clash/dns/client.go
2020-04-24 23:48:55 +08:00

72 lines
1.3 KiB
Go

package dns
import (
"context"
"fmt"
"net"
"strings"
"github.com/Dreamacro/clash/component/dialer"
D "github.com/miekg/dns"
)
type client struct {
*D.Client
r *Resolver
port string
host string
}
func (c *client) Exchange(m *D.Msg) (msg *D.Msg, err error) {
return c.ExchangeContext(context.Background(), m)
}
func (c *client) ExchangeContext(ctx context.Context, m *D.Msg) (msg *D.Msg, err error) {
var ip net.IP
if c.r == nil {
// a default ip dns
ip = net.ParseIP(c.host)
} else {
var err error
if ip, err = c.r.ResolveIP(c.host); err != nil {
return nil, fmt.Errorf("use default dns resolve failed: %w", err)
}
}
d, err := dialer.Dialer()
if err != nil {
return nil, err
}
if dialer.DialHook != nil {
network := "udp"
if strings.HasPrefix(c.Client.Net, "tcp") {
network = "tcp"
}
if err := dialer.DialHook(d, network, ip); err != nil {
return nil, err
}
}
c.Client.Dialer = d
// miekg/dns ExchangeContext doesn't respond to context cancel.
// this is a workaround
type result struct {
msg *D.Msg
err error
}
ch := make(chan result, 1)
go func() {
msg, _, err := c.Client.Exchange(m, net.JoinHostPort(ip.String(), c.port))
ch <- result{msg, err}
}()
select {
case <-ctx.Done():
return nil, ctx.Err()
case ret := <-ch:
return ret.msg, ret.err
}
}