IPv6 only setup using BPF not possible #4415
Description
I'm trying to setup an IPv6-only cluster using BPF - but it failed. (I have a IPv6-only setup using Iptables.)
Effect
Even if IPv4 is switched off, these logs appear:
2026-02-10 06:13:32.861 [INFO][9] startup/node.go 573: Cannot pick an IPv4 tunnel address from the given CIDR podCIDR="2a11:157:111:1039:77:223:11:0/112"
2026-02-10 06:13:32.868 [INFO][9] startup/startup.go 609: Initialize BGP data
2026-02-10 06:13:32.872 [WARNING][9] startup/autodetection_methods.go 99: Unable to auto-detect an IPv4 address: no valid IPv4 addresses found on the host interfaces
2026-02-10 06:13:32.872 [WARNING][9] startup/startup.go 632: Couldn't autodetect an IPv4 address. If auto-detecting, choose a different autodetection method. Otherwise provide an explicit address.
2026-02-10 06:13:32.872 [INFO][9] startup/startup.go 516: Clearing out-of-date IPv4 address from this node IP=""
2026-02-10 06:13:32.872 [INFO][9] startup/startup.go 520: Clearing out-of-date IPv6 address from this node IP=""
2026-02-10 06:13:32.879 [INFO][9] startup/node.go 573: Cannot pick an IPv4 tunnel address from the given CIDR podCIDR="2a11:157:111:1039:77:223:11:0/112"
2026-02-10 06:13:32.879 [WARNING][9] startup/utils.go 47: Terminating
Calico node failed to start
An attempt at analysis
For me there is a strange line in the code which sets needIPv4Autodetection unconditional to true when using BPF (core_controller.go; line 591).
needIPv4Autodetection := *instance.Spec.CalicoNetwork.LinuxDataplane == operatorv1.LinuxDataplaneBPF
Should this maybe read as:
needIPv4Autodetection := *instance.Spec.CalicoNetwork.LinuxDataplane == operatorv1.LinuxDataplaneBPF && hasIPv4Pools(instance)
IMHO the current implementation contradicts the validation logic. Please double-check. This is the first time I had a look at the source.
Versions:
- Operator version: v1.40.3
- Calico version: v3.31.3