Martin Schiller (6):
net/x25: handle additional netdev events
net/x25: make neighbour params configurable
net/x25: replace x25_kill_by_device with x25_kill_by_neigh
net/x25: support NETDEV_CHANGE notifier
net/lapb: support netdev events
net/lapb: fix t1 timer handling
include/net/x25.h | 10 +-
include/uapi/linux/x25.h | 56 ++++++-----
net/lapb/lapb_iface.c | 83 ++++++++++++++++
net/lapb/lapb_timer.c | 11 ++-
net/x25/af_x25.c | 206 +++++++++++++++++++++++++++++++--------
net/x25/x25_facilities.c | 6 +-
net/x25/x25_link.c | 142 +++++++++++++++++++++++----
net/x25/x25_subr.c | 22 ++++-
8 files changed, 445 insertions(+), 91 deletions(-)
--
2.20.1
Remove unnecessary function x25_kill_by_device.
Signed-off-by: Martin Schiller <[email protected]>
---
Change from v1:
fix 'subject_prefix' warning
---
net/x25/af_x25.c | 22 +++++-----------------
1 file changed, 5 insertions(+), 17 deletions(-)
diff --git a/net/x25/af_x25.c b/net/x25/af_x25.c
index 4c2a395fdbdb..25726120fcc7 100644
--- a/net/x25/af_x25.c
+++ b/net/x25/af_x25.c
@@ -212,22 +212,6 @@ static void x25_remove_socket(struct sock *sk)
write_unlock_bh(&x25_list_lock);
}
-/*
- * Kill all bound sockets on a dropped device.
- */
-static void x25_kill_by_device(struct net_device *dev)
-{
- struct sock *s;
-
- write_lock_bh(&x25_list_lock);
-
- sk_for_each(s, &x25_list)
- if (x25_sk(s)->neighbour && x25_sk(s)->neighbour->dev == dev)
- x25_disconnect(s, ENETUNREACH, 0, 0);
-
- write_unlock_bh(&x25_list_lock);
-}
-
/*
* Handle device status changes.
*/
@@ -273,7 +257,11 @@ static int x25_device_event(struct notifier_block *this, unsigned long event,
case NETDEV_DOWN:
pr_debug("X.25: got event NETDEV_DOWN for device: %s\n",
dev->name);
- x25_kill_by_device(dev);
+ nb = x25_get_neigh(dev);
+ if (nb) {
+ x25_kill_by_neigh(nb);
+ x25_neigh_put(nb);
+ }
x25_route_device_down(dev);
x25_link_device_down(dev);
break;
--
2.20.1
This makes it possible to handle carrier lost and detection.
In case of carrier lost, we shutdown layer 3 and flush all sessions.
Signed-off-by: Martin Schiller <[email protected]>
---
Change from v1:
fix 'subject_prefix' and 'checkpatch' warnings
---
net/x25/af_x25.c | 13 +++++++++++++
1 file changed, 13 insertions(+)
diff --git a/net/x25/af_x25.c b/net/x25/af_x25.c
index 25726120fcc7..6a95ca11694e 100644
--- a/net/x25/af_x25.c
+++ b/net/x25/af_x25.c
@@ -275,6 +275,19 @@ static int x25_device_event(struct notifier_block *this, unsigned long event,
dev->name);
x25_link_device_remove(dev);
break;
+ case NETDEV_CHANGE:
+ pr_debug("X.25: got event NETDEV_CHANGE for device: %s\n",
+ dev->name);
+ if (!netif_carrier_ok(dev)) {
+ pr_debug("X.25: Carrier lost -> set link state down: %s\n",
+ dev->name);
+ nb = x25_get_neigh(dev);
+ if (nb) {
+ x25_link_terminated(nb);
+ x25_neigh_put(nb);
+ }
+ }
+ break;
}
}
--
2.20.1
This makes it possible to handle carrier loss and detection.
