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Optional syslog support #1590

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Optional syslog support #1590

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src/main: add optional syslog support 
This patch adds an optional syslog backend alternative to the default
stdout/stderr logging.

The syslog backend is enabled with `--syslog` on the command line.  It
logs directly to the local syslog daemon, via the POSIX syslog() API,
using a default 'daemon' facility.  This facility can be changed if an
optional argument is given, e.g., `--syslog=local0`.  Useful for basic
message filtering to a dedicated log file.

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>
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@troglobit
troglobit committed Jan 8, 2025
commit ccd2af807af6a583c82e62dbae769e65e2a1e125
13 changes: 7 additions & 6 deletions docs/reference.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -1288,12 +1288,13 @@ Command Line Tool
rauc [OPTION?] <COMMAND>

Options:
-c, --conf=FILENAME config file
--keyring=PEMFILE keyring file
--mount=PATH mount prefix
-d, --debug enable debug output
--version display version
-h, --help display help and exit
-c, --conf=FILENAME config file
--keyring=PEMFILE keyring file
--mount=PATH mount prefix
-d, --debug enable debug output
-s, --syslog=[facility] enable syslog output, optional facility, default: daemon
--version display version
-h, --help display help and exit

Command-specific help:
rauc <COMMAND> --help
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64 changes: 64 additions & 0 deletions src/main.c
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Expand Up @@ -10,6 +10,8 @@
#include <locale.h>
#include <stdio.h>
#include <string.h>
#define SYSLOG_NAMES
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Is this really needed? https://sourceware.org/bugzilla/show_bug.cgi?id=16355 sounds like we should avoid this define.

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The define opens up the use of facilitynames[]. It has been a long standing practice, but we can replace that with a local array of the same names if you want.

#include <syslog.h>
#include <sys/ioctl.h>
#include <unistd.h>

Expand Down Expand Up @@ -2646,6 +2648,67 @@ static void create_option_groups(void)
g_option_group_add_entries(service_group, entries_service);
}

static int log_level(GLogLevelFlags level)
{
if (level & G_LOG_FLAG_FATAL)
return LOG_EMERG;
if (level & G_LOG_FLAG_RECURSION)
return LOG_ALERT;
if (level & G_LOG_LEVEL_CRITICAL)
return LOG_CRIT;
if (level & G_LOG_LEVEL_ERROR)
return LOG_ERR;
if (level & G_LOG_LEVEL_WARNING)
return LOG_WARNING;
if (level & G_LOG_LEVEL_MESSAGE)
return LOG_NOTICE;
if (level & G_LOG_LEVEL_INFO)
return LOG_INFO;
if (level & G_LOG_LEVEL_DEBUG)
return LOG_DEBUG;

return LOG_INFO; /* Fallback to INFO for unknown levels */
}

static void syslog_handler(const gchar *domain, GLogLevelFlags level, const gchar *message, gpointer arg)
{
int prio = log_level(level);

if (g_strcmp0(domain, G_LOG_DOMAIN))
syslog(prio, "%s: %s", domain, message);
else
syslog(prio, "%s", message);
}

static gboolean syslog_option_cb(const gchar *option_name, const gchar *value,
gpointer data, GError **error)
{
int facility = LOG_DAEMON;

if (value) {
gboolean found = FALSE;

for (const CODE *f = facilitynames; f->c_name != NULL; f++) {
if (g_ascii_strcasecmp(value, f->c_name) == 0) {
facility = f->c_val;
found = TRUE;
break;
}
}

if (!found) {
g_set_error(error, G_OPTION_ERROR, G_OPTION_ERROR_BAD_VALUE,
"Invalid syslog facility: %s", value);
return FALSE;
}
}

openlog(G_LOG_DOMAIN, LOG_PID | LOG_NOWAIT, facility);
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syslog(3) mentions that LOG_NOWAIT has no effect on Linux, so it could be removed.

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Well, it depends a bit on the backend. I maintain sysklogd, which today supplies an RFC5424 compliant syslogp(), as well as replacement syslog() API, this is one implementation that can replace the stanard C-library APIs for syslog.

There's no overhead to supporting LOG_NOWAIT, but if you only want to support GLIBC or standard C-library, that is fine and I can remove it.

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What's the effect of LOG_NOWAIT with sysklogd?

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Internally it will connect immediately to the /dev/log socket instead of postponing it until the first syslogd() call.

g_log_set_default_handler(syslog_handler, NULL);

return TRUE;
}

static void cmdline_handler(int argc, char **argv)
{
gboolean help = FALSE, debug = FALSE, version = FALSE;
Expand All @@ -2661,6 +2724,7 @@ static void cmdline_handler(int argc, char **argv)
{"intermediate", '\0', G_OPTION_FLAG_HIDDEN, G_OPTION_ARG_FILENAME_ARRAY, &intermediate, "intermediate CA file or PKCS#11 URL", "PEMFILE|PKCS11-URL"},
{"mount", '\0', 0, G_OPTION_ARG_FILENAME, &mount, "mount prefix", "PATH"},
{"debug", 'd', 0, G_OPTION_ARG_NONE, &debug, "enable debug output", NULL},
{"syslog", 's', G_OPTION_FLAG_OPTIONAL_ARG, G_OPTION_ARG_CALLBACK, syslog_option_cb, "enable syslog output, optional facility, default: daemon", "[facility]"},
{"version", '\0', 0, G_OPTION_ARG_NONE, &version, "display version", NULL},
{"help", 'h', 0, G_OPTION_ARG_NONE, &help, "display help and exit", NULL},
{0}
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