applications: serial_lte_modem: Drop AT responsed to closed DLCI

SeppoTakalo · SeppoTakalo · commit d239cae02e1d · 2025-03-20T13:02:58.000+02:00
If DLCI channel for AT commands has been closed, avoid sending
data to the pipe.

Channel is resumed once remote end connects to the DLCI channel.

Signed-off-by: Seppo Takalo &lt;seppo.takalo@nordicsemi.no&gt;
diff --git a/applications/serial_lte_modem/src/slm_cmux.c b/applications/serial_lte_modem/src/slm_cmux.c
@@ -114,6 +114,10 @@ static void init_dlci(size_t dlci_idx, uint16_t recv_buf_size,
 
 static int cmux_write_at_channel(const uint8_t *data, size_t len)
 {
+	if (cmux.dlcis[cmux.at_channel].instance.state != MODEM_CMUX_DLCI_STATE_OPEN) {
+		return 0;
+	}
+
 	int ret = modem_pipe_transmit(cmux.dlcis[cmux.at_channel].pipe, data, len);
 
 	if (ret != len) {

Original file line number	Diff line number	Diff line change
`@@ -114,6 +114,10 @@ static void init_dlci(size_t dlci_idx, uint16_t recv_buf_size,`
`114`	`114`
`115`	`115`	`static int cmux_write_at_channel(const uint8_t *data, size_t len)`
`116`	`116`	`{`
	`117`	`+ if (cmux.dlcis[cmux.at_channel].instance.state != MODEM_CMUX_DLCI_STATE_OPEN) {`
	`118`	`+ return 0;`
	`119`	`+ }`
	`120`	`+`
`117`	`121`	`int ret = modem_pipe_transmit(cmux.dlcis[cmux.at_channel].pipe, data, len);`
`118`	`122`
`119`	`123`	`if (ret != len) {`