In case of Carrier Loss, layer 2 is terminated
In case of Carrier Detection, we start timer t1 on a DCE interface,
and on a DTE interface we change to state LAPB_STATE_1 and start
sending SABM(E).
Signed-off-by: Martin Schiller <[email protected]>
---
Change from v1:
fix 'subject_prefix' and 'checkpatch' warnings
---
net/lapb/lapb_iface.c | 83 +++++++++++++++++++++++++++++++++++++++++++
1 file changed, 83 insertions(+)
diff --git a/net/lapb/lapb_iface.c b/net/lapb/lapb_iface.c
index 3c03f6512c5f..63124cdf1926 100644
--- a/net/lapb/lapb_iface.c
+++ b/net/lapb/lapb_iface.c
@@ -418,14 +418,97 @@ int lapb_data_transmit(struct lapb_cb *lapb, struct sk_buff *skb)
return used;
}
+/* Handle device status changes. */
+static int lapb_device_event(struct notifier_block *this, unsigned long event,
+ void *ptr)
+{
+ struct net_device *dev = ptr;
+ struct lapb_cb *lapb;
+
+ if (!net_eq(dev_net(dev), &init_net))
+ return NOTIFY_DONE;
+
+ if (dev->type == ARPHRD_X25) {
+ switch (event) {
+ case NETDEV_REGISTER:
+ lapb_dbg(0, "(%p): got event NETDEV_REGISTER for device: %s\n",
+ dev, dev->name);
+ break;
+ case NETDEV_POST_TYPE_CHANGE:
+ lapb_dbg(0, "(%p): got event NETDEV_POST_TYPE_CHANGE for device: %s\n",
+ dev, dev->name);
+ break;
+ case NETDEV_UP:
+ lapb_dbg(0, "(%p): got event NETDEV_UP for device: %s\n",
+ dev, dev->name);
+ break;
+ case NETDEV_GOING_DOWN:
+ lapb_dbg(0, "(%p): got event NETDEV_GOING_DOWN for device: %s\n",
+ dev, dev->name);
+ break;
+ case NETDEV_DOWN:
+ lapb_dbg(0, "(%p): got event NETDEV_DOWN for device: %s\n",
+ dev, dev->name);
+ break;
+ case NETDEV_PRE_TYPE_CHANGE:
+ lapb_dbg(0, "(%p): got event NETDEV_PRE_TYPE_CHANGE for device: %s\n",
+ dev, dev->name);
+ break;
+ case NETDEV_UNREGISTER:
+ lapb_dbg(0, "(%p): got event NETDEV_UNREGISTER for device: %s\n",
+ dev, dev->name);
+ break;
+ case NETDEV_CHANGE:
+ lapb_dbg(0, "(%p): got event NETDEV_CHANGE for device: %s\n",
+ dev, dev->name);
+ lapb = lapb_devtostruct(dev);
+ if (!lapb)
+ break;
+
+ if (!netif_carrier_ok(dev)) {
+ lapb_dbg(0, "(%p): Carrier lost -> Entering LAPB_STATE_0: %s\n",
+ dev, dev->name);
+ lapb_disconnect_indication(lapb, LAPB_OK);
+ lapb_clear_queues(lapb);
+ lapb->state = LAPB_STATE_0;
+ lapb->n2count = 0;
+ lapb_stop_t1timer(lapb);
+ lapb_stop_t2timer(lapb);
+ } else {
+ lapb_dbg(0, "(%p): Carrier detected: %s\n",
+ dev, dev->name);
+ if (lapb->mode & LAPB_DCE) {
+ lapb_start_t1timer(lapb);
+ } else {
+ if (lapb->state == LAPB_STATE_0) {
+ lapb->state = LAPB_STATE_1;
+ lapb_establish_data_link(lapb);
+ }
+ }
+ }
+ break;
+ }
+ }
+
+ return NOTIFY_DONE;
+}
+
+static struct notifier_block lapb_dev_notifier = {
+ .notifier_call = lapb_device_event,
+};
+
static int __init lapb_init(void)
{
+ register_netdevice_notifier(&lapb_dev_notifier);
+
return 0;
}
static void __exit lapb_exit(void)
{
WARN_ON(!list_empty(&lapb_list));
+
+ unregister_netdevice_notifier(&lapb_dev_notifier);
}
MODULE_AUTHOR("Jonathan Naylor <[email protected]>");
--
2.20.1
On Mon, Nov 16, 2020 at 6:01 AM Martin Schiller <[email protected]> wrote:
>
> This makes it possible to handle carrier loss and detection.
