[FS#1462] odhcp6c fails to renew and rebind addresses

[LEDE Bugs]

A new Flyspray task has been opened.  Details are below. 

User who did this - clefru (clefru) 

Attached to Project - OpenWrt/LEDE Project
Summary - odhcp6c fails to renew and rebind addresses
Task Type - Bug Report
Category - Base system
Status - Unconfirmed
Assigned To - 
Operating System - All
Severity - High
Priority - Very Low
Reported Version - Trunk
Due in Version - Undecided
Due Date - Undecided
Details - odhcp6c sents all its packets to  [[https://github.com/openwrt/odhcp6c/blob/33a2ba1c14eb5447326945c120e0b64a587ed151/src/dhcpv6.c#L499|ff02::1:2]]. However a trace captured from my wan interface shows that the source-IP and dest-IP are completely changed for the RENEW message, hence ignored by the DHCP server, effectively crippling DHCPv6. See attached screenshot of wireshark for the failed conversation, where the RENEW messages are not sent to ff02::1:2, but to some random public address.

While I can understand that there are routing tables and preferred egress addresses that can make the public IP be preferred over the link local IP (used in the beginning of the conversation), but what leads to mangling of ff02::1:2 into something public is beyond me.

This breaks IPv6 support after initial assignment. As seen in the wireshark trace, despite a response from my ISP dhcp server, odhcp6c ignores it, and keeps retrying.

OpenWrt SNAPSHOT, r6565-fd588db


One or more files have been attached.

More information can be found at the following URL:
https://bugs.openwrt.org/index.php?do=details&task_id=1462