NAME

       Cnetdb - LCG netdb utilities

SYNOPSIS

       #include <Cnetdb.h>

       char  *Cgetnetaddress(int  sock, const void *sa, size_t salen, int *skey, const char **numeric_out, const
       char **name_out, int flags, int cflags);

DESCRIPTION

       Cnetdb provides several netdb like functions including  Cgethostbyname,  Cgethostbyaddr,  Cgetservbyname,
       Cgetnameinfo,  Cgetaddrinfo,  Cgai_strerror  which behave in a somewhat similar way to their system netdb
       counterparts. In addition Cnetdb provides a function called Cgetnetaddress which is  currently  the  only
       one documented here.

       Cgetnetaddress  returns  a  DNS  domain  name (often called a hostname) given either a network socket, in
       which case the hostname corresponds to the peer address of the socket, or a sockaddr structure. The  name
       will be returned as a numeric IP address and/or optionaly a DNS domain name.

       Exactly  one  of either sock or sa must be specified, the other should be set to -1 or NULL respectively.
       If both are set the behaviour should be considered undefined and may change in the  future.  If  skey  is
       NULL  the  memory  for  pointers  returned  by Cgetnetaddress will be dynamically allocated and it is the
       responsibility of the caller to free them when done. If not NULL skey should point to  an  int  which  is
       initially  set  to a value of -1. The memory used to store the results returned by Cgetnetaddress will be
       allocated internally and will be reused during subsequent calls to Cgetnetaddress from  the  same  thread
       and that share the same value of skey.

       If  numeric_out or name_out are not NULL the char pointer which they reference will be reset to a pointer
       to a character array containig the numeric or domain name address to be returned  by  the  function.  The
       output  will  be  NULL  if  the  function is unable to find an IP or domain name.  flags accepts the same
       bitmaped flags that can be set for getnameinfo(). cflags accepts  bitmaped  flags  which  are  unique  to
       Cgetnetaddress.

       If  NI_NUMERICHOST  is  specified  in flags no attempt is made to obtain a domain name. If NI_NAMEREQD is
       specified nothing is returned unless  a  domain  name  address  can  be  determined.  NI_NUMERICHOST  and
       NI_NAMEREQD are mutually exclusive. Other flags options may be set and will have the effect described for
       getnameinfo().

       cflags may take the bitmaped flags CNA_WANTLOOPBACK, CNA_NOFWDLOOKUP and CNA_FWDLOOKUP.

       By default if the address to be returned is determined  to  be  the  loopback  address  any  domain  name
       returned  will  be  that of the local machine.  If CNA_WANTLOOPBACK is specified any domain name returned
       will be that associated with the loopback address, usually localhost.localdomain.

       A forward lookup verification of the domain name may be optionally specified with the CNA_FWDLOOKUP flag.
       The  forward  lookup means that one of the address to which a domain name resolves must match the address
       passed to Cgetnetaddress. If the match failes the domain name will be considered to not be available.  By
       default,  or if the option CNA_NOFWDLOOKUP is passed in cflags, the forward lookup check is not performed
       or required. The behavior if both CNA_FWDLOOKUP and CNA_NOFWDLOOKUP are specified is undefined.

RETURN VALUE

       Cgetnetaddress() returns a pointer to the domain name, if available,  or  otherwise  to  the  numeric  IP
       address, if available.  If neither is available NULL is returned.

SEE ALSO

       gethostbyname(3), gethostbyaddr(3), getservbyname(3), getnameinfo(3), getaddrinfo(3), gai_strerror(3)

AUTHOR

       LCG Grid Deployment Team  and DPM Team <hep-service-dpm@cern.ch>