tcp2 not working with ppp

[shlomow]

Describe the bug
When running ppp and tcp with the new tcp stack, it does not work.
After switching to the legacy tcp stack everything worked as expected.

To Reproduce
Build the ppp support with the network shell support. The default tcp stack is tcp2.
Then, try to connect to a server using net tcp connect command.

[jukkar]

More information is needed.
What version (upstream, 2.5 or what) are you using?
How does it not work, connect fails or data transfer fails or what exactly is failing?

I do not have a SIM card so cannot try this myself with gsm modem.

[shlomow]

I am using the latest master commit. You do not need the modem reproduce the issue. Just enable ppp in your configuration. From what I saw no tcp packet exit the target device

[jukkar]

You do not need the modem reproduce the issue. Just enable ppp in your configuration.

Yep, I realized that too. I have a test environment now ready.

[jukkar]

Hmm, at least a simple tcp connect/send test to Linux works ok. In linux side I have

nc -l 192.0.2.2 4242

and when connecting to it from zephyr

uart:~$ net tcp connect 192.0.2.2 4242
Connecting from 192.0.2.1:0 to 192.0.2.2:4242
uart:~$ net tcp send bar
Message sent

I am seeing data in the linux terminal. Also receiving works.

Could you elaborate in more details how to replicate this issue?

[jukkar]

BTW, I used following config in Zephyr side (need three terminals):

$ cd net-tools
$ ./loop-ppp-dev.sh

$ cd net-tools
$ sudo ./loop-pppd.sh

$ cd samples/net/sockets/echo_server
$ cmake . -Bbuild -DBOARD=qemu_x86 -DOVERLAY_CONFIG=overlay-ppp.conf -DCONFIG_NET_PPP_UART_NAME=\"UART_1\"
$ make -Cbuild run

[mniestroj]

I guess the problem is not with PPP itself, but with net tcp connect command. This command uses non-blocking connect(), which is not supported by TCP2. In TCP (old) case the "non-blocking" request was still "blocking" internally in tcp implementation, which is why it worked.

[jukkar]

I was using TCP2 with net-shell and it worked just fine. The commit 9eb46d9 made it possible to use TCP2 in net-shell.