> In case of Carrier Loss, layer 2 is terminated
> In case of Carrier Detection, we start timer t1 on a DCE interface,
> and on a DTE interface we change to state LAPB_STATE_1 and start
> sending SABM(E).
> + lapb_dbg(0, "(%p): Carrier detected: %s\n",
> + dev, dev->name);
> + if (lapb->mode & LAPB_DCE) {
> + lapb_start_t1timer(lapb);
> + } else {
> + if (lapb->state == LAPB_STATE_0) {
> + lapb->state = LAPB_STATE_1;
> + lapb_establish_data_link(lapb);
> + }
> + }
Do you mean we will now automatically establish LAPB connections
without upper layers instructing us to do so?
If that is the case, is the one-byte header for instructing the LAPB
layer to connect / disconnect no longer needed?
fix t1 timer handling in LAPB_STATE_0:
o DTE interface changes immediately to LAPB_STATE_1 and start sending
SABM(E).
o DCE interface sends N2-times DM and changes to LAPB_STATE_1
afterwards if there is no response in the meantime.
Signed-off-by: Martin Schiller <[email protected]>
---
Change from v1:
fix 'subject_prefix' and 'checkpatch' warnings
---
net/lapb/lapb_timer.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)
diff --git a/net/lapb/lapb_timer.c b/net/lapb/lapb_timer.c
index 8f5b17001a07..baa247fe4ed0 100644
--- a/net/lapb/lapb_timer.c
+++ b/net/lapb/lapb_timer.c
@@ -85,11 +85,18 @@ static void lapb_t1timer_expiry(struct timer_list *t)
switch (lapb->state) {
/*
- * If we are a DCE, keep going DM .. DM .. DM
+ * If we are a DCE, send DM up to N2 times, then switch to
+ * STATE_1 and send SABM(E).
*/
case LAPB_STATE_0:
- if (lapb->mode & LAPB_DCE)
+ if (lapb->mode & LAPB_DCE &&
+ lapb->n2count != lapb->n2) {
+ lapb->n2count++;
lapb_send_control(lapb, LAPB_DM, LAPB_POLLOFF, LAPB_RESPONSE);
+ } else {
+ lapb->state = LAPB_STATE_1;
+ lapb_establish_data_link(lapb);
+ }
break;
/*
--
2.20.1
On 2020-11-16 21:16, Xie He wrote:
> Do you mean we will now automatically establish LAPB connections
> without upper layers instructing us to do so?
Yes, as soon as the physical link is established, the L2 and also the
L3 layer (restart handshake) is established.
In this context I also noticed that I should add another patch to this
patch-set to correct the restart handling.
As already mentioned I have a stack of fixes and extensions lying around
that I would like to get upstream.
> If that is the case, is the one-byte header for instructing the LAPB
> layer to connect / disconnect no longer needed?
The one-byte header is still needed to signal the status of the LAPB
connection to the upper layer.
On Tue, Nov 17, 2020 at 1:53 AM Martin Schiller <[email protected]> wrote:
>
> On 2020-11-16 21:16, Xie He wrote:
> > Do you mean we will now automatically establish LAPB connections
> > without upper layers instructing us to do so?
>
> Yes, as soon as the physical link is established, the L2 and also the
> L3 layer (restart handshake) is established.
