[PATCH v2 iproute2 1/2] tc/taprio: don't print netlink attributes which weren't reported by the kernel

When an admin schedule is pending and hasn't yet become operational, the
kernel will report only the parameters of the admin schedule in a nested
TCA_TAPRIO_ATTR_ADMIN_SCHED attribute.

However, we default to printing zeroes even for the parameters of the
operational base time, when that doesn't exist.

Link: https://lore.kernel.org/netdev/87il9w0xx7.fsf@intel.com/
Fixes: 0dd16449356f ("tc: Add support for configuring the taprio scheduler")
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Acked-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>
---
v1->v2:
- move variable declarations to their respective "if" blocks
- use "nla" instead of "tb[TCA_TAPRIO_ATTR_SCHED_CYCLE_TIME]"


 tc/q_taprio.c | 89 +++++++++++++++++++++++++++++++--------------------
 1 file changed, 54 insertions(+), 35 deletions(-)

diff --git a/tc/q_taprio.c b/tc/q_taprio.c
index 913197f68caa..6250871fb5f2 100644
--- a/tc/q_taprio.c
+++ b/tc/q_taprio.c

@@ -416,14 +416,11 @@ static int taprio_parse_opt(struct qdisc_util *qu, int argc,
 	return 0;
 }
 
-static int print_sched_list(FILE *f, struct rtattr *list)
+static void print_sched_list(FILE *f, struct rtattr *list)
 {
-	struct rtattr *item;
+	struct rtattr *item, *nla;
 	int rem;
 
-	if (list == NULL)
-		return 0;
-
 	rem = RTA_PAYLOAD(list);
 
 	open_json_array(PRINT_JSON, "schedule");

@@ -432,60 +429,82 @@ static int print_sched_list(FILE *f, struct rtattr *list)
 
 	for (item = RTA_DATA(list); RTA_OK(item, rem); item = RTA_NEXT(item, rem)) {
 		struct rtattr *tb[TCA_TAPRIO_SCHED_ENTRY_MAX + 1];
-		__u32 index = 0, gatemask = 0, interval = 0;
-		__u8 command = 0;
 
 		parse_rtattr_nested(tb, TCA_TAPRIO_SCHED_ENTRY_MAX, item);
 
-		if (tb[TCA_TAPRIO_SCHED_ENTRY_INDEX])
-			index = rta_getattr_u32(tb[TCA_TAPRIO_SCHED_ENTRY_INDEX]);
+		open_json_object(NULL);
 
-		if (tb[TCA_TAPRIO_SCHED_ENTRY_CMD])
-			command = rta_getattr_u8(tb[TCA_TAPRIO_SCHED_ENTRY_CMD]);
+		nla = tb[TCA_TAPRIO_SCHED_ENTRY_INDEX];
+		if (nla) {
+			__u32 index = rta_getattr_u32(nla);
 
-		if (tb[TCA_TAPRIO_SCHED_ENTRY_GATE_MASK])
-			gatemask = rta_getattr_u32(tb[TCA_TAPRIO_SCHED_ENTRY_GATE_MASK]);
+			print_uint(PRINT_ANY, "index", "\tindex %u", index);
+		}
 
-		if (tb[TCA_TAPRIO_SCHED_ENTRY_INTERVAL])
-			interval = rta_getattr_u32(tb[TCA_TAPRIO_SCHED_ENTRY_INTERVAL]);
+		nla = tb[TCA_TAPRIO_SCHED_ENTRY_CMD];
+		if (nla) {
+			__u8 command = rta_getattr_u8(nla);
+
+			print_string(PRINT_ANY, "cmd", " cmd %s",
+				     entry_cmd_to_str(command));
+		}
+
+		nla = tb[TCA_TAPRIO_SCHED_ENTRY_GATE_MASK];
+		if (nla) {
+			__u32 gatemask = rta_getattr_u32(nla);
+
+			print_0xhex(PRINT_ANY, "gatemask", " gatemask %#llx",
+				    gatemask);
+		}
+
+		nla = tb[TCA_TAPRIO_SCHED_ENTRY_INTERVAL];
+		if (nla) {
+			__u32 interval = rta_getattr_u32(nla);
+
+			print_uint(PRINT_ANY, "interval", " interval %u",
+				   interval);
+		}
 
