[nrf toup] Derive BDX download timeout from session round trip

The OTA requestor used a fixed five-minute BDX download timeout, which is
far too long for sessions with short retransmission intervals and does
not adapt to the peer's advertised session parameters.
Compute the timeout from the session round trip time plus the expected
provider processing time.

Signed-off-by: Dominik Michalczyk <dominik.michalczyk@nordicsemi.no>

Author: dominik-michalczyk-nordic

src/app/clusters/ota-requestor/DefaultOTARequestor.cpp

@@ -31,6 +31,8 @@
 #include "BDXDownloader.h"
 #include "DefaultOTARequestor.h"
 
+#include <algorithm>
+
 namespace chip {
 
 using namespace app;
@@ -50,8 +52,22 @@ OTARequestorInterface * globalOTARequestorInstance = nullptr;
 // Global callback to call when globalOTARequestorInstance is set.
 void (*gInternalOnSetRequestorInstance)(OTARequestorInterface * instance) = nullptr;
 
-// Abort the QueryImage download request if there's been no progress for 5 minutes
-static constexpr System::Clock::Timeout kDownloadTimeoutSec = chip::System::Clock::Seconds32(5 * 60);
+// Maximum expected time for the provider to produce a BDX block.
+constexpr System::Clock::Timeout kExpectedProviderProcessingTime = System::Clock::Seconds16(2);
+
+// Number of round trips without any BDX progress that is treated as a stalled download.
+constexpr uint32_t kDownloadTimeoutRoundTrips = 2;
+
+// Upper bound on the download timeout.
+constexpr System::Clock::Timeout kMaxDownloadTimeout = System::Clock::Seconds32(5 * 60);
+
+static System::Clock::Timeout ComputeDownloadTimeout(const SessionHandle & session)
+{
+    System::Clock::Timeout roundTrip = session->ComputeRoundTripTimeout(kExpectedProviderProcessingTime, true);
+    System::Clock::Timeout timeout = std::min(roundTrip * kDownloadTimeoutRoundTrips, kMaxDownloadTimeout);
+
+    return timeout;
+}
 
 static void LogQueryImageResponse(const QueryImageResponse::DecodableType & response)
 {
@@ -831,7 +847,9 @@ CHIP_ERROR DefaultOTARequestor::StartDownload(Messaging::ExchangeManager & excha
     mBdxDownloader->SetMessageDelegate(&mBdxMessenger);
     mBdxDownloader->SetStateDelegate(this);
 
-    CHIP_ERROR err = mBdxDownloader->SetBDXParams(initOptions, kDownloadTimeoutSec);
+    const System::Clock::Timeout downloadTimeout = ComputeDownloadTimeout(sessionHandle);
+
+    CHIP_ERROR err = mBdxDownloader->SetBDXParams(initOptions, downloadTimeout);
     if (err == CHIP_NO_ERROR)
     {
         err = mBdxDownloader->BeginPrepareDownload();