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git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
Merge branch 'netconsole-msgid' into main
Gustavo Luiz Duarte says:
====================
netconsole: Add support for msgid in sysdata
This patch series introduces a new feature to netconsole which allows
appending a message ID to the userdata dictionary.
If the msgid feature is enabled, the message ID is built from a per-target 32
bit counter that is incremented and appended to every message sent to the target.
Example::
echo 1 > "/sys/kernel/config/netconsole/cmdline0/userdata/msgid_enabled"
echo "This is message #1" > /dev/kmsg
echo "This is message #2" > /dev/kmsg
13,434,54928466,-;This is message #1
msgid=1
13,435,54934019,-;This is message #2
msgid=2
This feature can be used by the target to detect if messages were dropped or
reordered before reaching the target. This allows system administrators to
assess the reliability of their netconsole pipeline and detect loss of messages
due to network contention or temporary unavailability.
---
Changes in v3:
- Add kdoc documentation for msgcounter.
- Link to v2: https://lore.kernel.org/r/20250612-netconsole-msgid-v2-0-d4c1abc84bac@gmail.com
Changes in v2:
- Use wrapping_assign_add() to avoid warnings in UBSAN and friends.
- Improve documentation to clarify wrapping and distinguish msgid from sequnum.
- Rebase and fix conflict in prepare_extradata().
- Link to v1: https://lore.kernel.org/r/20250611-netconsole-msgid-v1-0-1784a51feb1e@gmail.com
====================
Suggested-by: Breno Leitao <leitao@debian.org>
Signed-off-by: Gustavo Luiz Duarte <gustavold@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
+128
+32
Documentation/networking/netconsole.rst
+32
Documentation/networking/netconsole.rst
···
340
340
cpu=42 # kernel-populated value
341
341
342
342
343
+
Message ID auto population in userdata
344
+
--------------------------------------
345
+
346
+
Within the netconsole configfs hierarchy, there is a file named `msgid_enabled`
347
+
located in the `userdata` directory. This file controls the message ID
348
+
auto-population feature, which assigns a numeric id to each message sent to a
349
+
given target and appends the ID to userdata dictionary in every message sent.
350
+
351
+
The message ID is generated using a per-target 32 bit counter that is
352
+
incremented for every message sent to the target. Note that this counter will
353
+
eventually wrap around after reaching uint32_t max value, so the message ID is
354
+
not globally unique over time. However, it can still be used by the target to
355
+
detect if messages were dropped before reaching the target by identifying gaps
356
+
in the sequence of IDs.
357
+
358
+
It is important to distinguish message IDs from the message <sequnum> field.
359
+
Some kernel messages may never reach netconsole (for example, due to printk
360
+
rate limiting). Thus, a gap in <sequnum> cannot be solely relied upon to
361
+
indicate that a message was dropped during transmission, as it may never have
362
+
been sent via netconsole. The message ID, on the other hand, is only assigned
363
+
to messages that are actually transmitted via netconsole.
364
+
365
+
Example::
366
+
367
+
echo "This is message #1" > /dev/kmsg
368
+
echo "This is message #2" > /dev/kmsg
369
+
13,434,54928466,-;This is message #1
370
+
msgid=1
371
+
13,435,54934019,-;This is message #2
372
+
msgid=2
373
+
374
+
343
375
Extended console:
344
376
=================
345
377
+66
drivers/net/netconsole.c
+66
drivers/net/netconsole.c
···
113
113
SYSDATA_TASKNAME = BIT(1),
114
114
/* Kernel release/version as part of sysdata */
115
115
SYSDATA_RELEASE = BIT(2),
116
+
/* Include a per-target message ID as part of sysdata */
117
+
SYSDATA_MSGID = BIT(3),
116
118
};
117
119
118
120
/**
···
125
123
* @extradata_complete: Cached, formatted string of append
126
124
* @userdata_length: String length of usedata in extradata_complete.
127
125
* @sysdata_fields: Sysdata features enabled.
126
+
* @msgcounter: Message sent counter.
128
127
* @stats: Packet send stats for the target. Used for debugging.
129
128
* @enabled: On / off knob to enable / disable target.
