Simplify and always retry DNS64 prefix discovery.android-cts-5.0_r9android-cts-5.0_r8android-cts-5.0_r7android-cts-5.0_r6android-cts-5.0_r5android-cts-5.0_r4android-cts-5.0_r3android-5.0.2_r3android-5.0.2_r1android-5.0.1_r1android-5.0.0_r7android-5.0.0_r6android-5.0.0_r5.1android-5.0.0_r5android-5.0.0_r4android-5.0.0_r3android-5.0.0_r2android-5.0.0_r1lollipop-releaselollipop-devlollipop-cts-release

  - Only request AAAAs for the IPv4-only hostname, since that's
    all the information being used.  Perhaps at some point in the
    future when _validation_ of the IPv4 address(es)'s presence
    within the IPv6 address(es) is being done this should be
    revisited.

  - Only use the first AAAA returned to find the DNS64 prefix.
    It's not clear how to properly resolve any potential DNS64
    prefix conflicts anyway.

  - Re-try DNS64 prefix discovery on any type of error.
    If clatd was started (presumably an IPv6-only network), retry
    DNS64 prefix discovery with exponential backoff.  Some
    "permanent" errors can be indistinguishable from transient
    errors (e.g. receiving an erroneous SERVFAIL from a DNS
    resolver, ...).

  - Fix-up back-off logic to not sleep 128 then 120, 120, ...
    :-)

Bug: 17569702
Change-Id: I226ea7772cd7c88d2b60153ef76e5435400e11aa

1 files changed, 2 insertions, 7 deletions

diff --git a/config.c b/config.c
index d8bec80..13889a0 100644
--- a/config.c
+++ b/config.c
@@ -165,16 +165,11 @@ void dns64_detection(unsigned net_id) {
       memcpy(&Global_Clatd_Config.plat_subnet, &tmp_ptr, sizeof(struct in6_addr));
       return;
     }
-    if(status < 0) {
-      logmsg(ANDROID_LOG_FATAL, "dns64_detection/no dns64, giving up\n");
-      exit(1);
-    }
-    logmsg(ANDROID_LOG_WARN, "dns64_detection failed, sleeping for %d seconds", backoff_sleep);
+    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;
-    } else {
-      backoff_sleep *= 2;
     }
   }
 }