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

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Date:   Tue, 2 Jan 2018 21:59:38 +0800
From:   Chris Mi <chrism@...lanox.com>
To:     David Ahern <dsahern@...il.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.
Thanks for your suggestion. Done.
>
>> +		       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.
Actually, I divide the variables in two parts, none-struct variables and 
struct variables.
Not sure if that meets the reverse xmac tree style, but I think it is 
more readable.
>
>>   	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);