32-incorporate-dns

Incorporated a DNS server. A DNS server can be run to resolve host
names.

pkg/dns/dns.go

@@ -0,0 +1,114 @@
+package smegdns
+
+import (
+	"encoding/json"
+	"fmt"
+	"net"
+	"net/rpc"
+
+	"github.com/miekg/dns"
+	"github.com/tim-beatham/wgmesh/pkg/ipc"
+	"github.com/tim-beatham/wgmesh/pkg/lib"
+	logging "github.com/tim-beatham/wgmesh/pkg/log"
+	"github.com/tim-beatham/wgmesh/pkg/query"
+)
+
+const SockAddr = "/tmp/wgmesh_ipc.sock"
+
+const MeshRegularExpression = `(?P<meshId>.+)\.(?P<alias>.+)\.smeg\.`
+
+type DNSHandler struct {
+	client *rpc.Client
+	server *dns.Server
+}
+
+// queryMesh: queries the mesh network for the given meshId and node
+// with alias
+func (d *DNSHandler) queryMesh(meshId, alias string) net.IP {
+	var reply string
+
+	err := d.client.Call("IpcHandler.Query", &ipc.QueryMesh{
+		MeshId: meshId,
+		Query:  "[?alias == 'tim'] | [0]",
+	}, &reply)
+
+	if err != nil {
+		return nil
+	}
+
+	var node *query.QueryNode
+
+	err = json.Unmarshal([]byte(reply), &node)
+
+	if err != nil || node == nil {
+		return nil
+	}
+
+	ip, _, _ := net.ParseCIDR(node.WgHost)
+	return ip
+}
+
+func (d *DNSHandler) handleQuery(m *dns.Msg) {
+	for _, q := range m.Question {
+		switch q.Qtype {
+		case dns.TypeAAAA:
+			logging.Log.WriteInfof("Query for %s", q.Name)
+
+			groups := lib.MatchCaptureGroup(MeshRegularExpression, q.Name)
+
+			if len(groups) == 0 {
+				continue
+			}
+
+			ip := d.queryMesh(groups["meshId"], groups["alias"])
+
+			rr, err := dns.NewRR(fmt.Sprintf("%s AAAA %s", q.Name, ip))
+
+			if err != nil {
+				logging.Log.WriteErrorf(err.Error())
+			}
+
+			if err == nil {
+				m.Answer = append(m.Answer, rr)
+			}
+		}
+	}
+}
+
+func (h *DNSHandler) handleDnsRequest(w dns.ResponseWriter, r *dns.Msg) {
+	msg := new(dns.Msg)
+	msg.SetReply(r)
+	msg.Authoritative = true
+
+	switch r.Opcode {
+	case dns.OpcodeQuery:
+		h.handleQuery(msg)
+	}
+
+	w.WriteMsg(msg)
+}
+
+func (h *DNSHandler) Listen() error {
+	return h.server.ListenAndServe()
+}
+
+func (h *DNSHandler) Close() error {
+	return h.server.Shutdown()
+}
+
+func NewDns(udpPort int) (*DNSHandler, error) {
+	client, err := rpc.DialHTTP("unix", SockAddr)
+
+	if err != nil {
+		return nil, err
+	}
+
+	dnsHander := DNSHandler{
+		client: client,
+	}
+
+	dns.HandleFunc("smeg.", dnsHander.handleDnsRequest)
+
+	dnsHander.server = &dns.Server{Addr: fmt.Sprintf(":%d", udpPort), Net: "udp"}
+	return &dnsHander, nil
+}