I see. Looking at your code in Patch 1 and this patch, I see after the
device goes up, L3 code will instruct L2 to establish the connection,
and before the device goes down, L3 will instruct L2 to terminate the
connection. But if there is a carrier up/down event, L2 will
automatically handle this without being instructed by L3, and it will
establish the connection automatically when the carrier goes up. L2
will notify L3 on any L2 link status change.
Is this right? I think for a DCE, it doesn't need to initiate the L2
connection on device-up. It just needs to wait for a connection to
come. But L3 seems to be still instructing it to initiate the L2
connection. This seems to be a problem.
It feels unclean to me that the L2 connection will sometimes be
initiated by L3 and sometimes by L2 itself. Can we make L2 connections
always be initiated by L2 itself? If L3 needs to do something after L2
links up, L2 will notify it anyway.
> In this context I also noticed that I should add another patch to this
> patch-set to correct the restart handling.
Do you mean you will add code to let L3 restart any L3 connections
previously abnormally terminated after L2 link up?
> As already mentioned I have a stack of fixes and extensions lying around
> that I would like to get upstream.
Please do so! Thanks!
I previously found a locking problem in X.25 code and tried to address it in:
https://patchwork.kernel.org/project/netdevbpf/patch/[email protected]/
But later I found I needed to fix more code than I previously thought.
Do you already have a fix for this problem?
> > If that is the case, is the one-byte header for instructing the LAPB
> > layer to connect / disconnect no longer needed?
>
> The one-byte header is still needed to signal the status of the LAPB
> connection to the upper layer.
On Mon, Nov 16, 2020 at 6:00 AM Martin Schiller <[email protected]> wrote:
>
> This makes it possible to handle carrier lost and detection.
> In case of carrier lost, we shutdown layer 3 and flush all sessions.
>
> @@ -275,6 +275,19 @@ static int x25_device_event(struct notifier_block *this, unsigned long event,
> dev->name);
> x25_link_device_remove(dev);
> break;
> + case NETDEV_CHANGE:
> + pr_debug("X.25: got event NETDEV_CHANGE for device: %s\n",
> + dev->name);
> + if (!netif_carrier_ok(dev)) {
> + pr_debug("X.25: Carrier lost -> set link state down: %s\n",
> + dev->name);
> + nb = x25_get_neigh(dev);
> + if (nb) {
> + x25_link_terminated(nb);
> + x25_neigh_put(nb);
> + }
> + }
> + break;
> }
> }
I think L2 will notify L3 if the L2 connection is terminated. Is this
patch necessary?
On 2020-11-17 12:41, Xie He wrote:
> On Mon, Nov 16, 2020 at 6:00 AM Martin Schiller <[email protected]> wrote:
>>
>> This makes it possible to handle carrier lost and detection.
>> In case of carrier lost, we shutdown layer 3 and flush all sessions.
>>
>> @@ -275,6 +275,19 @@ static int x25_device_event(struct notifier_block
>> *this, unsigned long event,
>> dev->name);
>> x25_link_device_remove(dev);
>> break;
>> + case NETDEV_CHANGE:
>> + pr_debug("X.25: got event NETDEV_CHANGE for
>> device: %s\n",
>> + dev->name);
>> + if (!netif_carrier_ok(dev)) {
>> + pr_debug("X.25: Carrier lost -> set
>> link state down: %s\n",
>> + dev->name);
>> + nb = x25_get_neigh(dev);
>> + if (nb) {
>> + x25_link_terminated(nb);
>> + x25_neigh_put(nb);
>> + }
>> + }
>> + break;
>> }
>> }
>
> I think L2 will notify L3 if the L2 connection is terminated. Is this
> patch necessary?
Hmm... well I guess you're right. Admittedly, these patches were made
about 7 - 8 years ago and I have to keep thinking about them.
But I can't think of any situation where this patch should be necessary
at the moment.
I will drop this patch from the patch-set.
