netdev - Re: [patch iproute2 net-next v11 2/4] tc: introduce tc_qdisc_block

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Date:   Sat, 20 Jan 2018 10:33:42 +0100
From:   Jiri Pirko <jiri@...nulli.us>
To:     David Ahern <dsahern@...il.com>
Cc:     netdev@...r.kernel.org, davem@...emloft.net, jhs@...atatu.com,
        xiyou.wangcong@...il.com, mlxsw@...lanox.com, andrew@...n.ch,
        vivien.didelot@...oirfairelinux.com, f.fainelli@...il.com,
        michael.chan@...adcom.com, ganeshgr@...lsio.com,
        saeedm@...lanox.com, matanb@...lanox.com, leonro@...lanox.com,
        idosch@...lanox.com, jakub.kicinski@...ronome.com,
        simon.horman@...ronome.com, pieter.jansenvanvuuren@...ronome.com,
        john.hurley@...ronome.com, alexander.h.duyck@...el.com,
        ogerlitz@...lanox.com, john.fastabend@...il.com,
        daniel@...earbox.net
Subject: Re: [patch iproute2 net-next v11 2/4] tc: introduce
 tc_qdisc_block_exists helper

Fri, Jan 19, 2018 at 09:45:57PM CET, dsahern@...il.com wrote:
>On 1/17/18 2:48 AM, Jiri Pirko wrote:
>> From: Jiri Pirko <jiri@...lanox.com>
>> 
>> This hepler used qdisc dump to list all qdisc and find if block index in
>> question is used by any of them. That means the block with specified
>> index exists.
>> 
>> Signed-off-by: Jiri Pirko <jiri@...lanox.com>
>> ---
>>  tc/tc_qdisc.c | 61 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>>  tc/tc_util.h  |  2 ++
>>  2 files changed, 63 insertions(+)
>> 
>> diff --git a/tc/tc_qdisc.c b/tc/tc_qdisc.c
>> index 70279b9..3f91558 100644
>> --- a/tc/tc_qdisc.c
>> +++ b/tc/tc_qdisc.c
>> @@ -412,3 +412,64 @@ int do_qdisc(int argc, char **argv)
>>  	fprintf(stderr, "Command \"%s\" is unknown, try \"tc qdisc help\".\n", *argv);
>>  	return -1;
>>  }
>> +
>> +struct tc_qdisc_block_exists_ctx {
>> +	__u32 block_index;
>> +	bool found;
>> +};
>> +
>> +static int tc_qdisc_block_exists_cb(const struct sockaddr_nl *who,
>> +				    struct nlmsghdr *n, void *arg)
>> +{
>> +	struct tc_qdisc_block_exists_ctx *ctx = arg;
>> +	struct tcmsg *t = NLMSG_DATA(n);
>> +	int len = n->nlmsg_len;
>> +	struct rtattr *tb[TCA_MAX+1];
>
>reverse xmas tree

:) Will fix


>
>> +
>> +	if (n->nlmsg_type != RTM_NEWQDISC)
>> +		return 0;
>> +
>> +	len -= NLMSG_LENGTH(sizeof(*t));
>> +	if (len < 0)
>> +		return -1;
>> +
>> +	parse_rtattr(tb, TCA_MAX, TCA_RTA(t), len);
>> +
>> +	if (tb[TCA_KIND] == NULL)
>> +		return -1;
>> +
>> +	if (tb[TCA_INGRESS_BLOCK] &&
>> +	    RTA_PAYLOAD(tb[TCA_INGRESS_BLOCK]) >= sizeof(__u32)) {
>
>why not just == sizeof(__u32) since that's what it should be?

test1:~/iproute2$ git grep "== sizeof(__u32)" | grep RTA_PAYLOAD| wc -l
1
test1:~/iproute2$ git grep ">= sizeof(__u32)" | grep RTA_PAYLOAD| wc -l
42

I just go with the flow :)


>
>> +		__u32 block = rta_getattr_u32(tb[TCA_INGRESS_BLOCK]);
>> +
>> +		if (block && block == ctx->block_index)
>
>block > 0 test should not be needed. If someone is calling
>tc_qdisc_block_exists, then block_index should be > 0 in which case you
>just need block == ctx->block_index

Right. Will Fix.


>
>
>> +			ctx->found = true;
>> +	}
>> +
>> +	if (tb[TCA_EGRESS_BLOCK] &&
>> +	    RTA_PAYLOAD(tb[TCA_EGRESS_BLOCK]) >= sizeof(__u32)) {
>> +		__u32 block = rta_getattr_u32(tb[TCA_EGRESS_BLOCK]);
>> +
>> +		if (block && block == ctx->block_index)
>
>same 2 comments for this block

ack


>
>> +			ctx->found = true;
>> +	}
>> +	return 0;
>> +}
>> +
>> +int tc_qdisc_block_exists(__u32 block_index)
>
>This should be bool since you are returning true / false

Ah, missed that. Fixing.


>
>> +{
>> +	struct tc_qdisc_block_exists_ctx ctx = { .block_index = block_index };
>> +	struct tcmsg t = { .tcm_family = AF_UNSPEC };
>> +
>> +	if (rtnl_dump_request(&rth, RTM_GETQDISC, &t, sizeof(t)) < 0) {
>> +		perror("Cannot send dump request");
>> +		return false;
>> +	}
>> +
>> +	if (rtnl_dump_filter(&rth, tc_qdisc_block_exists_cb, &ctx) < 0) {
>> +		perror("Dump terminated\n");
>> +		return false;
>> +	}
>> +
>> +	return ctx.found;
>> +}
>> diff --git a/tc/tc_util.h b/tc/tc_util.h
>> index 1218610..72f4282 100644
>> --- a/tc/tc_util.h
>> +++ b/tc/tc_util.h
>> @@ -132,4 +132,6 @@ int prio_print_opt(struct qdisc_util *qu, FILE *f, struct rtattr *opt);
>>  int cls_names_init(char *path);
>>  void cls_names_uninit(void);
>>  
>> +int tc_qdisc_block_exists(__u32 block_index);
>> +
>>  #endif
>> 
>