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RedHat 9 (Linux i386) - man page for freeaddrinfo (redhat section 3)

getaddrinfo(3)			    Linux Programmer's Manual			   getaddrinfo(3)

NAME
       getaddrinfo - network address and service translation

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

       int getaddrinfo(const char *node, const char *service,
		       const struct addrinfo *hints,
		       struct addrinfo **res);

       void freeaddrinfo(struct addrinfo *res);

       const char *gai_strerror(int errcode);

DESCRIPTION
       The getaddrinfo(3) function combines the functionality provided by the getipnodebyname(3),
       getipnodebyaddr(3), getservbyname(3), and getservbyport(3) functions into a single  inter-
       face.   The  thread-safe getaddrinfo(3) function creates one or more socket address struc-
       tures that can be used by the bind(2) and connect(2) system calls to create a client or	a
       server socket.

       The  getaddrinfo(3)  function  is  not limited to creating IPv4 socket address structures;
       IPv6 socket address structures can be created if IPv6 support is available.  These  socket
       address structures can be used directly by bind(2) or connect(2), to prepare a client or a
       server socket.

       The addrinfo structure used by this function contains the following members:

       struct addrinfo {
	   int	   ai_flags;
	   int	   ai_family;
	   int	   ai_socktype;
	   int	   ai_protocol;
	   size_t  ai_addrlen;
	   struct sockaddr *ai_addr;
	   char   *ai_canonname;
	   struct addrinfo *ai_next;
       };

       getaddrinfo(3) sets res to point to a dynamically-allocated link list of  addrinfo  struc-
       tures, linked by the ai_next member.  There are several reasons why the link list may have
       more than one addrinfo structure, including: if the network host is multi-homed; or if the
       same  service  is  available  from  multiple socket protocols (one SOCK_STREAM address and
       another SOCK_DGRAM address, for example).

       The members ai_family, ai_socktype, and ai_protocol have the same meaning  as  the  corre-
       sponding  parameters  in  the  socket(2) system call.  The getaddrinfo(3) function returns
       socket addresses in either IPv4 or IPv6 address family, (ai_family will be set  to  either
       PF_INET or PF_INET6).

       The hints parameter specifies the preferred socket type, or protocol.  A NULL hints speci-
       fies that any network address or protocol is acceptable.  If this parameter is not NULL it
       points  to  an  addrinfo  structure  whose ai_family, ai_socktype, and ai_protocol members
       specify the preferred socket type.  PF_UNSPEC in ai_family specifies any  protocol  family
       (either	IPv4  or  IPv6, for example).  0 in ai_socktype or ai_protocol specifies that any
       socket type or protocol is acceptable as well.  The ai_flags member  specifies  additional
       options,  defined  below.  Multiple flags are specified by logically OR-ing them together.
       All the other members in the hints parameter must contain either 0, or a null pointer.

       The node or service parameter, but not both, may be NULL.  node specifies either a numeri-
       cal  network  address  (dotted-decimal  format for IPv4, hexadecimal format for IPv6) or a
       network hostname, whose network addresses are looked up and  resolved.	If  the  ai_flags
       member  in  the	hints  parameter contains the AI_NUMERICHOST flag then the node parameter
       must be a numerical network address.  The AI_NUMERICHOST flag suppresses  any  potentially
       lengthy network host address lookups.

       The  getaddrinfo(3) function creates a link list of addrinfo structures, one for each net-
       work address subject to any restrictions imposed by the hints parameter.  ai_canonname  is
       set to point to the official name of the host, if ai_flags in hints includes the AI_CANON-
       NAME flag.  ai_family, ai_socktype, and ai_protocol specify the	socket	creation  parame-
       ters.   A pointer to the socket address is placed in the ai_addr member, and the length of
       the socket address, in bytes, is placed in the ai_addrlen member.

       If node is NULL, the network address in each socket structure is initialized according  to
       the AI_PASSIVE flag, which is set in the ai_flags member of the hints parameter.  The net-
       work address in each socket structure will be left unspecified if AI_PASSIVE flag is  set.
       This is used by server applications, which intend to accept client connections on any net-
       work address.  The network address will be set to the loopback interface  address  if  the
       AI_PASSIVE  flag is not set.  This is used by client applications, which intend to connect
       to a server running on the same network host.

       service sets the port number in the network address of each socket structure.  If  service
       is NULL the port number will be left uninitialized.

       The freeaddrinfo(3) function frees the memory that was allocated for the dynamically allo-
       cated link list res.

RETURN VALUE
       getaddrinfo(3) returns 0 if it succeeds, or one of the following non-zero error codes:

       EAI_FAMILY
	      The requested address family is not supported at all.

       EAI_SOCKTYPE
	      The requested socket type is not supported at all.

       EAI_BADFLAGS
	      ai_flags contains invalid flags.

       EAI_NONAME
	      The node or service is not known.  This error is also returned  if  both	node  and
	      service are NULL.

       EAI_SERVICE
	      The  requested  service  is not available for the requested socket type.	It may be
	      available through another socket type.

       EAI_ADDRFAMILY
	      The specified network host does not have any network  addresses  in  the	requested
	      address family.

       EAI_NODATA
	      The specified network host exists, but does not have any network addresses defined.

       EAI_MEMORY
	      Out of memory.

       EAI_FAIL
	      The name server returned a permanent failure indication.

       EAI_AGAIN
	      The name server returned a temporary failure indication.	Try again later.

       EAI_SYSTEM
	      Other system error, check errno for details.

       The  gai_strerror(3)  function  translates  these  error codes to a human readable string,
       suitable for error reporting.

SEE ALSO
       getipnodebyname(3), getipnodebyaddr(3)

Linux Man Page				    2000-12-18				   getaddrinfo(3)


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