package/ppp/patches/206-compensate_time_change.patch

   1 pppd: Watch out for time warps
   2
   3 On many embedded systems there is no battery backed RTC and a proper system
   4 time only becomes available through NTP after establishing a connection.
   5
   6 When the clock suddenly jumps forward, the internal accounting (connect time)
   7 is confused resulting in unreliable data.
   8
   9 This patch implements periodic clock checking to look for time warps, if one
  10 is detected, the internal counters are adjusted accordingly.
  11
  12 Signed-off-by: Jo-Philipp Wich <jow@openwrt.org>
  13
  14 --- a/pppd/main.c
  15 +++ b/pppd/main.c
  16 @@ -90,6 +90,7 @@
  17  #include <sys/socket.h>
  18  #include <netinet/in.h>
  19  #include <arpa/inet.h>
  20 +#include <sys/sysinfo.h>
  21
  22  #include "pppd.h"
  23  #include "magic.h"
  24 @@ -228,6 +229,7 @@ static struct subprocess *children;
  25
  26  /* Prototypes for procedures local to this file. */
  27
  28 +static void check_time(void);
  29  static void setup_signals __P((void));
  30  static void create_pidfile __P((int pid));
  31  static void create_linkpidfile __P((int pid));
  32 @@ -535,6 +537,7 @@ main(argc, argv)
  33             info("Starting link");
  34         }
  35
  36 +       check_time();
  37         gettimeofday(&start_time, NULL);
  38         script_unsetenv("CONNECT_TIME");
  39         script_unsetenv("BYTES_SENT");
  40 @@ -1267,6 +1270,36 @@ struct   callout {
  41
  42  static struct callout *callout = NULL; /* Callout list */
  43  static struct timeval timenow;         /* Current time */
  44 +static long uptime_diff = 0;
  45 +static int uptime_diff_set = 0;
  46 +
  47 +static void check_time(void)
  48 +{
  49 +       long new_diff;
  50 +       struct timeval t;
  51 +       struct sysinfo i;
  52 +    struct callout *p;
  53 +
  54 +       gettimeofday(&t, NULL);
  55 +       sysinfo(&i);
  56 +       new_diff = t.tv_sec - i.uptime;
  57 +
  58 +       if (!uptime_diff_set) {
  59 +               uptime_diff = new_diff;
  60 +               uptime_diff_set = 1;
  61 +               return;
  62 +       }
  63 +
  64 +       if ((new_diff - 5 > uptime_diff) || (new_diff + 5 < uptime_diff)) {
  65 +               /* system time has changed, update counters and timeouts */
  66 +               info("System time change detected.");
  67 +               start_time.tv_sec += new_diff - uptime_diff;
  68 +
  69 +       for (p = callout; p != NULL; p = p->c_next)
  70 +                       p->c_time.tv_sec += new_diff - uptime_diff;
  71 +       }
  72 +       uptime_diff = new_diff;
  73 +}
  74
  75  /*
  76   * timeout - Schedule a timeout.
  77 @@ -1337,6 +1370,8 @@ calltimeout()
  78  {
  79      struct callout *p;
  80
  81 +       check_time();
  82 +
  83      while (callout != NULL) {
  84         p = callout;
  85
  86 @@ -1364,6 +1399,8 @@ timeleft(tvp)
  87  {
  88      if (callout == NULL)
  89         return NULL;
  90 +
  91 +       check_time();
  92
  93      gettimeofday(&timenow, NULL);
  94      tvp->tv_sec = callout->c_time.tv_sec - timenow.tv_sec;