netdev - Re: BUG REPORT: iproute2 seems to have bug with dsfield/tos in ip-rule and ip-route

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Date:   Wed, 13 Dec 2017 15:40:13 -0700
From:   David Ahern <dsahern@...il.com>
To:     Daniel Lakeland <dlakelan@...eet-artists.org>,
        Stephen Hemminger <stephen@...workplumber.org>
Cc:     netdev@...r.kernel.org
Subject: Re: BUG REPORT: iproute2 seems to have bug with dsfield/tos in
 ip-rule and ip-route

On 12/13/17 12:05 PM, Daniel Lakeland wrote:
> Following up my previous email with output from the machine:
> Note that like some of those other people I was able to get ip rule to
> accept tos values with just low order bits set
> 
> Here is example of how ip rule accepts low order dsfield bits but not
> modern DSCP type bits, also including some version info
> 
> dlakelan@...gpong:~$ sudo ip rule add dsfield 0x0c table 100
> dlakelan@...gpong:~$ ip rule show
> 0:    from all lookup local
> 32765:    from all tos 0x0c lookup 100
> 32766:    from all lookup main
> 32767:    from all lookup default
> 
> 
> dlakelan@...gpong:~$ sudo ip rule add dsfield 0xc0 table 100
> RTNETLINK answers: Invalid argument

In fib4_rule_configure, this the check that is failing:

    if (frh->tos & ~IPTOS_TOS_MASK)
        goto errout;

and EINVAL is returned.

IPv4 routes has not checking on tos -- it is passed from user and
rtm_tos to fc_tos to fib alias tos.