[PATCH net] net: fib_rules: add protocol check in rule_find

[PATCH net] net: fib_rules: add protocol check in rule_find

[Roopa Prabhu]

From: Roopa Prabhu <roopa@cumulusnetworks.com>

After commit f9d4b0c1e969 ("fib_rules: move common handling of newrule
delrule msgs into fib_nl2rule"), rule_find is strict about checking
for an existing rule. rule_find must check against all
user given attributes, else it may match against a subset
of attributes and return an existing rule.

In the below case, without support for protocol match, rule_find
will match only against 'table main' and return an existing rule.

$ip -4 rule add table main protocol boot
RTNETLINK answers: File exists

This patch adds protocol support to rule_find, forcing it to
check protocol match if given by the user.

Fixes: f9d4b0c1e969 ("fib_rules: move common handling of newrule delrule msgs into fib_nl2rule")
Signed-off-by: Roopa Prabhu <roopa@cumulusnetworks.com>
---
I spent some time looking at all match keys today and protocol
was the only missing one (protocol is not in a released kernel yet).
The only way this could be avoided is to move back to the old loose
rule_find. I am worried about this new strict checking surprising users,
but going back to the previous loose checking does not seem right either.
If there is a reason to believe that users did rely on the previous
behaviour, I will be happy to revert. Here is another example of old and
new behaviour.

old rule_find behaviour:
$ip -4 rule add table main protocol boot
$ip -4 rule add table main protocol boot
$ip -4 rule add table main protocol boot
$ip rule show
0:      from all lookup local 
32763:  from all lookup main  proto boot 
32764:  from all lookup main  proto boot 
32765:  from all lookup main  proto boot 
32766:  from all lookup main 
32767:  from all lookup default 

new rule_find behaviour (after this patch):
$ip -4 rule add table main protocol boot
$ip -4 rule add table main protocol boot
RTNETLINK answers: File exists

 net/core/fib_rules.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/core/fib_rules.c b/net/core/fib_rules.c
index bc8425d..5905567 100644
--- a/net/core/fib_rules.c
+++ b/net/core/fib_rules.c
@@ -444,6 +444,9 @@ static struct fib_rule *rule_find(struct fib_rules_ops *ops,
 		if (rule->ip_proto && r->ip_proto != rule->ip_proto)
 			continue;
 
+		if (rule->proto && r->proto != rule->proto)
+			continue;
+
 		if (fib_rule_port_range_set(&rule->sport_range) &&
 		    !fib_rule_port_range_compare(&r->sport_range,
 						 &rule->sport_range))
-- 
2.1.4

Re: [PATCH net] net: fib_rules: add protocol check in rule_find

[David Ahern]

On 6/27/18 7:27 PM, Roopa Prabhu wrote:
> From: Roopa Prabhu <roopa@cumulusnetworks.com>
> 
> After commit f9d4b0c1e969 ("fib_rules: move common handling of newrule
> delrule msgs into fib_nl2rule"), rule_find is strict about checking
> for an existing rule. rule_find must check against all
> user given attributes, else it may match against a subset
> of attributes and return an existing rule.
> 
> In the below case, without support for protocol match, rule_find
> will match only against 'table main' and return an existing rule.
> 
> $ip -4 rule add table main protocol boot
> RTNETLINK answers: File exists
> 
> This patch adds protocol support to rule_find, forcing it to
> check protocol match if given by the user.
> 
> Fixes: f9d4b0c1e969 ("fib_rules: move common handling of newrule delrule msgs into fib_nl2rule")
> Signed-off-by: Roopa Prabhu <roopa@cumulusnetworks.com>
> ---

Reviewed-by: David Ahern <dsahern@gmail.com>

Re: [PATCH net] net: fib_rules: add protocol check in rule_find

[Roopa Prabhu]

