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[v4,6/8] tty: n_gsm: increase gsm_mux unsupported counted where appropriate

Message ID 20230426080315.7595-6-daniel.starke@siemens.com
State Superseded
Headers show
Series [v4,1/8] tty: n_gsm: add restart flag to DLC specific ioctl config | expand

Commit Message

D. Starke April 26, 2023, 8:03 a.m. UTC 
From: Daniel Starke <daniel.starke@siemens.com>

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@siemens.com>
---
 drivers/tty/n_gsm.c | 3 +++
 1 file changed, 3 insertions(+)

v3 -> v4:
No changes.

Link: https://lore.kernel.org/all/20230424075251.5216-6-daniel.starke@siemens.com/
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Patch

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index 5b6a03668c78..42a8507aae4a 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;