Initialize all the name services we need

- A long time ago in a far away commit, "somebody" had this less than
  brilliant idea that calling gethostbyname() loads all the required
  name service libraries (commit 39b75d2).
  This is of course only true if hosts db happens to use the same
  database as passwd and group... which often is the case, but by
  no means guaranteed or always the case.
- Add an explicit initializer for rpmug to force loading the name service
  libraries early in initialization so we dont need to worry about going
  chroot later on. Of course, the "host" name service configuration might
  not actually make sense for the chroot, but this commit doesn't make
  that any worse than it already was.

lib/rpmrc.c

@@ -12,7 +12,6 @@
 #if HAVE_SYS_UTSNAME_H
 #include <sys/utsname.h>
 #endif
-#include <netdb.h>
 #include <ctype.h>	/* XXX for /etc/rpm/platform contents */
 
 #if HAVE_SYS_SYSTEMCFG_H
@@ -36,6 +35,7 @@
 #include "rpmio/rpmio_internal.h"	/* XXX for rpmioSlurp */
 #include "lib/misc.h"
 #include "lib/rpmliblua.h"
+#include "lib/rpmug.h"
 
 #include "debug.h"
 
@@ -1520,7 +1520,9 @@ int rpmReadConfigFiles(const char * file, const char * target)
     rpmrcCtx ctx = rpmrcCtxAcquire(1);
 
     /* Force preloading of dlopen()'ed libraries in case we go chrooting */
-    (void) gethostbyname("localhost");
+    if (rpmugInit())
+	goto exit;
+
     if (rpmInitCrypto())
 	goto exit;
 

lib/rpmug.c

@@ -1,7 +1,9 @@
 #include "system.h"
 
+#include <pthread.h>
 #include <pwd.h>
 #include <grp.h>
+#include <netdb.h>
 #include <rpm/rpmlog.h>
 #include <rpm/rpmstring.h>
 
@@ -166,6 +168,23 @@ const char * rpmugGname(gid_t gid)
     }
 }
 
+static void loadLibs(void)
+{
+    (void) getpwnam("root");
+    endpwent();
+    (void) getgrnam("root");
+    endgrent();
+    (void) gethostbyname("localhost");
+}
+
+int rpmugInit(void)
+{
+    static pthread_once_t libsLoaded = PTHREAD_ONCE_INIT;
+
+    pthread_once(&libsLoaded, loadLibs);
+    return 0;
+}
+
 void rpmugFree(void)
 {
     rpmugUid(NULL, NULL);

lib/rpmug.h

@@ -11,6 +11,8 @@ const char * rpmugUname(uid_t uid);
 
 const char * rpmugGname(gid_t gid);
 
+int rpmugInit(void);
+
 void rpmugFree(void);
 
 #endif /* _RPMUG_H */