[PATCH v2] netconsole: Append kernel version to message

From: Breno Leitao
Date: Fri Jul 07 2023 - 09:30:32 EST

Create a new netconsole runtime option that prepends the kernel version in
the netconsole message. This is useful to map kernel messages to kernel
version in a simple way, i.e., without checking somewhere which kernel
version the host that sent the message is using.

If this option is selected, then the "<release>," is prepended before the
netconsole message. This is an example of a netconsole output, with
release feature enabled:

6.4.0-01762-ga1ba2ffe946e;12,426,112883998,-;this is a test

Calvin Owens send a RFC about this problem in 2016[1], but his
approach was a bit more intrusive, changing the printk subsystem. This
approach is lighter, and just append the information in the last mile,
just before netconsole push the message to netpoll.

[1] Link: https://lore.kernel.org/all/51047c0f6e86abcb9ee13f60653b6946f8fcfc99.1463172791.git.calvinowens@xxxxxx/

Cc: Dave Jones <davej@xxxxxxxxxxxxxxxxx>
Signed-off-by: Breno Leitao <leitao@xxxxxxxxxx>
---
V1 -> V2:
* Configured at runtime instead of at compilation time
* Reuse send_ext_msg_udp to avoid extra memory allocation
---

Documentation/networking/netconsole.rst | 11 +++-
drivers/net/netconsole.c | 80 ++++++++++++++++++++++++-
2 files changed, 87 insertions(+), 4 deletions(-)

diff --git a/Documentation/networking/netconsole.rst b/Documentation/networking/netconsole.rst
index dd0518e002f6..7a9de0568e84 100644
--- a/Documentation/networking/netconsole.rst
+++ b/Documentation/networking/netconsole.rst
@@ -13,6 +13,8 @@ IPv6 support by Cong Wang <xiyou.wangcong@xxxxxxxxx>, Jan 1 2013

Extended console support by Tejun Heo <tj@xxxxxxxxxx>, May 1 2015

+Release prepend support by Breno Leitao <leitao@xxxxxxxxxx>, Jul 7 2023
+
Please send bug reports to Matt Mackall <mpm@xxxxxxxxxxx>
Satyam Sharma <satyam.sharma@xxxxxxxxx>, and Cong Wang <xiyou.wangcong@xxxxxxxxx>

@@ -34,10 +36,11 @@ Sender and receiver configuration:
It takes a string configuration parameter "netconsole" in the
following format::

- netconsole=[+][src-port]@[src-ip]/[<dev>],[tgt-port]@<tgt-ip>/[tgt-macaddr]
+ netconsole=[+][r][src-port]@[src-ip]/[<dev>],[tgt-port]@<tgt-ip>/[tgt-macaddr]

where
+ if present, enable extended console support
+ r if present, prepend kernel version (release) to the message
src-port source for UDP packets (defaults to 6665)
src-ip source IP to use (interface address)
dev network interface (eth0)
@@ -125,6 +128,7 @@ The interface exposes these parameters of a netconsole target to userspace:
============== ================================= ============
enabled Is this target currently enabled? (read-write)
extended Extended mode enabled (read-write)
+ release Prepend kernel release to message (read-write)
dev_name Local network interface name (read-write)
local_port Source UDP port to use (read-write)
remote_port Remote agent's UDP port (read-write)
@@ -165,6 +169,11 @@ following format which is the same as /dev/kmsg::

<level>,<sequnum>,<timestamp>,<contflag>;<message text>

+If 'r' (release) feature is enabled, the kernel release version is
+prepended to the start of the message. Example::
+
+ 6.4.0,6,444,501151268,-;netconsole: network logging started
+
Non printable characters in <message text> are escaped using "\xff"
notation. If the message contains optional dictionary, verbatim
newline is used as the delimiter.
diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c
index 4f4f79532c6c..a72f471ddf02 100644
--- a/drivers/net/netconsole.c
+++ b/drivers/net/netconsole.c
@@ -36,6 +36,7 @@
#include <linux/inet.h>
#include <linux/configfs.h>
#include <linux/etherdevice.h>
+#include <linux/utsname.h>

MODULE_AUTHOR("Maintainer: Matt Mackall <mpm@xxxxxxxxxxx>");
MODULE_DESCRIPTION("Console driver for network interfaces");
@@ -84,6 +85,8 @@ static struct console netconsole_ext;
* Also, other parameters of a target may be modified at
* runtime only when it is disabled (enabled == 0).
* @extended: Denotes whether console is extended or not.
+ * @release: Denotes whether kernel release version should be prepended
+ * to the message. Depends on extended console.
* @np: The netpoll structure for this target.
* Contains the other userspace visible parameters:
* dev_name (read-write)
@@ -101,6 +104,7 @@ struct netconsole_target {
#endif
bool enabled;
bool extended;
+ bool release;
struct netpoll np;
};

