Re: [PATCH net 1/1] net/sched: act_ct: Fix flow table lookup failure with no originating ifindex

[Pablo Neira Ayuso <pablo@netfilter.org>]

On Thu, Feb 17, 2022 at 11:34:24AM +0200, Paul Blakey wrote:
> After cited commit optimizted hw insertion, flow table entries are
> populated with ifindex information which was intended to only be used
> for HW offload. This tuple ifindex is hashed in the flow table key, so
> it must be filled for lookup to be successful. But tuple ifindex is only
> relevant for the netfilter flowtables (nft), so it's not filled in
> act_ct flow table lookup, resulting in lookup failure, and no SW
> offload and no offload teardown for TCP connection FIN/RST packets.
> 
> To fix this, allow flow tables that don't hash the ifindex.
> Netfilter flow tables will keep using ifindex for a more specific
> offload, while act_ct will not.

Using iif == zero should be enough to specify not set?

> Fixes: 9795ded7f924 ("net/sched: act_ct: Fill offloading tupledx")
> Signed-off-by: Paul Blakey <paulb@nvidia.com>
> ---
>  include/net/netfilter/nf_flow_table.h | 8 ++++----
>  net/netfilter/nf_flow_table_core.c    | 6 ++++++
>  net/sched/act_ct.c                    | 3 ++-
>  3 files changed, 12 insertions(+), 5 deletions(-)
> 
> diff --git a/include/net/netfilter/nf_flow_table.h b/include/net/netfilter/nf_flow_table.h
> index a3647fadf1cc..9b474414a936 100644
> --- a/include/net/netfilter/nf_flow_table.h
> +++ b/include/net/netfilter/nf_flow_table.h
> @@ -64,8 +64,9 @@ struct nf_flowtable_type {
>  };
>  
>  enum nf_flowtable_flags {
> -	NF_FLOWTABLE_HW_OFFLOAD		= 0x1,	/* NFT_FLOWTABLE_HW_OFFLOAD */
> -	NF_FLOWTABLE_COUNTER		= 0x2,	/* NFT_FLOWTABLE_COUNTER */
> +	NF_FLOWTABLE_HW_OFFLOAD			= 0x1,	/* NFT_FLOWTABLE_HW_OFFLOAD */
> +	NF_FLOWTABLE_COUNTER			= 0x2,	/* NFT_FLOWTABLE_COUNTER */
> +	NF_FLOWTABLE_NO_IFINDEX_FILTERING	= 0x4,	/* Only used by act_ct */
>  };
>  
>  struct nf_flowtable {
> @@ -114,8 +115,6 @@ struct flow_offload_tuple {
>  		__be16			dst_port;
>  	};
>  
> -	int				iifidx;
> -
>  	u8				l3proto;
>  	u8				l4proto;
>  	struct {
> @@ -126,6 +125,7 @@ struct flow_offload_tuple {
>  	/* All members above are keys for lookups, see flow_offload_hash(). */
>  	struct { }			__hash;
>  
> +	int				iifidx;
>  	u8				dir:2,
>  					xmit_type:2,
>  					encap_num:2,
> diff --git a/net/netfilter/nf_flow_table_core.c b/net/netfilter/nf_flow_table_core.c
> index b90eca7a2f22..f0cb2c7075c0 100644
> --- a/net/netfilter/nf_flow_table_core.c
> +++ b/net/netfilter/nf_flow_table_core.c
> @@ -254,9 +254,15 @@ static u32 flow_offload_hash_obj(const void *data, u32 len, u32 seed)
>  static int flow_offload_hash_cmp(struct rhashtable_compare_arg *arg,
>  					const void *ptr)
>  {
> +	const struct nf_flowtable *flow_table = container_of(arg->ht, struct nf_flowtable,
> +							     rhashtable);
>  	const struct flow_offload_tuple *tuple = arg->key;
>  	const struct flow_offload_tuple_rhash *x = ptr;
>  
> +	if (!(flow_table->flags & NF_FLOWTABLE_NO_IFINDEX_FILTERING) &&
> +	    x->tuple.iifidx != tuple->iifidx)
> +		return 1;
> +
>  	if (memcmp(&x->tuple, tuple, offsetof(struct flow_offload_tuple, __hash)))
>  		return 1;
>  
> diff --git a/net/sched/act_ct.c b/net/sched/act_ct.c
> index f99247fc6468..22cd32ec9889 100644
> --- a/net/sched/act_ct.c
> +++ b/net/sched/act_ct.c
> @@ -305,7 +305,8 @@ static int tcf_ct_flow_table_get(struct tcf_ct_params *params)
>  
>  	ct_ft->nf_ft.type = &flowtable_ct;
>  	ct_ft->nf_ft.flags |= NF_FLOWTABLE_HW_OFFLOAD |
> -			      NF_FLOWTABLE_COUNTER;
> +			      NF_FLOWTABLE_COUNTER |
> +			      NF_FLOWTABLE_NO_IFINDEX_FILTERING;
>  	err = nf_flow_table_init(&ct_ft->nf_ft);
>  	if (err)
>  		goto err_init;
> -- 
> 2.30.1
>