Make padding in struct sockaddr_storage explicit [BZ #20111]

This avoids aliasing issues with GCC 6 in -fno-strict-aliasing
mode.  (With implicit padding, not all data is copied.)

This change makes it explicit that struct sockaddr_storage is
only 126 bytes large on m68k (unlike elsewhere, where we end up
with the requested 128 bytes).  The new test case makes sure that
this does not happen on other architectures.

2 files changed, 128 insertions, 1 deletions

diff --git a/inet/Makefile b/inet/Makefile
index 0e7a3c3..2207b93 100644
--- a/inet/Makefile
+++ b/inet/Makefile
@@ -50,7 +50,7 @@ aux := check_pf check_native ifreq
 
 tests := htontest test_ifindex tst-ntoa tst-ether_aton tst-network \
 	 tst-gethnm test-ifaddrs bug-if1 test-inet6_opt tst-ether_line \
-	 tst-getni1 tst-getni2 tst-inet6_rth tst-checks
+	 tst-getni1 tst-getni2 tst-inet6_rth tst-checks tst-sockaddr
 
 include ../Rules
 
@@ -84,6 +84,8 @@ CFLAGS-either_hton.c = -fexceptions
 CFLAGS-getnetgrent.c = -fexceptions
 CFLAGS-getnetgrent_r.c = -fexceptions
 
+CFLAGS-tst-sockaddr.c = -fno-strict-aliasing
+
 endif
 
 ifeq ($(build-static-nss),yes)
diff --git a/inet/tst-sockaddr.c b/inet/tst-sockaddr.c
new file mode 100644
index 0000000..fe0307b
--- /dev/null
+++ b/inet/tst-sockaddr.c
@@ -0,0 +1,125 @@
+/* Tests for socket address type definitions.
+   Copyright (C) 2016 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public License as
+   published by the Free Software Foundation; either version 2.1 of the
+   License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; see the file COPYING.LIB.  If
+   not, see <http://www.gnu.org/licenses/>.  */
+
+#include <netinet/in.h>
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+
+/* This is a copy of the previous definition of struct
+   sockaddr_storage.  It is not equal to the old value of _SS_SIZE
+   (128) on all architectures.  We must stay compatible with the old
+   definition.  */
+
+#define OLD_REFERENCE_SIZE 128
+#define OLD_PADSIZE (OLD_REFERENCE_SIZE - (2 * sizeof (__ss_aligntype)))
+struct sockaddr_storage_old
+  {
+    __SOCKADDR_COMMON (old_);
+    __ss_aligntype old_align;
+    char old_padding[OLD_PADSIZE];
+  };
+
+static bool errors;
+
+static void
+check (bool ok, const char *message)
+{
+  if (!ok)
+    {
+      printf ("error: failed check: %s\n", message);
+      errors = true;
+    }
+}
+
+static int
+do_test (void)
+{
+  check (OLD_REFERENCE_SIZE >= _SS_SIZE,
+         "old target size is not smaller than actual size");
+  check (sizeof (struct sockaddr_storage_old)
+         == sizeof (struct sockaddr_storage),
+         "old and new sizes match");
+  check (__alignof (struct sockaddr_storage_old)
+         == __alignof (struct sockaddr_storage),
+         "old and new alignment matches");
+  check (offsetof (struct sockaddr_storage_old, old_family)
+         == offsetof (struct sockaddr_storage, ss_family),
+         "old and new family offsets match");
+  check (sizeof (struct sockaddr_storage) == _SS_SIZE,
+         "struct sockaddr_storage size");
+
+  /* Check for lack of holes in the struct definition.   */
+  check (offsetof (struct sockaddr_storage, __ss_padding)
+         == __SOCKADDR_COMMON_SIZE,
+         "implicit padding before explicit padding");
+  check (offsetof (struct sockaddr_storage, __ss_align)
+         == __SOCKADDR_COMMON_SIZE
+           + sizeof (((struct sockaddr_storage) {}).__ss_padding),
+         "implicit padding before explicit padding");
+
+  /* Check for POSIX compatibility requirements between struct
+     sockaddr_storage and struct sockaddr_un.  */
+  check (sizeof (struct sockaddr_storage) >= sizeof (struct sockaddr_un),
+         "sockaddr_storage is at least as large as sockaddr_un");
+  check (__alignof (struct sockaddr_storage)
+         >= __alignof (struct sockaddr_un),
+         "sockaddr_storage is at least as aligned as sockaddr_un");
+  check (offsetof (struct sockaddr_storage, ss_family)
+         == offsetof (struct sockaddr_un, sun_family),
+         "family offsets match");
+
+  /* Check that the compiler preserves bit patterns in aggregate
+     copies.  Based on <https://gcc.gnu.org/PR71120>.  */
+  check (sizeof (struct sockaddr_storage) >= sizeof (struct sockaddr_in),
+         "sockaddr_storage is at least as large as sockaddr_in");
+  {
+    struct sockaddr_storage addr;
+    memset (&addr, 0, sizeof (addr));
+    {
+      struct sockaddr_in *sinp = (struct sockaddr_in *)&addr;
+      sinp->sin_family = AF_INET;
+      sinp->sin_addr.s_addr = htonl (INADDR_LOOPBACK);
+      sinp->sin_port = htons (80);
+    }
+    struct sockaddr_storage copy;
+    copy = addr;
+
+    struct sockaddr_storage *p = malloc (sizeof (*p));
+    if (p == NULL)
+      {
+        printf ("error: malloc: %m\n");
+        return 1;
+      }
+    *p = copy;
+    const struct sockaddr_in *sinp = (const struct sockaddr_in *)p;
+    check (sinp->sin_family == AF_INET, "sin_family");
+    check (sinp->sin_addr.s_addr == htonl (INADDR_LOOPBACK), "sin_addr");
+    check (sinp->sin_port == htons (80), "sin_port");
+    free (p);
+  }
+
+  return errors;
+}
+
+#define TEST_FUNCTION do_test ()
+#include "../test-skeleton.c"