130
129
* Visible from userspace (read-write).
···
156
153
size_t userdata_length;
157
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/* bit-wise with sysdata_feature bits */
158
155
u32 sysdata_fields;
156
+
/* protected by target_list_lock */
157
+
u32 msgcounter;
159
158
#endif
160
159
struct netconsole_target_stats stats;
161
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bool enabled;
···
509
504
unregister_console(&netconsole);
510
505
}
511
506
507
+
static ssize_t sysdata_msgid_enabled_show(struct config_item *item,
508
+
char *buf)
509
+
{
510
+
struct netconsole_target *nt = to_target(item->ci_parent);
511
+
bool msgid_enabled;
512
+
513
+
mutex_lock(&dynamic_netconsole_mutex);
514
+
msgid_enabled = !!(nt->sysdata_fields & SYSDATA_MSGID);
515
+
mutex_unlock(&dynamic_netconsole_mutex);
516
+
517
+
return sysfs_emit(buf, "%d\n", msgid_enabled);
518
+
}
519
+
512
520
/*
513
521
* This one is special -- targets created through the configfs interface
514
522
* are not enabled (and the corresponding netpoll activated) by default.
···
817
799
entries += 1;
818
800
if (nt->sysdata_fields & SYSDATA_RELEASE)
819
801
entries += 1;
802
+
if (nt->sysdata_fields & SYSDATA_MSGID)
803
+
entries += 1;
820
804
821
805
return entries;
822
806
}
···
955
935
nt->extradata_complete[nt->userdata_length] = 0;
956
936
}
957
937
938
+
static ssize_t sysdata_msgid_enabled_store(struct config_item *item,
939
+
const char *buf, size_t count)
940
+
{
941
+
struct netconsole_target *nt = to_target(item->ci_parent);
942
+
bool msgid_enabled, curr;
943
+
ssize_t ret;
944
+
945
+
ret = kstrtobool(buf, &msgid_enabled);
946
+
if (ret)
947
+
return ret;
948
+
949
+
mutex_lock(&dynamic_netconsole_mutex);
950
+
curr = !!(nt->sysdata_fields & SYSDATA_MSGID);
951
+
if (msgid_enabled == curr)
952
+
goto unlock_ok;
953
+
954
+
if (msgid_enabled &&
955
+
count_extradata_entries(nt) >= MAX_EXTRADATA_ITEMS) {
956
+
ret = -ENOSPC;
957
+
goto unlock;
958
+
}
959
+
960
+
if (msgid_enabled)
961
+
nt->sysdata_fields |= SYSDATA_MSGID;
962
+
else
963
+
disable_sysdata_feature(nt, SYSDATA_MSGID);
964
+
965
+
unlock_ok:
966
+
ret = strnlen(buf, count);
967
+
unlock:
968
+
mutex_unlock(&dynamic_netconsole_mutex);
969
+
return ret;
970
+
}
971
+
958
972
static ssize_t sysdata_release_enabled_store(struct config_item *item,
959
973
const char *buf, size_t count)
960
974
{
···
1104
1050
CONFIGFS_ATTR(sysdata_, cpu_nr_enabled);
1105
1051
CONFIGFS_ATTR(sysdata_, taskname_enabled);
1106
1052
CONFIGFS_ATTR(sysdata_, release_enabled);
1053
+
CONFIGFS_ATTR(sysdata_, msgid_enabled);
1107
1054
1108
1055
static struct configfs_attribute *userdatum_attrs[] = {
1109
1056
&userdatum_attr_value,
···
1167
1112
&sysdata_attr_cpu_nr_enabled,
1168
1113
&sysdata_attr_taskname_enabled,
1169
1114
&sysdata_attr_release_enabled,
1115
+
&sysdata_attr_msgid_enabled,
1170
1116
NULL,
1171
1117
};
1172
1118
···
1365
1309
init_utsname()->release);
1366
1310
}
1367
1311
1312
+
static int sysdata_append_msgid(struct netconsole_target *nt, int offset)