On 2020-11-17 12:32, Xie He wrote:
> On Tue, Nov 17, 2020 at 1:53 AM Martin Schiller <[email protected]> wrote:
>>
>> On 2020-11-16 21:16, Xie He wrote:
>> > Do you mean we will now automatically establish LAPB connections
>> > without upper layers instructing us to do so?
>>
>> Yes, as soon as the physical link is established, the L2 and also the
>> L3 layer (restart handshake) is established.
>
> I see. Looking at your code in Patch 1 and this patch, I see after the
> device goes up, L3 code will instruct L2 to establish the connection,
> and before the device goes down, L3 will instruct L2 to terminate the
> connection. But if there is a carrier up/down event, L2 will
> automatically handle this without being instructed by L3, and it will
> establish the connection automatically when the carrier goes up. L2
> will notify L3 on any L2 link status change.
>
> Is this right?
Yes, this is right.
> I think for a DCE, it doesn't need to initiate the L2
> connection on device-up. It just needs to wait for a connection to
> come. But L3 seems to be still instructing it to initiate the L2
> connection. This seems to be a problem.
The "ITU-T Recommendation X.25 (10/96) aka "Blue Book" [1] says under
point 2.4.4.1:
"Either the DTE or the DCE may initiate data link set-up."
Experience shows that there are also DTEs that do not establish a
connection themselves.
That is also the reason why I've added this patch:
https://patchwork.kernel.org/project/netdevbpf/patch/[email protected]/
> It feels unclean to me that the L2 connection will sometimes be
> initiated by L3 and sometimes by L2 itself. Can we make L2 connections
> always be initiated by L2 itself? If L3 needs to do something after L2
> links up, L2 will notify it anyway.
My original goal was to change as little as possible of the original
code. And in the original code the NETDEV_UP/NETDEV_DOWN events were/are
handled in L3. But it is of course conceivable to shift this to L2.
But you have to keep in mind that the X.25 L3 stack can also be used
with tap interfaces (e.g. for XOT), where you do not have a L2 at all.
>
>> In this context I also noticed that I should add another patch to this
>> patch-set to correct the restart handling.
>
> Do you mean you will add code to let L3 restart any L3 connections
> previously abnormally terminated after L2 link up?
No, I mean the handling of Restart Request and Restart Confirm is buggy
and needs to be fixed also.
>
>> As already mentioned I have a stack of fixes and extensions lying
>> around
>> that I would like to get upstream.
>
> Please do so! Thanks!
>
> I previously found a locking problem in X.25 code and tried to address
> it in:
> https://patchwork.kernel.org/project/netdevbpf/patch/[email protected]/
> But later I found I needed to fix more code than I previously thought.
> Do you already have a fix for this problem?
No, sorry.
[1] https://www.itu.int/rec/T-REC-X.25-199610-I/
On Tue, Nov 17, 2020 at 5:26 AM Martin Schiller <[email protected]> wrote:
>
> On 2020-11-17 12:32, Xie He wrote:
> >
> > I think for a DCE, it doesn't need to initiate the L2
> > connection on device-up. It just needs to wait for a connection to
> > come. But L3 seems to be still instructing it to initiate the L2
> > connection. This seems to be a problem.
>
> The "ITU-T Recommendation X.25 (10/96) aka "Blue Book" [1] says under
> point 2.4.4.1:
> "Either the DTE or the DCE may initiate data link set-up."
>
> Experience shows that there are also DTEs that do not establish a
> connection themselves.
>
> That is also the reason why I've added this patch:
> https://patchwork.kernel.org/project/netdevbpf/patch/[email protected]/
Yes, I understand that either the DTE or the DCE *may* initiate the L2
connection. This is also the way the current code (before this patch
set) works. But I see both the DTE and the DCE will try to initiate
the L2 connection after device-up, because according to your 1st
patch, L3 will always instruct L2 to do this on device-up. However,
looking at your 6th patch (in the link you gave), you seem to want the
DCE to wait for a while before initiating the connection by itself. So
I'm unclear which way you want to go. Making DCE initiate the L2
connection on device-up, or making DCE wait for a while before
initiating the L2 connection? I think the second way is more
reasonable.
