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forked from extern/smegmesh
smegmesh/pkg/dns/dns.go

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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,
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Query: fmt.Sprintf("[?alias == '%s'] | [0]", alias),
}, &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
}