From: Daniel Starke <[email protected]>
gsm_config and gsm_netconfig includes unused fields that have been included
to allow future extension without changing the structure size.
Unfortunately, no checks have been included for these field. The actual
value set by old user space code remains undefined.
This means that future extensions can not use these fields without breaking
old user space code which may set unexpected values.
Mark these fields accordingly to avoid breaking code changes.
Signed-off-by: Daniel Starke <[email protected]>
---
include/uapi/linux/gsmmux.h | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)
v3 -> v4:
No changes.
Link: https://lore.kernel.org/all/[email protected]/
diff --git a/include/uapi/linux/gsmmux.h b/include/uapi/linux/gsmmux.h
index cb8693b39cb7..785d6b253f6d 100644
--- a/include/uapi/linux/gsmmux.h
+++ b/include/uapi/linux/gsmmux.h
@@ -19,8 +19,7 @@ struct gsm_config
unsigned int mtu;
unsigned int k;
unsigned int i;
- unsigned int unused[8]; /* Padding for expansion without
- breaking stuff */
+ unsigned int unused[8]; /* Can not be used */
};
#define GSMIOC_GETCONF _IOR('G', 0, struct gsm_config)
@@ -29,9 +28,9 @@ struct gsm_config
struct gsm_netconfig {
unsigned int adaption; /* Adaption to use in network mode */
unsigned short protocol;/* Protocol to use - only ETH_P_IP supported */
- unsigned short unused2;
+ unsigned short unused2; /* Can not be used */
char if_name[IFNAMSIZ]; /* interface name format string */
- __u8 unused[28]; /* For future use */
+ __u8 unused[28]; /* Can not be used */
};
#define GSMIOC_ENABLE_NET _IOW('G', 2, struct gsm_netconfig)
--
2.34.1
From: Daniel Starke <[email protected]>
n_gsm is based on the 3GPP 07.010 and its newer version is the 3GPP 27.010.
See https://portal.3gpp.org/desktopmodules/Specifications/SpecificationDetails.aspx?specificationId=1516
The changes from 07.010 to 27.010 are non-functional. Therefore, I refer to
the newer 27.010 here. Chapters 5.4.6.3.4 and 5.1.8.1.3 describe the test
command which can be used to test the mux connection between both sides.
Currently, no algorithm is implemented to make use of this command. This
requires that each multiplexed upper layer protocol supervises the
underlying muxer connection to handle possible connection losses.
Introduce an ioctl commands and functions to optionally enable keep alive
handling via the test command as described in chapter 5.4.6.3.4. A single
incrementing octet is being used to distinguish between multiple retries.
Retry count and interval are taken from the general parameters N2 and T2.
Note that support for the test command is mandatory and already present in
the muxer implementation since the very first version.
Also note that the previous ioctl structure gsm_config cannot be extended
due to missing checks against zero of the field "unused".
Signed-off-by: Daniel Starke <[email protected]>
---
drivers/tty/n_gsm.c | 107 +++++++++++++++++++++++++++++++++++-
include/uapi/linux/gsmmux.h | 10 ++++
2 files changed, 115 insertions(+), 2 deletions(-)
v3 -> v4:
Changed gsm_config_ext() to perform the reserved fields check before taking
the keep-alive parameter as recommended in the review.
