mirror of https://github.com/Dreamacro/clash.git
89 lines
1.6 KiB
Go
89 lines
1.6 KiB
Go
package dhcp
|
|
|
|
import (
|
|
"context"
|
|
"errors"
|
|
"net"
|
|
|
|
"github.com/Dreamacro/clash/component/iface"
|
|
|
|
"github.com/insomniacslk/dhcp/dhcpv4"
|
|
)
|
|
|
|
var (
|
|
ErrNotResponding = errors.New("DHCP not responding")
|
|
ErrNotFound = errors.New("DNS option not found")
|
|
)
|
|
|
|
func ResolveDNSFromDHCP(context context.Context, ifaceName string) ([]net.IP, error) {
|
|
conn, err := ListenDHCPClient(context, ifaceName)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
defer conn.Close()
|
|
|
|
result := make(chan []net.IP, 1)
|
|
|
|
ifaceObj, err := iface.ResolveInterface(ifaceName)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
discovery, err := dhcpv4.NewDiscovery(ifaceObj.HardwareAddr, dhcpv4.WithBroadcast(true), dhcpv4.WithRequestedOptions(dhcpv4.OptionDomainNameServer))
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
go receiveOffer(conn, discovery.TransactionID, result)
|
|
|
|
_, err = conn.WriteTo(discovery.ToBytes(), &net.UDPAddr{IP: net.IPv4bcast, Port: 67})
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
select {
|
|
case r, ok := <-result:
|
|
if !ok {
|
|
return nil, ErrNotFound
|
|
}
|
|
return r, nil
|
|
case <-context.Done():
|
|
return nil, ErrNotResponding
|
|
}
|
|
}
|
|
|
|
func receiveOffer(conn net.PacketConn, id dhcpv4.TransactionID, result chan<- []net.IP) {
|
|
defer close(result)
|
|
|
|
buf := make([]byte, dhcpv4.MaxMessageSize)
|
|
|
|
for {
|
|
n, _, err := conn.ReadFrom(buf)
|
|
if err != nil {
|
|
return
|
|
}
|
|
|
|
pkt, err := dhcpv4.FromBytes(buf[:n])
|
|
if err != nil {
|
|
continue
|
|
}
|
|
|
|
if pkt.MessageType() != dhcpv4.MessageTypeOffer {
|
|
continue
|
|
}
|
|
|
|
if pkt.TransactionID != id {
|
|
continue
|
|
}
|
|
|
|
dns := pkt.DNS()
|
|
if len(dns) == 0 {
|
|
return
|
|
}
|
|
|
|
result <- dns
|
|
|
|
return
|
|
}
|
|
}
|