Subject: Re: Setting security path with IPsec packet offload mode

From: Leon Romanovsky <[email-masked]>
Date: Thu, 22 Jun 2023 11:35:00 +0300

On Thu, Jun 22, 2023 at 06:58:06AM +0000, Bharat Bhushan wrote:
> Hi All,
> 
> Have a query related to security patch (secpath_set()) with packet offload mode on egress side. Working to enable ipsec packet offload while Crypto offload is working.
> For packet offload xfrm_offload(*skb) returns false in driver. While looking in xfrm framework, cannot find where security patch (secpath_set()) is set with packet offload mode on egress side.

The idea of packet offload is to take plain text packets and perform all needed magic
in HW without need from driver and stack to make anything.

We don't set secpath in TX path as such packets exit from XFRM as "plain" ones toward HW.
It is different in RX, we set there, as XFRM core still needs to perform some code on
the arrived packets, before forwarding them to stack.

Thanks

> 
> For sure I might be missing something here and looking for help to understand same. Meantime just tried below hack:
> 
> diff --git a/net/xfrm/xfrm_output.c b/net/xfrm/xfrm_output.c
> index ff114d68cc43..8499c0e74a5a 100644
> --- a/net/xfrm/xfrm_output.c
> +++ b/net/xfrm/xfrm_output.c
> @@ -718,12 +718,24 @@ int xfrm_output(struct sock *sk, struct sk_buff *skb)
>         }
>  
>         if (x->xso.type == XFRM_DEV_OFFLOAD_PACKET) {
> +               struct sec_path *sp;
>                 if (!xfrm_dev_offload_ok(skb, x)) {
>                         XFRM_INC_STATS(net, LINUX_MIB_XFRMOUTERROR);
>                         kfree_skb(skb);
>                         return -EHOSTUNREACH;
>                 }
>  
> +               sp = secpath_set(skb);
> +               if (!sp) {
> +                       XFRM_INC_STATS(net, LINUX_MIB_XFRMOUTERROR);
> +                       kfree_skb(skb);
> +                       return -ENOMEM;
> +               }
> +
> +               sp->olen++;
> +               sp->xvec[sp->len++] = x;
> +               xfrm_state_hold(x);
> +
>                 return xfrm_output_resume(sk, skb, 0);
>         }
>  
> 
> Thanks in advance,
> -Bharat
>