1313
+
{
1314
+
wrapping_assign_add(nt->msgcounter, 1);
1315
+
return scnprintf(&nt->extradata_complete[offset],
1316
+
MAX_EXTRADATA_ENTRY_LEN, " msgid=%u\n",
1317
+
nt->msgcounter);
1318
+
}
1319
+
1368
1320
/*
1369
1321
* prepare_extradata - append sysdata at extradata_complete in runtime
1370
1322
* @nt: target to send message to
···
1395
1331
extradata_len += sysdata_append_taskname(nt, extradata_len);
1396
1332
if (nt->sysdata_fields & SYSDATA_RELEASE)
1397
1333
extradata_len += sysdata_append_release(nt, extradata_len);
1334
+
if (nt->sysdata_fields & SYSDATA_MSGID)
1335
+
extradata_len += sysdata_append_msgid(nt, extradata_len);
1398
1336
1399
1337
WARN_ON_ONCE(extradata_len >
1400
1338
MAX_EXTRADATA_ENTRY_LEN * MAX_EXTRADATA_ITEMS);
+30
tools/testing/selftests/drivers/net/netcons_sysdata.sh
+30
tools/testing/selftests/drivers/net/netcons_sysdata.sh
···
53
53
echo 1 > "${NETCONS_PATH}/userdata/release_enabled"
54
54
}
55
55
56
+
# Enable the msgid to be appended to sysdata
57
+
function set_msgid() {
58
+
if [[ ! -f "${NETCONS_PATH}/userdata/msgid_enabled" ]]
59
+
then
60
+
echo "Not able to enable msgid sysdata append. Configfs not available in ${NETCONS_PATH}/userdata/msgid_enabled" >&2
61
+
exit "${ksft_skip}"
62
+
fi
63
+
64
+
echo 1 > "${NETCONS_PATH}/userdata/msgid_enabled"
65
+
}
66
+
56
67
# Disable the sysdata cpu_nr feature
57
68
function unset_cpu_nr() {
58
69
echo 0 > "${NETCONS_PATH}/userdata/cpu_nr_enabled"
···
78
67
echo 0 > "${NETCONS_PATH}/userdata/release_enabled"
79
68
}
80
69
70
+
function unset_msgid() {
71
+
echo 0 > "${NETCONS_PATH}/userdata/msgid_enabled"
72
+
}
73
+
81
74
# Test if MSG contains sysdata
82
75
function validate_sysdata() {
83
76
# OUTPUT_FILE will contain something like:
···
89
74
# userdatakey=userdatavalue
90
75
# cpu=X
91
76
# taskname=<taskname>
77
+
# msgid=<id>
92
78
93
79
# Echo is what this test uses to create the message. See runtest()
94
80
# function
···
116
100
117
101
if ! grep -q "taskname=${SENDER}" "${OUTPUT_FILE}"; then
118
102
echo "FAIL: 'taskname=echo' not found in ${OUTPUT_FILE}" >&2
103
+
cat "${OUTPUT_FILE}" >&2
104
+
exit "${ksft_fail}"
105
+
fi
106
+
107
+
if ! grep -q "msgid=[0-9]\+$" "${OUTPUT_FILE}"; then
108
+
echo "FAIL: 'msgid=<id>' not found in ${OUTPUT_FILE}" >&2
119
109
cat "${OUTPUT_FILE}" >&2
120
110
exit "${ksft_fail}"
121
111
fi
···
177
155
exit "${ksft_fail}"
178
156
fi
179
157
158
+
if grep -q "msgid=" "${OUTPUT_FILE}"; then
159
+
echo "FAIL: 'msgid= found in ${OUTPUT_FILE}" >&2
160
+
cat "${OUTPUT_FILE}" >&2
161
+
exit "${ksft_fail}"
162
+
fi
163
+
180
164
rm "${OUTPUT_FILE}"
181
165
}
182
166
···
234
206
# Enable taskname to be appended to sysdata
235
207
set_taskname
236
208
set_release
209
+
set_msgid
237
210
runtest
238
211
# Make sure the message was received in the dst part
239
212
# and exit
···
264
235
unset_cpu_nr
265
236
unset_taskname
266
237
unset_release
238
+
unset_msgid
267
239
runtest
268
240
# At this time, cpu= shouldn't be present in the msg
269
241
validate_no_sysdata