XPost: linux.debian.bugs.dist   
   From: carnil@debian.org   
      
   Control: tags -1 + moreinfo   
      
   Hi George,   
      
   Thanks for your report.   
      
   On Thu, Feb 12, 2026 at 12:41:28PM +0300, George Koukiss wrote:   
   > Package: src:linux   
   > Version: 6.12.69-1   
   > Severity: important   
   >   
   > Dear Maintainer,   
   >   
   > After upgrading from kernel 6.12.63 to 6.12.69 on Debian 13, I am   
   > experiencing constant network disconnects (link flapping) on my Ethernet   
   > interface.   
   >   
   > Hardware:   
   > Realtek Semiconductor Co., Ltd. RTL8111/8168/8211/8411 PCI Express Gigabit   
   > Ethernet Controller [10ec:8168] (rev 11)   
   >   
   > Symptoms:   
   > The dmesg log shows the link going Up and Down repeatedly every few   
   > seconds/minutes. Sometimes it downgrades from 1Gbps to 100Mbps before   
   > dropping again.   
   >   
   > Logs (dmesg):   
   > [ 5202.128177] r8169 0000:03:00.0 enp3s0: Link is Down   
   > [ 5205.071512] r8169 0000:03:00.0 enp3s0: Link is Up - 1Gbps/Full   
   > [ 5205.655468] r8169 0000:03:00.0 enp3s0: Link is Down   
   > [ 5223.796420] r8169 0000:03:00.0 enp3s0: Link is Up - 100Mbps/Full   
   >   
   > Troubleshooting:   
   > 1. Booting back to kernel 6.12.63-1 resolves the issue completely (no Link   
   > Down events).   
   > 2. The issue persists across different cables/ports on the newer kernel.   
   > 3. This appears to be a regression in the r8169 driver between .63 and .69.   
   >   
   > Please let me know if you need more logs or testing.   
      
   It would be great if you could bisect the problem. That would involve   
   compiling and testing a few kernels:   
      
       git clone --single-branch -b linux-6.12.y https://git.kernel   
   org/pub/scm/linux/kernel/git/stable/linux-stable.git   
       cd linux-stable   
       git checkout v6.12.63   
       cp /boot/config-$(uname -r) .config   
       yes '' | make localmodconfig   
       make savedefconfig   
       mv defconfig arch/x86/configs/my_defconfig   
      
       # test 6.12.63 to ensure this is "good"   
       make my_defconfig   
       make -j $(nproc) bindeb-pkg   
       ... install the resulting .deb package and confirm the problem does not   
   exist   
      
       # test 6.12.69 to ensure this is "bad"   
       git checkout v6.12.35   
       make my_defconfig   
       make -j $(nproc) bindeb-pkg   
       ... install the resulting .deb package and confirm the problem exists.   
      
   With that confirmed, the bisection can start:   
      
       git bisect start   
       git bisect good v6.12.63   
       git bisect bad v6.12.69   
      
   In each bisection step git checks out a state between the oldest   
   known-bad and the newest known-good commit. In each step test using:   
      
       make my_defconfig   
       make -j $(nproc) bindeb-pkg   
       ... install, verify if problem exists   
      
   and if the problem is hit run:   
      
       git bisect bad   
      
   and if the problem doesn't trigger run:   
      
       git bisect good   
      
   . Please pay attention to always select the just built kernel for   
   booting, it won't always be the default kernel picked up by grub.   
      
   Iterate until git announces to have identified the first bad commit.   
      
   Then provide the output of   
      
       git bisect log   
      
   In the course of the bisection you might have to uninstall previous   
   kernels again to not exhaust the disk space in /boot. Also in the end   
   uninstall all self-built kernels again.   
      
   Regards,   
   Salvatore   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)