Fix PTF/DUT subnet mismatch when VLAN has multiple IPv4 addresses#23204
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StormLiangMS merged 1 commit intosonic-net:masterfrom Mar 24, 2026
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After the community added a second VLAN IP (192.169.0.1), get_first_vlan_ipv4 and ip_and_intf_info diverged: the former returned the first IPv4 (192.168.0.1) while the latter assigned PTF an IP in the last IPv4's subnet (192.169.x.x). This put PTF and DUT in different subnets, causing ping failures and MAC learning tests to break. Rename get_first_vlan_ipv4 to get_vlan_last_ipv4 and change it to return the last IPv4 in the VLAN, matching the behavior of ip_and_intf_info in conftest. Also improve robustness by using ip_network/IPv4Network type checking instead of the naive ":" in addr heuristic, and add try/except for malformed addresses. Signed-off-by: Shivashankar CR <shivashankar.c.r@gmail.com>
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LGTM — correctly aligns DUT/PTF subnet selection by using the last IPv4 address. CI all green.
Minor (non-blocking): Prefer isinstance(ip_network(addr, strict=False), IPv4Network) over type(...) is IPv4Network for Pythonic type checking.
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…nic-net#23204) After the community added a second VLAN IP (192.169.0.1), get_first_vlan_ipv4 and ip_and_intf_info diverged: the former returned the first IPv4 (192.168.0.1) while the latter assigned PTF an IP in the last IPv4's subnet (192.169.x.x). This put PTF and DUT in different subnets, causing ping failures and MAC learning tests to break. Rename get_first_vlan_ipv4 to get_vlan_last_ipv4 and change it to return the last IPv4 in the VLAN, matching the behavior of ip_and_intf_info in conftest. Also improve robustness by using ip_network/IPv4Network type checking instead of the naive ":" in addr heuristic, and add try/except for malformed addresses. Signed-off-by: Shivashankar CR <shivashankar.c.r@gmail.com>
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Description of PR
Summary:
Fix PTF/DUT subnet mismatch in ARP tests when a VLAN interface has multiple IPv4 addresses.
Root Cause
After the community added a second VLAN IP (
192.169.0.1), two APIs used by the ARP tests diverged in which IPv4 they selected:get_first_vlan_ipv4192.168.0.1(DUT)ip_and_intf_info(conftest)192.169.x.x(PTF)This put PTF and DUT in different subnets, causing ping failures and MAC learning tests to break.
Fix
Rename
get_first_vlan_ipv4toget_vlan_last_ipv4so it returns the last IPv4 in the VLAN, matching the behavior ofip_and_intf_info. Both APIs now consistently use192.169.0.1, keeping PTF and DUT in the same subnet.Additionally, improve robustness:
ip_network/IPv4Networktype checking for IPv4 detection instead of the":" in addrheuristictry/exceptforValueErroron malformed addressesFiles Changed
tests/arp/arp_utils.py— renamed function, updated import, new selection logictests/arp/test_arp_update.py— updated import and call siteType of change
Back port request
Approach
What is the motivation for this PR?
How did you do it?
How did you verify/test it?
Any platform specific information?
Supported testbed topology if it's a new test case?
Documentation