lwres_freeaddrinfo

LWRES_GETADDRINFO(3)                                      LWRES_GETADDRINFO(3)



NAME
       lwres_getaddrinfo, lwres_freeaddrinfo - socket address structure to
       host and service name

SYNOPSIS
       #include <lwres/netdb.h>

       int lwres_getaddrinfo(const char *hostname, const char *servname, const
       struct addrinfo *hints, struct addrinfo **res);

       void lwres_freeaddrinfo(struct addrinfo *ai); .PP If the operating
       system does not provide a struct addrinfo, the following structure is
       used:

       struct  addrinfo {
               int             ai_flags;       /* AI_PASSIVE, AI_CANONNAME */
               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 hostname */
               struct sockaddr *ai_addr;       /* binary address */
               struct addrinfo *ai_next;       /* next structure in linked list */
       };


DESCRIPTION
       lwres_getaddrinfo() is used to get a list of IP addresses and port
       numbers for host hostname and service servname.  The function is the
       lightweight resolver's implementation of getaddrinfo() as defined in
       RFC2133.  hostname and servname are pointers to null-terminated strings
       or NULL.  hostname is either a host name or a numeric host address
       string: a dotted decimal IPv4 address or an IPv6 address.  servname is
       either a decimal port number or a service name as listed in
       /etc/services.

       hints is an optional pointer to a struct addrinfo.  This structure can
       be used to provide hints concerning the type of socket that the caller
       supports or wishes to use.  The caller can supply the following
       structure elements in *hints:

       ai_family
              The protocol family that should be used.  When ai_family is set
              to PF_UNSPEC, it means the caller will accept any protocol
              family supported by the operating system.

       ai_socktype
              denotes the type of socket — SOCK_STREAM, SOCK_DGRAM or SOCK_RAW
              — that is wanted.  When ai_socktype is zero the caller will
              accept any socket type.

       ai_protocol
              indicates which transport protocol is wanted: IPPROTO_UDP or
              IPPROTO_TCP.  If ai_protocol is zero the caller will accept any
              protocol.

       ai_flags
              Flag bits.  If the AI_CANONNAME bit is set, a successful call to
              lwres_getaddrinfo() will return a a null-terminated string
              containing the canonical name of the specified hostname in
              ai_canonname of the first addrinfo structure returned.  Setting
              the AI_PASSIVE bit indicates that the returned socket address
              structure is intended for used in a call to bind(2).  In this
              case, if the hostname 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.

              When ai_flags does not set the AI_PASSIVE bit, the returned
              socket address structure will be ready for use in a call to
              connect(2) for a connection-oriented protocol or connect(2),
              sendto(2), or sendmsg(2) if a connectionless protocol was
              chosen.  The IP address portion of the socket address structure
              will be set to the loopback address if hostname is a NULL
              pointer and AI_PASSIVE is not set in ai_flags.

              If ai_flags is set to AI_NUMERICHOST it indicates that hostname
              should be treated as a numeric string defining an IPv4 or IPv6
              address and no name resolution should be attempted.

       All other elements of the struct addrinfo passed via hints must be
       zero.

       A hints of NULL is treated as if the caller provided a struct addrinfo
       initialized to zero with ai_familyset to PF_UNSPEC.

       After a successful call to lwres_getaddrinfo(), *res is a pointer to a
       linked list of one or more addrinfo structures.  Each struct addrinfo
       in this list cn be processed by following the ai_next pointer, until a
       NULL pointer is encountered.  The three members ai_family, ai_socktype,
       and ai_protocol in each returned addrinfo structure contain the
       corresponding arguments for a call to socket(2).  For each addrinfo
       structure in the list, the ai_addr member points to a filled-in socket
       address structure of length ai_addrlen.

       All of the information returned by lwres_getaddrinfo() is dynamically
       allocated: the addrinfo structures, and the socket address structures
       and canonical host name strings pointed to by the addrinfostructures.
       Memory allocated for the dynamically allocated structures created by a
       successful call to lwres_getaddrinfo() is released by
       lwres_freeaddrinfo().  ai is a pointer to a struct addrinfo created by
       a call to lwres_getaddrinfo().

RETURN VALUES
       lwres_getaddrinfo() returns zero on success or one of the error codes
       listed in gai_strerror(3) if an error occurs.  If both hostname and
       servname are NULL lwres_getaddrinfo() returns EAI_NONAME.

SEE ALSO
       lwres(3), lwres_getaddrinfo(3), lwres_freeaddrinfo(3),
       lwres_gai_strerror(3), RFC2133, getservbyname(3), bind(2), connect(2),
       sendto(2), sendmsg(2), socket(2).



BIND9                            Jun 30, 2000             LWRES_GETADDRINFO(3)