netdev - Re: [PATCH iproute2-next v2 1/6] ipaddress: Improve print

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Date:   Wed, 31 Jan 2018 20:29:05 -0700
From:   David Ahern <dsahern@...il.com>
To:     Serhey Popovych <serhe.popovych@...il.com>, netdev@...r.kernel.org
Subject: Re: [PATCH iproute2-next v2 1/6] ipaddress: Improve print_linkinfo()

On 1/30/18 11:09 AM, Serhey Popovych wrote:

> diff --git a/ip/ipaddress.c b/ip/ipaddress.c
> index 051a05f..f8fd392 100644
> --- a/ip/ipaddress.c
> +++ b/ip/ipaddress.c
> @@ -948,14 +948,14 @@ int print_linkinfo_brief(const struct sockaddr_nl *who,
>  	parse_rtattr(tb, IFLA_MAX, IFLA_RTA(ifi), len);
>  	if (tb[IFLA_IFNAME] == NULL) {
>  		fprintf(stderr, "BUG: device with ifindex %d has nil ifname\n", ifi->ifi_index);
> -		name = "<nil>";
> +		name = ll_index_to_name(ifi->ifi_index);

This is one of those "should never happen checks" since the kernel
always adds IFLA_IFNAME. Going to a cache to get a name for the index
when the existing message is missing that attribute seems wrong. I
realize the expectation is that the cache is empty today so if%d is
returned, but that could change and it is the idea of consulting a cache
that I think is wrong.

If that intention is to have a name I think it is safer to just have it
set to if%d here (or in a helper that the cache also uses).

>  	} else {
>  		name = rta_getattr_str(tb[IFLA_IFNAME]);
>  	}
>  
>  	if (pfilter->label &&
>  	    (!pfilter->family || pfilter->family == AF_PACKET) &&
> -	    fnmatch(pfilter->label, RTA_DATA(tb[IFLA_IFNAME]), 0))
> +	    fnmatch(pfilter->label, name, 0))
>  		return -1;
>  
>  	if (tb[IFLA_GROUP]) {
> @@ -1057,6 +1057,7 @@ int print_linkinfo(const struct sockaddr_nl *who,
>  	struct ifinfomsg *ifi = NLMSG_DATA(n);
>  	struct rtattr *tb[IFLA_MAX+1];
>  	int len = n->nlmsg_len;
> +	const char *name;
>  	unsigned int m_flag = 0;
>  
>  	if (n->nlmsg_type != RTM_NEWLINK && n->nlmsg_type != RTM_DELLINK)
> @@ -1067,18 +1068,22 @@ int print_linkinfo(const struct sockaddr_nl *who,
>  		return -1;
>  
>  	if (filter.ifindex && ifi->ifi_index != filter.ifindex)
> -		return 0;
> +		return -1;
>  	if (filter.up && !(ifi->ifi_flags&IFF_UP))
> -		return 0;
> +		return -1;
>  
>  	parse_rtattr(tb, IFLA_MAX, IFLA_RTA(ifi), len);
> -	if (tb[IFLA_IFNAME] == NULL)
> +	if (tb[IFLA_IFNAME] == NULL) {
>  		fprintf(stderr, "BUG: device with ifindex %d has nil ifname\n", ifi->ifi_index);
> +		name = ll_index_to_name(ifi->ifi_index);

same here


> +	} else {
> +		name = rta_getattr_str(tb[IFLA_IFNAME]);
> +	}
>  
>  	if (filter.label &&
>  	    (!filter.family || filter.family == AF_PACKET) &&
> -	    fnmatch(filter.label, RTA_DATA(tb[IFLA_IFNAME]), 0))
> -		return 0;
> +	    fnmatch(filter.label, name, 0))
> +		return -1;
>  
>  	if (tb[IFLA_GROUP]) {
>  		int group = rta_getattr_u32(tb[IFLA_GROUP]);
> @@ -1105,16 +1110,7 @@ int print_linkinfo(const struct sockaddr_nl *who,
>  		print_bool(PRINT_ANY, "deleted", "Deleted ", true);
>  
>  	print_int(PRINT_ANY, "ifindex", "%d: ", ifi->ifi_index);
> -	if (tb[IFLA_IFNAME]) {
> -		print_color_string(PRINT_ANY,
> -				   COLOR_IFNAME,
> -				   "ifname", "%s",
> -				   rta_getattr_str(tb[IFLA_IFNAME]));
> -	} else {
> -		print_null(PRINT_JSON, "ifname", NULL, NULL);
> -		print_color_null(PRINT_FP, COLOR_IFNAME,
> -				 "ifname", "%s", "<nil>");
> -	}
> +	print_color_string(PRINT_ANY, COLOR_IFNAME, "ifname", "%s", name);
>  
>  	if (tb[IFLA_LINK]) {
>  		int iflink = rta_getattr_u32(tb[IFLA_LINK]);
>