netdev - Re: [PATCH net v2 1/1] openvswitch: Fix setting ipv6 fields causing hw csum failure

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Message-ID: <20220214212708.7e69482a@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Mon, 14 Feb 2022 21:27:08 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Paul Blakey <paulb@...dia.com>
Cc:     <dev@...nvswitch.org>, <netdev@...r.kernel.org>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        "Pravin B Shelar" <pshelar@....org>, <davem@...emloft.net>,
        Eelco Chaudron <echaudro@...hat.com>,
        Oz Shlomo <ozsh@...dia.com>, Vlad Buslov <vladbu@...dia.com>,
        Roi Dayan <roid@...dia.com>,
        Ariel Levkovich <lariel@...dia.com>
Subject: Re: [PATCH net v2 1/1] openvswitch: Fix setting ipv6 fields causing
 hw csum failure

On Mon, 14 Feb 2022 14:48:51 +0200 Paul Blakey wrote:
> Ipv6 ttl, label and tos fields are modified without first
> pulling/pushing the ipv6 header, which would have updated
> the hw csum (if available). This might cause csum validation
> when sending the packet to the stack, as can be seen in
> the trace below.
> 
> Fix this by updating skb->csum if available.

> Fixes: 3fdbd1ce11e5 ("openvswitch: add ipv6 'set' action")
> Signed-off-by: Paul Blakey <paulb@...dia.com>
> ---
>  Changelog:
>     v1->v2:
>       Replaced push pull rcsum checksum calc with actual checksum calc

Well, what I had in mind was an skb helper which would take skb, u32
new_val, u32 old_val, but this works, too.

Please fix the new sparse warnings tho, and..

> diff --git a/net/openvswitch/actions.c b/net/openvswitch/actions.c
> index 076774034bb9..3725801cb040 100644
> --- a/net/openvswitch/actions.c
> +++ b/net/openvswitch/actions.c
> @@ -423,12 +423,44 @@ static void set_ipv6_addr(struct sk_buff *skb, u8 l4_proto,
>  	memcpy(addr, new_addr, sizeof(__be32[4]));
>  }
>  
> -static void set_ipv6_fl(struct ipv6hdr *nh, u32 fl, u32 mask)
> +static void set_ipv6_dsfield(struct sk_buff *skb, struct ipv6hdr *nh, __u8 ipv6_tclass, __u8 mask)
>  {
> +	__u8 old_ipv6_tclass = ipv6_get_dsfield(nh);

use normal u8, __u8 is for uAPI.