netdev - Re: [PATCH net-next] ipv6: Reject routes configurations that specify dsfield (tos)

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Message-ID: <7bbeba35-17a7-f8ba-0587-4bb1c9b6721e@linuxfoundation.org>
Date:   Thu, 10 Feb 2022 11:23:20 -0700
From:   Shuah Khan <skhan@...uxfoundation.org>
To:     Guillaume Nault <gnault@...hat.com>,
        David Miller <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     netdev@...r.kernel.org,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        David Ahern <dsahern@...nel.org>,
        Shuah Khan <shuah@...nel.org>, linux-kselftest@...r.kernel.org,
        Toke Høiland-Jørgensen <toke@...hat.com>,
        Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [PATCH net-next] ipv6: Reject routes configurations that specify
 dsfield (tos)

On 2/10/22 8:08 AM, Guillaume Nault wrote:
> The ->rtm_tos option is normally used to route packets based on both
> the destination address and the DS field. However it's ignored for
> IPv6 routes. Setting ->rtm_tos for IPv6 is thus invalid as the route
> is going to work only on the destination address anyway, so it won't
> behave as specified.
> 
> Suggested-by: Toke Høiland-Jørgensen <toke@...hat.com>
> Signed-off-by: Guillaume Nault <gnault@...hat.com>
> ---
> The same problem exists for ->rtm_scope. I'm working only on ->rtm_tos
> here because IPv4 recently started to validate this option too (as part
> of the DSCP/ECN clarification effort).
> I'll give this patch some soak time, then send another one for
> rejecting ->rtm_scope in IPv6 routes if nobody complains.
> 
>   net/ipv6/route.c                         |  6 ++++++
>   tools/testing/selftests/net/fib_tests.sh | 13 +++++++++++++
>   2 files changed, 19 insertions(+)
> 
> diff --git a/net/ipv6/route.c b/net/ipv6/route.c
> index f4884cda13b9..dd98a11fbdb6 100644
> --- a/net/ipv6/route.c
> +++ b/net/ipv6/route.c
> @@ -5009,6 +5009,12 @@ static int rtm_to_fib6_config(struct sk_buff *skb, struct nlmsghdr *nlh,
>   	err = -EINVAL;
>   	rtm = nlmsg_data(nlh);
>   
> +	if (rtm->rtm_tos) {
> +		NL_SET_ERR_MSG(extack,
> +			       "Invalid dsfield (tos): option not available for IPv6");

Is this an expected failure on ipv6, in which case should this test report
pass? Should it print "failed as expected" or is returning fail from errout
is what should happen?

> +		goto errout;
> +	}
> +
>   	*cfg = (struct fib6_config){
>   		.fc_table = rtm->rtm_table,
>   		.fc_dst_len = rtm->rtm_dst_len,
> diff --git a/tools/testing/selftests/net/fib_tests.sh b/tools/testing/selftests/net/fib_tests.sh
> index bb73235976b3..e2690cc42da3 100755
> --- a/tools/testing/selftests/net/fib_tests.sh
> +++ b/tools/testing/selftests/net/fib_tests.sh
> @@ -988,12 +988,25 @@ ipv6_rt_replace()
>   	ipv6_rt_replace_mpath
>   }
>   
> +ipv6_rt_dsfield()
> +{
> +	echo
> +	echo "IPv6 route with dsfield tests"
> +
> +	run_cmd "$IP -6 route flush 2001:db8:102::/64"
> +
> +	# IPv6 doesn't support routing based on dsfield
> +	run_cmd "$IP -6 route add 2001:db8:102::/64 dsfield 0x04 via 2001:db8:101::2"
> +	log_test $? 2 "Reject route with dsfield"
> +}
> +
>   ipv6_route_test()
>   {
>   	route_setup
>   
>   	ipv6_rt_add
>   	ipv6_rt_replace
> +	ipv6_rt_dsfield
>   
>   	route_cleanup
>   }
> 

With the above comment addressed or explained.

Reviewed-by: Shuah Khan <skhan@...uxfoundation.org>

thanks,
-- Shuah