From: Daniel Starke <daniel.starke@xxxxxxxxxxx> The structure gsm_mux contains the 'unsupported' field. However, there is currently no place in the code which increases this counter. Increase the 'unsupported' statistics counter in the following case: - an unsupported frame type has been requested by the peer via parameter negotiation - a control frame with an unsupported but known command has been received Note that we have no means to detect an inconsistent/unsupported adaptation sufficient accuracy as this changes the structure of the UI/UIH frames. E.g. a one byte header is added in case of convergence layer type 2 instead of 1 and contains the modem signal octet with the state of the signal lines. There is no checksum or other value which indicates of this field is correct or should be present. Therefore, we can only assume protocol correctness here. See also 'gsm_dlci_data()' where this is handled. Signed-off-by: Daniel Starke <daniel.starke@xxxxxxxxxxx> --- drivers/tty/n_gsm.c | 3 +++ 1 file changed, 3 insertions(+) v2 -> v3: No changes. Link: https://lore.kernel.org/all/20230420085017.7314-7-daniel.starke@xxxxxxxxxxx/ diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c index 10fc02133efa..941489230f9f 100644 --- a/drivers/tty/n_gsm.c +++ b/drivers/tty/n_gsm.c @@ -1590,6 +1590,7 @@ static int gsm_process_negotiation(struct gsm_mux *gsm, unsigned int addr, if (debug & DBG_ERRORS) pr_info("%s unsupported I frame request in PN\n", __func__); + gsm->unsupported++; return -EINVAL; default: if (debug & DBG_ERRORS) @@ -1897,6 +1898,8 @@ static void gsm_control_message(struct gsm_mux *gsm, unsigned int command, /* Optional unsupported commands */ case CMD_RPN: /* Remote port negotiation */ case CMD_SNC: /* Service negotiation command */ + gsm->unsupported++; + fallthrough; default: /* Reply to bad commands with an NSC */ buf[0] = command; -- 2.34.1
