netdev - Re: [PATCH net v2] net/smc: fix fallback failed while sendmsg with fastopen

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Date:   Wed, 8 Mar 2023 16:24:15 +0800
From:   Tony Lu <tonylu@...ux.alibaba.com>
To:     "D. Wythe" <alibuda@...ux.alibaba.com>
Cc:     kgraul@...ux.ibm.com, wenjia@...ux.ibm.com, jaka@...ux.ibm.com,
        simon.horman@...igine.com, kuba@...nel.org, davem@...emloft.net,
        netdev@...r.kernel.org, linux-s390@...r.kernel.org,
        linux-rdma@...r.kernel.org
Subject: Re: [PATCH net v2] net/smc: fix fallback failed while sendmsg with
 fastopen

On Tue, Mar 07, 2023 at 11:23:46AM +0800, D. Wythe wrote:
> From: "D. Wythe" <alibuda@...ux.alibaba.com>
> 
> Before determining whether the msg has unsupported options, it has been
> prematurely terminated by the wrong status check.
> 
> For the application, the general usages of MSG_FASTOPEN likes
> 
> fd = socket(...)
> /* rather than connect */
> sendto(fd, data, len, MSG_FASTOPEN)
> 
> Hence, We need to check the flag before state check, because the sock
> state here is always SMC_INIT when applications tries MSG_FASTOPEN.
> Once we found unsupported options, fallback it to TCP.
> 
> Fixes: ee9dfbef02d1 ("net/smc: handle sockopts forcing fallback")
> Signed-off-by: D. Wythe <alibuda@...ux.alibaba.com>
> Signed-off-by: Simon Horman <simon.horman@...igine.com>

Reviewed-by: Tony Lu <tonylu@...ux.alibaba.com>

Thanks.

> v2 -> v1: Optimize code style
> 
> ---
>  net/smc/af_smc.c | 13 ++++++++-----
>  1 file changed, 8 insertions(+), 5 deletions(-)
> 
> diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
> index b233c94..1c580ac 100644
> --- a/net/smc/af_smc.c
> +++ b/net/smc/af_smc.c
> @@ -2659,16 +2659,14 @@ static int smc_sendmsg(struct socket *sock, struct msghdr *msg, size_t len)
>  {
>  	struct sock *sk = sock->sk;
>  	struct smc_sock *smc;
> -	int rc = -EPIPE;
> +	int rc;
>  
>  	smc = smc_sk(sk);
>  	lock_sock(sk);
> -	if ((sk->sk_state != SMC_ACTIVE) &&
> -	    (sk->sk_state != SMC_APPCLOSEWAIT1) &&
> -	    (sk->sk_state != SMC_INIT))
> -		goto out;
>  
> +	/* SMC does not support connect with fastopen */
>  	if (msg->msg_flags & MSG_FASTOPEN) {
> +		/* not connected yet, fallback */
>  		if (sk->sk_state == SMC_INIT && !smc->connect_nonblock) {
>  			rc = smc_switch_to_fallback(smc, SMC_CLC_DECL_OPTUNSUPP);
>  			if (rc)
> @@ -2677,6 +2675,11 @@ static int smc_sendmsg(struct socket *sock, struct msghdr *msg, size_t len)
>  			rc = -EINVAL;
>  			goto out;
>  		}
> +	} else if ((sk->sk_state != SMC_ACTIVE) &&
> +		   (sk->sk_state != SMC_APPCLOSEWAIT1) &&
> +		   (sk->sk_state != SMC_INIT)) {
> +		rc = -EPIPE;
> +		goto out;
>  	}
>  
>  	if (smc->use_fallback) {
> -- 
> 1.8.3.1