RDKB-66929 : [Rogers][8.6p4s4] Device inaccessible and loses internet | When GW switch back to router from bridge mode.

[LakshminarayananShenbagaraj]

Reason for change:
When the CPE is in bridge mode router advertisement has been received for solicit via rdisc6 due to the reason IPv6 default gateway has not been filled up for connectivity checki. For Recovery, we have to restart connectivity check either IPv4 or IPv6 default gateway not valid case.

Test Procedure:

1. Connectivity check should start with valid parameters.

Risks: High

[Copilot]

Copilot review overview

🟡 Changes recommended

STOP validation precedence, persistent DAD delays, and failing test expectations must be addressed.

Review effort: Balanced
Findings: 1 · 1

Open (2)

• STOP gateway validation incorrectly prevents stop events · New
• Stop polling immediately when DAD has failed · New

What changed in this PR

Improves connectivity-check recovery after bridge-to-router transitions by validating gateways and IPv6 readiness.

Changes:

• Restarts connectivity checks after DHCP updates.
• Adds IPv6 DAD readiness detection.
• Validates DNS and gateway availability before TAD startup.

File	Description
source/​WanManager/​wanmgr_interface_sm.c	Adds DAD checks and TAD success handling.
source/​WanManager/​wanmgr_dhcp_event_handler.c	Triggers checks after DHCP lease updates.
source/​TR-181/​middle_layer_src/​wanmgr_rbus_handler_apis.c	Adds gateway validation for TAD.

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[Copilot]

Copilot review overview

🟡 Changes recommended

DAD can incorrectly pass on link-local addresses, gateway validation permits mismatched families, and existing tests will fail.

Review effort: Balanced
Findings: 1

Open (1)

• Validate DNS and gateway pairs within each address family · New

Resolved since last review (2)

• STOP gateway validation incorrectly prevents stop events
• Stop polling immediately when DAD has failed

Previously missed (1)

In code that hasn't changed since last review

Restrict DAD completion check to global-scope IPv6 addresses

source/​WanManager/​wanmgr_interface_sm.c:1100

This treats any IPv6 address on the interface as proof that DAD is complete. A stable link-local address is normally already present, so the helper can return true before the newly assigned global WAN address even appears; scope is parsed but never used. Restrict the match to global-scope addresses so the wait actually covers the WAN address.

This issue also appears on line 1141 of the same file.