netdev - Re: [patch iproute2 v3 1/4] lib/libnetlink: Add a function rtnl_talk

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Date:   Wed, 27 Dec 2017 08:33:22 -0600
From:   David Ahern <dsahern@...il.com>
To:     Chris Mi <chrism@...lanox.com>, netdev@...r.kernel.org
Cc:     gerlitz.or@...il.com, stephen@...workplumber.org
Subject: Re: [patch iproute2 v3 1/4] lib/libnetlink: Add a function
 rtnl_talk_msg

On 12/25/17 2:46 AM, Chris Mi wrote:
> diff --git a/lib/libnetlink.c b/lib/libnetlink.c
> index 00e6ce0c..f5f675cf 100644
> --- a/lib/libnetlink.c
> +++ b/lib/libnetlink.c
> @@ -581,36 +581,21 @@ static void rtnl_talk_error(struct nlmsghdr *h, struct nlmsgerr *err,
>  		strerror(-err->error));
>  }
>  
> -static int __rtnl_talk(struct rtnl_handle *rtnl, struct nlmsghdr *n,
> -		       struct nlmsghdr **answer,
> -		       bool show_rtnl_err, nl_ext_ack_fn_t errfn)
> +static int __rtnl_check_ack(struct rtnl_handle *rtnl, struct nlmsghdr **answer,

Make this function __rtnl_talk_msg. Include the assignment of nlmsg_seq
and ack setting using the for loop below and sendmsg() call. All of that
code can be common for both the single and multiple iov case.


> +		       bool show_rtnl_err, nl_ext_ack_fn_t errfn,
> +		       unsigned int seq)
>  {
>  	int status;
> -	unsigned int seq;
> -	struct nlmsghdr *h;
> +	char *buf;

Please order variables in the reverse xmas tree style used in the net code.

>  	struct sockaddr_nl nladdr = { .nl_family = AF_NETLINK };
> -	struct iovec iov = {
> -		.iov_base = n,
> -		.iov_len = n->nlmsg_len
> -	};
> +	struct nlmsghdr *h;
> +	struct iovec iov;
>  	struct msghdr msg = {
>  		.msg_name = &nladdr,
>  		.msg_namelen = sizeof(nladdr),
>  		.msg_iov = &iov,
>  		.msg_iovlen = 1,
>  	};
> -	char *buf;
> -
> -	n->nlmsg_seq = seq = ++rtnl->seq;
> -
> -	if (answer == NULL)
> -		n->nlmsg_flags |= NLM_F_ACK;
> -
> -	status = sendmsg(rtnl->fd, &msg, 0);
> -	if (status < 0) {
> -		perror("Cannot talk to rtnetlink");
> -		return -1;
> -	}
>  
>  	while (1) {
>  		status = rtnl_recvmsg(rtnl->fd, &msg, &buf);