netdev - [patch iproute2 net-next v12 1/3] tc: introduce tc_qdisc_block

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Date:   Sat, 20 Jan 2018 11:00:27 +0100
From:   Jiri Pirko <jiri@...nulli.us>
To:     netdev@...r.kernel.org
Cc:     mlxsw@...lanox.com, dsahern@...il.com
Subject: [patch iproute2 net-next v12 1/3] tc: introduce tc_qdisc_block_exists helper

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>
---
v11->v12:
- fixed return type of tc_qdisc_block_exists
- removed 0 checks for block in tc_qdisc_block_exists
- rever xmas tree variables in tc_qdisc_block_exists
---
 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 70279b9d..54701c26 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);
+	struct rtattr *tb[TCA_MAX+1];
+	int len = n->nlmsg_len;
+
+	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)) {
+		__u32 block = rta_getattr_u32(tb[TCA_INGRESS_BLOCK]);
+
+		if (block == ctx->block_index)
+			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 == ctx->block_index)
+			ctx->found = true;
+	}
+	return 0;
+}
+
+bool tc_qdisc_block_exists(__u32 block_index)
+{
+	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 1218610d..682dd4fd 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);
 
+bool tc_qdisc_block_exists(__u32 block_index);
+
 #endif
-- 
2.14.3