mirror of
https://github.com/SagerNet/sing-box.git
synced 2025-01-30 20:56:54 +00:00
30 lines
691 B
Go
30 lines
691 B
Go
package dns
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import (
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"github.com/sagernet/sing/common/buf"
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"github.com/miekg/dns"
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)
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func TruncateDNSMessage(request *dns.Msg, response *dns.Msg, headroom int) (*buf.Buffer, error) {
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maxLen := 512
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if edns0Option := request.IsEdns0(); edns0Option != nil {
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if udpSize := int(edns0Option.UDPSize()); udpSize > 512 {
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maxLen = udpSize
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}
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}
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responseLen := response.Len()
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if responseLen > maxLen {
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response.Truncate(maxLen)
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}
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buffer := buf.NewSize(headroom*2 + 1 + responseLen)
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buffer.Resize(headroom, 0)
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rawMessage, err := response.PackBuffer(buffer.FreeBytes())
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if err != nil {
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buffer.Release()
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return nil, err
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}
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buffer.Truncate(len(rawMessage))
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return buffer, nil
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}
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