53 lines
1.2 KiB
Markdown
53 lines
1.2 KiB
Markdown
# UDP 心跳
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`efka` 通过独立的 `efka_iot_heartbeat` 进程向 `iot` 发送 UDP 心跳。该心跳只表示主机存活，不依赖 TLS control channel 是否在线。
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## 配置
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TLS 和 UDP 共用同一个 `iot_server.host`：
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```erlang
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{iot_server, [
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{host, "localhost"},
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{tls_port, 443},
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{udp_port, 18080}
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]},
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{heartbeat, [
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{interval, 5000}
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]},
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{auth, [
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{uuid, "qbxmjyzrkpntfgswaevodhluicqzxplkm"},
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{token, "zpxlkvmqwnbghytrujsdieofazxcvbnm"}
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]}
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```
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- `tls_port` 用于 `efka_iot_client` 建立 TLS 连接。
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- `udp_port` 用于 `efka_iot_heartbeat` 发送 UDP 心跳。
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- `heartbeat.interval` 是发送间隔，单位毫秒，默认 5000。
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- UDP 心跳和 TLS 鉴权复用 `auth.uuid` 和 `auth.token`。
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## 包格式
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```erlang
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<<
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Version:8,
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UuidLen:16,
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UUID:UuidLen/binary,
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Timestamp:64/unsigned-big,
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Nonce:16/binary,
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Mac:32/binary
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>>
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```
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`Mac` 使用 HMAC-SHA256：
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```erlang
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HeartbeatSecret = crypto:hash(sha256, Token),
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Payload = <<Version:8, UuidLen:16, UUID:UuidLen/binary, Timestamp:64/unsigned-big, Nonce:16/binary>>,
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Mac = crypto:mac(hmac, sha256, HeartbeatSecret, Payload)
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```
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其中 `Token` 是 `auth.token`。`iot` 侧注册 efka client 时保存同样的 `SHA256(Token)` 派生值，并用它校验心跳。
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