139 lines
3.3 KiB
Go
139 lines
3.3 KiB
Go
/*
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* Copyright (C) 2020-2022, IrineSistiana
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*
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* This file is part of mosdns.
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*
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* mosdns is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* mosdns is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <https://www.gnu.org/licenses/>.
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*/
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package dnsutils
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import (
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"encoding/binary"
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"errors"
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"fmt"
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"io"
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"github.com/IrineSistiana/mosdns/v5/pkg/pool"
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"github.com/miekg/dns"
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)
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const (
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DnsHeaderLen = 12 // minimum dns msg size
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)
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var (
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ErrPayloadTooSmall = errors.New("payload is to small for a valid dns msg")
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)
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// ReadRawMsgFromTCP reads msg from c in RFC 1035 format (msg is prefixed
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// with a two byte length field).
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// n represents how many bytes are read from c.
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// The returned the *[]byte should be released by pool.ReleaseBuf.
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func ReadRawMsgFromTCP(c io.Reader) (*[]byte, error) {
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h := pool.GetBuf(2)
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defer pool.ReleaseBuf(h)
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_, err := io.ReadFull(c, *h)
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if err != nil {
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return nil, err
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}
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// dns length
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length := binary.BigEndian.Uint16(*h)
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if length <= DnsHeaderLen {
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return nil, ErrPayloadTooSmall
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}
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b := pool.GetBuf(int(length))
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_, err = io.ReadFull(c, *b)
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if err != nil {
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pool.ReleaseBuf(b)
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return nil, err
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}
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return b, nil
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}
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// ReadMsgFromTCP reads msg from c in RFC 1035 format (msg is prefixed
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// with a two byte length field).
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// n represents how many bytes are read from c.
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func ReadMsgFromTCP(c io.Reader) (*dns.Msg, int, error) {
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b, err := ReadRawMsgFromTCP(c)
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if err != nil {
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return nil, 0, err
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}
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defer pool.ReleaseBuf(b)
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m, err := unpackMsgWithDetailedErr(*b)
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return m, len(*b) + 2, err
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}
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// WriteMsgToTCP packs and writes m to c in RFC 1035 format.
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// n represents how many bytes are written to c.
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func WriteMsgToTCP(c io.Writer, m *dns.Msg) (n int, err error) {
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buf, err := pool.PackTCPBuffer(m)
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if err != nil {
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return 0, err
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}
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defer pool.ReleaseBuf(buf)
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return c.Write(*buf)
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}
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// WriteRawMsgToTCP See WriteMsgToTCP
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func WriteRawMsgToTCP(c io.Writer, b []byte) (n int, err error) {
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if len(b) > dns.MaxMsgSize {
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return 0, fmt.Errorf("payload length %d is greater than dns max msg size", len(b))
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}
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buf := pool.GetBuf(len(b) + 2)
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defer pool.ReleaseBuf(buf)
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binary.BigEndian.PutUint16((*buf)[:2], uint16(len(b)))
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copy((*buf)[2:], b)
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return c.Write((*buf))
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}
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func WriteMsgToUDP(c io.Writer, m *dns.Msg) (int, error) {
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b, err := pool.PackBuffer(m)
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if err != nil {
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return 0, err
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}
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defer pool.ReleaseBuf(b)
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return c.Write(*b)
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}
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func ReadMsgFromUDP(c io.Reader, bufSize int) (*dns.Msg, int, error) {
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if bufSize < dns.MinMsgSize {
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bufSize = dns.MinMsgSize
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}
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b := pool.GetBuf(bufSize)
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defer pool.ReleaseBuf(b)
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n, err := c.Read(*b)
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if err != nil {
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return nil, n, err
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}
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m, err := unpackMsgWithDetailedErr((*b)[:n])
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return m, n, err
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}
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func unpackMsgWithDetailedErr(b []byte) (*dns.Msg, error) {
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m := new(dns.Msg)
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if err := m.Unpack(b); err != nil {
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return nil, fmt.Errorf("failed to unpack msg [%x], %w", b, err)
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}
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return m, nil
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}
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