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       Cnetdb - LCG netdb utilities


       #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


       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

       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

       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

       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.


       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.


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


       LCG Grid Deployment Team  and DPM Team <>