* Re: [Bugme-new] [Bug 16517] New: rp_filter fails to filter with CONFIG_IP_ROUTE_MULTIPATH and more than one 0/0 nexthop dev
[not found] <bug-16517-10286@https.bugzilla.kernel.org/>
@ 2010-08-05 20:46 ` Andrew Morton
2010-09-07 5:35 ` David Miller
0 siblings, 1 reply; 2+ messages in thread
From: Andrew Morton @ 2010-08-05 20:46 UTC (permalink / raw)
To: netfilter, netdev
Cc: bugzilla-daemon, bugme-daemon, for.poige+bugzilla.kernel.org
(switched to email. Please respond via emailed reply-to-all, not via the
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On Thu, 5 Aug 2010 01:48:01 GMT
bugzilla-daemon@bugzilla.kernel.org wrote:
> https://bugzilla.kernel.org/show_bug.cgi?id=16517
>
> Summary: rp_filter fails to filter with
> CONFIG_IP_ROUTE_MULTIPATH and more than one 0/0
> nexthop dev
> Product: Networking
> Version: 2.5
> Kernel Version: at least 2.6.18 and newer
> Platform: All
> OS/Version: Linux
> Tree: Mainline
> Status: NEW
> Severity: high
> Priority: P1
> Component: IPV4
> AssignedTo: shemminger@linux-foundation.org
> ReportedBy: for.poige+bugzilla.kernel.org@gmail.com
> Regression: No
>
>
> I think the problem is net/ipv4/fib_frontend.c fib_validate_source()
>
> ...
> #ifdef CONFIG_IP_ROUTE_MULTIPATH
> if (FIB_RES_DEV(res) == dev || res.fi->fib_nhs > 1)
> #else
> if (FIB_RES_DEV(res) == dev)
> #endif
> ...
>
> I'm not sure, but this code is quite trivial and self-speaking. In case we have
> several default routes, we'd better iterate over each of them and compare
> resulting devices with the input one. So, fix is also trivial, specially for
> network kernel developers. ;-)
>
> I've set priority "High" cause it doesn't affects usual Linux users directly,
> but indirectly it can affect any host on Internet, so the problem is
> significant, of course.
>
> P. S. Kernel docs say: {
> rp_filter - INTEGER
> 0 - No source validation.
> 1 - Strict mode as defined in RFC3704 Strict Reverse Path
> Each incoming packet is tested against the FIB and if the interface
> is not the best reverse path the packet check will fail.
> By default failed packets are discarded.
> 2 - Loose mode as defined in RFC3704 Loose Reverse Path
> Each incoming packet's source address is also tested against the
> FIB
> and if the source address is not reachable via any interface
> the packet check will fail.
>
> Current recommended practice in RFC3704 is to enable strict mode
> to prevent IP spoofing from DDos attacks. If using asymmetric routing
> or other complicated routing, then loose mode is recommended.
>
> conf/all/rp_filter must also be set to non-zero to do source validation
> on the interface
>
> Default value is 0. Note that some distributions enable it
> in startup scripts.
> }, but is in reality level "2" of rp_filtering implemented?
>
> P. P. S. netfilter would be the best place to have Reverse Path checks. But
> that's another story.
>
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [Bugme-new] [Bug 16517] New: rp_filter fails to filter with CONFIG_IP_ROUTE_MULTIPATH and more than one 0/0 nexthop dev
2010-08-05 20:46 ` [Bugme-new] [Bug 16517] New: rp_filter fails to filter with CONFIG_IP_ROUTE_MULTIPATH and more than one 0/0 nexthop dev Andrew Morton
@ 2010-09-07 5:35 ` David Miller
0 siblings, 0 replies; 2+ messages in thread
From: David Miller @ 2010-09-07 5:35 UTC (permalink / raw)
To: akpm
Cc: netfilter, netdev, bugzilla-daemon, bugme-daemon,
for.poige+bugzilla.kernel.org
From: Andrew Morton <akpm@linux-foundation.org>
Date: Thu, 5 Aug 2010 13:46:53 -0700
>> I think the problem is net/ipv4/fib_frontend.c fib_validate_source()
>>
>> ...
>> #ifdef CONFIG_IP_ROUTE_MULTIPATH
>> if (FIB_RES_DEV(res) == dev || res.fi->fib_nhs > 1)
>> #else
>> if (FIB_RES_DEV(res) == dev)
>> #endif
>> ...
>>
>> I'm not sure, but this code is quite trivial and self-speaking. In case we have
>> several default routes, we'd better iterate over each of them and compare
>> resulting devices with the input one. So, fix is also trivial, specially for
>> network kernel developers. ;-)
Please test this patch:
ipv4: Fix reverse path filtering with multipath routing.
Actually iterate over the next-hops to make sure we have
a device match. Otherwise RP filtering is always elided
when the route matched has multiple next-hops.
Reported-by: Igor M Podlesny <for.poige@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c
index a439689..7d02a9f 100644
--- a/net/ipv4/fib_frontend.c
+++ b/net/ipv4/fib_frontend.c
@@ -246,6 +246,7 @@ int fib_validate_source(__be32 src, __be32 dst, u8 tos, int oif,
struct fib_result res;
int no_addr, rpf, accept_local;
+ bool dev_match;
int ret;
struct net *net;
@@ -273,12 +274,22 @@ int fib_validate_source(__be32 src, __be32 dst, u8 tos, int oif,
}
*spec_dst = FIB_RES_PREFSRC(res);
fib_combine_itag(itag, &res);
+ dev_match = false;
+
#ifdef CONFIG_IP_ROUTE_MULTIPATH
- if (FIB_RES_DEV(res) == dev || res.fi->fib_nhs > 1)
+ for (ret = 0; ret < res.fi->fib_nhs; ret++) {
+ struct fib_nh *nh = &res.fi->fib_nh[ret];
+
+ if (nh->nh_dev == dev) {
+ dev_match = true;
+ break;
+ }
+ }
#else
if (FIB_RES_DEV(res) == dev)
+ dev_match = true;
#endif
- {
+ if (dev_match) {
ret = FIB_RES_NH(res).nh_scope >= RT_SCOPE_HOST;
fib_res_put(&res);
return ret;
^ permalink raw reply related [flat|nested] 2+ messages in thread
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2010-08-05 20:46 ` [Bugme-new] [Bug 16517] New: rp_filter fails to filter with CONFIG_IP_ROUTE_MULTIPATH and more than one 0/0 nexthop dev Andrew Morton
2010-09-07 5:35 ` David Miller
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