/
conn.go
159 lines (134 loc) · 2.92 KB
/
conn.go
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// Copyright © by Jeff Foley 2022. All rights reserved.
// Use of this source code is governed by Apache 2 LICENSE that can be found in the LICENSE file.
// SPDX-License-Identifier: Apache-2.0
package resolve
import (
"fmt"
"net"
"sync"
"time"
"github.com/caffix/queue"
"github.com/miekg/dns"
)
const maxUDPBufferSize = 64 * 1024 * 1024
type resp struct {
Msg *dns.Msg
Addr *net.UDPAddr
}
type connections struct {
sync.Mutex
done chan struct{}
conns []*net.UDPConn
resps queue.Queue
rbufSize int
wbufSize int
nextWrite int
}
func newConnections(cpus int, resps queue.Queue) *connections {
conns := &connections{
done: make(chan struct{}, 1),
resps: resps,
}
for i := 0; i < cpus; i++ {
if err := conns.Add(); err != nil {
conns.Close()
return nil
}
}
return conns
}
func (c *connections) Close() {
select {
case <-c.done:
return
default:
}
close(c.done)
for _, conn := range c.conns {
conn.Close()
}
}
func (c *connections) Next() *net.UDPConn {
c.Lock()
defer c.Unlock()
cur := c.nextWrite
c.nextWrite = (c.nextWrite + 1) % len(c.conns)
return c.conns[cur]
}
func (c *connections) Add() error {
var err error
var addr *net.UDPAddr
var conn *net.UDPConn
if addr, err = net.ResolveUDPAddr("udp", ":0"); err == nil {
if conn, err = net.ListenUDP("udp", addr); err == nil {
_ = conn.SetDeadline(time.Time{})
c.setMaxReadBufSize(conn)
c.setMaxWriteBufSize(conn)
c.conns = append(c.conns, conn)
go c.responses(conn)
}
}
return err
}
func (c *connections) WriteMsg(msg *dns.Msg, addr *net.UDPAddr) error {
var n int
var err error
var out []byte
if out, err = msg.Pack(); err == nil {
conn := c.Next()
conn.SetWriteDeadline(time.Now().Add(500 * time.Millisecond))
if n, err = conn.WriteToUDP(out, addr); err == nil && n < len(out) {
err = fmt.Errorf("only wrote %d bytes of the %d byte message", n, len(out))
}
}
return err
}
func (c *connections) responses(conn *net.UDPConn) {
b := make([]byte, dns.DefaultMsgSize)
for {
select {
case <-c.done:
return
default:
}
if n, addr, err := conn.ReadFromUDP(b); err == nil && n >= headerSize {
m := new(dns.Msg)
if err := m.Unpack(b[:n]); err == nil && len(m.Question) > 0 {
c.resps.Append(&resp{
Msg: m,
Addr: addr,
})
}
}
}
}
func (c *connections) setMaxReadBufSize(conn *net.UDPConn) {
c.Lock()
defer c.Unlock()
if c.rbufSize != 0 {
_ = conn.SetReadBuffer(c.rbufSize)
return
}
min := 1024
for size := maxUDPBufferSize; size > min; size /= 2 {
if err := conn.SetReadBuffer(size); err == nil {
c.rbufSize = size
return
}
}
}
func (c *connections) setMaxWriteBufSize(conn *net.UDPConn) {
c.Lock()
defer c.Unlock()
if c.wbufSize != 0 {
_ = conn.SetWriteBuffer(c.wbufSize)
return
}
min := 1024
for size := maxUDPBufferSize; size > min; size /= 2 {
if err := conn.SetWriteBuffer(size); err == nil {
c.wbufSize = size
return
}
}
}