-		open_json_object(NULL);
-		print_uint(PRINT_ANY, "index", "\tindex %u", index);
-		print_string(PRINT_ANY, "cmd", " cmd %s", entry_cmd_to_str(command));
-		print_0xhex(PRINT_ANY, "gatemask", " gatemask %#llx", gatemask);
-		print_uint(PRINT_ANY, "interval", " interval %u", interval);
 		close_json_object();
 
 		print_nl();
 	}
 
 	close_json_array(PRINT_ANY, "");
-
-	return 0;
 }
 
 static int print_schedule(FILE *f, struct rtattr **tb)
 {
-	int64_t base_time = 0, cycle_time = 0, cycle_time_extension = 0;
+	struct rtattr *nla;
 
-	if (tb[TCA_TAPRIO_ATTR_SCHED_BASE_TIME])
-		base_time = rta_getattr_s64(tb[TCA_TAPRIO_ATTR_SCHED_BASE_TIME]);
+	nla = tb[TCA_TAPRIO_ATTR_SCHED_BASE_TIME];
+	if (nla) {
+		int64_t base_time = rta_getattr_s64(nla);
 
-	if (tb[TCA_TAPRIO_ATTR_SCHED_CYCLE_TIME])
-		cycle_time = rta_getattr_s64(tb[TCA_TAPRIO_ATTR_SCHED_CYCLE_TIME]);
+		print_lluint(PRINT_ANY, "base_time", "\tbase-time %lld",
+			     base_time);
+	}
 
-	if (tb[TCA_TAPRIO_ATTR_SCHED_CYCLE_TIME_EXTENSION])
-		cycle_time_extension = rta_getattr_s64(
-			tb[TCA_TAPRIO_ATTR_SCHED_CYCLE_TIME_EXTENSION]);
+	nla = tb[TCA_TAPRIO_ATTR_SCHED_CYCLE_TIME];
+	if (nla) {
+		int64_t cycle_time = rta_getattr_s64(nla);
 
-	print_lluint(PRINT_ANY, "base_time", "\tbase-time %lld", base_time);
+		print_lluint(PRINT_ANY, "cycle_time", " cycle-time %lld",
+			     cycle_time);
+	}
 
-	print_lluint(PRINT_ANY, "cycle_time", " cycle-time %lld", cycle_time);
+	nla = tb[TCA_TAPRIO_ATTR_SCHED_CYCLE_TIME_EXTENSION];
+	if (nla) {
+		int64_t cycle_time_extension = rta_getattr_s64(nla);
 
-	print_lluint(PRINT_ANY, "cycle_time_extension",
-		     " cycle-time-extension %lld", cycle_time_extension);
+		print_lluint(PRINT_ANY, "cycle_time_extension",
+			     " cycle-time-extension %lld",
+			     cycle_time_extension);
+	}
 
-	print_sched_list(f, tb[TCA_TAPRIO_ATTR_SCHED_ENTRY_LIST]);
+	nla = tb[TCA_TAPRIO_ATTR_SCHED_ENTRY_LIST];
+	if (nla)
+		print_sched_list(f, nla);
 
 	return 0;
 }

-- 
2.34.1

When the kernel reports that a configuration change is pending
(and that the schedule is still in the administrative state and
not yet operational), we (tc -j -p qdisc show) produce the following
output:

[ {
        "kind": "taprio",
        "handle": "8001:",
        "root": true,
        "refcnt": 9,
        "options": {
            "tc": 8,
            "map": [ 0,1,2,3,4,5,6,7,0,0,0,0,0,0,0,0 ],
            "queues": [ {
                    "offset": 0,
                    "count": 1
                },{
                    "offset": 1,
                    "count": 1
                },{
                    "offset": 2,
                    "count": 1
                },{
                    "offset": 3,
                    "count": 1
                },{
                    "offset": 4,
                    "count": 1
                },{
                    "offset": 5,
                    "count": 1
                },{
                    "offset": 6,
                    "count": 1
                },{
                    "offset": 7,
                    "count": 1
                } ],
            "clockid": "TAI",
            "base_time": 0,
            "cycle_time": 20000000,
            "cycle_time_extension": 0,
            "schedule": [ {
                    "index": 0,
                    "cmd": "S",
                    "gatemask": "0xff",
                    "interval": 20000000
                } ],{
                "base_time": 1691160103110424418,
                "cycle_time": 20000000,
                "cycle_time_extension": 0,
                "schedule": [ {
                        "index": 0,
                        "cmd": "S",
                        "gatemask": "0xff",
                        "interval": 20000000
                    } ]
            },
            "max-sdu": [ 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 ],
            "fp": [ "E","E","E","E","E","E","E","E","E","E","E","E","E","E","E","E" ]
        }
    } ]

