Fix for Bug#52923 (Inadequate documentation of "Can't get hostname for your address" error).

The thing is that on some platforms (e.g. Mac OS X) sockaddr_in / sockaddr_in6
contain a non-standard field (sin_len / sin6_len), that must be set.

The problem was that only standard fields were set, thus getnameinfo() returned
EAI_SYSTEM instead of EAI_NONAME.

The fix is to introduce configure-time checks (for GNU auto-tools and CMake) for
those additional fields and to set them if they are available.

config.h.cmake

@@ -282,6 +282,8 @@
 #cmakedefine HAVE_NETINET_IN6_H 1
 #cmakedefine HAVE_IPV6 1
 #cmakedefine ss_family @ss_family@
+#cmakedefine HAVE_SOCKADDR_IN_SIN_LEN 1
+#cmakedefine HAVE_SOCKADDR_IN6_SIN6_LEN 1
 #cmakedefine HAVE_TIMESPEC_TS_SEC 1
 #cmakedefine STRUCT_DIRENT_HAS_D_INO 1
 #cmakedefine STRUCT_DIRENT_HAS_D_NAMLEN 1

configure.cmake

@@ -1000,6 +1000,21 @@ IF(NOT HAVE_SOCKADDR_STORAGE_SS_FAMILY)
     SET(ss_family __ss_family)
   ENDIF()
 ENDIF()
+
+#
+# Check if struct sockaddr_in::sin_len is available.
+#
+
+CHECK_STRUCT_HAS_MEMBER("struct sockaddr_in" sin_len
+  "${CMAKE_EXTRA_INCLUDE_FILES}" HAVE_SOCKADDR_IN_SIN_LEN)
+
+#
+# Check if struct sockaddr_in6::sin6_len is available.
+#
+
+CHECK_STRUCT_HAS_MEMBER("struct sockaddr_in6" sin6_len
+  "${CMAKE_EXTRA_INCLUDE_FILES}" HAVE_SOCKADDR_IN6_SIN6_LEN)
+
 SET(CMAKE_EXTRA_INCLUDE_FILES) 
 
 CHECK_STRUCT_HAS_MEMBER("struct dirent" d_ino "dirent.h"  STRUCT_DIRENT_HAS_D_INO)

configure.in

@@ -1012,6 +1012,66 @@ else
   AC_MSG_RESULT([yes])
 fi
 
+#--------------------------------------------------------------------------
+# Check if struct sockaddr_in::sin_len is available
+#--------------------------------------------------------------------------
+
+AC_CACHE_CHECK(
+  [if sockaddr_in::sin_len is available],
+  mysql_cv_have_sockaddr_in_sin_len,
+  AC_TRY_COMPILE(
+    [
+      #ifdef WIN32
+        #include <winsock2.h>
+      #else
+        #include <sys/types.h>
+        #include <netinet/in.h>
+        #include <sys/socket.h>
+      #endif
+    ],
+    [unsigned int i = sizeof(((struct sockaddr_in *) 0)->sin_len)],
+    mysql_cv_have_sockaddr_in_sin_len=yes,
+    mysql_cv_have_sockaddr_in_sin_len=no))
+
+if test "$mysql_cv_have_sockaddr_in_sin_len" = "yes"; then
+  AC_DEFINE(
+    [HAVE_SOCKADDR_IN_SIN_LEN],
+    [1],
+    [If sockaddr_in::sin_len is available])
+fi
+
+#--------------------------------------------------------------------------
+# Check if struct sockaddr_in6::sin6_len is available
+#--------------------------------------------------------------------------
+
+AC_CACHE_CHECK(
+  [if sockaddr_in6::sin6_len is available],
+  mysql_cv_have_sockaddr_in6_sin6_len,
+  AC_TRY_COMPILE(
+    [
+      #ifdef WIN32
+        #include <winsock2.h>
+      #else
+        #include <sys/types.h>
+        #include <netinet/in.h>
+        #include <sys/socket.h>
+      #endif
+
+      #ifdef HAVE_NETINET_IN6_H
+        #include <netinet/in6.h>
+      #endif
+    ],
+    [unsigned int i = sizeof(((struct sockaddr_in6 *) 0)->sin6_len)],
+    mysql_cv_have_sockaddr_in6_sin6_len=yes,
+    mysql_cv_have_sockaddr_in6_sin6_len=no))
+
+if test "$mysql_cv_have_sockaddr_in_sin6_len" = "yes"; then
+  AC_DEFINE(
+    [HAVE_SOCKADDR_IN6_SIN6_LEN],
+    [1],
+    [If sockaddr_in6::sin6_len is available])
+fi
+
 #--------------------------------------------------------------------
 # Check for TCP wrapper support
 #--------------------------------------------------------------------
@@ -3121,6 +3181,7 @@ esac
 
 AC_SUBST([RDTSC_SPARC_ASSEMBLY])
 
+
 #--------------------------------------------------------------------
 # Output results
 #--------------------------------------------------------------------

vio/viosocket.c

@@ -1057,9 +1057,11 @@ ssize_t vio_pending(Vio *vio)
 
 /**
   This is a wrapper for the system getnameinfo(), because different OS
-  differ in the getnameinfo() implementation. For instance, Solaris 10
-  requires that the 2nd argument (salen) must match the actual size of the
-  struct sockaddr_storage passed to it.
+  differ in the getnameinfo() implementation:
+    - Solaris 10 requires that the 2nd argument (salen) must match the
+      actual size of the struct sockaddr_storage passed to it;
+    - Mac OS X has sockaddr_in::sin_len and sockaddr_in6::sin6_len and
+      requires them to be filled.
 */
 
 int vio_getnameinfo(const struct sockaddr *sa,
@@ -1072,11 +1074,17 @@ int vio_getnameinfo(const struct sockaddr *sa,
   switch (sa->sa_family) {
   case AF_INET:
     sa_length= sizeof (struct sockaddr_in);
+#ifdef HAVE_SOCKADDR_IN_SIN_LEN
+    ((struct sockaddr_in *) sa)->sin_len= sa_length;
+#endif /* HAVE_SOCKADDR_IN_SIN_LEN */
     break;
 
 #ifdef HAVE_IPV6
   case AF_INET6:
     sa_length= sizeof (struct sockaddr_in6);
+# ifdef HAVE_SOCKADDR_IN6_SIN6_LEN
+    ((struct sockaddr_in6 *) sa)->sin6_len= sa_length;
+# endif /* HAVE_SOCKADDR_IN6_SIN6_LEN */
     break;
 #endif /* HAVE_IPV6 */
   }