bpf: l3: limit kube-proxy workaround in l3_local_delivery() to bpf_overlay #27908
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…erlay cilium#22333 fixed a bug for configs with tunnel-routing and per-EP routes. Here ingress policy was applied twice: first via tail-call, and then a second time by the to-container program as the packet traverses the veth pair. The fix was to avoid the tail-call, and only apply policy with the to-container program. But the tail-call also contains a kube-proxy workaround (potential service replies need to pass through kube-proxy for RevDNAT, so the tail-call punts them to the stack instead of calling redirect_ep() to forward them straight to the endpoint). So we copied that workaround into the l3_local_delivery() path. The tail-call is compiled as part of bpf_lxc, and thus couldn't easily tell if a packet was received from the tunnel. But as l3_local_delivery() is inlined into bpf_overlay, we can now limit the work-around to IS_BPF_OVERLAY. This ensures that the workaround is not applied to eg. plain pod-to-pod traffic, where bpf_lxc also calls l3_local_delivery(). Fixes: 3d2ceaf ("bpf: Preserve overlay->lxc path with kube-proxy") Signed-off-by: Julian Wiedmann <jwi@isovalent.com>
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#22333 fixed a bug for configs with tunnel-routing and per-EP routes. Here ingress policy was applied twice: first via tail-call, and then a second time by the to-container program as the packet traverses the veth pair.
The fix was to avoid the tail-call, and only apply policy with the to-container program. But the tail-call also contains a kube-proxy workaround (potential service replies need to pass through kube-proxy for RevDNAT, so the tail-call punts them to the stack instead of calling redirect_ep() to forward them straight to the endpoint). So we copied that workaround into the l3_local_delivery() path.
The tail-call is compiled as part of bpf_lxc, and thus couldn't easily tell if a packet was received from the tunnel. But as l3_local_delivery() is inlined into bpf_overlay, we can now limit the work-around to IS_BPF_OVERLAY. This ensures that the workaround is not applied to eg. plain pod-to-pod traffic, where bpf_lxc also calls l3_local_delivery().
Fixes: 3d2ceaf ("bpf: Preserve overlay->lxc path with kube-proxy")