Link: https://lore.kernel.org/all/[email protected]/
diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index 5783801d6524..c94df9cd282f 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -318,6 +318,11 @@ struct gsm_mux {
struct gsm_control *pending_cmd;/* Our current pending command */
spinlock_t control_lock; /* Protects the pending command */
+ /* Keep-alive */
+ struct timer_list ka_timer; /* Keep-alive response timer */
+ u8 ka_num; /* Keep-alive match pattern */
+ int ka_retries; /* Keep-alive retry counter */
+
/* Configuration */
int adaption; /* 1 or 2 supported */
u8 ftype; /* UI or UIH */
@@ -325,6 +330,7 @@ struct gsm_mux {
unsigned int t3; /* Power wake-up timer in seconds. */
int n2; /* Retry count */
u8 k; /* Window size */
+ u32 keep_alive; /* Control channel keep-alive in ms */
/* Statistics (not currently exposed) */
unsigned long bad_fcs;
@@ -1897,11 +1903,13 @@ static void gsm_control_response(struct gsm_mux *gsm, unsigned int command,
const u8 *data, int clen)
{
struct gsm_control *ctrl;
+ struct gsm_dlci *dlci;
unsigned long flags;
spin_lock_irqsave(&gsm->control_lock, flags);
ctrl = gsm->pending_cmd;
+ dlci = gsm->dlci[0];
command |= 1;
/* Does the reply match our command */
if (ctrl != NULL && (command == ctrl->cmd || command == CMD_NSC)) {
@@ -1916,6 +1924,54 @@ static void gsm_control_response(struct gsm_mux *gsm, unsigned int command,
/* Or did we receive the PN response to our PN command */
} else if (command == CMD_PN) {
gsm_control_negotiation(gsm, 0, data, clen);
+ /* Or did we receive the TEST response to our TEST command */
+ } else if (command == CMD_TEST && clen == 1 && *data == gsm->ka_num) {
+ gsm->ka_retries = -1; /* trigger new keep-alive message */
+ if (dlci && !dlci->dead)
+ mod_timer(&gsm->ka_timer,
+ jiffies + gsm->keep_alive * HZ / 100);
+ }
+ spin_unlock_irqrestore(&gsm->control_lock, flags);
+}
+
+/**
+ * gsm_control_keep_alive - check timeout or start keep-alive
+ * @t: timer contained in our gsm object
+ *
+ * Called off the keep-alive timer expiry signaling that our link
+ * partner is not responding anymore. Link will be closed.
+ * This is also called to startup our timer.
+ */
+
+static void gsm_control_keep_alive(struct timer_list *t)
+{
+ struct gsm_mux *gsm = from_timer(gsm, t, ka_timer);
+ unsigned long flags;
+
+ spin_lock_irqsave(&gsm->control_lock, flags);
+ if (gsm->ka_num && gsm->ka_retries == 0) {
+ /* Keep-alive expired -> close the link */
+ if (debug & DBG_ERRORS)
+ pr_info("%s keep-alive timed out\n", __func__);
+ spin_unlock_irqrestore(&gsm->control_lock, flags);
+ if (gsm->dlci[0])
+ gsm_dlci_begin_close(gsm->dlci[0]);
+ return;
+ } else if (gsm->keep_alive && gsm->dlci[0] && !gsm->dlci[0]->dead) {
+ if (gsm->ka_retries > 0) {
+ /* T2 expired for keep-alive -> resend */
+ gsm->ka_retries--;
+ } else {
+ /* Start keep-alive timer */
+ gsm->ka_num++;
+ if (!gsm->ka_num)
+ gsm->ka_num++;
+ gsm->ka_retries = gsm->n2;
+ }
+ gsm_control_command(gsm, CMD_TEST, &gsm->ka_num,
+ sizeof(gsm->ka_num));
+ mod_timer(&gsm->ka_timer,
+ jiffies + gsm->t2 * HZ / 100);
}
spin_unlock_irqrestore(&gsm->control_lock, flags);
}
@@ -2061,8 +2117,10 @@ static void gsm_dlci_close(struct gsm_dlci *dlci)
/* Ensure that gsmtty_open() can return. */
tty_port_set_initialized(&dlci->port, false);
wake_up_interruptible(&dlci->port.open_wait);
- } else
+ } else {
+ del_timer(&dlci->gsm->ka_timer);
dlci->gsm->dead = true;
+ }
/* A DLCI 0 close is a MUX termination so we need to kick that
back to userspace somehow */
gsm_dlci_data_kick(dlci);
@@ -2078,6 +2136,8 @@ static void gsm_dlci_close(struct gsm_dlci *dlci)
static void gsm_dlci_open(struct gsm_dlci *dlci)
{
+ struct gsm_mux *gsm = dlci->gsm;
+
