netdev - Re: [PATCH iproute2] tc: m_tunnel

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Message-ID: <20200618105107.GB27897@netronome.com>
Date:   Thu, 18 Jun 2020 12:51:08 +0200
From:   Simon Horman <simon.horman@...ronome.com>
To:     Hangbin Liu <liuhangbin@...il.com>
Cc:     netdev@...r.kernel.org, Davide Caratti <dcaratti@...hat.com>,
        lucien.xin@...il.com,
        Stephen Hemminger <stephen@...workplumber.org>
Subject: Re: [PATCH iproute2] tc: m_tunnel_key: fix geneve opt output

On Thu, Jun 18, 2020 at 06:44:20PM +0800, Hangbin Liu wrote:
> Commit f72c3ad00f3b changed the geneve option output from "geneve_opt"
> to "geneve_opts", which may break the program compatibility. Reset
> it back to geneve_opt.
> 
> Fixes: f72c3ad00f3b ("tc: m_tunnel_key: add options support for vxlan")
> Signed-off-by: Hangbin Liu <liuhangbin@...il.com>

Thanks Hangbin.

I agree that the patch in question did change the name of the option
as you describe, perhaps inadvertently. But I wonder if perhaps this fix
is too simple as the patch mentioned also:

1. Documents the option as geneve_opts
2. Adds vxlan_opts

So this patch invalidates the documentation and creates asymmetry between
the VXLAN and Geneve variants of this feature.

Another problem is that any user of geneve_opts will break.

Perhaps a way out of this mess is to:
1. make geneve_opt an alias for geneve_opts (i.e. two names for the same
   thing)
2. Document geneve_opt, possibly marking it as deprecated.

> ---
>  tc/m_tunnel_key.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tc/m_tunnel_key.c b/tc/m_tunnel_key.c
> index bfec9072..0074f744 100644
> --- a/tc/m_tunnel_key.c
> +++ b/tc/m_tunnel_key.c
> @@ -534,7 +534,7 @@ static void tunnel_key_print_geneve_options(struct rtattr *attr)
>  	struct rtattr *i = RTA_DATA(attr);
>  	int ii, data_len = 0, offset = 0;
>  	int rem = RTA_PAYLOAD(attr);
> -	char *name = "geneve_opts";
> +	char *name = "geneve_opt";
>  	char strbuf[rem * 2 + 1];
>  	char data[rem * 2 + 1];
>  	uint8_t data_r[rem];
> -- 
> 2.25.4
>