which is invalid json, because the second group of "base_time",
"cycle_time", etc etc is placed in an unlabeled sub-object. If we pipe
it into jq, it complains:

parse error: Objects must consist of key:value pairs at line 53, column 14

Since it represents the administrative schedule, give this unnamed JSON
object the "admin" name. We now print valid JSON which looks like this:

[ {
        "kind": "taprio",
        "handle": "8001:",
        "root": true,
        "refcnt": 9,
        "options": {
            "tc": 8,
            "map": [ 0,1,2,3,4,5,6,7,0,0,0,0,0,0,0,0 ],
            "queues": [ {
                    "offset": 0,
                    "count": 1
                },{
                    "offset": 1,
                    "count": 1
                },{
                    "offset": 2,
                    "count": 1
                },{
                    "offset": 3,
                    "count": 1
                },{
                    "offset": 4,
                    "count": 1
                },{
                    "offset": 5,
                    "count": 1
                },{
                    "offset": 6,
                    "count": 1
                },{
                    "offset": 7,
                    "count": 1
                } ],
            "clockid": "TAI",
            "base_time": 0,
            "cycle_time": 20000000,
            "cycle_time_extension": 0,
            "schedule": [ {
                    "index": 0,
                    "cmd": "S",
                    "gatemask": "0xff",
                    "interval": 20000000
                } ],
            "admin": {
                "base_time": 1691160511783528178,
                "cycle_time": 20000000,
                "cycle_time_extension": 0,
                "schedule": [ {
                        "index": 0,
                        "cmd": "S",
                        "gatemask": "0xff",
                        "interval": 20000000
                    } ]
            },
            "max-sdu": [ 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 ],
            "fp": [ "E","E","E","E","E","E","E","E","E","E","E","E","E","E","E","E" ]
        }
    } ]

Fixes: 602fae856d80 ("taprio: Add support for changing schedules")
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Acked-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>
---
v1->v2: none

 tc/q_taprio.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tc/q_taprio.c b/tc/q_taprio.c
index 6250871fb5f2..ef8fc7a05fc2 100644
--- a/tc/q_taprio.c
+++ b/tc/q_taprio.c

@@ -654,7 +654,7 @@ static int taprio_print_opt(struct qdisc_util *qu, FILE *f, struct rtattr *opt)
 		parse_rtattr_nested(t, TCA_TAPRIO_ATTR_MAX,
 				    tb[TCA_TAPRIO_ATTR_ADMIN_SCHED]);
 
-		open_json_object(NULL);
+		open_json_object("admin");
 
 		print_schedule(f, t);
 

-- 
2.34.1

Hello:

This series was applied to iproute2/iproute2.git (main)
by Stephen Hemminger [off-list ref]:

On Tue,  8 Aug 2023 01:09:35 +0300 you wrote:

When an admin schedule is pending and hasn't yet become operational, the
kernel will report only the parameters of the admin schedule in a nested
TCA_TAPRIO_ATTR_ADMIN_SCHED attribute.

However, we default to printing zeroes even for the parameters of the
operational base time, when that doesn't exist.

[...]

Here is the summary with links:
  - [v2,iproute2,1/2] tc/taprio: don't print netlink attributes which weren't reported by the kernel
    https://git.kernel.org/pub/scm/network/iproute2/iproute2.git/commit/?id=a5f695cbb130
  - [v2,iproute2,2/2] tc/taprio: fix JSON output when TCA_TAPRIO_ATTR_ADMIN_SCHED is present
    https://git.kernel.org/pub/scm/network/iproute2/iproute2.git/commit/?id=f848310a7279

You are awesome, thank you!
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