/* Note that SABM UA .. SABM UA first UA lost can mean that we go
open -> open */
del_timer(&dlci->t1);
@@ -2087,8 +2147,15 @@ static void gsm_dlci_open(struct gsm_dlci *dlci)
if (debug & DBG_ERRORS)
pr_debug("DLCI %d goes open.\n", dlci->addr);
/* Send current modem state */
- if (dlci->addr)
+ if (dlci->addr) {
gsm_modem_update(dlci, 0);
+ } else {
+ /* Start keep-alive control */
+ gsm->ka_num = 0;
+ gsm->ka_retries = -1;
+ mod_timer(&gsm->ka_timer,
+ jiffies + gsm->keep_alive * HZ / 100);
+ }
gsm_dlci_data_kick(dlci);
wake_up(&dlci->gsm->event);
}
@@ -2840,6 +2907,7 @@ static void gsm_cleanup_mux(struct gsm_mux *gsm, bool disc)
/* Finish outstanding timers, making sure they are done */
del_timer_sync(&gsm->kick_timer);
del_timer_sync(&gsm->t2_timer);
+ del_timer_sync(&gsm->ka_timer);
/* Finish writing to ldisc */
flush_work(&gsm->tx_work);
@@ -2987,6 +3055,7 @@ static struct gsm_mux *gsm_alloc_mux(void)
INIT_LIST_HEAD(&gsm->tx_data_list);
timer_setup(&gsm->kick_timer, gsm_kick_timer, 0);
timer_setup(&gsm->t2_timer, gsm_control_retransmit, 0);
+ timer_setup(&gsm->ka_timer, gsm_control_keep_alive, 0);
INIT_WORK(&gsm->tx_work, gsmld_write_task);
init_waitqueue_head(&gsm->event);
spin_lock_init(&gsm->control_lock);
@@ -3003,6 +3072,7 @@ static struct gsm_mux *gsm_alloc_mux(void)
gsm->mru = 64; /* Default to encoding 1 so these should be 64 */
gsm->mtu = 64;
gsm->dead = true; /* Avoid early tty opens */
+ gsm->keep_alive = 0; /* Disabled */
/* Store the instance to the mux array or abort if no space is
* available.
@@ -3138,6 +3208,29 @@ static int gsm_config(struct gsm_mux *gsm, struct gsm_config *c)
return 0;
}
+static void gsm_copy_config_ext_values(struct gsm_mux *gsm,
+ struct gsm_config_ext *ce)
+{
+ memset(ce, 0, sizeof(*ce));
+ ce->keep_alive = gsm->keep_alive;
+}
+
+static int gsm_config_ext(struct gsm_mux *gsm, struct gsm_config_ext *ce)
+{
+ unsigned int i;
+
+ /*
+ * Check that userspace doesn't put stuff in here to prevent breakages
+ * in the future.
+ */
+ for (i = 0; i < ARRAY_SIZE(ce->reserved); i++)
+ if (ce->reserved[i])
+ return -EINVAL;
+
+ gsm->keep_alive = ce->keep_alive;
+ return 0;
+}
+
/**
* gsmld_output - write to link
* @gsm: our mux
@@ -3456,6 +3549,7 @@ static int gsmld_ioctl(struct tty_struct *tty, unsigned int cmd,
unsigned long arg)
{
struct gsm_config c;
+ struct gsm_config_ext ce;
struct gsm_mux *gsm = tty->disc_data;
unsigned int base;
@@ -3472,6 +3566,15 @@ static int gsmld_ioctl(struct tty_struct *tty, unsigned int cmd,
case GSMIOC_GETFIRST:
base = mux_num_to_base(gsm);
return put_user(base + 1, (__u32 __user *)arg);
+ case GSMIOC_GETCONF_EXT:
+ gsm_copy_config_ext_values(gsm, &ce);
+ if (copy_to_user((void __user *)arg, &ce, sizeof(ce)))
+ return -EFAULT;
+ return 0;
+ case GSMIOC_SETCONF_EXT:
+ if (copy_from_user(&ce, (void __user *)arg, sizeof(ce)))
+ return -EFAULT;
+ return gsm_config_ext(gsm, &ce);
default:
return n_tty_ioctl_helper(tty, cmd, arg);
}
diff --git a/include/uapi/linux/gsmmux.h b/include/uapi/linux/gsmmux.h
index 785d6b253f6d..98de2570d79b 100644
--- a/include/uapi/linux/gsmmux.h
+++ b/include/uapi/linux/gsmmux.h
@@ -39,4 +39,14 @@ struct gsm_netconfig {
/* get the base tty number for a configured gsmmux tty */
#define GSMIOC_GETFIRST _IOR('G', 4, __u32)
+struct gsm_config_ext {
+ __u32 keep_alive; /* Control channel keep-alive in 1/100th of a
+ * second (0 to disable)
+ */
+ __u32 reserved[7]; /* For future use */
+};
+
+#define GSMIOC_GETCONF_EXT _IOR('G', 5, struct gsm_config_ext)
+#define GSMIOC_SETCONF_EXT _IOW('G', 6, struct gsm_config_ext)
+
#endif
--
2.34.1
From: Daniel Starke <[email protected]>
Add support for the TIOCMIWAIT ioctl on the virtual ttys. This enables the
user to wait for virtual modem signals like RING.
