clash/dns/dhcp.go

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package dns
import (
"bytes"
"context"
"net"
"sync"
"time"
"github.com/Dreamacro/clash/component/dhcp"
"github.com/Dreamacro/clash/component/iface"
"github.com/Dreamacro/clash/component/resolver"
D "github.com/miekg/dns"
)
const (
IfaceTTL = time.Second * 20
DHCPTTL = time.Hour
DHCPTimeout = time.Minute
)
type dhcpClient struct {
ifaceName string
lock sync.Mutex
ifaceInvalidate time.Time
dnsInvalidate time.Time
ifaceAddr *net.IPNet
done chan struct{}
resolver *Resolver
err error
}
func (d *dhcpClient) Exchange(m *D.Msg) (msg *D.Msg, err error) {
ctx, cancel := context.WithTimeout(context.Background(), resolver.DefaultDNSTimeout)
defer cancel()
return d.ExchangeContext(ctx, m)
}
func (d *dhcpClient) ExchangeContext(ctx context.Context, m *D.Msg) (msg *D.Msg, err error) {
res, err := d.resolve(ctx)
if err != nil {
return nil, err
}
return res.ExchangeContext(ctx, m)
}
func (d *dhcpClient) resolve(ctx context.Context) (*Resolver, error) {
d.lock.Lock()
invalidated, err := d.invalidate()
if err != nil {
d.err = err
} else if invalidated {
done := make(chan struct{})
d.done = done
go func() {
ctx, cancel := context.WithTimeout(context.Background(), DHCPTimeout)
defer cancel()
var res *Resolver
dns, err := dhcp.ResolveDNSFromDHCP(ctx, d.ifaceName)
if err == nil {
nameserver := make([]NameServer, 0, len(dns))
for _, item := range dns {
nameserver = append(nameserver, NameServer{
Addr: net.JoinHostPort(item.String(), "53"),
Interface: d.ifaceName,
})
}
res = NewResolver(Config{
Main: nameserver,
})
}
d.lock.Lock()
defer d.lock.Unlock()
close(done)
d.done = nil
d.resolver = res
d.err = err
}()
}
d.lock.Unlock()
for {
d.lock.Lock()
res, err, done := d.resolver, d.err, d.done
d.lock.Unlock()
// initializing
if res == nil && err == nil {
select {
case <-done:
continue
case <-ctx.Done():
return nil, ctx.Err()
}
}
// dirty return
return res, err
}
}
func (d *dhcpClient) invalidate() (bool, error) {
if time.Now().Before(d.ifaceInvalidate) {
return false, nil
}
d.ifaceInvalidate = time.Now().Add(IfaceTTL)
ifaceObj, err := iface.ResolveInterface(d.ifaceName)
if err != nil {
return false, err
}
addr, err := ifaceObj.PickIPv4Addr(nil)
if err != nil {
return false, err
}
if time.Now().Before(d.dnsInvalidate) && d.ifaceAddr.IP.Equal(addr.IP) && bytes.Equal(d.ifaceAddr.Mask, addr.Mask) {
return false, nil
}
d.dnsInvalidate = time.Now().Add(DHCPTTL)
d.ifaceAddr = addr
return d.done == nil, nil
}
func newDHCPClient(ifaceName string) *dhcpClient {
return &dhcpClient{ifaceName: ifaceName}
}