[PATCH] x_tables: fix alignment on [at least] ppc32 (was Re: 2.6.16-rc1: iptables broken on ppc32?)

[Harald Welte <laforge@netfilter.org>]

Hi,

the patch below fixes the problem on ppc32. Dave: Please apply.

[NETFILTER] x_tables: Fix XT_ALIGN() macro on [at least] ppc32

To keep backwards compatibility with old iptables userspace programs,
the new XT_ALIGN macro always has to return the same value as IPT_ALIGN,
IP6T_ALIGN or ARPT_ALIGN in previous kernels.

However, in those kernels the macro was defined in dependency to the
respective layer3 specifi data structures, which we can no longer do with
x_tables.

The fix is an ugly kludge, but it has been tested to solve the problem. Yet
another reason to move away from the current {ip,ip6,arp,eb}tables like
data structures.

Signed-off-by: Harald Welte <laforge@netfilter.org>

---
commit 470faeb379560fe877b685ca69be6a7e4f0e91ed
tree 5732ecd9bcab28469805752514e5c57ba26189a1
parent 44718bbfa186d58477163418d37df173aa2dd079
author Harald Welte <laforge@netfilter.org> Fri, 20 Jan 2006 01:44:24 +0100
committer Harald Welte <laforge@netfilter.org> Fri, 20 Jan 2006 01:44:24 +0100

 include/linux/netfilter/x_tables.h |   15 ++++++++++++++-
 1 files changed, 14 insertions(+), 1 deletions(-)

diff --git a/include/linux/netfilter/x_tables.h b/include/linux/netfilter/x_tables.h
index 472f048..65f9cd8 100644
--- a/include/linux/netfilter/x_tables.h
+++ b/include/linux/netfilter/x_tables.h
@@ -19,7 +19,20 @@ struct xt_get_revision
 /* For standard target */
 #define XT_RETURN (-NF_REPEAT - 1)
 
-#define XT_ALIGN(s) (((s) + (__alignof__(void *)-1)) & ~(__alignof__(void *)-1))
+/* this is a dummy structure to find out the alignment requirement for a struct
+ * containing all the fundamental data types that are used in ipt_entry, ip6t_entry
+ * and arpt_entry.  This sucks, and it is a hack.  It will be my personal pleasure
+ * to remove it -HW */
+struct _xt_align
+{
+	u_int8_t u8;
+	u_int16_t u16;
+	u_int32_t u32;
+	u_int64_t u64;
+};
+
+#define XT_ALIGN(s) (((s) + (__alignof__(struct _xt_align)-1)) 	\
+			& ~(__alignof__(struct _xt_align)-1))
 
 /* Standard return verdict, or do jump. */
 #define XT_STANDARD_TARGET ""
-- 
- Harald Welte <laforge@netfilter.org>                 http://netfilter.org/
============================================================================
  "Fragmentation is like classful addressing -- an interesting early
   architectural error that shows how much experimentation was going
   on while IP was being designed."                    -- Paul Vixie

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