[meshnet] Use gRPC streaming - #732
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Replace the veth pair and libpcap packet capture implementation in meshnetd with persistent Linux TAP devices created directly inside container network namespaces. Reason for Change: - Eliminates packet loss under high traffic loads caused by libpcap's kernel- to-userspace drop policy. - Provides native Linux socket buffer flow control and backpressure (`txqueuelen`) up to the container application when gRPC processing falls behind. - Guarantees protocol transparent packet handling (including LACP and LLDP frames). - Ensures process crash resilience: setting `TUNSETPERSIST=1` keeps TAP interfaces alive in the container netns across daemon restarts without link flaps. - Synchronizes CNI plugin pod readiness with complete end-to-end gRPC wire setup, preventing test/ping race conditions upon pod startup. - Eliminates CGO and `libpcap-dev` build dependencies, producing a pure Go static binary (`CGO_ENABLED=0`). Key Changes: - Added `CreateOrAttachTAP` in `wireutil` using `TUNSETIFF` & `TUNSETPERSIST`. - Replaced `pcap.Handle` with `*os.File` in `gwire_map.go`, `grpcwire.go`, and `handler.go`. - Updated `ReconcilePodLinks` in `controller.go` to use TAP interfaces directly without host-side veth creation. - Updated `GRPCWireExists` and CNI `cmdAdd` readiness check to block until gRPC wire handshakes are fully established. - Removed `libpcap-dev` and updated Dockerfile to build `meshnetd` with `CGO_ENABLED=0`.
Add package & public method comments, and format Go
1. Bidirectional Streaming (SendToStream) Receiver (handler.go):
• Implemented SendToStream(stream mpb.WireProtocol_SendToStreamServer) error.
• In a loop, stream.Recv() continuously ingests incoming mpb.Packet frames and writes them directly to the
destination TAP interface (wrHandle.Write(pkt.Frame)), bypassing per-packet unary RPC overhead.
2. Streaming Sender & Auto-Reconnect (grpcwire.go):
• Updated RecvFrmLocalPodThread to establish a persistent client stream (wireClient.SendToStream(ctx)).
• Frames read from the local TAP interface are streamed out via st.Send(payload) without blocking for individual
RPC responses.
• If the stream encounters a network or peer reset, RecvFrmLocalPodThread automatically clears its stream handle
and transparently re-establishes SendToStream on the next packet.
3. HTTP/2 Window Size & Buffer Tuning:
• Server Configuration (meshnet.go):
• Stream window size: 4 MB (grpc.InitialWindowSize(4 * 1024 * 1024)).
• Connection window size: 16 MB (grpc.InitialConnWindowSize(16 * 1024 * 1024)).
• Max message payload: 64 MB (grpc.MaxRecvMsgSize / grpc.MaxSendMsgSize).
• Client Configuration (grpcwire.go):
• Configured matching initial window size and message payload limits on client grpc.Dial.
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Note: Stacks on top of #731, new changes start at sha:6c4cadb3e02b85a880015fa7561ae40d2ad12d53. Please merge that PR first.