netdev - Re: [PATCH iproute2] dcb: unblock mnl_socket

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Date:   Thu, 20 Oct 2022 07:23:05 -0600
From:   David Ahern <dsahern@...nel.org>
To:     Hao Lan <lanhao@...wei.com>, lipeng321@...wei.com,
        shenjian15@...wei.com, huangguangbin2@...wei.com,
        chenjunxin1@...wei.com, netdev@...r.kernel.org,
        stephen@...workplumber.org, Petr Machata <me@...chata.org>
Cc:     davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com
Subject: Re: [PATCH iproute2] dcb: unblock mnl_socket_recvfrom if not message
 received

[ cc Petr ]

always add authors of patches you are fixing.

On 10/18/22 7:20 PM, Hao Lan wrote:
> From: Junxin Chen <chenjunxin1@...wei.com>
> 
> Currently, the dcb command sinks to the kernel through the netlink
> to obtain information. However, if the kernel fails to obtain infor-
> mation or is not processed, the dcb command is suspended.
> 
> For example, if we don't implement dcbnl_ops->ieee_getpfc in the
> kernel, the command "dcb pfc show dev eth1" will be stuck and subsequent
> commands cannot be executed.
> 
> This patch adds the NLM_F_ACK flag to the netlink in mnlu_msg_prepare
> to ensure that the kernel responds to user requests.
> 
> After the problem is solved, the execution result is as follows:
> $ dcb pfc show dev eth1
> Attribute not found: Success
> 
> Fixes: 67033d1c1c ("Add skeleton of a new tool, dcb")
> Signed-off-by: Junxin Chen <chenjunxin1@...wei.com>
> ---
>  dcb/dcb.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/dcb/dcb.c b/dcb/dcb.c
> index 8d75ab0a..a6f457fb 100644
> --- a/dcb/dcb.c
> +++ b/dcb/dcb.c
> @@ -156,7 +156,7 @@ static struct nlmsghdr *dcb_prepare(struct dcb *dcb, const char *dev,
>  	};
>  	struct nlmsghdr *nlh;
>  
> -	nlh = mnlu_msg_prepare(dcb->buf, nlmsg_type, NLM_F_REQUEST, &dcbm, sizeof(dcbm));
> +	nlh = mnlu_msg_prepare(dcb->buf, nlmsg_type, NLM_F_REQUEST | NLM_F_ACK, &dcbm, sizeof(dcbm));
>  	mnl_attr_put_strz(nlh, DCB_ATTR_IFNAME, dev);
>  	return nlh;
>  }