> > It feels unclean to me that the L2 connection will sometimes be
> > initiated by L3 and sometimes by L2 itself. Can we make L2 connections
> > always be initiated by L2 itself? If L3 needs to do something after L2
> > links up, L2 will notify it anyway.
>
> My original goal was to change as little as possible of the original
> code. And in the original code the NETDEV_UP/NETDEV_DOWN events were/are
> handled in L3. But it is of course conceivable to shift this to L2.
I suggested moving L2 connection handling to L2 because I think having
both L2 and L3 to handle this makes the logic of the code too complex.
For example, after a device-up event, L3 will instruct L2 to initiate
the L2 connection. But L2 code has its own way of initiating
connections. For a DCE, L2 wants to wait a while before initiating the
connection. So currently L2 and L3 want to do things differently and
they are doing things at the same time.
> But you have to keep in mind that the X.25 L3 stack can also be used
> with tap interfaces (e.g. for XOT), where you do not have a L2 at all.
Can we treat XOT the same as LAPB? I think XOT should be considered a
L2 in this case. So maybe XOT can establish the TCP connection by
itself without being instructed by L3. I'm not sure if this is
feasible in practice but it'd be good if it is.
This also simplifies the L3 code.
On Mon, Nov 16, 2020 at 6:00 AM Martin Schiller <[email protected]> wrote:
>
> Remove unnecessary function x25_kill_by_device.
> -/*
> - * Kill all bound sockets on a dropped device.
> - */
> -static void x25_kill_by_device(struct net_device *dev)
> -{
> - struct sock *s;
> -
> - write_lock_bh(&x25_list_lock);
> -
> - sk_for_each(s, &x25_list)
> - if (x25_sk(s)->neighbour && x25_sk(s)->neighbour->dev == dev)
> - x25_disconnect(s, ENETUNREACH, 0, 0);
> -
> - write_unlock_bh(&x25_list_lock);
> -}
> -
> /*
> * Handle device status changes.
> */
> @@ -273,7 +257,11 @@ static int x25_device_event(struct notifier_block *this, unsigned long event,
> case NETDEV_DOWN:
> pr_debug("X.25: got event NETDEV_DOWN for device: %s\n",
> dev->name);
> - x25_kill_by_device(dev);
> + nb = x25_get_neigh(dev);
> + if (nb) {
> + x25_kill_by_neigh(nb);
> + x25_neigh_put(nb);
> + }
> x25_route_device_down(dev);
> x25_link_device_down(dev);
> break;
This patch might not be entirely necessary. x25_kill_by_neigh and
x25_kill_by_device are just two helper functions. One function takes
nb as the argument and the other one takes dev as the argument. But
they do almost the same things. It doesn't harm to keep both. In C++
we often have different functions with the same name doing almost the
same things.
The original code also seems to be a little more efficient than the new code.
On 2020-11-17 20:50, Xie He wrote:
> On Mon, Nov 16, 2020 at 6:00 AM Martin Schiller <[email protected]> wrote:
>>
>> Remove unnecessary function x25_kill_by_device.
>
>> -/*
>> - * Kill all bound sockets on a dropped device.
>> - */
>> -static void x25_kill_by_device(struct net_device *dev)
>> -{
>> - struct sock *s;
>> -
>> - write_lock_bh(&x25_list_lock);
>> -
>> - sk_for_each(s, &x25_list)
>> - if (x25_sk(s)->neighbour && x25_sk(s)->neighbour->dev
>> == dev)
>> - x25_disconnect(s, ENETUNREACH, 0, 0);
>> -
>> - write_unlock_bh(&x25_list_lock);
>> -}
>> -
>> /*
>> * Handle device status changes.