More work is needed to support also TIOCGICOUNT.
Signed-off-by: Daniel Starke <[email protected]>
---
drivers/tty/n_gsm.c | 33 ++++++++++++++++++++++++++++++++-
1 file changed, 32 insertions(+), 1 deletion(-)
v3 -> v4:
No changes.
Link: https://lore.kernel.org/all/[email protected]/
diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index 79efbfd27171..e405d76cb696 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -1542,6 +1542,7 @@ static void gsm_process_modem(struct tty_struct *tty, struct gsm_dlci *dlci,
if (brk & 0x01)
tty_insert_flip_char(&dlci->port, 0, TTY_BREAK);
dlci->modem_rx = mlines;
+ wake_up_interruptible(&dlci->gsm->event);
}
/**
@@ -2129,7 +2130,7 @@ static void gsm_dlci_close(struct gsm_dlci *dlci)
/* A DLCI 0 close is a MUX termination so we need to kick that
back to userspace somehow */
gsm_dlci_data_kick(dlci);
- wake_up(&dlci->gsm->event);
+ wake_up_all(&dlci->gsm->event);
}
/**
@@ -2339,6 +2340,7 @@ static void gsm_dlci_begin_close(struct gsm_dlci *dlci)
dlci->state = DLCI_CLOSING;
gsm_command(dlci->gsm, dlci->addr, DISC|PF);
mod_timer(&dlci->t1, jiffies + gsm->t1 * HZ / 100);
+ wake_up_interruptible(&gsm->event);
}
/**
@@ -3878,6 +3880,33 @@ static int gsm_modem_update(struct gsm_dlci *dlci, u8 brk)
return -EPROTONOSUPPORT;
}
+/**
+ * gsm_wait_modem_change - wait for modem status line change
+ * @dlci: channel
+ * @mask: modem status line bits
+ *
+ * The function returns if:
+ * - any given modem status line bit changed
+ * - the wait event function got interrupted (e.g. by a signal)
+ * - the underlying DLCI was closed
+ * - the underlying ldisc device was removed
+ */
+static int gsm_wait_modem_change(struct gsm_dlci *dlci, u32 mask)
+{
+ struct gsm_mux *gsm = dlci->gsm;
+ u32 old = dlci->modem_rx;
+ int ret;
+
+ ret = wait_event_interruptible(gsm->event, gsm->dead ||
+ dlci->state != DLCI_OPEN ||
+ (old ^ dlci->modem_rx) & mask);
+ if (gsm->dead)
+ return -ENODEV;
+ if (dlci->state != DLCI_OPEN)
+ return -EL2NSYNC;
+ return ret;
+}
+
static bool gsm_carrier_raised(struct tty_port *port)
{
struct gsm_dlci *dlci = container_of(port, struct gsm_dlci, port);
@@ -4137,6 +4166,8 @@ static int gsmtty_ioctl(struct tty_struct *tty,
gsm_destroy_network(dlci);
mutex_unlock(&dlci->mutex);
return 0;
+ case TIOCMIWAIT:
+ return gsm_wait_modem_change(dlci, (u32)arg);
default:
return -ENOIOCTLCMD;
}
--
2.34.1
From: Daniel Starke <[email protected]>
The status lines ring and carrier detect are used by the modem to signal
incoming calls (RING) or an established connection (CD). This is
implemented as physical lines on a standard RS232 connection. However,
the muxer protocol encodes these status lines as modem bits IC and DV.
These incoming lines are masked by tty driver (see tty_io.c) and cannot be
set by a user application.
Allow setting RING via TIOCM_OUT1 and CD via TIOCM_OUT2 to allow
implementation of a modem or modem emulator.
Signed-off-by: Daniel Starke <[email protected]>
---
drivers/tty/n_gsm.c | 5 +++++
1 file changed, 5 insertions(+)
v3 -> v4:
No changes.
