bpf: Add missing packet trace in handle_nat_fwd #19158
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Apr 12, 2022
src_id variable in to_netdev in bpf_host.c is always zero, so safe to delete. Signed-off-by: Yutaro Hayakawa <yutaro.hayakawa@isovalent.com>
In to-netdev in bpf_host.c, the packet tracing is missing when the handle_nat_fwd uses tailcall. This PR adds new packet tracing inside the handle_nat_fwd, but there were two complicated issue in here. 1. handle_nat_fwd is called from to-netdev as well as to-overlay There are two possible caller for this function, so we needed to use IS_BPF_OVERLAY macro to make sure where it is called. 2. handle_nat_fwd does not always tailcalls Internally, it uses conditional tailcall. When it returns without tailcall, we will hit the packet tracing hook at the bottom of the to_netdev and have duplicated packet trace. We need to make sure whether we already trace the packet or not and skip it. Below is an example of simple ICMP Echo to outside of Pod network Before the fix (with tailcall) ``` <- endpoint ... 10.0.1.185 -> 1.1.1.1 EchoRequest -> stack ... 10.0.1.185 -> 1.1.1.1 EchoRequest ["-> network" is missing here] <- network ... 1.1.1.1 -> 172.18.0.3 EchoReply <- host ... 1.1.1.1 -> 10.0.1.185 EchoReply -> endpoint ... 1.1.1.1 -> 10.0.1.185 EchoReply ``` Before the fix (without tailcall) ``` <- endpoint ... 10.0.1.185 -> 1.1.1.1 EchoRequest -> stack ... 10.0.1.185 -> 1.1.1.1 EchoRequest -> network ... 172.18.0.3 -> 1.1.1.1 EchoRequest <- network ... 1.1.1.1 -> 172.18.0.3 EchoReply <- host ... 1.1.1.1 -> 10.0.1.185 EchoReply -> endpoint ... 1.1.1.1 -> 10.0.1.185 EchoReply [no problem] ``` After the fix (with tailcall) ``` <- endpoint ... 10.0.1.185 -> 1.1.1.1 EchoRequest -> stack ... 10.0.1.185 -> 1.1.1.1 EchoRequest -> network ... 172.18.0.3 -> 1.1.1.1 EchoRequest <- network ... 1.1.1.1 -> 172.18.0.3 EchoReply <- host ... 1.1.1.1 -> 10.0.1.185 EchoReply -> endpoint ... 1.1.1.1 -> 10.0.1.185 EchoReply [no problem] ``` After the fix (without tailcall) ``` <- endpoint ... 10.0.1.185 -> 1.1.1.1 EchoRequest -> stack ... 10.0.1.185 -> 1.1.1.1 EchoRequest -> network ... 172.18.0.3 -> 1.1.1.1 EchoRequest <- network ... 1.1.1.1 -> 172.18.0.3 EchoReply <- host ... 1.1.1.1 -> 10.0.1.185 EchoReply -> endpoint ... 1.1.1.1 -> 10.0.1.185 EchoReply [no duplicated trace, no problem] ``` Fixes: cilium#18909 Signed-off-by: Yutaro Hayakawa <yutaro.hayakawa@isovalent.com>
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joamaki
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Apr 28, 2022
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/test Job 'Cilium-PR-K8s-GKE' has 1 failure but they might be new flake since it also hit 1 known flake: #17628 (93.58) |
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Fixes: #18909