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- pppd: Watch out for time warps
- On many embedded systems there is no battery backed RTC and a proper system
- time only becomes available through NTP after establishing a connection.
- When the clock suddenly jumps forward, the internal accounting (connect time)
- is confused resulting in unreliable data.
- This patch implements periodic clock checking to look for time warps, if one
- is detected, the internal counters are adjusted accordingly.
- Signed-off-by: Jo-Philipp Wich <jo@mein.io>
- --- a/pppd/main.c
- +++ b/pppd/main.c
- @@ -90,6 +90,7 @@
- #include <sys/socket.h>
- #include <netinet/in.h>
- #include <arpa/inet.h>
- +#include <sys/sysinfo.h>
-
- #include "pppd.h"
- #include "magic.h"
- @@ -228,6 +229,7 @@ static struct subprocess *children;
-
- /* Prototypes for procedures local to this file. */
-
- +static void check_time(void);
- static void setup_signals __P((void));
- static void create_pidfile __P((int pid));
- static void create_linkpidfile __P((int pid));
- @@ -535,6 +537,7 @@ main(argc, argv)
- info("Starting link");
- }
-
- + check_time();
- gettimeofday(&start_time, NULL);
- script_unsetenv("CONNECT_TIME");
- script_unsetenv("BYTES_SENT");
- @@ -1267,6 +1270,36 @@ struct callout {
-
- static struct callout *callout = NULL; /* Callout list */
- static struct timeval timenow; /* Current time */
- +static long uptime_diff = 0;
- +static int uptime_diff_set = 0;
- +
- +static void check_time(void)
- +{
- + long new_diff;
- + struct timeval t;
- + struct sysinfo i;
- + struct callout *p;
- +
- + gettimeofday(&t, NULL);
- + sysinfo(&i);
- + new_diff = t.tv_sec - i.uptime;
- +
- + if (!uptime_diff_set) {
- + uptime_diff = new_diff;
- + uptime_diff_set = 1;
- + return;
- + }
- +
- + if ((new_diff - 5 > uptime_diff) || (new_diff + 5 < uptime_diff)) {
- + /* system time has changed, update counters and timeouts */
- + info("System time change detected.");
- + start_time.tv_sec += new_diff - uptime_diff;
- +
- + for (p = callout; p != NULL; p = p->c_next)
- + p->c_time.tv_sec += new_diff - uptime_diff;
- + }
- + uptime_diff = new_diff;
- +}
-
- /*
- * timeout - Schedule a timeout.
- @@ -1337,6 +1370,8 @@ calltimeout()
- {
- struct callout *p;
-
- + check_time();
- +
- while (callout != NULL) {
- p = callout;
-
- @@ -1364,6 +1399,8 @@ timeleft(tvp)
- {
- if (callout == NULL)
- return NULL;
- +
- + check_time();
-
- gettimeofday(&timenow, NULL);
- tvp->tv_sec = callout->c_time.tv_sec - timenow.tv_sec;
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