netdev - Re: [patch iproute2 v7 1/2] lib/libnetlink: Add functions rtnl_talk_msg and rtnl_talk

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Date:   Tue, 9 Jan 2018 20:24:27 +0100
From:   Phil Sutter <phil@....cc>
To:     Chris Mi <chrism@...lanox.com>
Cc:     netdev@...r.kernel.org, gerlitz.or@...il.com,
        stephen@...workplumber.org, dsahern@...il.com,
        marcelo.leitner@...il.com
Subject: Re: [patch iproute2 v7 1/2] lib/libnetlink: Add functions
 rtnl_talk_msg and rtnl_talk_iov

Hi,

On Tue, Jan 09, 2018 at 03:59:07PM +0900, Chris Mi wrote:
[...]
> diff --git a/lib/libnetlink.c b/lib/libnetlink.c
> index 00e6ce0c..ae0059f9 100644
> --- a/lib/libnetlink.c
> +++ b/lib/libnetlink.c
> @@ -581,39 +581,43 @@ 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_talk_msg(struct rtnl_handle *rtnl, struct msghdr *m,
> +			   struct nlmsghdr **answer,
> +			   bool show_rtnl_err, nl_ext_ack_fn_t errfn)
>  {
> -	int status;
> -	unsigned int seq;
> -	struct nlmsghdr *h;
>  	struct sockaddr_nl nladdr = { .nl_family = AF_NETLINK };
> -	struct iovec iov = {
> -		.iov_base = n,
> -		.iov_len = n->nlmsg_len
> -	};
> +	int i, status, iovlen = m->msg_iovlen;
> +	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;
> +	unsigned int seq = 0;
> +	struct nlmsghdr *h;
>  
> -	if (answer == NULL)
> -		n->nlmsg_flags |= NLM_F_ACK;
> +	for (i = 0; i < iovlen; i++) {
> +		struct iovec *v;
> +		v = &m->msg_iov[i];
> +		h = v->iov_base;
> +		h->nlmsg_seq = seq = ++rtnl->seq;
> +		if (answer == NULL)
> +			h->nlmsg_flags |= NLM_F_ACK;
> +	}
>  
> -	status = sendmsg(rtnl->fd, &msg, 0);
> +	status = sendmsg(rtnl->fd, m, 0);
>  	if (status < 0) {
>  		perror("Cannot talk to rtnetlink");
>  		return -1;
>  	}
>  
> +	i = 0;
>  	while (1) {

for (i = 1; ; i++) ?

> +		char *buf;

Why did you move this declaration?

> +next:

Drop this and use 'continue' instead of 'goto next' below?

>  		status = rtnl_recvmsg(rtnl->fd, &msg, &buf);
> +		++i;
>  
>  		if (status < 0)
>  			return status;
> @@ -642,7 +646,7 @@ static int __rtnl_talk(struct rtnl_handle *rtnl, struct nlmsghdr *n,
>  
>  			if (nladdr.nl_pid != 0 ||
>  			    h->nlmsg_pid != rtnl->local.nl_pid ||
> -			    h->nlmsg_seq != seq) {
> +			    h->nlmsg_seq > seq || h->nlmsg_seq < seq - iovlen) {
>  				/* Don't forget to skip that message. */
>  				status -= NLMSG_ALIGN(len);
>  				h = (struct nlmsghdr *)((char *)h + NLMSG_ALIGN(len));
> @@ -662,7 +666,10 @@ static int __rtnl_talk(struct rtnl_handle *rtnl, struct nlmsghdr *n,
>  						*answer = (struct nlmsghdr *)buf;
>  					else
>  						free(buf);
> -					return 0;
> +					if (h->nlmsg_seq == seq)
> +						return 0;
> +					else
> +						goto next;
>  				}
>  
>  				if (rtnl->proto != NETLINK_SOCK_DIAG &&

Cheers, Phil