Patchwork netfilter: fix IPv6 NTP checksum calculation

login
register
mail settings
Submitter Jean-Michel DILLY
Date Jan. 24, 2013, 5:09 p.m.
Message ID <06023CFA-4D28-43B3-8C7F-B8223F3390DD@dilly.me>
Download mbox | patch
Permalink /patch/215456/
State Not Applicable
Headers show

Comments

Jean-Michel DILLY - Jan. 24, 2013, 5:09 p.m.
Hi all,
This patch doesn't work as expected. I tried with few IP and each time 0x0100 were missing. csum_add seems buggy too.
I have reimplemented csum16s functions with the Ulrich's fix. It seems to work now.
I'm a noob, so I guess someone will propose a better patch for this.

Regards,
JMichel

On Fri, Jan 04, 2013 at 10:20:43AM +0100, Patrick McHardy wrote:
> > On Wed, Jan 02, 2013 at 04:24:40PM +0100, Ulrich Weber wrote:
> > > csum16_add() has a broken carry detection, should be:
> > > sum += sum < (__force u16)b;
> > > 
> > > Instead of fixing csum16_add, remove the custom checksum
> > > functions and use the generic csum_add/csum_sub ones.
> > 
> > Looks good to me.
> > 
> > Acked-by: Patrick McHardy <kaber@trash.net>

>Applied, thanks!

--
To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Florian Westphal - Jan. 24, 2013, 10:49 p.m.
Jean-Michel DILLY <jm@dilly.me> wrote:
> Hi all,
> This patch doesn't work as expected. I tried with few IP and each time 0x0100 were missing. csum_add seems buggy too.
> I have reimplemented csum16s functions with the Ulrich's fix. It seems to work now.
> I'm a noob, so I guess someone will propose a better patch for this.

We can't use csum_add after all, patch looks correct.

Can you re-send with proper Signoff?

[ carry detection breaks on overflow, e.g. a==1 and b=0xffff yields
  0 for csum_add (65536 < 1) and 1 for csum16_add (0 < 1) ]
--
To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Patch

diff --git a/ip6t_NPT.c b/linux-3.8-rc4/net/ipv6/netfilter/ip6t_NPT.c
index 787748b..29ef720 100644
--- a/ip6t_NPT.c
+++ b/linux-3.8-rc4/net/ipv6/netfilter/ip6t_NPT.c
@@ -14,24 +14,44 @@ 
 #include <linux/netfilter_ipv6/ip6t_NPT.h>
 #include <linux/netfilter/x_tables.h>
 
+static __sum16 csum16_add(__sum16 a, __sum16 b)
+{
+       __u16 result;
+
+       result = (__force __u16) a + (__force __u16) b;
+       result += result < (__force u16)b; 
+               
+
+       return (__force __sum16) result;
+}
+
+static __sum16 csum16_complement(__sum16 a)
+{
+       return (__force __sum16)(0xffff - (__force u16)a);
+}
+
+static __sum16 csum16_sub(__sum16 a, __sum16 b)
+{
+       return csum16_add(a, csum16_complement(b));
+}
 
 static int ip6t_npt_checkentry(const struct xt_tgchk_param *par)
 {
        struct ip6t_npt_tginfo *npt = par->targinfo;
-       __wsum src_sum = 0, dst_sum = 0;
+       __sum16 src_sum = 0, dst_sum = 0;
        unsigned int i;
 
        if (npt->src_pfx_len > 64 || npt->dst_pfx_len > 64)
                return -EINVAL;
 
        for (i = 0; i < ARRAY_SIZE(npt->src_pfx.in6.s6_addr16); i++) {
-               src_sum = csum_add(src_sum,
-                       (__force __wsum)npt->src_pfx.in6.s6_addr16[i]);
-               dst_sum = csum_add(dst_sum,
-                       (__force __wsum)npt->dst_pfx.in6.s6_addr16[i]);
+               src_sum = csum16_add(src_sum, 
+                                       (__force __sum16)npt->src_pfx.in6.s6_addr16[i]);
+               dst_sum = csum16_add(dst_sum, 
+                                       (__force __sum16)npt->dst_pfx.in6.s6_addr16[i]);
        }
 
-       npt->adjustment = (__force __sum16) csum_sub(src_sum, dst_sum);
+       npt->adjustment = csum16_sub(src_sum, dst_sum);
        return 0;
 }
 
@@ -67,8 +87,8 @@  static bool ip6t_npt_map_pfx(const struct ip6t_npt_tginfo *npt,
                        return false;
        }
 
-       sum = (__force __sum16) csum_add((__force __wsum)addr->s6_addr16[idx],
-                        npt->adjustment);
+       sum = csum16_add((__force __sum16)addr->s6_addr16[idx],
+                               npt->adjustment);
        if (sum == CSUM_MANGLED_0)
                sum = 0;
        *(__force __sum16 *)&addr->s6_addr16[idx] = sum;