Link: https://lore.kernel.org/all/[email protected]/
diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index c94df9cd282f..79efbfd27171 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -546,6 +546,11 @@ static u8 gsm_encode_modem(const struct gsm_dlci *dlci)
modembits |= MDM_IC;
if (dlci->modem_tx & TIOCM_CD || dlci->gsm->initiator)
modembits |= MDM_DV;
+ /* special mappings for passive side to operate as UE */
+ if (dlci->modem_tx & TIOCM_OUT1)
+ modembits |= MDM_IC;
+ if (dlci->modem_tx & TIOCM_OUT2)
+ modembits |= MDM_DV;
return modembits;
}
--
2.34.1
On Mon, Feb 06, 2023 at 12:46:04PM +0100, D. Starke wrote:
> From: Daniel Starke <[email protected]>
>
> n_gsm is based on the 3GPP 07.010 and its newer version is the 3GPP 27.010.
> See https://portal.3gpp.org/desktopmodules/Specifications/SpecificationDetails.aspx?specificationId=1516
> The changes from 07.010 to 27.010 are non-functional. Therefore, I refer to
> the newer 27.010 here. Chapters 5.4.6.3.4 and 5.1.8.1.3 describe the test
> command which can be used to test the mux connection between both sides.
>
> Currently, no algorithm is implemented to make use of this command. This
> requires that each multiplexed upper layer protocol supervises the
> underlying muxer connection to handle possible connection losses.
>
> Introduce an ioctl commands and functions to optionally enable keep alive
> handling via the test command as described in chapter 5.4.6.3.4. A single
> incrementing octet is being used to distinguish between multiple retries.
> Retry count and interval are taken from the general parameters N2 and T2.
>
> Note that support for the test command is mandatory and already present in
> the muxer implementation since the very first version.
> Also note that the previous ioctl structure gsm_config cannot be extended
> due to missing checks against zero of the field "unused".
>
> Signed-off-by: Daniel Starke <[email protected]>
> ---
> drivers/tty/n_gsm.c | 107 +++++++++++++++++++++++++++++++++++-
> include/uapi/linux/gsmmux.h | 10 ++++
> 2 files changed, 115 insertions(+), 2 deletions(-)
>
> v3 -> v4:
> Changed gsm_config_ext() to perform the reserved fields check before taking
> the keep-alive parameter as recommended in the review.
>
> Link: https://lore.kernel.org/all/[email protected]/
>
> diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
> index 5783801d6524..c94df9cd282f 100644
> --- a/drivers/tty/n_gsm.c
> +++ b/drivers/tty/n_gsm.c
> @@ -318,6 +318,11 @@ struct gsm_mux {
> struct gsm_control *pending_cmd;/* Our current pending command */
> spinlock_t control_lock; /* Protects the pending command */
>
> + /* Keep-alive */
> + struct timer_list ka_timer; /* Keep-alive response timer */
> + u8 ka_num; /* Keep-alive match pattern */
What do you mean by "pattern"?
> + int ka_retries; /* Keep-alive retry counter */
I know padding doesn't really matter much here, but you are adding holes
here to this structure, is that intentional?
And why "int"? What is the range here? And shouldn't this be "signed
int" to be explicit you set this to -1 in places (and what does -1
mean?)
> +
> /* Configuration */
> int adaption; /* 1 or 2 supported */
> u8 ftype; /* UI or UIH */
> @@ -325,6 +330,7 @@ struct gsm_mux {
> unsigned int t3; /* Power wake-up timer in seconds. */
> int n2; /* Retry count */
> u8 k; /* Window size */
> + u32 keep_alive; /* Control channel keep-alive in ms */
>
> /* Statistics (not currently exposed) */
> unsigned long bad_fcs;
> @@ -1897,11 +1903,13 @@ static void gsm_control_response(struct gsm_mux *gsm, unsigned int command,
> const u8 *data, int clen)
> {
> struct gsm_control *ctrl;
> + struct gsm_dlci *dlci;
> unsigned long flags;
>
> spin_lock_irqsave(&gsm->control_lock, flags);
>
> ctrl = gsm->pending_cmd;
> + dlci = gsm->dlci[0];
> command |= 1;
> /* Does the reply match our command */
> if (ctrl != NULL && (command == ctrl->cmd || command == CMD_NSC)) {
> @@ -1916,6 +1924,54 @@ static void gsm_control_response(struct gsm_mux *gsm, unsigned int command,
> /* Or did we receive the PN response to our PN command */
> } else if (command == CMD_PN) {
> gsm_control_negotiation(gsm, 0, data, clen);
> + /* Or did we receive the TEST response to our TEST command */
> + } else if (command == CMD_TEST && clen == 1 && *data == gsm->ka_num) {
> + gsm->ka_retries = -1; /* trigger new keep-alive message */
> + if (dlci && !dlci->dead)
> + mod_timer(&gsm->ka_timer,
> + jiffies + gsm->keep_alive * HZ / 100);
We can use 100 columns now if you want to.
