netdev - Re: [PATCH iproute2-next] rtnetlink: add new function rtnl_echo

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Date:   Tue, 27 Sep 2022 21:12:35 -0600
From:   David Ahern <dsahern@...nel.org>
To:     Hangbin Liu <liuhangbin@...il.com>, netdev@...r.kernel.org
Cc:     Stephen Hemminger <stephen@...workplumber.org>,
        Guillaume Nault <gnault@...hat.com>
Subject: Re: [PATCH iproute2-next] rtnetlink: add new function
 rtnl_echo_talk()

On 9/22/22 9:20 PM, Hangbin Liu wrote:
> Add a new function rtnl_echo_talk() that could be used when the
> sub-component supports NLM_F_ECHO flag. With this function we can
> remove the redundant code added by commit b264b4c6568c7 ("ip: add
> NLM_F_ECHO support").
> 
> Signed-off-by: Hangbin Liu <liuhangbin@...il.com>
> ---
>  include/libnetlink.h |  4 ++++
>  include/utils.h      |  1 -
>  ip/ipaddress.c       | 24 +-----------------------
>  ip/iplink.c          | 20 +-------------------
>  ip/ipnexthop.c       | 23 +----------------------
>  ip/iproute.c         | 24 +-----------------------
>  ip/iprule.c          | 24 +-----------------------
>  lib/libnetlink.c     | 31 +++++++++++++++++++++++++++++++
>  8 files changed, 40 insertions(+), 111 deletions(-)
> 
> diff --git a/include/libnetlink.h b/include/libnetlink.h
> index a7b0f352..e9125f04 100644
> --- a/include/libnetlink.h
> +++ b/include/libnetlink.h
> @@ -44,6 +44,7 @@ struct ipstats_req {
>  };
>  
>  extern int rcvbuf;
> +extern int echo_request;
>  
>  int rtnl_open(struct rtnl_handle *rth, unsigned int subscriptions)
>  	__attribute__((warn_unused_result));
> @@ -171,6 +172,9 @@ int rtnl_dump_filter_errhndlr_nc(struct rtnl_handle *rth,
>  #define rtnl_dump_filter_errhndlr(rth, filter, farg, errhndlr, earg) \
>  	rtnl_dump_filter_errhndlr_nc(rth, filter, farg, errhndlr, earg, 0)
>  
> +int rtnl_echo_talk(struct rtnl_handle *rtnl, struct nlmsghdr *n,
> +		   int (*print_info)(struct nlmsghdr *n, void *arg))
> +	__attribute__((warn_unused_result));
>  int rtnl_talk(struct rtnl_handle *rtnl, struct nlmsghdr *n,
>  	      struct nlmsghdr **answer)
>  	__attribute__((warn_unused_result));
> diff --git a/include/utils.h b/include/utils.h
> index 2eb80b3e..eeb23a64 100644
> --- a/include/utils.h
> +++ b/include/utils.h
> @@ -36,7 +36,6 @@ extern int max_flush_loops;
>  extern int batch_mode;
>  extern int numeric;
>  extern bool do_all;
> -extern int echo_request;
>  
>  #ifndef CONFDIR
>  #define CONFDIR		"/etc/iproute2"
> diff --git a/ip/ipaddress.c b/ip/ipaddress.c
> index 986cfbc3..89acfeaa 100644
> --- a/ip/ipaddress.c
> +++ b/ip/ipaddress.c
> @@ -2422,11 +2422,6 @@ static int ipaddr_modify(int cmd, int flags, int argc, char **argv)
>  	__u32 preferred_lft = INFINITY_LIFE_TIME;
>  	__u32 valid_lft = INFINITY_LIFE_TIME;
>  	unsigned int ifa_flags = 0;
> -	struct nlmsghdr *answer;
> -	int ret;
> -
> -	if (echo_request)
> -		req.n.nlmsg_flags |= NLM_F_ECHO | NLM_F_ACK;
>  
>  	while (argc > 0) {
>  		if (strcmp(*argv, "peer") == 0 ||
> @@ -2608,24 +2603,7 @@ static int ipaddr_modify(int cmd, int flags, int argc, char **argv)
>  		return -1;
>  	}
>  
> -	if (echo_request)
> -		ret = rtnl_talk(&rth, &req.n, &answer);
> -	else
> -		ret = rtnl_talk(&rth, &req.n, NULL);
> -
> -	if (ret < 0)
> -		return -2;
> -
> -	if (echo_request) {
> -		new_json_obj(json);
> -		open_json_object(NULL);
> -		print_addrinfo(answer, stdout);
> -		close_json_object();
> -		delete_json_obj();
> -		free(answer);
> -	}
> -
> -	return 0;
> +	return rtnl_echo_talk(&rth, &req.n, print_addrinfo);

I was thinking something more like:

if (echo_request)
	return rtnl_echo_talk(&rth, &req.n, print_addrinfo);

return rtnl_talk(&rth, &req.n, NULL);


> diff --git a/lib/libnetlink.c b/lib/libnetlink.c
> index c27627fe..00feb69b 100644
> --- a/lib/libnetlink.c
> +++ b/lib/libnetlink.c
> @@ -42,7 +42,9 @@
>  #define MIN(a, b) ((a) < (b) ? (a) : (b))
>  #endif
>  
> +int json;
>  int rcvbuf = 1024 * 1024;
> +int echo_request = 0;

which means you don't need this; the json arg will need to be passed to
rtnl_echo_talk since it is owned by the commands.


>  
>  #ifdef HAVE_LIBMNL
>  #include <libmnl/libmnl.h>
> @@ -1139,6 +1141,35 @@ static int __rtnl_talk(struct rtnl_handle *rtnl, struct nlmsghdr *n,
>  	return __rtnl_talk_iov(rtnl, &iov, 1, answer, show_rtnl_err, errfn);
>  }
>  
> +int rtnl_echo_talk(struct rtnl_handle *rtnl, struct nlmsghdr *n,
> +		   int (*print_info)(struct nlmsghdr *n, void *arg))
> +{
> +	struct nlmsghdr *answer;
> +	int ret;
> +
> +	if (echo_request)
> +		n->nlmsg_flags |= NLM_F_ECHO | NLM_F_ACK;
> +
> +	if (echo_request)
> +		ret = rtnl_talk(rtnl, n, &answer);
> +	else
> +		ret = rtnl_talk(rtnl, n, NULL);
> +
> +	if (ret < 0)
> +		return -2;
> +
> +	if (echo_request) {
> +		new_json_obj(json);
> +		open_json_object(NULL);
> +		print_info(answer, stdout);
> +		close_json_object();
> +		delete_json_obj();
> +		free(answer);
> +	}
> +
> +	return 0;
> +}
> +
>  int rtnl_talk(struct rtnl_handle *rtnl, struct nlmsghdr *n,
>  	      struct nlmsghdr **answer)
>  {