jeanvetorello opened a new pull request, #13127: URL: https://github.com/apache/cloudstack/pull/13127
### Description
Fixes #13121 — IPv6 SLAAC broken on Redundant VPC Virtual Router due to a
missing
Prefix Information Option (PIO) in `radvd.conf`.
In `CsVpcGuestNetwork.add_radvd_conf()`, the `prefix { ... }` block was
emitted
only when `router_guest_ip6 == router_guest_ip6_gateway`. That condition
is true
for non-redundant VRs (where the router itself is the gateway), but never
for
redundant VRs:
As a result, on a redundant VPC tier the radvd daemon was started but
advertised
RAs without a Prefix Information Option, so guest VMs could only configure
link-local `fe80::` addresses and never obtained a global IPv6 via SLAAC.
The fix removes the conditional and always emits the prefix block when
radvd is
configured for the tier. This aligns the VPC path with the non-VPC path
(`systemvm/debian/opt/cloud/bin/setup/common.sh` + `radvd.conf.tmpl`),
which
already emits the prefix block unconditionally.
## Types of changes
- [x] Bug fix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)
- [ ] Enhancement (improves an existing feature and functionality)
- [ ] Cleanup (Code refactoring and cleanup, that may add test cases)
- [ ] build/CI
- [ ] test (unit or integration test code)
## Feature/Enhancement Scale or Bug Severity
### Bug Severity
- [ ] BLOCKER
- [] Critical
- [x] Major
- [ ] Minor
- [ ] Trivial
## Screenshots (if appropriate):
N/A — config file change.
## How Has This Been Tested?
Tested on a VPC with IPv6 enabled and Redundant VR enabled, SystemVM
template
based on Debian, SLAAC only (no DHCPv6).
Before the fix:
- `cat /etc/radvd.conf` on the primary VR showed the `interface ethX { ...
}`
block but no `prefix` section.
- `tcpdump -i ethX -vv 'icmp6 and ip6[40] = 134'` showed Router
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without a Prefix Information Option.
- Guest VMs only configured a link-local `fe80::` address.
After the fix:
- `/etc/radvd.conf` contains the expected
`prefix <gateway>/64 { AdvOnLink on; AdvAutonomous on; };` block.
- `tcpdump` confirms RAs include the Prefix Information Option.
- Guest VMs auto-configure global IPv6 addresses via SLAAC.
- Failover from primary to backup still works: backup VR keeps radvd
disabled
via `CsRedundant._disable_radvd`, so no duplicate RAs are emitted; on
promotion, radvd is started with the correct configuration.
Non-redundant VPC VRs are unchanged (`router_guest_ip6 ==
router_guest_ip6_gateway`
in that case, which already produced the same output as the unconditional
path).
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