feat: support system dns for windows
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parent
d6931ec491
commit
94f990da31
1 changed files with 107 additions and 2 deletions
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@ -2,6 +2,111 @@
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package dns
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func loadSystemResolver() (clients []dnsClient, err error) {
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return nil, errors.New("system resolver is not yet supported on Windows")
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import (
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"fmt"
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"net"
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"os"
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"syscall"
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"unsafe"
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"golang.org/x/sys/windows"
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)
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var (
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defaultNS = []string{"114.114.114.114:53"}
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)
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type dnsConfig struct {
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servers []string // server addresses (in host:port form) to use
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}
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func loadSystemResolver() (clients []dnsClient, err error) {
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content, err := dnsReadConfig()
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if err != nil {
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err = fmt.Errorf("failed to read system DNS: %w", err)
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}
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nameservers := content.servers
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if len(nameservers) == 0 {
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err = fmt.Errorf("no nameserver found in windows system")
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return
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}
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servers := make([]NameServer, 0, len(nameservers))
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for _, addr := range nameservers {
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servers = append(servers, NameServer{
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Addr: addr,
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Net: "udp",
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})
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}
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return transform(servers, nil), nil
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}
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func dnsReadConfig() (conf *dnsConfig, err error) {
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conf = &dnsConfig{}
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defer func() {
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if len(conf.servers) == 0 {
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conf.servers = defaultNS
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}
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}()
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aas, err := adapterAddresses()
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if err != nil {
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return conf, err
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}
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for _, aa := range aas {
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for dns := aa.FirstDnsServerAddress; dns != nil; dns = dns.Next {
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sa, err := dns.Address.Sockaddr.Sockaddr()
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if err != nil {
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continue
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}
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var ip net.IP
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switch sa := sa.(type) {
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case *syscall.SockaddrInet4:
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ip = net.IPv4(sa.Addr[0], sa.Addr[1], sa.Addr[2], sa.Addr[3])
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case *syscall.SockaddrInet6:
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//ip = make(net.IP, net.IPv6len)
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//copy(ip, sa.Addr[:])
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//if ip[0] == 0xfe && ip[1] == 0xc0 {
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// // Ignore these fec0/10 ones. Windows seems to
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// // populate them as defaults on its misc rando
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// // interfaces.
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// continue
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//}
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continue
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default:
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// Unexpected type.
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continue
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}
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conf.servers = append(conf.servers, net.JoinHostPort(ip.String(), "53"))
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}
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}
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return conf, nil
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}
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// adapterAddresses returns a list of IP adapter and address
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// structures. The structure contains an IP adapter and flattened
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// multiple IP addresses including unicast, anycast and multicast
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// addresses.
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func adapterAddresses() ([]*windows.IpAdapterAddresses, error) {
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var b []byte
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l := uint32(15000) // recommended initial size
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for {
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b = make([]byte, l)
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err := windows.GetAdaptersAddresses(syscall.AF_UNSPEC, windows.GAA_FLAG_INCLUDE_PREFIX, 0, (*windows.IpAdapterAddresses)(unsafe.Pointer(&b[0])), &l)
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if err == nil {
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if l == 0 {
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return nil, nil
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}
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break
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}
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if err.(syscall.Errno) != syscall.ERROR_BUFFER_OVERFLOW {
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return nil, os.NewSyscallError("getadaptersaddresses", err)
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}
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if l <= uint32(len(b)) {
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return nil, os.NewSyscallError("getadaptersaddresses", err)
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}
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}
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var aas []*windows.IpAdapterAddresses
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for aa := (*windows.IpAdapterAddresses)(unsafe.Pointer(&b[0])); aa != nil; aa = aa.Next {
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aas = append(aas, aa)
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}
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return aas, nil
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}
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