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Fix #42: add option to always trust kernel timestamp

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Signed-off-by: Joachim Wiberg <troglobit@gmail.com>
This commit is contained in:
Joachim Wiberg 2021-11-26 06:50:31 +01:00
parent e69b0fe812
commit 9856e07e40
2 changed files with 29 additions and 5 deletions
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20
man/syslogd.8
View File

@ -38,7 +38,7 @@
.Nd log systems messages
.Sh SYNOPSIS
.Nm
.Op Fl ?46AdFHknsTv
.Op Fl ?46AdFHKknsTv
.Op Fl a Ar addr[/len][:port]
.Op Fl a Ar name[:port]
.Op Fl b Ar addr[:port]
@ -255,6 +255,24 @@ and wants to monitor when and how it exits.
.It Fl H
When logging remote messages use hostname from the message (if supplied)
instead of using address from which the message was received.
.It Fl K
Keep (trust) kernel timestamp.
.Pp
On Linux systems the
.Pa /dev/kmsg
timestamp is a monotonic clock, in microseconds, relative to the boot of
the system. This timestamp is, among other things,
.Sy not
adjusted for suspend/resume cycles, meaning the kernel logs can start to
go out of sync with the rest of the system. This in turn can make it
really hard to correlate events.
.Pp
.Nm
by default only trusts the kernel timestamp when starting up the first
time. As soon as the the kernel ring buffer has been emptied,
.Nm
uses its own current time for each received kernel log message. This
option disables that behavior.
.It Fl k
Disable the translation of
messages received with facility

12
src/syslogd.c
View File

@ -141,6 +141,7 @@ static int RemoteAddDate; /* Always set the date on remote messages */
static int RemoteHostname; /* Log remote hostname from the message */
static int KeepKernFac; /* Keep remotely logged kernel facility */
static int KeepKernTime; /* Keep kernel timestamp, evern after initial read */
static off_t RotateSz = 0; /* Max file size (bytes) before rotating, disabled by default */
static int RotateCnt = 5; /* Max number (count) of log files to keep, set with -c <NUM> */
@ -253,7 +254,7 @@ static void sys_seqno_save(void)
int usage(int code)
{
printf("Usage:\n"
" syslogd [-46AdFknsTv?] [-a PEER] [-b NAME] [-f FILE] [-m INTERVAL]\n"
" syslogd [-46AdFKknsTv?] [-a PEER] [-b NAME] [-f FILE] [-m INTERVAL]\n"
" [-P PID_FILE] [-p SOCK_PATH] [-r SIZE[:NUM]]\n"
"Options:\n"
" -4 Force IPv4 only\n"
@ -284,6 +285,7 @@ int usage(int code)
" -F Run in foreground, required when monitored by init(1)\n"
" -f FILE Alternate .conf file, default: %s\n"
" -k Allow logging with facility 'kernel', otherwise remapped to 'user'\n"
" -K Keep kernel timestamp, even after initial ring buffer emptying\n"
" -m MINS Interval between MARK messages, 0 to disable, default: 20 min\n"
" -n Disable DNS query for every request\n"
" -P FILE File to store the process ID, default: %s\n"
@ -315,7 +317,7 @@ int main(int argc, char *argv[])
int pflag = 0, bflag = 0;
int ch;
while ((ch = getopt(argc, argv, "46Aa:b:C:dHFf:km:nP:p:r:sTv?")) != EOF) {
while ((ch = getopt(argc, argv, "46Aa:b:C:dHFf:Kkm:nP:p:r:sTv?")) != EOF) {
switch ((char)ch) {
case '4':
family = PF_INET;
@ -370,6 +372,10 @@ int main(int argc, char *argv[])
KeepKernFac = 1;
break;
case 'K': /* keep/trust kernel timestamp always */
KeepKernTime = 1;
break;
case 'm': /* mark interval */
MarkInterval = atoi(optarg) * 60;
break;
@ -1238,7 +1244,7 @@ void printsys(char *msg)
* current time of any new kernel messages.
* -- Joachim Wiberg Nov 23, 2021
*/
if (!sys_seqno_init) {
if (KeepKernTime || !sys_seqno_init) {
now = boot_time + ustime / 1000000;
buffer.timestamp.usec = ustime % 1000000;
localtime_r(&now, &buffer.timestamp.tm);