Adjust shift cap for DNS backoff retries

Author: danielinux

src/test/unit/unit.c

@@ -353,6 +353,7 @@ Suite *wolf_suite(void)
     tcase_add_test(tc_utils, test_sock_opts_and_names);
     tcase_add_test(tc_utils, test_dns_send_query_errors);
     tcase_add_test(tc_utils, test_dns_schedule_timer_initial_jitter_and_cancel);
+    tcase_add_test(tc_utils, test_dns_schedule_timer_caps_large_retry_shift);
     tcase_add_test(tc_utils, test_dns_send_query_schedules_timeout);
     tcase_add_test(tc_utils, test_dns_resend_query_uses_stored_query_buffer);
     tcase_add_test(tc_utils, test_dns_abort_query_clears_timer_and_query_state);

src/test/unit/unit_tests_dns_dhcp.c

@@ -1902,6 +1902,20 @@ START_TEST(test_dns_schedule_timer_initial_jitter_and_cancel)
 }
 END_TEST
 
+START_TEST(test_dns_schedule_timer_caps_large_retry_shift)
+{
+    struct wolfIP s;
+
+    wolfIP_init(&s);
+    s.last_tick = 100U;
+    s.dns_retry_count = 64U;
+
+    dns_schedule_timer(&s);
+    ck_assert_int_ne(s.dns_timer, NO_TIMER);
+    ck_assert_uint_eq(find_timer_expiry(&s, s.dns_timer), UINT64_MAX);
+}
+END_TEST
+
 START_TEST(test_dns_send_query_schedules_timeout)
 {
     struct wolfIP s;

src/wolfip.c

@@ -6468,6 +6468,7 @@ static void dns_schedule_timer(struct wolfIP *s)
 {
     struct wolfIP_timer tmr = { };
     uint64_t interval = DNS_QUERY_TIMEOUT;
+    uint8_t shift;
 
     if (!s)
         return;
@@ -6478,7 +6479,11 @@ static void dns_schedule_timer(struct wolfIP *s)
         interval = DNS_QUERY_TIMEOUT_INITIAL +
                 (wolfIP_getrandom() % DNS_QUERY_TIMEOUT_INITIAL_JITTER);
     } else {
-        interval <<= s->dns_retry_count;
+        shift = s->dns_retry_count;
+        if (shift >= 64U || interval > (UINT64_MAX >> shift))
+            interval = UINT64_MAX - s->last_tick;
+        else
+            interval <<= shift;
     }
     tmr.expires = s->last_tick + interval;
     tmr.arg = s;