OpenOCD - Open On-Chip Debugger / Tickets / #294 libjaylink fails to discover devices when network is down and J-Link S/N is specified

On Thu, Jan 21, 2021 at 9:36 PM Marc Schink dev@zapb.de wrote:

Hi Bohdan,

thank you for your report. I'm aware of this issue but I don't consider
this as bug in libjaylink. We ask libjaylink to discover TCP devices
but there are no ethernet devices available.

Marc,
it's a little tricky to say who is responsible for the issue, if the
caller (openocd) or the lib (libjaylink).
The call in openocd
ret = jaylink_discovery_scan(jayctx, JAYLINK_HIF_USB | JAYLINK_HIF_TCP);
for me means "look for a jlink everywhere, either on usb OR on tcp".
But looking at the implementation, it returns error if there is an
error opening libusb (respectively network), even if there is the
jlink on the network (respectively libusb).
Actually it depends on the API implementation, but without
documentation it's hard to guess.

If you think this is the expected behavior on the libjaylink side, we
can change the caller, by calling jaylink_discovery_scan() twice, once
for usb and once for network.
Would it make more sense for you?

Antonio

Maybe I will introduce a special check for "network not available" but
I'm not sure if and when. We could introduction a switch to disable TCP
discovery in openocd but this would be a bit ugly IMO. For the moment,
I would suggest to use a dummy ethernet device as workaround:

$ ip link add eth23 type dummy
$ ip address change dev eth23 10.0.0.1
$ ip link set eth23 up
$ route add default gw 10.0.0.1 dev eth23

I hope this solves your problem for the moment. Anyway, I'm open for
input if you have a proper solution for this issue.

Best regards,
Marc

On Mon, 2021-01-18 at 12:26 +0000, Bohdan Tymkiv via OpenOCD-devel
wrote:

[tickets:#294] libjaylink fails to discover devices when network is
down and J-Link S/N is specified

Status: new
Milestone: 0.10.0
Created: Mon Jan 18, 2021 12:26 PM UTC by Bohdan Tymkiv
Last Updated: Mon Jan 18, 2021 12:26 PM UTC
Owner: nobody

This issue is rather related to libjaylink library but I was unable
to find any public libjaylink bug tracker so I'm posting the issue
here.

libjaylink is unable to find the probe by it's serial number when all
network interfaces are down/disconnected. This makes it impossible to
use OpenOCD on offline machines with several JLink probes connected.

Steps to reproduce:
Put you computer offline (disconnect all Ethernet cables and turn
WiFi off)
Run the following script:

source [find interface/jlink.cfg]
jlink serial <your_serial_here>
source [find target/psoc6.cfg]
init
exit
Observe the following error:</your_serial_here>

Error: Failed to send discovery message.
Error: TCP/IP device discovery failed.
Error: jaylink_discovery_scan() failed: input/output error.
I've tracked the issue down to discovery_tcp_scan function which
fails on offline machines (which is OK) but this error is treated as
fatal in jaylink_discovery_scan so whole device discovery fails.

Bohdan

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#294 libjaylink fails to discover devices when network is down and J-Link S/N is specified

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