netdev - Re: [PATCH ipsec] xfrm: lwtunnel: squelch kernel warning in case XFRM encap type is not available

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Date:   Tue, 11 Oct 2022 12:07:48 +0300
From:   Nikolay Aleksandrov <razor@...ckwall.org>
To:     Eyal Birger <eyal.birger@...il.com>, idosch@...sch.org,
        davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, steffen.klassert@...unet.com,
        herbert@...dor.apana.org.au, dsahern@...nel.org,
        contact@...elbtn.com, pablo@...filter.org,
        nicolas.dichtel@...nd.com, daniel@...earbox.net
Cc:     netdev@...r.kernel.org
Subject: Re: [PATCH ipsec] xfrm: lwtunnel: squelch kernel warning in case XFRM
 encap type is not available

On 11/10/2022 11:01, Eyal Birger wrote:
> Ido reported that a kernel warning [1] can be triggered from
> user space when the kernel is compiled with CONFIG_MODULES=y and
> CONFIG_XFRM=n when adding an xfrm encap type route, e.g:
> 
> $ ip route add 198.51.100.0/24 dev dummy1 encap xfrm if_id 1
> Error: lwt encapsulation type not supported.
> 
> The reason for the warning is that the LWT infrastructure has an
> autoloading feature which is meant only for encap types that don't
> use a net device,  which is not the case in xfrm encap.
> 
> Mute this warning for xfrm encap as there's no encap module to autoload
> in this case.
> 
> [1]
>  WARNING: CPU: 3 PID: 2746262 at net/core/lwtunnel.c:57 lwtunnel_valid_encap_type+0x4f/0x120
> [...]
>  Call Trace:
>   <TASK>
>   rtm_to_fib_config+0x211/0x350
>   inet_rtm_newroute+0x3a/0xa0
>   rtnetlink_rcv_msg+0x154/0x3c0
>   netlink_rcv_skb+0x49/0xf0
>   netlink_unicast+0x22f/0x350
>   netlink_sendmsg+0x208/0x440
>   ____sys_sendmsg+0x21f/0x250
>   ___sys_sendmsg+0x83/0xd0
>   __sys_sendmsg+0x54/0xa0
>   do_syscall_64+0x35/0x80
>   entry_SYSCALL_64_after_hwframe+0x63/0xcd
> 
> Reported-by: Ido Schimmel <idosch@...sch.org>
> Fixes: 2c2493b9da91 ("xfrm: lwtunnel: add lwtunnel support for xfrm interfaces in collect_md mode")
> Signed-off-by: Eyal Birger <eyal.birger@...il.com>
> ---
>  net/core/lwtunnel.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/net/core/lwtunnel.c b/net/core/lwtunnel.c
> index 6fac2f0ef074..711cd3b4347a 100644
> --- a/net/core/lwtunnel.c
> +++ b/net/core/lwtunnel.c
> @@ -48,9 +48,11 @@ static const char *lwtunnel_encap_str(enum lwtunnel_encap_types encap_type)
>  		return "RPL";
>  	case LWTUNNEL_ENCAP_IOAM6:
>  		return "IOAM6";
> +	case LWTUNNEL_ENCAP_XFRM:
> +		/* module autoload not supported for encap type */
> +		return NULL;
>  	case LWTUNNEL_ENCAP_IP6:
>  	case LWTUNNEL_ENCAP_IP:
> -	case LWTUNNEL_ENCAP_XFRM:
>  	case LWTUNNEL_ENCAP_NONE:
>  	case __LWTUNNEL_ENCAP_MAX:
>  		/* should not have got here */

Reviewed-by: Nikolay Aleksandrov <razor@...ckwall.org>