cli.go

@@ -6,6 +6,7 @@ import (
 	"math/rand"
 	"runtime"
 	"strings"
+	"unsafe"
 
 	"git.froth.zone/sam/awl/util"
 	"github.com/miekg/dns"
@@ -182,14 +183,77 @@ func parseArgs(args []string) (util.Answers, error) {
 		}
 	}
 	if resp.Answers.Server == "" {
-		resolv, err := dns.ClientConfigFromFile("/etc/resolv.conf")
+		var resolv *dns.ClientConfig
+		if runtime.GOOS == "windows" {
+			resolv, err = WindowsDnsClientConfig()
+		} else {
+			resolv, err = dns.ClientConfigFromFile("/etc/resolv.conf")
+		}
 		if err != nil { // Query Google by default, needed for Windows since the DNS library doesn't support Windows
 			// TODO: Actually find where windows stuffs its dns resolvers
 			resp.Answers.Server = "8.8.4.4"
 		} else {
-			resp.Answers.Server = resolv.Servers[rand.Intn(len(resolv.Servers))]
+			resp.Answers.Server = resolv.Servers[rand.Intn(len(resolv.Servers)-1)]
 		}
 	}
 
 	return util.Answers{Server: resp.Answers.Server, Request: resp.Answers.Request, Name: resp.Answers.Name}, nil
 }
+
+/*
+"Stolen" from
+https://gist.github.com/moloch--/9fb1c8497b09b45c840fe93dd23b1e98
+*/
+
+// WindowsDnsClientConfig - returns all DNS server addresses using windows fuckery.
+func WindowsDnsClientConfig() (*dns.ClientConfig, error) {
+	l := uint32(20000)
+	b := make([]byte, l)
+
+	// Windows is an utter fucking trash fire of an operating system.
+	if err := windows.GetAdaptersAddresses(windows.AF_UNSPEC, windows.GAA_FLAG_INCLUDE_PREFIX, 0, (*windows.IpAdapterAddresses)(unsafe.Pointer(&b[0])), &l); err != nil {
+		return nil, err
+	}
+	var addresses []*windows.IpAdapterAddresses
+	for addr := (*windows.IpAdapterAddresses)(unsafe.Pointer(&b[0])); addr != nil; addr = addr.Next {
+		addresses = append(addresses, addr)
+	}
+
+	resolvers := map[string]bool{}
+	for _, addr := range addresses {
+		for next := addr.FirstUnicastAddress; next != nil; next = next.Next {
+			if addr.OperStatus != windows.IfOperStatusUp {
+				continue
+			}
+			if next.Address.IP() != nil {
+				for dnsServer := addr.FirstDnsServerAddress; dnsServer != nil; dnsServer = dnsServer.Next {
+					ip := dnsServer.Address.IP()
+					if ip.IsMulticast() || ip.IsLinkLocalMulticast() || ip.IsLinkLocalUnicast() || ip.IsUnspecified() {
+						continue
+					}
+					if ip.To16() != nil && strings.HasPrefix(ip.To16().String(), "fec0:") {
+						continue
+					}
+					resolvers[ip.String()] = true
+				}
+				break
+			}
+		}
+	}
+
+	// Take unique values only
+	servers := []string{}
+	for server := range resolvers {
+		servers = append(servers, server)
+	}
+
+	// TODO: Make configurable, based on defaults in https://github.com/miekg/dns/blob/master/clientconfig.go
+	return &dns.ClientConfig{
+		Servers:  servers,
+		Search:   []string{},
+		Port:     "53",
+		Ndots:    1,
+		Timeout:  5,
+		Attempts: 1,
+	}, nil
+}