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net_io.go
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net_io.go
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// Copyright (C) 2020-2021, IrineSistiana
//
// This file is part of mosdns.
//
// mosdns is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// mosdns is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program. If not, see <https://www.gnu.org/licenses/>.
package dnsutils
import (
"encoding/binary"
"fmt"
"github.com/IrineSistiana/mosdns/dispatcher/pkg/pool"
"github.com/miekg/dns"
"io"
"net"
)
const (
IPv4UdpMaxPayload = 1472 // MTU 1500 - 20 IPv4 header - 8 udp header
IPv6UdpMaxPayload = 1452 // MTU 1500 - 40 IPv6 header - 8 udp header
)
type IOErr struct {
err error
}
func WrapIOErr(err error) *IOErr {
return &IOErr{err: err}
}
func (e *IOErr) Error() string {
return e.err.Error()
}
func IsIOErr(err error) (innerErr error) {
innerErr, ok := err.(*IOErr)
if ok {
return innerErr
}
return nil
}
func (e *IOErr) Unwrap() error {
return e.err
}
// ReadUDPMsgFrom reads dns msg from c in a wire format.
// The bufSize should not be greater than dns.MaxMsgSize.
// Typically IPv4UdpMaxPayload is big enough.
// An io err will be wrapped into an IOErr.
// IsIOErr(err) can check and unwrap the inner io err.
func ReadUDPMsgFrom(c net.PacketConn, bufSize int) (m *dns.Msg, from net.Addr, n int, err error) {
buf := pool.GetBuf(bufSize)
defer pool.ReleaseBuf(buf)
n, from, err = c.ReadFrom(buf)
if err != nil {
err = WrapIOErr(err)
return
}
if n < 12 {
err = dns.ErrShortRead
return
}
m = new(dns.Msg)
err = m.Unpack(buf[:n])
if err != nil {
return
}
return
}
// ReadMsgFromUDP See ReadUDPMsgFrom.
func ReadMsgFromUDP(c io.Reader, bufSize int) (m *dns.Msg, n int, err error) {
buf := pool.GetBuf(bufSize)
defer pool.ReleaseBuf(buf)
n, err = c.Read(buf)
if err != nil {
err = WrapIOErr(err)
return nil, n, err
}
if n < 12 {
return nil, n, dns.ErrShortRead
}
m = new(dns.Msg)
err = m.Unpack(buf[:n])
if err != nil {
return nil, n, err
}
return m, n, nil
}
// WriteMsgToUDP packs and writes m to c in a wire format.
// An io err will be wrapped into an IOErr.
// IsIOErr(err) can check and unwrap the inner io err.
func WriteMsgToUDP(c io.Writer, m *dns.Msg) (n int, err error) {
mRaw, buf, err := pool.PackBuffer(m)
if err != nil {
return 0, err
}
defer pool.ReleaseBuf(buf)
return WriteRawMsgToUDP(c, mRaw)
}
// WriteRawMsgToUDP See WriteMsgToUDP.
func WriteRawMsgToUDP(c io.Writer, b []byte) (n int, err error) {
n, err = c.Write(b)
if err != nil {
err = WrapIOErr(err)
}
return
}
// WriteUDPMsgTo See WriteMsgToUDP.
func WriteUDPMsgTo(m *dns.Msg, c net.PacketConn, to net.Addr) (n int, err error) {
mRaw, buf, err := pool.PackBuffer(m)
if err != nil {
return 0, err
}
defer pool.ReleaseBuf(buf)
n, err = c.WriteTo(mRaw, to)
if err != nil {
err = WrapIOErr(err)
}
return
}
// ReadMsgFromTCP reads msg from c in RFC 7766 format.
// n represents how many bytes are read from c.
// This includes two-octet length field.
// An io err will be wrapped into an IOErr.
// IsIOErr(err) can check and unwrap the inner io err.
func ReadMsgFromTCP(c io.Reader) (m *dns.Msg, n int, err error) {
lengthRaw := make([]byte, 2)
n1, err := io.ReadFull(c, lengthRaw)
n = n + n1
if err != nil {
err = WrapIOErr(err)
return nil, n, err
}
// dns length
length := binary.BigEndian.Uint16(lengthRaw)
if length < 12 {
return nil, n, dns.ErrShortRead
}
buf := pool.GetBuf(int(length))
defer pool.ReleaseBuf(buf)
n2, err := io.ReadFull(c, buf)
n = n + n2
if err != nil {
err = WrapIOErr(err)
return nil, n, err
}
m = new(dns.Msg)
err = m.Unpack(buf)
if err != nil {
return nil, n, err
}
return m, n, nil
}
// WriteMsgToTCP packs and writes m to c in RFC 7766 format.
// n represents how many bytes are written to c.
// This includes 2 bytes length header.
// An io err will be wrapped into an IOErr.
// IsIOErr(err) can check and unwrap the inner io err.
func WriteMsgToTCP(c io.Writer, m *dns.Msg) (n int, err error) {
mRaw, buf, err := pool.PackBuffer(m)
if err != nil {
return 0, err
}
defer pool.ReleaseBuf(buf)
return WriteRawMsgToTCP(c, mRaw)
}
// WriteRawMsgToTCP See WriteMsgToTCP
func WriteRawMsgToTCP(c io.Writer, b []byte) (n int, err error) {
if len(b) > dns.MaxMsgSize {
return 0, fmt.Errorf("payload length %d is greater than dns max msg size", len(b))
}
if tcpConn, ok := c.(*net.TCPConn); ok {
h := make([]byte, 2)
h[0] = byte(len(b) >> 8)
h[1] = byte(len(b))
buf := net.Buffers{h, b}
wn, err := buf.WriteTo(tcpConn)
return int(wn), err
}
wb := pool.GetBuf(2 + len(b))
defer pool.ReleaseBuf(wb)
binary.BigEndian.PutUint16(wb[:2], uint16(len(b)))
copy(wb[2:], b)
n, err = c.Write(wb)
if err != nil {
err = WrapIOErr(err)
}
return
}