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https://github.com/ls-2018/mdns
Simple mDNS client/server library in Golang
https://github.com/ls-2018/mdns
dns
Last synced: 5 days ago
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Simple mDNS client/server library in Golang
- Host: GitHub
- URL: https://github.com/ls-2018/mdns
- Owner: ls-2018
- Created: 2021-12-28T10:31:48.000Z (almost 3 years ago)
- Default Branch: master
- Last Pushed: 2021-12-28T10:36:52.000Z (almost 3 years ago)
- Last Synced: 2024-10-12T12:36:08.931Z (about 1 month ago)
- Topics: dns
- Language: Go
- Homepage:
- Size: 345 KB
- Stars: 1
- Watchers: 3
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: readme.md
Awesome Lists containing this project
README
server、client 是服务注册于发现时 应用的角色；并且两者都可以作为dns消息的发送、接受端
整体可以理解为 ： 通过dns协议， 获取对应服务其中一台节点的hostname、port
### Server
（接收消息依靠mainloop协程;发送消息probe依靠协程）
启动后会初始化
### probe step 1
`服务启动后主动发送的消息 示例`
``````
;; opcode: QUERY, status: NOERROR, id: 4352
;; flags:; QUERY: 1, ANSWER: 0, AUTHORITY: 2, ADDITIONAL: 0
;; QUESTION SECTION:
;GoZeroconfGo._workstation._tcp.local. IN PTR
;; AUTHORITY SECTION:
GoZeroconfGo._workstation._tcp.local. 3200 IN SRV 0 0 42424 pc1.local.
GoZeroconfGo._workstation._tcp.local. 3200 IN TXT "txtv=0" "lo=1" "la=2"
``````
```
假设有3个适配器
# 启动流程
- 1、构建ipv4连接、ipv6连接
- 2、multicastResponse(ifindex=0)
- 3、重复2次，依次向ipv4、ipv6连接 发送相同的dns.Msg 数据包;
- 4、会收到 重试2次 * 3个适配器 * （每个适配器的ipv4、ipv6）次数据，但是此时并不会对数据进行Query
- 5、判断逻辑 len(query.NS)>0 （实际收到了SRV、TXT）； 不会有结果返回
```
### probe step 2
`服务启动后主动发送的消息 示例`
``````
;; opcode: QUERY, status: NOERROR, id: 0
;; flags: qr; QUERY: 0, ANSWER: 5, AUTHORITY: 0, ADDITIONAL: 0
;; ANSWER SECTION:
GoZeroconfGo._workstation._tcp.local. 3200 CLASS32769 SRV 0 0 42424 pc1.local.
GoZeroconfGo._workstation._tcp.local. 3200 CLASS32769 TXT "txtv=0" "lo=1" "la=2"
_workstation._tcp.local. 3200 IN PTR GoZeroconfGo._workstation._tcp.local.
_services._dns-sd._udp.local. 3200 IN PTR _workstation._tcp.local.
pc1.local. 120 CLASS32769 AAAA ::1
``````
- 1、发送消息（上面的示例）
multicastResponse(ifindex=适配器的net.interface.Index)
重试2次 * 3个适配器 * （每个适配器的ipv4、ipv6）
- 2、接收消息
没有;; QUESTION SECTION:不会调用 handleQuery 函数
- 3、根据Name进程分支判断
``````
HostName
serviceTypeName
serviceInstanceName
``````
- 4、将请求信息、server的SRV、TXT等信息封装到响应信息中
- 5、并根据intf.Index 让对应适配器将消息通过ipv4、ipv6协议发送出去
### 响应数据包
``````
;; opcode: QUERY, status: NOERROR, id: 33537
;; flags: qr aa; QUERY: 0, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 3
;; ANSWER SECTION:
_workstation._tcp.local. 3200 IN PTR GoZeroconfGo._workstation._tcp.local.
;; ADDITIONAL SECTION:
GoZeroconfGo._workstation._tcp.local. 3200 IN SRV 0 0 42424 pc1.local.
GoZeroconfGo._workstation._tcp.local. 3200 IN TXT "txtv=0" "lo=1" "la=2"
pc1.local. 120 IN AAAA ::1
``````
``````
id : 16bits 随机数，用于标识消息
``````
# Client
- 1、启动后发包查询所有同一域下的机器(数据包如下)；该数据包会发往 ----> 3个适配器 * （每个适配器的ipv4、ipv6）一般QUESTION SECTION 只有一个;并且server会对每一个Question作出响应
``````
;; opcode: QUERY, status: NOERROR, id: 6500
;; flags:; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 0
;; QUESTION SECTION:
;_workstation._tcp.local. IN PTR
``````
- 2、go func(){初始化sentEntries = make(map[string]*ServiceEntry)}
- 生命周期：
- 1、先启动该协程，接收符合要求的相应，放入 sentEntries ，并发往 <-chan *zeroconf.ServiceEntry
- 2、然后发消息
- 3、终止该协程
- ``````
问题：
如果在终止前，没有及时收到响应，就不会有响应了
``````
- 3、通过chan 接收符合要求的服务端，0个或1个 （由 sentEntries 决定）
