From 004b09af900fac9ad2b20f09c69dc8d1daea4464 Mon Sep 17 00:00:00 2001
From: Jyrki Gadinger <nilsding@nilsding.org>
Date: Wed, 22 Oct 2025 17:18:22 +0200
Subject: [PATCH] fix(network): fall back to unlimited bandwidth in case the
 legacy global limit is still set

`-2` used to mean "Use global limits", which no longer exist since

3.17.0.  As any negative value results in the auto bandwidth limiter to

engage, this could result in unexpected slower sync speeds after a

client upgrade.

Let's just keep handling that value and assume that we want to use

unlimited bandwidth.

Fixes #8743

Signed-off-by: Jyrki Gadinger <nilsding@nilsding.org>

[skip ci]
---
 src/libsync/account.cpp | 20 +++++++++++++++++---
 src/libsync/account.h   |  1 +
 2 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/src/libsync/account.cpp b/src/libsync/account.cpp
index b957894bfe..2293fd8c75 100644
--- a/src/libsync/account.cpp
+++ b/src/libsync/account.cpp
@@ -1314,7 +1314,14 @@ void Account::setUploadLimitSetting(const AccountNetworkTransferLimitSetting set
         return;
     }
 
-    _uploadLimitSetting = setting;
+    auto targetSetting = setting;
+
+    if (setting == AccountNetworkTransferLimitSetting::LegacyGlobalLimit) {
+        qCInfo(lcAccount) << "Upload limit setting was requested to be set to the legacy global limit, falling back to unlimited";
+        targetSetting = AccountNetworkTransferLimitSetting::NoLimit;
+    }
+
+    _uploadLimitSetting = targetSetting;
     emit uploadLimitSettingChanged();
 }
 
@@ -1328,8 +1335,15 @@ void Account::setDownloadLimitSetting(const AccountNetworkTransferLimitSetting s
     if (setting == _downloadLimitSetting) {
         return;
     }
-    
-    _downloadLimitSetting = setting;
+
+    auto targetSetting = setting;
+
+    if (setting == AccountNetworkTransferLimitSetting::LegacyGlobalLimit) {
+        qCInfo(lcAccount) << "Download limit setting was requested to be set to the legacy global limit, falling back to unlimited";
+        targetSetting = AccountNetworkTransferLimitSetting::NoLimit;
+    }
+
+    _downloadLimitSetting = targetSetting;
     emit downloadLimitSettingChanged();
 }
 
diff --git a/src/libsync/account.h b/src/libsync/account.h
index 0e1b38d8cd..9746f24934 100644
--- a/src/libsync/account.h
+++ b/src/libsync/account.h
@@ -98,6 +98,7 @@ class OWNCLOUDSYNC_EXPORT Account : public QObject
 
 public:
     enum class AccountNetworkTransferLimitSetting {
+        LegacyGlobalLimit = -2, // Until 3.17.0 a value of -2 was interpreted as "Use global network settings", it's now used to fall back to "No limit".  See also GH#8743
         AutoLimit = -1, // Value under 0 is interpreted as auto in general
         NoLimit,
         ManualLimit,