In sdp.c and rfcomm.c l2cap local_mtu is changed from within the _config_ind functions. This has the effect that the non-initiating l2cap peer fails to advertise it's mtu when it calls l2cap_config_req. This works fine for protocols whose mtu is less than or equal to the default mtu, but causes problems when mtus larged than the l2cap default of 672 bytes are required.
I'd suggest that the assignment of local_mtu is removed from the rfcomm_config_ind and sdp_config_ind, if only to help people who use the code as a basis for other protocols, and that the old D_RCV message about the local mtu is removed from test_config_ind.
All the best,