Zephyr TCP Delay

[ofirshe]

Hi all,
I'm running a TCP server on Zephyr, and I'm experiencing a significant delay when a new client, one that the board hasn’t seen before, tries to connect. Even simple ping requests from the new client take a long time to get a response.
I assume this delay is due to the client's address not being updated in the ARP table quickly enough. Has anyone encountered this issue before, and if so, how did you resolve it?

My Ethernet Configuration:

CONFIG_NETWORKING=y
CONFIG_NET_UDP=y
CONFIG_NET_TCP=y
CONFIG_NET_IPV4=y
CONFIG_INIT_STACKS=y
CONFIG_NET_LOG=y
CONFIG_NET_CONFIG_SETTINGS=y
CONFIG_NET_CONFIG_NEED_IPV4=y
CONFIG_NET_CONFIG_MY_IPV4_ADDR="172.18.133.10"
CONFIG_NET_CONFIG_MY_IPV4_NETMASK="255.255.240.0"
CONFIG_NET_CONFIG_MY_IPV4_GW="172.18.143.254"
CONFIG_NET_L2_ETHERNET=y
CONFIG_NET_CONFIG_INIT_TIMEOUT=0
CONFIG_NET_CONTEXT_RCVTIMEO=y
CONFIG_NET_SOCKETS=y
CONFIG_POSIX_API=y
CONFIG_NET_TX_STACK_SIZE=8192
CONFIG_NET_RX_STACK_SIZE=8192
CONFIG_SYSTEM_WORKQUEUE_STACK_SIZE=8192
CONFIG_NET_PKT_RX_COUNT=40
CONFIG_NET_PKT_TX_COUNT=40
CONFIG_NET_BUF_RX_COUNT=160
CONFIG_NET_BUF_TX_COUNT=160
CONFIG_NET_BUF_DATA_SIZE=256
CONFIG_NET_MAX_CONTEXTS=64

[jukkar]

What zephyr version are you using?
How long delays are we talking about?
If ARP needs to be done, then in worst case it can take some time to finish, not sure how you could speed this up.

[rlubos]

Configs are fine, I've tested with the same. I'm afraid this must be something board-specific, tested on real HW (nucleo_h723zg) and gratuitous ARP is being sent on boot just fine (note I've added some extra logs, second ARP is after plugging cable out/in):

[ofirshe]

Screen Recording 2025-02-13 144951.zip
I've built samples/hello_world with the necessary configurations, setting 172.18.133.10 as my interface IP and CONFIG_NET_ARP_GRATUITOUS_INTERVAL=30.

Even after the message net_config: IPv4 address: 172.18.133.10 appears on the console, I don't see any gratuitous ARP in Wireshark. However, when I continue past the breakpoint, the first gratuitous ARP is triggered from arp_gratuitous_work_handler, as confirmed by the call stack in Eclipse on the left panel.

[ofirshe]

@rlubos So do you think it's a board specific issue ? What could be missing ?

[ofirshe]

Hi @decsny,

Could you or someone else at NXP check this issue? When gratuitous ARP transmission is enabled, the RT1060 should send a packet as soon as the interface is up after boot. However, that’s not what I’m seeing on my side.

[rlubos]

@rlubos So do you think it's a board specific issue ? What could be missing ?

Definitely nothing generic because gratuitous ARP worked just as expected on 3 different platforms I've tested, just as I wrote above.