Re: [PATCH net] ipv4: Fix route deletion when nexthop info is not specified

[Nikolay Aleksandrov <razor@blackwall.org>]

On 24/11/2022 23:09, Ido Schimmel wrote:
> When the kernel receives a route deletion request from user space it
> tries to delete a route that matches the route attributes specified in
> the request.
> 
> If only prefix information is specified in the request, the kernel
> should delete the first matching FIB alias regardless of its associated
> FIB info. However, an error is currently returned when the FIB info is
> backed by a nexthop object:
> 
>  # ip nexthop add id 1 via 192.0.2.2 dev dummy10
>  # ip route add 198.51.100.0/24 nhid 1
>  # ip route del 198.51.100.0/24
>  RTNETLINK answers: No such process
> 
> Fix by matching on such a FIB info when legacy nexthop attributes are
> not specified in the request. An earlier check already covers the case
> where a nexthop ID is specified in the request.
> 
> Add tests that cover these flows. Before the fix:
> 
>  # ./fib_nexthops.sh -t ipv4_fcnal
>  ...
>  TEST: Delete route when not specifying nexthop attributes           [FAIL]
> 
>  Tests passed:  11
>  Tests failed:   1
> 
> After the fix:
> 
>  # ./fib_nexthops.sh -t ipv4_fcnal
>  ...
>  TEST: Delete route when not specifying nexthop attributes           [ OK ]
> 
>  Tests passed:  12
>  Tests failed:   0
> 
> No regressions in other tests:
> 
>  # ./fib_nexthops.sh
>  ...
>  Tests passed: 228
>  Tests failed:   0
> 
>  # ./fib_tests.sh
>  ...
>  Tests passed: 186
>  Tests failed:   0
> 
> Cc: stable@vger.kernel.org
> Reported-by: Jonas Gorski <jonas.gorski@gmail.com>
> Tested-by: Jonas Gorski <jonas.gorski@gmail.com>
> Fixes: 493ced1ac47c ("ipv4: Allow routes to use nexthop objects")
> Fixes: 6bf92d70e690 ("net: ipv4: fix route with nexthop object delete warning")
> Fixes: 61b91eb33a69 ("ipv4: Handle attempt to delete multipath route when fib_info contains an nh reference")
> Signed-off-by: Ido Schimmel <idosch@nvidia.com>
> ---
>  net/ipv4/fib_semantics.c                    |  8 +++++---
>  tools/testing/selftests/net/fib_nexthops.sh | 11 +++++++++++
>  2 files changed, 16 insertions(+), 3 deletions(-)
> 

Reviewed-by: Nikolay Aleksandrov <razor@blackwall.org>

> diff --git a/net/ipv4/fib_semantics.c b/net/ipv4/fib_semantics.c
> index f721c308248b..19a662003eef 100644
> --- a/net/ipv4/fib_semantics.c
> +++ b/net/ipv4/fib_semantics.c
> @@ -888,9 +888,11 @@ int fib_nh_match(struct net *net, struct fib_config *cfg, struct fib_info *fi,
>  		return 1;
>  	}
>  
> -	/* cannot match on nexthop object attributes */
> -	if (fi->nh)
> -		return 1;
> +	if (fi->nh) {
> +		if (cfg->fc_oif || cfg->fc_gw_family || cfg->fc_mp)
> +			return 1;
> +		return 0;
> +	}
>  
>  	if (cfg->fc_oif || cfg->fc_gw_family) {
>  		struct fib_nh *nh;
> diff --git a/tools/testing/selftests/net/fib_nexthops.sh b/tools/testing/selftests/net/fib_nexthops.sh
> index ee5e98204d3d..a47b26ab48f2 100755
> --- a/tools/testing/selftests/net/fib_nexthops.sh
> +++ b/tools/testing/selftests/net/fib_nexthops.sh
> @@ -1228,6 +1228,17 @@ ipv4_fcnal()
>  	run_cmd "$IP ro add 172.16.101.0/24 nhid 21"
>  	run_cmd "$IP ro del 172.16.101.0/24 nexthop via 172.16.1.7 dev veth1 nexthop via 172.16.1.8 dev veth1"
>  	log_test $? 2 "Delete multipath route with only nh id based entry"
> +
> +	run_cmd "$IP nexthop add id 22 via 172.16.1.6 dev veth1"
> +	run_cmd "$IP ro add 172.16.102.0/24 nhid 22"
> +	run_cmd "$IP ro del 172.16.102.0/24 dev veth1"
> +	log_test $? 2 "Delete route when specifying only nexthop device"
> +
> +	run_cmd "$IP ro del 172.16.102.0/24 via 172.16.1.6"
> +	log_test $? 2 "Delete route when specifying only gateway"
> +
> +	run_cmd "$IP ro del 172.16.102.0/24"
> +	log_test $? 0 "Delete route when not specifying nexthop attributes"
>  }
>  
>  ipv4_grp_fcnal()