show dhcp_server ipv4 info failed if gateway is not present

[yue-fred-gao]

Why I did it

gateway is optional field. In smartswitch use case, dhcp server runs in the switch and is used to offer addresses to DPU midplane. But we don't want to install default route over the midplane interface so gateway option is removed from DHCP server config. See #24495 (comment).

if gateway is not set, show dhcp_server ipv4 info failed.
Traceback (most recent call last):
File "/usr/local/bin/show", line 8, in
sys.exit(cli())
^^^^^
File "/usr/local/lib/python3.11/dist-packages/click/core.py", line 764, in call
return self.main(*args, **kwargs)
^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/usr/local/lib/python3.11/dist-packages/click/core.py", line 717, in main
rv = self.invoke(ctx)
^^^^^^^^^^^^^^^^
File "/usr/local/lib/python3.11/dist-packages/click/core.py", line 1137, in invoke
return _process_result(sub_ctx.command.invoke(sub_ctx))
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/usr/local/lib/python3.11/dist-packages/click/core.py", line 1137, in invoke
return _process_result(sub_ctx.command.invoke(sub_ctx))
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/usr/local/lib/python3.11/dist-packages/click/core.py", line 1137, in invoke
return _process_result(sub_ctx.command.invoke(sub_ctx))
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/usr/local/lib/python3.11/dist-packages/click/core.py", line 956, in invoke
return ctx.invoke(self.callback, **ctx.params)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/usr/local/lib/python3.11/dist-packages/click/core.py", line 555, in invoke
return callback(*args, **kwargs)
^^^^^^^^^^^^^^^^^^^^^^^^^
File "/usr/local/lib/python3.11/dist-packages/click/decorators.py", line 64, in new_func
return ctx.invoke(f, obj, *args, **kwargs)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/usr/local/lib/python3.11/dist-packages/click/core.py", line 555, in invoke
return callback(*args, **kwargs)
^^^^^^^^^^^^^^^^^^^^^^^^^
File "/usr/local/lib/python3.11/dist-packages/show/plugins/dhcp-server.py", line 113, in info
table.append([interface, entry["mode"], entry["gateway"], entry["netmask"], entry["lease_time"], entry["state"]])
~~~~~^^^^^^^^^^^
KeyError: 'gateway'

Work item tracking

• Microsoft ADO (number only):

How I did it

If gateway is not present, use empty string instead.

How to verify it

run the command when gateway is not present
+-----------------+--------+-----------+---------------+-----------------+---------+ | Interface | Mode | Gateway | Netmask | Lease Time(s) | State | +=================+========+===========+===============+=================+=========+ | bridge-midplane | PORT | | 255.255.255.0 | 600000000 | enabled | +-----------------+--------+-----------+---------------+-----------------+---------+

Which release branch to backport (provide reason below if selected)

• 202205
• 202211
• 202305
• 202311
• 202405
• 202411
• 202505

Tested branch (Please provide the tested image version)

master

Description for the changelog

Link to config_db schema for YANG module changes

A picture of a cute animal (not mandatory but encouraged)

[mssonicbld]

/azp run Azure.sonic-buildimage

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Azure Pipelines successfully started running 1 pipeline(s).

[yue-fred-gao]

@prabhataravind , please review

[mssonicbld]

/azp run Azure.sonic-buildimage

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[mssonicbld]

/azp run Azure.sonic-buildimage

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[mssonicbld]

/azp run Azure.sonic-buildimage

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[yxieca]

@yue-fred-gao @Blueve what is the use case for having an empty default gw but valid network mask?

[yue-fred-gao]

@yue-fred-gao @Blueve what is the use case for having an empty default gw but valid network mask?

hi @yxieca, default gateway only affects default route installing in dhcp clients. It doesn't affect dhcp network and subnet. The network comes from interfaces where DHCP are configured, not gateway. See

sonic-buildimage/src/sonic-dhcp-utilities/dhcp_utilities/dhcpservd/dhcp_cfggen.py

Line 87 in d938745

"network": ipaddress.ip_network(mid_plane["ip_prefix"], strict=False),

. So without gateway, it can still offer DHCP address to clients but not offering default route over the gateway. Clients can configure its default route in other ways.

[mssonicbld]

Cherry-pick PR to 202511: #25495