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Auto-detect if we're running in a container and disable klogd

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This patch adds a very rudimentary container check.  When one, of a
select few containers, are detected, sysklogd disables the kernel
logging -- since there's no point in logging kernel messages other
than from the host system.

Issue #48

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>
This commit is contained in:
Joachim Wiberg 2022-02-14 00:28:28 +01:00
parent 29e932008d
commit c534556790
1 changed files with 47 additions and 1 deletions
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48
src/syslogd.c
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@ -189,6 +189,40 @@ static int waitdaemon(int);
static void timedout(int);
/*
* Very basic, and incomplete, check if we're running in a container.
* If so, we probably want to disable kernel logging.
*/
static int in_container(void)
{
const char *files[] = {
"/run/.containerenv",
"/.dockerenv"
};
const char *containers[] = {
"lxc",
"docker",
"kubepod"
};
size_t i;
char *c;
c = getenv("container");
if (c) {
for (i = 0; i < NELEMS(containers); i++) {
if (!strcmp(containers[i], c))
return 1;
}
}
for (i = 0; i < NELEMS(files); i++) {
if (!access(files[i], F_OK))
return 1;
}
return 0;
}
static int addpeer(struct peer *pe0)
{
struct peer *pe;
@ -316,8 +350,10 @@ int usage(int code)
int main(int argc, char *argv[])
{
pid_t ppid = 1;
int no_sys = 0;
int pflag = 0;
int bflag = 0;
char *ptr;
int pflag = 0, bflag = 0;
int ch;
while ((ch = getopt(argc, argv, "46Aa:b:C:dHFf:Kkm:nP:p:r:sTtv?")) != EOF) {
@ -464,6 +500,11 @@ int main(int argc, char *argv[])
* systems is /proc/kmsg, and /dev/klog on *BSD.
*/
if (KernLog) {
if (in_container()) {
no_sys = 1;
goto no_klogd;
}
sys_seqno_load();
if (opensys("/dev/kmsg")) {
if (opensys(_PATH_KLOG))
@ -473,6 +514,7 @@ int main(int argc, char *argv[])
kern_console_off();
} else
kern_console_off();
no_klogd:
}
consfile.f_type = F_CONSOLE;
@ -513,6 +555,10 @@ int main(int argc, char *argv[])
if (ppid != 1)
kill(ppid, SIGALRM);
/* Log if we disabled klogd */
if (no_sys)
NOTE("Running in a container, disabling klogd.");
/* Main loop begins here. */
for (;;) {
int rc;