> + }
> + spin_unlock_irqrestore(&gsm->control_lock, flags);
> +}
> +
> +/**
> + * gsm_control_keep_alive - check timeout or start keep-alive
> + * @t: timer contained in our gsm object
> + *
> + * Called off the keep-alive timer expiry signaling that our link
> + * partner is not responding anymore. Link will be closed.
> + * This is also called to startup our timer.
> + */
> +
> +static void gsm_control_keep_alive(struct timer_list *t)
> +{
> + struct gsm_mux *gsm = from_timer(gsm, t, ka_timer);
> + unsigned long flags;
> +
> + spin_lock_irqsave(&gsm->control_lock, flags);
> + if (gsm->ka_num && gsm->ka_retries == 0) {
> + /* Keep-alive expired -> close the link */
> + if (debug & DBG_ERRORS)
> + pr_info("%s keep-alive timed out\n", __func__);
info for a debugging error? no, please don't do that. Please fix up
the debugging mess in this driver, don't add to it.
> + spin_unlock_irqrestore(&gsm->control_lock, flags);
> + if (gsm->dlci[0])
> + gsm_dlci_begin_close(gsm->dlci[0]);
> + return;
> + } else if (gsm->keep_alive && gsm->dlci[0] && !gsm->dlci[0]->dead) {
> + if (gsm->ka_retries > 0) {
> + /* T2 expired for keep-alive -> resend */
> + gsm->ka_retries--;
> + } else {
> + /* Start keep-alive timer */
> + gsm->ka_num++;
> + if (!gsm->ka_num)
> + gsm->ka_num++;
> + gsm->ka_retries = gsm->n2;
> + }
> + gsm_control_command(gsm, CMD_TEST, &gsm->ka_num,
> + sizeof(gsm->ka_num));
> + mod_timer(&gsm->ka_timer,
> + jiffies + gsm->t2 * HZ / 100);
> }
> spin_unlock_irqrestore(&gsm->control_lock, flags);
> }
> @@ -2061,8 +2117,10 @@ static void gsm_dlci_close(struct gsm_dlci *dlci)
> /* Ensure that gsmtty_open() can return. */
> tty_port_set_initialized(&dlci->port, false);
> wake_up_interruptible(&dlci->port.open_wait);
> - } else
> + } else {
> + del_timer(&dlci->gsm->ka_timer);
> dlci->gsm->dead = true;
> + }
> /* A DLCI 0 close is a MUX termination so we need to kick that
> back to userspace somehow */
> gsm_dlci_data_kick(dlci);
> @@ -2078,6 +2136,8 @@ static void gsm_dlci_close(struct gsm_dlci *dlci)
>
> static void gsm_dlci_open(struct gsm_dlci *dlci)
> {
> + struct gsm_mux *gsm = dlci->gsm;
> +
> /* Note that SABM UA .. SABM UA first UA lost can mean that we go
> open -> open */
> del_timer(&dlci->t1);
> @@ -2087,8 +2147,15 @@ static void gsm_dlci_open(struct gsm_dlci *dlci)
> if (debug & DBG_ERRORS)
> pr_debug("DLCI %d goes open.\n", dlci->addr);
> /* Send current modem state */
> - if (dlci->addr)
> + if (dlci->addr) {
> gsm_modem_update(dlci, 0);
> + } else {
> + /* Start keep-alive control */
> + gsm->ka_num = 0;
> + gsm->ka_retries = -1;
> + mod_timer(&gsm->ka_timer,
> + jiffies + gsm->keep_alive * HZ / 100);
> + }
> gsm_dlci_data_kick(dlci);
> wake_up(&dlci->gsm->event);
> }
> @@ -2840,6 +2907,7 @@ static void gsm_cleanup_mux(struct gsm_mux *gsm, bool disc)
> /* Finish outstanding timers, making sure they are done */
> del_timer_sync(&gsm->kick_timer);
> del_timer_sync(&gsm->t2_timer);
> + del_timer_sync(&gsm->ka_timer);
>
> /* Finish writing to ldisc */
> flush_work(&gsm->tx_work);
> @@ -2987,6 +3055,7 @@ static struct gsm_mux *gsm_alloc_mux(void)
> INIT_LIST_HEAD(&gsm->tx_data_list);
> timer_setup(&gsm->kick_timer, gsm_kick_timer, 0);
> timer_setup(&gsm->t2_timer, gsm_control_retransmit, 0);
> + timer_setup(&gsm->ka_timer, gsm_control_keep_alive, 0);
> INIT_WORK(&gsm->tx_work, gsmld_write_task);
> init_waitqueue_head(&gsm->event);
> spin_lock_init(&gsm->control_lock);
> @@ -3003,6 +3072,7 @@ static struct gsm_mux *gsm_alloc_mux(void)
> gsm->mru = 64; /* Default to encoding 1 so these should be 64 */
> gsm->mtu = 64;
> gsm->dead = true; /* Avoid early tty opens */
> + gsm->keep_alive = 0; /* Disabled */
>
> /* Store the instance to the mux array or abort if no space is
> * available.
