From 0fa4ab3fc8efce8bbf87c522ce9ce1344d98d9fb Mon Sep 17 00:00:00 2001
From: Ludvig Strigeus <strigeus@gmail.com>
Date: Fri, 19 Oct 2018 13:40:39 +0200
Subject: [PATCH] Allow dns request to be reattempted right away

---
 TunSafe.vcxproj         |  1 +
 TunSafe.vcxproj.filters |  3 +++
 tunsafe_dnsresolve.h    |  6 +++++-
 tunsafe_ipaddr.cpp      | 42 ++++++++++++++++++++++++++++++++++-------
 4 files changed, 44 insertions(+), 8 deletions(-)

diff --git a/TunSafe.vcxproj b/TunSafe.vcxproj
index 94651a4..ea793d3 100644
--- a/TunSafe.vcxproj
+++ b/TunSafe.vcxproj
@@ -195,6 +195,7 @@
     <ClInclude Include="crypto\blake2s\blake2s.h" />
     <ClInclude Include="crypto\chacha20poly1305.h" />
     <ClInclude Include="crypto\siphash\siphash.h" />
+    <ClInclude Include="tunsafe_dnsresolve.h" />
     <ClInclude Include="tunsafe_endian.h" />
     <ClInclude Include="ipzip2\ipzip2.h" />
     <ClInclude Include="netapi.h" />
diff --git a/TunSafe.vcxproj.filters b/TunSafe.vcxproj.filters
index a035bde..77805db 100644
--- a/TunSafe.vcxproj.filters
+++ b/TunSafe.vcxproj.filters
@@ -123,6 +123,9 @@
     <ClInclude Include="tunsafe_ipaddr.h">
       <Filter>Source Files</Filter>
     </ClInclude>
+    <ClInclude Include="tunsafe_dnsresolve.h">
+      <Filter>Source Files</Filter>
+    </ClInclude>
   </ItemGroup>
   <ItemGroup>
     <ClCompile Include="stdafx.cpp">
diff --git a/tunsafe_dnsresolve.h b/tunsafe_dnsresolve.h
index f3a1ff4..5733057 100644
--- a/tunsafe_dnsresolve.h
+++ b/tunsafe_dnsresolve.h
@@ -8,12 +8,14 @@ class DnsBlocker;
 
 class DnsResolverCanceller {
 public:
-  DnsResolverCanceller() : cancel_(false) {}
+  DnsResolverCanceller() : cancel_(false), cancel_sleep_once_(false) {}
   void Cancel();
+  void CancelSleepOnce();
   void Reset() { cancel_ = false; }
   bool is_cancelled() { return cancel_; }
 public:
   bool cancel_;
+  bool cancel_sleep_once_;
   ConditionVariable condvar_;
 };
 
@@ -25,6 +27,7 @@ public:
   bool Resolve(const char *hostname, IpAddr *result);
   void ClearCache();
 
+  void RetryNow();
   void Cancel() { token_.Cancel(); }
   void ResetCancel() { token_.Reset(); }
 private:
@@ -36,6 +39,7 @@ private:
   std::vector<Entry> cache_;
   DnsBlocker *dns_blocker_;
   DnsResolverCanceller token_;
+  int retry_attempt_;
 };
 
 #endif  // TUNSAFE_DNSRESOLVE_H_
\ No newline at end of file
diff --git a/tunsafe_ipaddr.cpp b/tunsafe_ipaddr.cpp
index aed2abf..94b0809 100644
--- a/tunsafe_ipaddr.cpp
+++ b/tunsafe_ipaddr.cpp
@@ -140,6 +140,15 @@ void DnsResolverCanceller::Cancel() {
   g_dns_mutex.Release();
 }
 
+void DnsResolverCanceller::CancelSleepOnce() {
+  g_dns_mutex.Acquire();
+  cancel_sleep_once_ = true;
+  condvar_.Wake();
+  g_dns_mutex.Release();
+}
+
+
+
 bool DnsResolverThread::Resolve(const char *hostname, IpAddr *result, DnsResolverCanceller *token) {
   if (token->cancel_)
     return false;
@@ -188,15 +197,23 @@ void DnsResolverThread::ThreadMain() {
     struct addrinfo hints = {0};
     hints.ai_family = PF_UNSPEC;
     hints.ai_socktype = SOCK_DGRAM;
+    // AI_V4MAPPED doesn't work on Android?!
+#if defined(OS_IOS)
     hints.ai_flags = AI_DEFAULT;
+#else
+    hints.ai_flags = AI_ADDRCONFIG ;
+#endif
     ai = NULL;
-    if (getaddrinfo(e->hostname, NULL, &hints, &ai) != 0)
+    int r =  getaddrinfo(e->hostname, NULL, &hints, &ai);
+    if (r != 0)
       ai = NULL;
+//    RINFO("r=%d errno=%d, %s", r, errno, gai_strerror(r));
     //    he = gethostbyname(e->hostname);
     g_dns_mutex.Acquire();
     if (e->state == Entry::CANCELLED) {
       delete e;
     } else {
+//      RINFO("ai=%p, family=%d", ai, ai ? ai->ai_family : -1);
       if (ai) {
         e->result->sin.sin_family = ai->ai_family;
         e->result->sin.sin_port = 0;
@@ -228,6 +245,11 @@ static bool InterruptibleSleep(int delay, DnsResolverCanceller *token) {
   g_dns_mutex.Acquire();
   uint32 time_at_start = (uint32)OsGetMilliseconds();
   while (delay > 0 && !token->cancel_) {
+    if (token->cancel_sleep_once_) {
+      token->cancel_sleep_once_ = false;
+      delay = 0;
+      break;
+    }
     token->condvar_.WaitTimed(&g_dns_mutex, delay);
     uint32 now = (uint32)OsGetMilliseconds();
     delay -= (now - time_at_start);
@@ -249,10 +271,11 @@ void DnsResolver::ClearCache() {
 }
 
 bool DnsResolver::Resolve(const char *hostname, IpAddr *result) {
-  int attempt = 0;
-  static const uint8 retry_delays[] = {1, 2, 3, 5, 10};
+  static const uint8 retry_delays[] = {1, 2, 3, 5, 10, 20, 40, 60, 120, 180, 255};
   char buf[kSizeOfAddress];
 
+  retry_attempt_ = 0;
+
   memset(result, 0, sizeof(IpAddr));
 
   // First check cache
@@ -283,15 +306,20 @@ bool DnsResolver::Resolve(const char *hostname, IpAddr *result) {
     if (token_.is_cancelled())
       return false;
 
-    RINFO("Unable to resolve %s. Trying again in %d second(s)", hostname, retry_delays[attempt]);
-    if (!InterruptibleSleep(retry_delays[attempt] * 1000, &token_))
+    RINFO("Unable to resolve %s. Trying again in %d second(s)", hostname, retry_delays[retry_attempt_]);
+    if (!InterruptibleSleep(retry_delays[retry_attempt_] * 1000, &token_))
       return false;
 
-    if (attempt != ARRAY_SIZE(retry_delays) - 1)
-      attempt++;
+    if (retry_attempt_ != ARRAY_SIZE(retry_delays) - 1)
+      retry_attempt_++;
   }
 }
 
+void DnsResolver::RetryNow() {
+  retry_attempt_ = 0;
+  token_.CancelSleepOnce();
+}
+
 // Parse an IPV4 address into sin, doing NAT64 translation if applicable (on IOS)
 static bool ParseIpv4WithNAT64Translation(const char *s, IpAddr *sin, int flags) {
   // First verify it's actually a valid ipv4 address to prevent getaddrinfo from doing a slow resolve