From: Andy Roulin Date: Sun, 5 Apr 2026 20:52:23 +0000 (-0700) Subject: docs: net: bridge: document stp_mode attribute X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=c4f2aab121cdc8400dcd5ec3cc0aa0fb3c06694f;p=thirdparty%2Fkernel%2Flinux.git docs: net: bridge: document stp_mode attribute Add documentation for the IFLA_BR_STP_MODE bridge attribute in the "User space STP helper" section of the bridge documentation. Reference the BR_STP_MODE_* values via kernel-doc and describe the use case for network namespace environments. Reviewed-by: Ido Schimmel Acked-by: Nikolay Aleksandrov Signed-off-by: Andy Roulin Link: https://patch.msgid.link/20260405205224.3163000-3-aroulin@nvidia.com Signed-off-by: Jakub Kicinski --- diff --git a/Documentation/networking/bridge.rst b/Documentation/networking/bridge.rst index ef8b73e157b2..c1e6ea52c9e5 100644 --- a/Documentation/networking/bridge.rst +++ b/Documentation/networking/bridge.rst @@ -148,6 +148,28 @@ called by the kernel when STP is enabled/disabled on a bridge stp_state <0|1>``). The kernel enables user_stp mode if that command returns 0, or enables kernel_stp mode if that command returns any other value. +STP mode selection +------------------ + +The ``IFLA_BR_STP_MODE`` bridge attribute allows explicit control over how +STP operates when enabled, bypassing the ``/sbin/bridge-stp`` helper +entirely for the ``user`` and ``kernel`` modes. + +.. kernel-doc:: include/uapi/linux/if_link.h + :doc: Bridge STP mode values + +The default mode is ``BR_STP_MODE_AUTO``, which preserves the traditional +behavior of invoking the ``/sbin/bridge-stp`` helper. The ``user`` and +``kernel`` modes are particularly useful in network namespace environments +where the helper mechanism is not available, as ``call_usermodehelper()`` +is restricted to the initial network namespace. + +Example:: + + ip link set dev br0 type bridge stp_mode user stp_state 1 + +The mode can only be changed while STP is disabled. + VLAN ====