for a call to the socket() function.  In each
     addrinfo structure	the ai_addr member points to a filled-in socket	ad-
     dress structure whose length is specified by the ai_addrlen member.

     If	the AI_PASSIVE bit is set in the ai_flags member of the	hints struc-
     ture, then	the caller plans to use	the returned socket address structure
     in	a call to bind().  In this case, if the	nodename argument is a NULL
     pointer, then the IP address portion of the socket	address	structure will
     be	set to INADDR_ANY for an IPv4 address or IN6ADDR_ANY_INIT for an IPv6
     address.

     If	the AI_PASSIVE bit is not set in the ai_flags member of	the hints
     structure,	then the returned socket address structure will	be ready for a
     call to connect() (for a connection-oriented protocol) or either
     connect(),	sendto(), or sendmsg() (for a connectionless protocol).	 In
     this case,	if the nodename	argument is a NULL pointer, then the IP	ad-
     dress portion of the socket address structure will	be set to the loopback
     address.

     If	the AI_CANONNAME bit is	set in the ai_flags member of the hints	struc-
     ture, then	upon successful	return the ai_canonname	member of the first
     addrinfo structure	in the linked list will	point to a null-terminated
     string containing the canonical name of the specified nodename.

     If	the AI_NUMERICHOST bit is set in the ai_flags member of	the hints
     structure,	then a non-NULL	nodename string	must be	a numeric host address
     string.  Otherwise	an error of EAI_NONAME is returned.  This flag pre-
     vents any type of name resolution service (e.g., the DNS) from being
     called.

     All of the	information returned by	getaddrinfo() is dynamically allo-
     cated: the	addrinfo structures, and the socket address structures and
     canonical node name strings pointed to by the addrinfo structures.	 To
     return this information to	the system the function	Fn freeaddrinfo	is
     called.  The addrinfo structure pointed to	by the ai argument is freed,
     along with	any dynamic storage pointed to by the structure.  This opera-
     tion is repeated until a NULL ai_next pointer is encountered.

     To	aid applications in printing error messages based on the EAI_xxx codes
     returned by getaddrinfo(),	gai_strerror() is defined.  The	argument is
     one of the	EAI_xxx	values defined earlier and the return value points to
     a string describing the error.  If	the argument is	not one	of the EAI_xxx
     values, the function still	returns	a pointer to a string whose contents
     indicate an unknown error.

FILES
     /etc/hosts
     /etc/host.conf
     /etc/resolv.conf

DIAGNOSTICS
     Error return status from getaddrinfo() is zero on success and non-zero on
     errors.  Non-zero error codes are defined in <netdb.h>, and as follows:

     EAI_ADDRFAMILY  address family for	nodename not supported
     EAI_AGAIN	     temporary failure in name resolution
     EAI_BADFLAGS    invalid value for ai_flags
     EAI_FAIL	     non-recoverable failure in	name resolution
     EAI_FAMILY	     ai_family not supported
     EAI_MEMORY	     memory allocation failure
     EAI_NODATA	     no	address	associated with	nodename
     EAI_NONAME	     nodename nor servname provided, or	not known
     EAI_SERVICE     servname not supported for	ai_socktype
     EAI_SOCKTYPE    ai_socktype not supported
     EAI_SYSTEM	     system error returned in errno

     If	called with proper argument, gai_strerror() returns a pointer to a
     string describing the given error code.  If the argument is not one of
     the EAI_xxx values, the function still returns a pointer to a string
     whose contents indicate an	unknown	error.

SEE ALSO
     getnameinfo(3), gethostbyname(3), getservbyname(3), hosts(5),
     services(5), hostname(7)

     R.	Gilligan, S.  Thomson, J. Bound, and W.	Stevens, ``Basic Socket	Inter-
     face Extensions for IPv6,'' RFC2133, April	1997.

HISTORY
     The implementation	first appeared in WIDE Hydrangea IPv6 protocol stack
     kit.

STANDARDS
     The getaddrinfo() function	is defined IEEE	POSIX 1003.1g draft specifica-
     tion, and documented in ``Basic Socket Interface Extensions for IPv6''
     (RFC2133).

BUGS
     The text was shamelessly copied from RFC2133.

KAME				 May 25, 1995				  KAME

NAME | SYNOPSIS | DESCRIPTION | FILES | DIAGNOSTICS | SEE ALSO | HISTORY | STANDARDS | BUGS

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