/*
         *      gethostybname --
         *
         *      The following code was contributed by Casper H.S. Dik
         *      to address the following problem:
         *
         *      gethostbyname() always returns null in h->aliases.
         *      Now, gethostbyX can be replaced its __switch_gethostbyX
         *      equivalents. However, these are missing from Solaris 2.3.
         *
         *      The _r functions are reentrant.  They have a different
         *      calling sequence. (The __switch_getXXXbyYYY are called
         *      like getXXXbyYYY, the _switch_getXXXbyYYY_r are called
         *      like getXXXbyYYY_r) 
         *
         *      With this bit of knowledge I constructed the code that
         *      follows this message. Just plug it in every program
         *      that requires gethostbyname to work. (Gethostbyaddr()
         *      is added for symmetry). 
         *
         *      You'll need to link with -lnsl -ldl.
         *
         *      It works for Solaris 2.2 and 2.3.  (Compiled on 2.3 or
         *      2.2 it will run 2.2 and 2.3)
         *
         *      Note that as with __switch* _switch*_r is undocumented
         *      and can be changed in the next release.
         *
         */
        
        /*
         *     Proper gethostbyXX function for Solaris 2.0-2.3
         *     (and later ?) 
         *
         *     Fixed in 2.4?
         *
         *     You'll need -ldl added to the link command line.
         *
         *     Casper Dik (casper@fwi.uva.nl)
         *
         */

        #include <netdb.h>
        #include <dlfcn.h>
        
        #define HBUFSIZE 4096
        
        static void *dlhandle;

        /* The gethostbyXXX function variables. Named after
        * then .so files they appear in. nsw*.so in SunOS 5.2
        * and earlier, nss_*.so in 5.3 */ 

        static struct hostent *(*nswghba)(const char *, int, int),
                              *(*nswghbn)(const char *),
                              *(*nss_ghba)(const char *, int, int, struct hostent *, char *, int, int *),
                              *(*nss_ghbn)(const char *, struct hostent *, char *, int, int *);
        
        static int dlinit(void)
        {
          static int dlstatus = 0;
        /* 0 = uninited, 1 = inited & ok, -1 = error */
        
        if (dlstatus)
          return dlstatus;
        
          dlstatus = -1;
        
          dlhandle = dlopen(0, RTLD_LAZY);
        
          if (dlhandle == 0)
            return dlstatus;
        
        /* SunOS 5.0 - 5.2 */
        
        nswghba = (struct hostent *(*)(const char *, int, int))
          dlsym(dlhandle, "__switch_gethostbyaddr");
        
        nswghbn = (struct hostent *(*)(const char *))
          dlsym(dlhandle, "__switch_gethostbyname");
        
        /* either both should exist or both should not exist */
        
        if ((nswghbn == 0) != (nswghba == 0))
          return dlstatus;
        
        if (nswghbn)
          return dlstatus = 1;
        
        /* SunOS 5.3 - ? */
        
        nss_ghba = (struct hostent *(*)
                      (const char *, int, int, struct hostent *, char *, int , int *))
            dlsym(dlhandle, "_switch_gethostbyaddr_r");
        
        nss_ghbn = (struct hostent *(*)
                      (const char *, struct hostent *, char *, int , int *))
            dlsym(dlhandle, "_switch_gethostbyname_r");
        
        /* these two must exist when we get here */
        
        if (nss_ghbn != 0 && nss_ghba != 0)
          dlstatus = 1;
        
        return dlstatus;
        }
        
        struct hostent *
        gethostbyname(const char *name) {
        
          static struct hostent hp;
          static char buf[HBUFSIZE];
        
          if (dlinit() == -1)
            return 0;
        
          if (nswghbn)
            return nswghbn(name);
          else
            return nss_ghbn(name, &hp, buf, sizeof(buf), &h_errno);
        }
        
        struct hostent *
        gethostbyaddr(const char *addr, int len, int type) {
          static struct hostent hp;
          static char buf[HBUFSIZE];
        
          if (dlinit() == -1)
            return 0;
        
          if (nswghba)
            return nswghba(addr, len, type);
          else
            return nss_ghba(addr,
                            len, type, &hp, buf, sizeof(buf), &h_errno);
        }