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