On Wed, Jun 27, 2018 at 6:27 PM, Roopa Prabhu <roopa@cumulusnetworks.com> wrote:
> From: Roopa Prabhu <roopa@cumulusnetworks.com>
>
> After commit f9d4b0c1e969 ("fib_rules: move common handling of newrule
> delrule msgs into fib_nl2rule"), rule_find is strict about checking
> for an existing rule. rule_find must check against all
> user given attributes, else it may match against a subset
> of attributes and return an existing rule.
>
> In the below case, without support for protocol match, rule_find
> will match only against 'table main' and return an existing rule.
>
> $ip -4 rule add table main protocol boot
> RTNETLINK answers: File exists
>
> This patch adds protocol support to rule_find, forcing it to
> check protocol match if given by the user.
>
> Fixes: f9d4b0c1e969 ("fib_rules: move common handling of newrule delrule msgs into fib_nl2rule")
> Signed-off-by: Roopa Prabhu <roopa@cumulusnetworks.com>
> ---
> I spent some time looking at all match keys today and protocol
> was the only missing one (protocol is not in a released kernel yet).
> The only way this could be avoided is to move back to the old loose
> rule_find. I am worried about this new strict checking surprising users,
> but going back to the previous loose checking does not seem right either.
> If there is a reason to believe that users did rely on the previous
> behaviour, I will be happy to revert. Here is another example of old and
> new behaviour.
>
> old rule_find behaviour:
> $ip -4 rule add table main protocol boot
> $ip -4 rule add table main protocol boot
> $ip -4 rule add table main protocol boot
> $ip rule show
> 0:      from all lookup local
> 32763:  from all lookup main  proto boot
> 32764:  from all lookup main  proto boot
> 32765:  from all lookup main  proto boot
> 32766:  from all lookup main
> 32767:  from all lookup default
>
> new rule_find behaviour (after this patch):
> $ip -4 rule add table main protocol boot
> $ip -4 rule add table main protocol boot
> RTNETLINK answers: File exists
>

I found the case where the new rule_find breaks for add.
$ip -4 rule add table main tos 10 fwmark 1
$ip -4 rule add table main tos 10
RTNETLINK answers: File exists

The key masks in the new and old rule need to be compared .
And it cannot be easily compared today without an elaborate if-else block.
Its best to introduce key masks for easier and accurate rule comparison.
But this is best done in net-next. I will submit an incremental patch
tomorrow to
restore previous rule_exists for the add case and the rest should be good.

The current patch in context is needed regardless.

Thanks (and sorry about the iterations).

Re: [PATCH net] net: fib_rules: add protocol check in rule_find

[Roopa Prabhu]

On Thu, Jun 28, 2018 at 9:59 PM, Roopa Prabhu <roopa@cumulusnetworks.com> wrote:
> On Wed, Jun 27, 2018 at 6:27 PM, Roopa Prabhu <roopa@cumulusnetworks.com> wrote:
>> From: Roopa Prabhu <roopa@cumulusnetworks.com>
>>
>> After commit f9d4b0c1e969 ("fib_rules: move common handling of newrule
>> delrule msgs into fib_nl2rule"), rule_find is strict about checking
>> for an existing rule. rule_find must check against all
>> user given attributes, else it may match against a subset
>> of attributes and return an existing rule.
>>
>> In the below case, without support for protocol match, rule_find
>> will match only against 'table main' and return an existing rule.
>>
>> $ip -4 rule add table main protocol boot
>> RTNETLINK answers: File exists
>>
>> This patch adds protocol support to rule_find, forcing it to
>> check protocol match if given by the user.
>>
>> Fixes: f9d4b0c1e969 ("fib_rules: move common handling of newrule delrule msgs into fib_nl2rule")
>> Signed-off-by: Roopa Prabhu <roopa@cumulusnetworks.com>
>> ---
>> I spent some time looking at all match keys today and protocol
>> was the only missing one (protocol is not in a released kernel yet).
>> The only way this could be avoided is to move back to the old loose
>> rule_find. I am worried about this new strict checking surprising users,
>> but going back to the previous loose checking does not seem right either.
>> If there is a reason to believe that users did rely on the previous
>> behaviour, I will be happy to revert. Here is another example of old and
>> new behaviour.
>>
>> old rule_find behaviour:
>> $ip -4 rule add table main protocol boot
>> $ip -4 rule add table main protocol boot
>> $ip -4 rule add table main protocol boot
>> $ip rule show
>> 0:      from all lookup local
>> 32763:  from all lookup main  proto boot
>> 32764:  from all lookup main  proto boot
>> 32765:  from all lookup main  proto boot
>> 32766:  from all lookup main
>> 32767:  from all lookup default
>>
>> new rule_find behaviour (after this patch):
>> $ip -4 rule add table main protocol boot
>> $ip -4 rule add table main protocol boot
>> RTNETLINK answers: File exists
>>
>
> I found the case where the new rule_find breaks for add.
> $ip -4 rule add table main tos 10 fwmark 1
> $ip -4 rule add table main tos 10
> RTNETLINK answers: File exists
>
> The key masks in the new and old rule need to be compared .
> And it cannot be easily compared today without an elaborate if-else block.
> Its best to introduce key masks for easier and accurate rule comparison.
> But this is best done in net-next. I will submit an incremental patch
> tomorrow to
> restore previous rule_exists for the add case and the rest should be good.
>
> The current patch in context is needed regardless.
>
> Thanks (and sorry about the iterations).

as I write the commit msg for the new incremental patch, it seems
better to merge this one with the new one.

Please ignore this patch, I will send an updated patch in a bit. thanks.