Re: [dpdk-dev] [PATCH 2/4] net/mlx5: fix Netlink communication routine

[Shahaf Shuler <shahafs@mellanox.com>]

Monday, November 12, 2018 10:02 PM, Slava Ovsiienko:
> Subject: [PATCH 2/4] net/mlx5: fix Netlink communication routine
> 
> While receiving the Netlink reply messages we should stop at DONE or ACK
> message. The existing implementation stops at DONE message or if no
> multiple message flag set ( NLM_F_MULTI). It prevents the single query
> requests from working, these requests send the single reply message
> without multi-message flag followed by ACK message. This patch fixes
> receiving part of Netlink communication routine.
> 
> Fixes: 6e74990b3463 ("net/mlx5: update E-Switch VXLAN netlink routines")
> 
> Signed-off-by: Viacheslav Ovsiienko <viacheslavo@mellanox.com>
> ---
>  drivers/net/mlx5/mlx5_flow_tcf.c | 58 +++++++++++++++++++++++++-----
> ----------
>  1 file changed, 37 insertions(+), 21 deletions(-)
> 
> diff --git a/drivers/net/mlx5/mlx5_flow_tcf.c
> b/drivers/net/mlx5/mlx5_flow_tcf.c
> index 5a38940..4d154b6 100644
> --- a/drivers/net/mlx5/mlx5_flow_tcf.c
> +++ b/drivers/net/mlx5/mlx5_flow_tcf.c
> @@ -3732,44 +3732,60 @@ struct pedit_parser {  {
>  	unsigned int portid = mnl_socket_get_portid(tcf->nl);
>  	uint32_t seq = tcf->seq++;
> -	int err, ret;
> +	int ret, err = 0;
> 
>  	assert(tcf->nl);
>  	assert(tcf->buf);
> -	if (!seq)
> +	if (!seq) {
>  		/* seq 0 is reserved for kernel event-driven notifications. */
>  		seq = tcf->seq++;
> +	}
>  	nlh->nlmsg_seq = seq;
>  	nlh->nlmsg_flags |= NLM_F_ACK;
>  	ret = mnl_socket_sendto(tcf->nl, nlh, nlh->nlmsg_len);
> -	err = (ret <= 0) ? errno : 0;
> +	if (ret <= 0) {
> +		/* Message send error occurres. */
> +		rte_errno = errno;
> +		return -rte_errno;
> +	}
>  	nlh = (struct nlmsghdr *)(tcf->buf);
>  	/*
>  	 * The following loop postpones non-fatal errors until multipart
>  	 * messages are complete.
>  	 */
> -	if (ret > 0)
> -		while (true) {
> -			ret = mnl_socket_recvfrom(tcf->nl, tcf->buf,
> -						  tcf->buf_size);
> +	while (true) {

This while(true) is a bit disturbing (I know it exists also before).

Can't we bound it to some limit, e.g. is there any multiply of tcf->buf_size that if we receive more than that it is for sure an error? 

> +		ret = mnl_socket_recvfrom(tcf->nl, tcf->buf, tcf->buf_size);
> +		if (ret < 0) {
> +			err = errno;
> +			/*
> +			 * In case of overflow Will receive till
> +			 * end of multipart message. We may lost part
> +			 * of reply messages but mark and return an error.
> +			 */
> +			if (err != ENOSPC ||
> +			    !(nlh->nlmsg_flags & NLM_F_MULTI) ||
> +			    nlh->nlmsg_type == NLMSG_DONE)
> +				break;
> +		} else {
> +			ret = mnl_cb_run(nlh, ret, seq, portid, cb, arg);
> +			if (!ret) {
> +				/*
> +				 * libmnl returns 0 if DONE or
> +				 * success ACK message found.
> +				 */
> +				break;
> +			}
>  			if (ret < 0) {
> +				/*
> +				 * ACK message with error found
> +				 * or some error occurred.
> +				 */
>  				err = errno;
> -				if (err != ENOSPC)
> -					break;
> -			}
> -			if (!err) {
> -				ret = mnl_cb_run(nlh, ret, seq, portid,
> -						 cb, arg);
> -				if (ret < 0) {
> -					err = errno;
> -					break;
> -				}
> -			}
> -			/* Will receive till end of multipart message */
> -			if (!(nlh->nlmsg_flags & NLM_F_MULTI) ||
> -			      nlh->nlmsg_type == NLMSG_DONE)
>  				break;
> +			}
> +			/* We should continue receiving. */
>  		}
> +	}
>  	if (!err)
>  		return 0;
>  	rte_errno = err;
> --
> 1.8.3.1