>> */
>> @@ -273,7 +257,11 @@ static int x25_device_event(struct notifier_block
>> *this, unsigned long event,
>> case NETDEV_DOWN:
>> pr_debug("X.25: got event NETDEV_DOWN for
>> device: %s\n",
>> dev->name);
>> - x25_kill_by_device(dev);
>> + nb = x25_get_neigh(dev);
>> + if (nb) {
>> + x25_kill_by_neigh(nb);
>> + x25_neigh_put(nb);
>> + }
>> x25_route_device_down(dev);
>> x25_link_device_down(dev);
>> break;
>
> This patch might not be entirely necessary. x25_kill_by_neigh and
> x25_kill_by_device are just two helper functions. One function takes
> nb as the argument and the other one takes dev as the argument. But
> they do almost the same things. It doesn't harm to keep both. In C++
> we often have different functions with the same name doing almost the
> same things.
>
Well I don't like to have 2 functions doing the same thing.
But after another look at this code, I've found that I also need to
remove the call to x25_clear_forward_by_dev() in the function
x25_route_device_down(). Otherwise, it will be called twice.
> The original code also seems to be a little more efficient than the new
> code.
The only difference would be the x25_get_neigh() and x25_neigh_put()
calls. That shouldn't cost to much.
On 2020-11-17 19:28, Xie He wrote:
> On Tue, Nov 17, 2020 at 5:26 AM Martin Schiller <[email protected]> wrote:
>>
>> On 2020-11-17 12:32, Xie He wrote:
>> >
>> > I think for a DCE, it doesn't need to initiate the L2
>> > connection on device-up. It just needs to wait for a connection to
>> > come. But L3 seems to be still instructing it to initiate the L2
>> > connection. This seems to be a problem.
>>
>> The "ITU-T Recommendation X.25 (10/96) aka "Blue Book" [1] says under
>> point 2.4.4.1:
>> "Either the DTE or the DCE may initiate data link set-up."
>>
>> Experience shows that there are also DTEs that do not establish a
>> connection themselves.
>>
>> That is also the reason why I've added this patch:
>> https://patchwork.kernel.org/project/netdevbpf/patch/[email protected]/
>
> Yes, I understand that either the DTE or the DCE *may* initiate the L2
> connection. This is also the way the current code (before this patch
> set) works. But I see both the DTE and the DCE will try to initiate
> the L2 connection after device-up, because according to your 1st
> patch, L3 will always instruct L2 to do this on device-up. However,
> looking at your 6th patch (in the link you gave), you seem to want the
> DCE to wait for a while before initiating the connection by itself. So
> I'm unclear which way you want to go. Making DCE initiate the L2
> connection on device-up, or making DCE wait for a while before
> initiating the L2 connection? I think the second way is more
> reasonable.
Ah, ok. Now I see what you mean.
Yes, we should check the lapb->mode in lapb_connect_request().
>> > It feels unclean to me that the L2 connection will sometimes be
>> > initiated by L3 and sometimes by L2 itself. Can we make L2 connections
>> > always be initiated by L2 itself? If L3 needs to do something after L2
>> > links up, L2 will notify it anyway.
>>
>> My original goal was to change as little as possible of the original
>> code. And in the original code the NETDEV_UP/NETDEV_DOWN events
>> were/are
>> handled in L3. But it is of course conceivable to shift this to L2.
>
> I suggested moving L2 connection handling to L2 because I think having
> both L2 and L3 to handle this makes the logic of the code too complex.
> For example, after a device-up event, L3 will instruct L2 to initiate
> the L2 connection. But L2 code has its own way of initiating
> connections. For a DCE, L2 wants to wait a while before initiating the
> connection. So currently L2 and L3 want to do things differently and
> they are doing things at the same time.
>
>> But you have to keep in mind that the X.25 L3 stack can also be used
>> with tap interfaces (e.g. for XOT), where you do not have a L2 at all.
