130 lines
2.6 KiB
Go
130 lines
2.6 KiB
Go
package do53
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import (
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"fmt"
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"log"
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"net"
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"sync"
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"github.com/miekg/dns"
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)
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type Config struct {
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HostAndPort string
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DNSSEC bool
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}
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type Client struct {
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udpAddr *net.UDPAddr
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conn *net.UDPConn
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responseChannels map[uint16]chan *dns.Msg
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responseMutex *sync.Mutex
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config Config
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}
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func New(config Config) (*Client, error) {
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udpAddr, err := net.ResolveUDPAddr("udp", config.HostAndPort)
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if err != nil {
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return nil, fmt.Errorf("do53: failed to resolve UDP address %q: %w", config.HostAndPort, err)
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}
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conn, err := net.DialUDP("udp", nil, udpAddr)
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if err != nil {
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return nil, fmt.Errorf("do53: failed to dial UDP connection to %s: %w", config.HostAndPort, err)
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}
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responseChannels := map[uint16]chan *dns.Msg{}
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rcMutex := new(sync.Mutex)
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client := &Client{
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udpAddr: udpAddr,
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conn: conn,
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responseChannels: responseChannels,
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responseMutex: rcMutex,
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config: config,
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}
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go client.receiveLoop()
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return client, nil
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}
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func (c *Client) Close() {
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if c.conn != nil {
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c.conn.Close()
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c.conn = nil
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}
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}
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func (c *Client) receiveLoop() {
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buffer := make([]byte, dns.MaxMsgSize)
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for {
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// Reads one UDP Datagram
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n, err := c.conn.Read(buffer)
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if err != nil {
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log.Printf("do53: failed to read DNS response: %s", err.Error())
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}
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recvMsg := new(dns.Msg)
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err = recvMsg.Unpack(buffer[:n])
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if err != nil {
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log.Printf("do53: failed to unpack DNS response: %s", err.Error())
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continue
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}
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c.responseMutex.Lock()
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respChan, ok := c.responseChannels[recvMsg.Id]
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delete(c.responseChannels, recvMsg.Id)
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c.responseMutex.Unlock()
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if ok {
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respChan <- recvMsg
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} else {
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log.Printf("Receiver: Received DNS response for unknown or already processed msg ID: %v\n", recvMsg.Id)
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}
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}
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}
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func (c *Client) Query(domain string, queryType uint16) (*dns.Msg, error) {
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msg := new(dns.Msg)
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msg.SetQuestion(dns.Fqdn(domain), queryType)
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msg.Id = dns.Id()
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msg.RecursionDesired = true
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if c.config.DNSSEC {
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msg.SetEdns0(4096, true)
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}
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respChan := make(chan *dns.Msg)
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c.responseMutex.Lock()
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c.responseChannels[msg.Id] = respChan
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c.responseMutex.Unlock()
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packedMsg, err := msg.Pack()
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if err != nil {
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c.responseMutex.Lock()
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delete(c.responseChannels, msg.Id)
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c.responseMutex.Unlock()
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return nil, fmt.Errorf("do53: failed to pack DNS message: %w", err)
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}
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_, err = c.conn.Write(packedMsg)
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if err != nil {
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c.responseMutex.Lock()
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delete(c.responseChannels, msg.Id)
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c.responseMutex.Unlock()
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return nil, fmt.Errorf("do53: failed to send DNS query: %w", err)
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}
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recvMsg := <-respChan
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return recvMsg, nil
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}
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