#include <string.h>
#include <unistd.h>
#include "XrdNet/XrdNetAddr.hh"
#include "XrdNet/XrdNetIdentity.hh"
#include "XrdNet/XrdNetIF.hh"
#include "XrdOuc/XrdOucTList.hh"
#include "XrdOuc/XrdOucUtils.hh"
#include "XrdSys/XrdSysE2T.hh"

Include dependency graph for XrdNetIdentity.cc:

Functions
static bool	getMyFQN ()

Variables
static const char *	DNS_Domain

static const char *	DNS_Error

static char	DNS_FQN [256]

static bool	FQN_DNS = getMyFQN()

Function Documentation

◆ getMyFQN()

static bool getMyFQN ( )

static

Definition at line 52 of file XrdNetIdentity.cc.

{
// Initialize name, domain, and error to empty strings
//
   memset(DNS_FQN, '\0', sizeof(DNS_FQN));
   DNS_Domain = DNS_FQN;
   DNS_Error = nullptr;
 
// The identity can be specified via an envar. In this case, it short circuits
// all the subsequent code.
//
   const char *dnsName = nullptr;
   if ((dnsName = getenv("XRDNET_IDENTITY")))
      {strlcpy(DNS_FQN, dnsName, sizeof(DNS_FQN));
       XrdOucUtils::toLower(DNS_FQN);
       if (XrdNetAddrInfo::isHostName(DNS_FQN) && !(DNS_Domain = index(DNS_FQN, '.')))
         DNS_Domain = "";
       return false;
      }
 
// Obtain the host name, this is mandatory.
//
   if (gethostname(DNS_FQN, sizeof(DNS_FQN)))
      {DNS_Error = XrdSysE2T(errno); DNS_Domain = ""; return false;}
 
   int hnLen = strlen(DNS_FQN);
   XrdOucUtils::toLower(DNS_FQN);
 
// First step it to get all IP addresses configured on this machine
//
   XrdOucTList *ifList = nullptr;
   if (!XrdNetIF::GetIF(&ifList, &DNS_Error))
      {DNS_Domain = ""; return true;}
 
// Run through the interfaces and try to get the hostname associated with
// this machine. Note that we may have public and private addresses and
// they may have different hostname attached. We only accept the hostname
// that matches what is returned by gethostname().
//
   XrdNetAddr theAddr;
   const char *domP = nullptr;
   char *theIPA[2]  = { nullptr, nullptr };
   char *theName[2] = { nullptr, nullptr };
   XrdOucTList *ifNow = nullptr;
 
   while((ifNow = ifList))
        {int i = (ifNow->sval[1] ? 1 : 0); // Private | public
 
         if (i >= 0 && theName[i] == 0 && !theAddr.Set(ifNow->text, 0)
         &&  (dnsName = theAddr.Name(0,&DNS_Error)) && (domP = index(dnsName,'.')))
            {int n = domP - dnsName;
             if (n == hnLen && !strncmp(DNS_FQN, dnsName, n))
                {theName[i] = strdup(dnsName);
                } else {
                 if (theIPA[i]) free(theIPA[i]);
                 theIPA[i] = strdup(ifNow->text);
               }
            }
         ifList = ifList->next;
         delete ifNow;
        }
 
// Fix up error pointer
//
  if (DNS_Error == 0) DNS_Error = "no error";
 
// We prefer the public name should we have it
//
   if (theName[0])
      {strlcpy(DNS_FQN, theName[0], sizeof(DNS_FQN));
       goto done;
      }
 
// Use the private name should we have it
//
   if (theName[1])
      {strlcpy(DNS_FQN, theName[1], sizeof(DNS_FQN));
       goto done;
      }
 
// Concote a name using old-style DNS resolution. This may not work if DNS
// namespaces are being used (e.g. k8s environments) or if the hostname is not
// resolvable. We will catch that here and move on.
//
   if ((DNS_Error = theAddr.Set(DNS_FQN,0))) dnsName = nullptr;
      else dnsName = theAddr.Name(0, &DNS_Error);
 
// Check if this worked
//
   if (dnsName)
      {strlcpy(DNS_FQN, dnsName, sizeof(DNS_FQN));
       goto done;
      }
 
// Prefrentially return the hostname as an address as the value of gethostname()
// may actually fail. So, we defer naming the machine until later but we do
// know its IP address and that can be used as an identity. Return the public
// address first. Note that we prefrentially return the IPv6 address here.
//
   if (theIPA[0])
      {strlcpy(DNS_FQN, theIPA[0], sizeof(DNS_FQN));
       goto done;
      }
 
   if (theIPA[1])
      {strlcpy(DNS_FQN, theIPA[1], sizeof(DNS_FQN));
       goto done;
      }
 
// Fallback to using the simple unqualified hostname, this still may be OK but
// this is likely to fail in certain situations where DNS is screwed up.
//
   DNS_Domain = "";
   return true;
 
done:
   free(theName[0]);
   free(theName[1]);
   free(theIPA[0]);
   free(theIPA[1]);
 
   if (!(DNS_Domain = index(DNS_FQN, '.')))
     DNS_Domain = "";
   return true;
}