>
> Can we treat XOT the same as LAPB? I think XOT should be considered a
> L2 in this case. So maybe XOT can establish the TCP connection by
> itself without being instructed by L3. I'm not sure if this is
> feasible in practice but it'd be good if it is.
>
> This also simplifies the L3 code.
I also have a patch here that implements an "on demand" link feature,
which we used for ISDN dialing connections.
As ISDN is de facto dead, this is not relevant anymore. But if we want
such kind of feature, I think we need to stay with the method to control
L2 link state from L3.
On Wed, Nov 18, 2020 at 12:49 AM Martin Schiller <[email protected]> wrote:
>
> Ah, ok. Now I see what you mean.
> Yes, we should check the lapb->mode in lapb_connect_request().
...
> I also have a patch here that implements an "on demand" link feature,
> which we used for ISDN dialing connections.
> As ISDN is de facto dead, this is not relevant anymore. But if we want
> such kind of feature, I think we need to stay with the method to control
> L2 link state from L3.
I see. Hmm...
I guess for ISDN, the current code (before this patch series) is the
best. We only establish the connection when L3 has packets to send.
Can we do this? We let L2 handle all device-up / device-down /
carrier-up / carrier-down events. And when L3 has some packets to send
but it still finds the L2 link is not up, it will then instruct L2 to
connect.
This way we may be able to both keep the logic simple and still keep
L3 compatible with ISDN.
On Wed, Nov 18, 2020 at 5:03 AM Xie He <[email protected]> wrote:
>
> On Wed, Nov 18, 2020 at 12:49 AM Martin Schiller <[email protected]> wrote:
> >
> > I also have a patch here that implements an "on demand" link feature,
> > which we used for ISDN dialing connections.
> > As ISDN is de facto dead, this is not relevant anymore. But if we want
> > such kind of feature, I think we need to stay with the method to control
> > L2 link state from L3.
>
> I see. Hmm...
>
> I guess for ISDN, the current code (before this patch series) is the
> best. We only establish the connection when L3 has packets to send.
>
> Can we do this? We let L2 handle all device-up / device-down /
> carrier-up / carrier-down events. And when L3 has some packets to send
> but it still finds the L2 link is not up, it will then instruct L2 to
> connect.
>
> This way we may be able to both keep the logic simple and still keep
> L3 compatible with ISDN.
Another solution might be letting ISDN automatically connect when it
receives the first packet from L3. This way we can still free L3 from
all handlings of L2 connections.
On 2020-11-18 14:46, Xie He wrote:
> On Wed, Nov 18, 2020 at 5:03 AM Xie He <[email protected]> wrote:
>>
>> On Wed, Nov 18, 2020 at 12:49 AM Martin Schiller <[email protected]>
>> wrote:
>> >
>> > I also have a patch here that implements an "on demand" link feature,
>> > which we used for ISDN dialing connections.
>> > As ISDN is de facto dead, this is not relevant anymore. But if we want
>> > such kind of feature, I think we need to stay with the method to control
>> > L2 link state from L3.
>>
>> I see. Hmm...
>>
>> I guess for ISDN, the current code (before this patch series) is the
>> best. We only establish the connection when L3 has packets to send.
>>
>> Can we do this? We let L2 handle all device-up / device-down /
>> carrier-up / carrier-down events. And when L3 has some packets to send
>> but it still finds the L2 link is not up, it will then instruct L2 to
>> connect.
>>
>> This way we may be able to both keep the logic simple and still keep
>> L3 compatible with ISDN.
>
> Another solution might be letting ISDN automatically connect when it
> receives the first packet from L3. This way we can still free L3 from
> all handlings of L2 connections.
ISDN is not important now. Also the I4L subsystem has been removed.
I have now completely reworked the patch-set and it is now much tidier.
For now I left the event handling completely in X.25 (L3).
I will now send the whole thing as v3 and we can discuss it further.