receiver: Avoid division by 0 after system start if CLOCK_MONOTONIC is used

Depending on how CLOCK_MONOTONIC is implemented, time_monotonic() might
return 0 within 1 second after the system is started.  If that's the
case, we just default to 0 for now to avoid a crash (doesn't "hide" the
system time, but it's only the uptime anyway in this case).

Closes strongswan/strongswan#435.

diff --git a/src/libcharon/network/receiver.c b/src/libcharon/network/receiver.c
index b191ed8d6a84afc383f3eeb05b490083361b1188..ab520fea6121211870830eee1b76cbe4ba61339b 100644 (file)
--- a/src/libcharon/network/receiver.c
+++ b/src/libcharon/network/receiver.c
@@ -629,7 +629,7 @@ receiver_t *receiver_create()
                },
                .esp_cb_mutex = mutex_create(MUTEX_TYPE_DEFAULT),
                .secret_switch = now,
-               .secret_offset = random() % now,
+               .secret_offset = now ? random() % now : 0,
        );
 
        if (lib->settings->get_bool(lib->settings,