netdev - Re: [PATCH net] net: sched: fix erspan_opt settings in cls

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Message-ID: <Z0kf8QQjeHjDr6IU@pop-os.localdomain>
Date: Thu, 28 Nov 2024 17:59:13 -0800
From: Cong Wang <xiyou.wangcong@...il.com>
To: Xin Long <lucien.xin@...il.com>
Cc: network dev <netdev@...r.kernel.org>, davem@...emloft.net,
	kuba@...nel.org, Eric Dumazet <edumazet@...gle.com>,
	Paolo Abeni <pabeni@...hat.com>,
	Jamal Hadi Salim <jhs@...atatu.com>, Jiri Pirko <jiri@...nulli.us>,
	Davide Caratti <dcaratti@...hat.com>,
	Simon Horman <horms@...nel.org>
Subject: Re: [PATCH net] net: sched: fix erspan_opt settings in cls_flower

On Mon, Nov 25, 2024 at 03:56:51PM -0500, Xin Long wrote:
> When matching erspan_opt in cls_flower, only the (version, dir, hwid)
> fields are relevant. However, in fl_set_erspan_opt() it initializes
> all bits of erspan_opt and its mask to 1. This inadvertently requires
> packets to match not only the (version, dir, hwid) fields but also the
> other fields that are unexpectedly set to 1.

Do you have a test case for this? Please consider adding one (in a
separate patch) to tools/testing/selftests/tc-testing/.

> 
> This patch resolves the issue by ensuring that only the (version, dir,
> hwid) fields are configured in fl_set_erspan_opt(), leaving the other
> fields to 0 in erspan_opt.
> 
> Fixes: 79b1011cb33d ("net: sched: allow flower to match erspan options")
> Reported-by: Shuang Li <shuali@...hat.com>
> Signed-off-by: Xin Long <lucien.xin@...il.com>
> ---
>  net/sched/cls_flower.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/net/sched/cls_flower.c b/net/sched/cls_flower.c
> index e280c27cb9f9..c89161c5a119 100644
> --- a/net/sched/cls_flower.c
> +++ b/net/sched/cls_flower.c
> @@ -1369,7 +1369,6 @@ static int fl_set_erspan_opt(const struct nlattr *nla, struct fl_flow_key *key,
>  	int err;
>  
>  	md = (struct erspan_metadata *)&key->enc_opts.data[key->enc_opts.len];
> -	memset(md, 0xff, sizeof(*md));
>  	md->version = 1;
>  
>  	if (!depth)
> @@ -1398,9 +1397,9 @@ static int fl_set_erspan_opt(const struct nlattr *nla, struct fl_flow_key *key,
>  			NL_SET_ERR_MSG(extack, "Missing tunnel key erspan option index");
>  			return -EINVAL;
>  		}
> +		memset(&md->u.index, 0xff, sizeof(md->u.index));
>  		if (tb[TCA_FLOWER_KEY_ENC_OPT_ERSPAN_INDEX]) {
>  			nla = tb[TCA_FLOWER_KEY_ENC_OPT_ERSPAN_INDEX];
> -			memset(&md->u, 0x00, sizeof(md->u));
>  			md->u.index = nla_get_be32(nla);
>  		}
>  	} else if (md->version == 2) {
> @@ -1409,10 +1408,12 @@ static int fl_set_erspan_opt(const struct nlattr *nla, struct fl_flow_key *key,
>  			NL_SET_ERR_MSG(extack, "Missing tunnel key erspan option dir or hwid");
>  			return -EINVAL;
>  		}
> +		md->u.md2.dir = 1;
>  		if (tb[TCA_FLOWER_KEY_ENC_OPT_ERSPAN_DIR]) {
>  			nla = tb[TCA_FLOWER_KEY_ENC_OPT_ERSPAN_DIR];
>  			md->u.md2.dir = nla_get_u8(nla);
>  		}
> +		set_hwid(&md->u.md2, 0x3f);

I think using 0xff is easier to understand, otherwise we would need to
look into set_hwid() to figure out what 0x3f means. :-/

Thanks!