/
handler.go
235 lines (183 loc) · 5.32 KB
/
handler.go
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package resolver
import (
"context"
"os"
"time"
"github.com/miekg/dns"
"github.com/semihalev/log"
"github.com/semihalev/sdns/authcache"
"github.com/semihalev/sdns/cache"
"github.com/semihalev/sdns/config"
"github.com/semihalev/sdns/dnsutil"
"github.com/semihalev/sdns/middleware"
)
// DNSHandler type
type DNSHandler struct {
resolver *Resolver
cfg *config.Config
}
type ctxKey string
var debugns bool
func init() {
middleware.Register(name, func(cfg *config.Config) middleware.Handler {
return New(cfg)
})
_, debugns = os.LookupEnv("SDNS_DEBUGNS")
}
// New returns a new Handler
func New(cfg *config.Config) *DNSHandler {
if cfg.Maxdepth == 0 {
cfg.Maxdepth = 30
}
return &DNSHandler{
resolver: NewResolver(cfg),
cfg: cfg,
}
}
// Name return middleware name
func (h *DNSHandler) Name() string { return name }
// ServeDNS implements the Handle interface.
func (h *DNSHandler) ServeDNS(ctx context.Context, ch *middleware.Chain) {
w, req := ch.Writer, ch.Request
if v := ctx.Value(ctxKey("reqid")); v == nil {
ctx = context.WithValue(ctx, ctxKey("reqid"), req.Id)
}
msg := h.handle(ctx, req)
w.WriteMsg(msg)
}
func (h *DNSHandler) handle(ctx context.Context, req *dns.Msg) *dns.Msg {
q := req.Question[0]
do := false
opt := req.IsEdns0()
if opt != nil {
do = opt.Do()
}
if q.Qtype == dns.TypeANY {
return dnsutil.HandleFailed(req, dns.RcodeNotImplemented, do)
}
// debug ns stats
if debugns && q.Qclass == dns.ClassCHAOS && q.Qtype == dns.TypeHINFO {
return h.nsStats(req)
}
// check purge query
if q.Qclass == dns.ClassCHAOS && q.Qtype == dns.TypeNULL {
if qname, qtype, ok := dnsutil.ParsePurgeQuestion(req); ok {
if qtype == dns.TypeNS {
h.purge(qname)
}
resp := dnsutil.HandleFailed(req, dns.RcodeSuccess, do)
txt, _ := dns.NewRR(q.Name + ` 20 IN TXT "cache purged"`)
resp.Extra = append(resp.Extra, txt)
return resp
}
}
if q.Name != rootzone && !req.RecursionDesired {
return dnsutil.HandleFailed(req, dns.RcodeServerFailure, do)
}
// we shouldn't send rd and ad flag to aa servers
req.RecursionDesired = false
req.AuthenticatedData = false
//TODO (semihalev): config setable after this
ctx, cancel := context.WithDeadline(ctx, time.Now().Add(30*time.Second))
defer cancel()
depth := h.cfg.Maxdepth
resp, err := h.resolver.Resolve(ctx, req, h.resolver.rootservers, true, depth, 0, false, nil)
if err != nil {
log.Info("Resolve query failed", "query", formatQuestion(q), "error", err.Error())
resp = dnsutil.HandleFailed(req, dns.RcodeServerFailure, do)
return resp
}
if resp.Rcode == dns.RcodeRefused {
log.Info("Resolve query refused", "query", formatQuestion(q))
resp = dnsutil.HandleFailed(req, dns.RcodeServerFailure, do)
return resp
}
resp = h.additionalAnswer(ctx, req, resp)
return resp
}
func (h *DNSHandler) additionalAnswer(ctx context.Context, req, msg *dns.Msg) *dns.Msg {
if req.Question[0].Qtype == dns.TypeCNAME ||
req.Question[0].Qtype == dns.TypeDS {
return msg
}
cnameReq := new(dns.Msg)
cnameReq.Extra = req.Extra
cnameReq.CheckingDisabled = req.CheckingDisabled
for _, answer := range msg.Answer {
if answer.Header().Rrtype == req.Question[0].Qtype {
return msg
}
if answer.Header().Rrtype == dns.TypeCNAME {
cr := answer.(*dns.CNAME)
if cr.Target == req.Question[0].Name {
return dnsutil.HandleFailed(req, dns.RcodeServerFailure, false)
}
cnameReq.SetQuestion(cr.Target, req.Question[0].Qtype)
}
}
if len(cnameReq.Question) > 0 {
respCname, err := dnsutil.ExchangeInternal(ctx, cnameReq)
if err == nil && (len(respCname.Answer) > 0 || len(respCname.Ns) > 0) {
for _, rr := range respCname.Answer {
if respCname.Question[0].Name == cnameReq.Question[0].Name {
msg.Answer = append(msg.Answer, dns.Copy(rr))
}
}
for _, rr := range respCname.Ns {
if respCname.Question[0].Name == cnameReq.Question[0].Name {
msg.Ns = append(msg.Ns, dns.Copy(rr))
}
}
}
}
return msg
}
func (h *DNSHandler) nsStats(req *dns.Msg) *dns.Msg {
q := req.Question[0]
msg := new(dns.Msg)
msg.SetReply(req)
msg.Authoritative = false
msg.RecursionAvailable = true
servers := h.resolver.rootservers
ttl := uint32(0)
name := rootzone
if q.Name != rootzone {
nsKey := cache.Hash(dns.Question{Name: q.Name, Qtype: dns.TypeNS, Qclass: dns.ClassINET}, msg.CheckingDisabled)
ns, err := h.resolver.ncache.Get(nsKey)
if err != nil {
nsKey = cache.Hash(dns.Question{Name: q.Name, Qtype: dns.TypeNS, Qclass: dns.ClassINET}, !msg.CheckingDisabled)
ns, err := h.resolver.ncache.Get(nsKey)
if err == nil {
servers = ns.Servers
name = q.Name
}
} else {
servers = ns.Servers
name = q.Name
}
}
var serversList []*authcache.AuthServer
servers.RLock()
serversList = append(serversList, servers.List...)
servers.RUnlock()
authcache.Sort(serversList, 1)
rrHeader := dns.RR_Header{
Name: name,
Rrtype: dns.TypeHINFO,
Class: dns.ClassCHAOS,
Ttl: ttl,
}
for _, server := range serversList {
hinfo := &dns.HINFO{Hdr: rrHeader, Cpu: "Host", Os: server.String()}
msg.Ns = append(msg.Ns, hinfo)
}
return msg
}
func (h *DNSHandler) purge(qname string) {
q := dns.Question{Name: qname, Qtype: dns.TypeNS}
key := cache.Hash(q, false)
h.resolver.ncache.Remove(key)
key = cache.Hash(q, true)
h.resolver.ncache.Remove(key)
}
const name = "resolver"