@@ -188,6 +192,14 @@ static struct netconsole_target *alloc_param_target(char *target_config)
target_config++;
}

+ if (*target_config == 'r') {
+ if (!nt->extended)
+ pr_err("Not enabling release feature, since extended message is disabled\n");
+ else
+ nt->release = true;
+ target_config++;
+ }
+
/* Parse parameters and setup netpoll */
err = netpoll_parse_options(&nt->np, target_config);
if (err)
@@ -222,6 +234,7 @@ static void free_param_target(struct netconsole_target *nt)
* |
* <target>/
* | enabled
+ * | release
* | dev_name
* | local_port
* | remote_port
@@ -254,6 +267,11 @@ static ssize_t extended_show(struct config_item *item, char *buf)
return snprintf(buf, PAGE_SIZE, "%d\n", to_target(item)->extended);
}

+static ssize_t release_show(struct config_item *item, char *buf)
+{
+ return snprintf(buf, PAGE_SIZE, "%d\n", to_target(item)->release);
+}
+
static ssize_t dev_name_show(struct config_item *item, char *buf)
{
return snprintf(buf, PAGE_SIZE, "%s\n", to_target(item)->np.dev_name);
@@ -332,6 +350,11 @@ static ssize_t enabled_store(struct config_item *item,
}

if (enabled) { /* true */
+ if (nt->release && !nt->extended) {
+ pr_err("release feature requires extended log message\n");
+ goto out_unlock;
+ }
+
if (nt->extended && !console_is_registered(&netconsole_ext))
register_console(&netconsole_ext);

@@ -366,6 +389,38 @@ static ssize_t enabled_store(struct config_item *item,
return err;
}

+static ssize_t release_store(struct config_item *item, const char *buf,
+ size_t count)
+{
+ struct netconsole_target *nt = to_target(item);
+ int release;
+ int err;
+
+ mutex_lock(&dynamic_netconsole_mutex);
+ if (nt->enabled) {
+ pr_err("target (%s) is enabled, disable to update parameters\n",
+ config_item_name(&nt->item));
+ err = -EINVAL;
+ goto out_unlock;
+ }
+
+ err = kstrtoint(buf, 10, &release);
+ if (err < 0)
+ goto out_unlock;
+ if (release < 0 || release > 1) {
+ err = -EINVAL;
+ goto out_unlock;
+ }
+
+ nt->release = release;
+
+ mutex_unlock(&dynamic_netconsole_mutex);
+ return strnlen(buf, count);
+out_unlock:
+ mutex_unlock(&dynamic_netconsole_mutex);
+ return err;
+}
+
static ssize_t extended_store(struct config_item *item, const char *buf,
size_t count)
{
@@ -576,10 +631,12 @@ CONFIGFS_ATTR(, local_ip);
CONFIGFS_ATTR(, remote_ip);
CONFIGFS_ATTR_RO(, local_mac);
CONFIGFS_ATTR(, remote_mac);
+CONFIGFS_ATTR(, release);

static struct configfs_attribute *netconsole_target_attrs[] = {
&attr_enabled,
&attr_extended,
+ &attr_release,
&attr_dev_name,
&attr_local_port,
&attr_remote_port,
@@ -772,9 +829,23 @@ static void send_ext_msg_udp(struct netconsole_target *nt, const char *msg,
const char *header, *body;
int offset = 0;
int header_len, body_len;
+ const char *msg_ready = msg;
+ const char *release;
+ int release_len = 0;
+
+ if (nt->release) {
+ release = init_utsname()->release;
+ release_len = strlen(release) + 1;
+ }

- if (msg_len <= MAX_PRINT_CHUNK) {
- netpoll_send_udp(&nt->np, msg, msg_len);
+ if (msg_len + release_len <= MAX_PRINT_CHUNK) {
+ /* No fragmentation needed */
+ if (nt->release) {
+ scnprintf(buf, MAX_PRINT_CHUNK, "%s,%s", release, msg);
+ msg_len += release_len;
+ msg_ready = buf;
+ }
+ netpoll_send_udp(&nt->np, msg_ready, msg_len);
return;
}

@@ -792,7 +863,10 @@ static void send_ext_msg_udp(struct netconsole_target *nt, const char *msg,
* Transfer multiple chunks with the following extra header.
* "ncfrag=<byte-offset>/<total-bytes>"
*/
- memcpy(buf, header, header_len);
+ if (nt->release)
+ scnprintf(buf, MAX_PRINT_CHUNK, "%s,", release);
+ memcpy(buf + release_len, header, header_len);
+ header_len += release_len;

while (offset < body_len) {
int this_header = header_len;
--
2.34.1