Open-Mesh » batman-adv

Does the code in batadv_tt_local_add allow concurrent unprotected updates to tt_local->common.flags and tt_global->common.flags?

Because batadv_interface_tx (the ndo_start_xmit handler) is configured with lltx = true, it executes without the netdev tx lock. This could allow multiple CPUs processing outgoing packets from the same client MAC to call batadv_tt_local_add() concurrently.

A concurrent execution could cause one CPU to overwrite the flag updates of another via non-atomic read-modify-write operations (|= and &=). For example, if CPU A clears the BATADV_TT_CLIENT_ROAM flag while CPU B simultaneously sets the BATADV_TT_CLIENT_WIFI flag, could the ROAM flag clearance be permanently lost, leaving the client stuck in an incorrect roaming state?

See https://sashiko.dev/#/patchset/20260603072527.174487-1-sw@simonwunderlich.de?part=15