> @@ -3138,6 +3208,29 @@ static int gsm_config(struct gsm_mux *gsm, struct gsm_config *c)
> return 0;
> }
>
> +static void gsm_copy_config_ext_values(struct gsm_mux *gsm,
> + struct gsm_config_ext *ce)
> +{
> + memset(ce, 0, sizeof(*ce));
> + ce->keep_alive = gsm->keep_alive;
> +}
> +
> +static int gsm_config_ext(struct gsm_mux *gsm, struct gsm_config_ext *ce)
> +{
> + unsigned int i;
> +
> + /*
> + * Check that userspace doesn't put stuff in here to prevent breakages
> + * in the future.
> + */
> + for (i = 0; i < ARRAY_SIZE(ce->reserved); i++)
> + if (ce->reserved[i])
> + return -EINVAL;
> +
> + gsm->keep_alive = ce->keep_alive;
> + return 0;
> +}
> +
> /**
> * gsmld_output - write to link
> * @gsm: our mux
> @@ -3456,6 +3549,7 @@ static int gsmld_ioctl(struct tty_struct *tty, unsigned int cmd,
> unsigned long arg)
> {
> struct gsm_config c;
> + struct gsm_config_ext ce;
> struct gsm_mux *gsm = tty->disc_data;
> unsigned int base;
>
> @@ -3472,6 +3566,15 @@ static int gsmld_ioctl(struct tty_struct *tty, unsigned int cmd,
> case GSMIOC_GETFIRST:
> base = mux_num_to_base(gsm);
> return put_user(base + 1, (__u32 __user *)arg);
> + case GSMIOC_GETCONF_EXT:
> + gsm_copy_config_ext_values(gsm, &ce);
> + if (copy_to_user((void __user *)arg, &ce, sizeof(ce)))
> + return -EFAULT;
> + return 0;
> + case GSMIOC_SETCONF_EXT:
> + if (copy_from_user(&ce, (void __user *)arg, sizeof(ce)))
> + return -EFAULT;
> + return gsm_config_ext(gsm, &ce);
> default:
> return n_tty_ioctl_helper(tty, cmd, arg);
> }
> diff --git a/include/uapi/linux/gsmmux.h b/include/uapi/linux/gsmmux.h
> index 785d6b253f6d..98de2570d79b 100644
> --- a/include/uapi/linux/gsmmux.h
> +++ b/include/uapi/linux/gsmmux.h
> @@ -39,4 +39,14 @@ struct gsm_netconfig {
> /* get the base tty number for a configured gsmmux tty */
> #define GSMIOC_GETFIRST _IOR('G', 4, __u32)
>
> +struct gsm_config_ext {
> + __u32 keep_alive; /* Control channel keep-alive in 1/100th of a
> + * second (0 to disable)
> + */
> + __u32 reserved[7]; /* For future use */
say "must be set to 0"?
Where are you documenting this ioctl so userspace knows how to use it?
Where is the userspace tool that uses it?
thanks,
greg k-h
Thank you for this detailed review.
> > + u8 ka_num; /* Keep-alive match pattern */
>
> What do you mean by "pattern"?
Keep alive uses the test command which expects a byte pattern. This pattern
is simply echoed by the peer. We use a different pattern / byte value for
each keep-alive packet to distinguish between interval and re-sent
attempts. I will add ka_num to the commit message to make it clear that the
"single incrementing octet" refers to this field.
> > + int ka_retries; /* Keep-alive retry counter */
>
> I know padding doesn't really matter much here, but you are adding holes
> here to this structure, is that intentional?
