Increase the maximum exponential backoff for DNS64 queries.oreo-mr1-dev

Currently, we only scale down DNS64 detection queries to one
every two minutes. This wastes power on true IPv6-only networks
such as the IMS networks of many operators. The only possible
benefit is that if a NAT64 were to appear on a previously
IPv6-only network, we detect it within two minutes.

Set the maximum backoff to one query per 30 minutes, while
maintaining the exponential backoff starting at 1 second.

(cherry picked from commit d1383bd268946d0c54e50e981b7d5c2c85509df4)

Bug: 62650901
Test: bullhead successfully detects NAT64 network
Change-Id: Ib6a7df5b25690d8b564079efbcaf8325c37c2e48

1 files changed, 5 insertions, 2 deletions

diff --git a/config.c b/config.c
index b147868..2d7085b 100644
--- a/config.c
+++ b/config.c
@@ -180,8 +180,11 @@ void dns64_detection(unsigned net_id) {
     logmsg(ANDROID_LOG_WARN, "dns64_detection -- error, sleeping for %d seconds", backoff_sleep);
     sleep(backoff_sleep);
     backoff_sleep *= 2;
-    if(backoff_sleep >= 120) {
-      backoff_sleep = 120;
+    if(backoff_sleep >= 1800) {
+      // Scale down to one DNS query per half hour. Unnecessary DNS queries waste power, and the
+      // benefit is minimal (basically, only limited to the case where a network goes from IPv6-only
+      // to IPv6 with NAT64).
+      backoff_sleep = 1800;
     }
   }
 }