This was not intentional. The same is already true for the ftype field and
I need ka_num to be 8-bit. Changing the field order does not really make
this any better. Therefore, I would like to keep it as it is.
> And why "int"? What is the range here? And shouldn't this be "signed
> int" to be explicit you set this to -1 in places (and what does -1
> mean?)
ka_retries takes the value from the field n2, which also happens to be
"int". I will add -1 to the field description as "not yet initialized".
I will also change it to "signed int" and add an appropriate cast from n2.
> > + /* Or did we receive the TEST response to our TEST command */
> > + } else if (command == CMD_TEST && clen == 1 && *data == gsm->ka_num) {
> > + gsm->ka_retries = -1; /* trigger new keep-alive message */
> > + if (dlci && !dlci->dead)
> > + mod_timer(&gsm->ka_timer,
> > + jiffies + gsm->keep_alive * HZ / 100);
>
> We can use 100 columns now if you want to.
I will change this for better readability.
> > + if (gsm->ka_num && gsm->ka_retries == 0) {
> > + /* Keep-alive expired -> close the link */
> > + if (debug & DBG_ERRORS)
> > + pr_info("%s keep-alive timed out\n", __func__);
>
> info for a debugging error? no, please don't do that. Please fix up
> the debugging mess in this driver, don't add to it.
I am aware that the current debugging concept of the driver does not align
with the kernel philosophy. However, this is the established way it is
handled in n_gsm right now. Cleaning this up should be done before adding
new concepts here. But not printing out any information in case of errors
does not help during use and development of/for this driver. Also note that
all these outputs are only enabled if explicitly set via kernel module
parameter. That means syslog does not get polluted if not intentionally
set so. Unfortunately, I do not have a better proposal for now as neither
ftrace nor dynamic debug are available to the normal Linux user.
> > +struct gsm_config_ext {
> > + __u32 keep_alive; /* Control channel keep-alive in 1/100th of a
> > + * second (0 to disable)
> > + */
> > + __u32 reserved[7]; /* For future use */
>
> say "must be set to 0"?
Right, I will add ", needs to be initialized to zero".
> Where are you documenting this ioctl so userspace knows how to use it?
> Where is the userspace tool that uses it?
I will extend the description and code example in
Documentation/driver-api/tty/n_gsm.rst. Should this go CC to
[email protected]?
Best regards,
Daniel Starke
On Thu, Feb 09, 2023 at 12:09:04PM +0000, Starke, Daniel wrote:
> > > + if (gsm->ka_num && gsm->ka_retries == 0) {
> > > + /* Keep-alive expired -> close the link */
> > > + if (debug & DBG_ERRORS)
> > > + pr_info("%s keep-alive timed out\n", __func__);
> >
> > info for a debugging error? no, please don't do that. Please fix up
> > the debugging mess in this driver, don't add to it.
>
> I am aware that the current debugging concept of the driver does not align
> with the kernel philosophy. However, this is the established way it is
> handled in n_gsm right now. Cleaning this up should be done before adding
> new concepts here. But not printing out any information in case of errors
> does not help during use and development of/for this driver. Also note that
> all these outputs are only enabled if explicitly set via kernel module
> parameter. That means syslog does not get polluted if not intentionally
> set so. Unfortunately, I do not have a better proposal for now as neither
> ftrace nor dynamic debug are available to the normal Linux user.
dynamic debug _is_ availble to the normal Linux user, and it's _the_
kernel debug facility and interface. To not use it is to somehow state
that this one tiny .c file is unique and special over the whole of the
rest of the kernel :)
I recommend just moving to the dynamic debug interface now and then
going forward, it's not going to be an issue at all.
> > > +struct gsm_config_ext {
> > > + __u32 keep_alive; /* Control channel keep-alive in 1/100th of a
> > > + * second (0 to disable)
> > > + */
> > > + __u32 reserved[7]; /* For future use */
> >
> > say "must be set to 0"?
>
> Right, I will add ", needs to be initialized to zero".
Use "must", that means more.
> > Where are you documenting this ioctl so userspace knows how to use it?
> > Where is the userspace tool that uses it?
>
> I will extend the description and code example in
> Documentation/driver-api/tty/n_gsm.rst. Should this go CC to
> [email protected]?
I don't know, if there is a man page for it, yes, if not, no need.
thanks,
greg k-h