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package server
import (
"context"
"io"
"log/slog"
"net/netip"
"time"
"codeberg.org/miekg/dns"
"codeberg.org/miekg/dns/rdata"
"linum/internal/blocklist"
"linum/internal/cache"
)
func (s *Server) handleQuery(ctx context.Context, w dns.ResponseWriter, req *dns.Msg) {
if len(req.Question) == 0 {
m := new(dns.Msg)
m.Rcode = dns.RcodeFormatError
m.Response = true
m.ID = req.ID
m.Question = req.Question
io.Copy(w, m)
return
}
resp, blocked := s.buildResponse(req)
resp.ID = req.ID
resp.Data = nil
if _, err := io.Copy(w, resp); err != nil {
slog.Error("write response failed",
"err", err,
"qname", req.Question[0].Header().Name,
"qtype", dns.TypeToString[dns.RRToType(req.Question[0])],
)
return
}
slog.Info("query served",
"qname", req.Question[0].Header().Name,
"qtype", dns.TypeToString[dns.RRToType(req.Question[0])],
"rcode", dns.RcodeToString[resp.Rcode],
"blocked", blocked,
)
}
func (s *Server) buildResponse(req *dns.Msg) (*dns.Msg, bool) {
if len(req.Question) == 0 {
m := new(dns.Msg)
m.Rcode = dns.RcodeFormatError
m.Response = true
m.ID = req.ID
m.Question = req.Question
return m, false
}
q := req.Question[0]
qname := q.Header().Name
qtype := dns.RRToType(q)
qclass := q.Header().Class
if s.blocklist != nil && s.blocklist.IsBlocked(qname) {
return s.blockedResponse(req), true
}
if s.cache != nil {
key := cache.Key{Name: qname, Qtype: qtype, Class: qclass}
if cached, ok := s.cache.Get(key); ok {
cached.ID = req.ID
return cached, false
}
}
ctx, cancel := context.WithTimeout(s.baseCtx, 10*time.Second)
defer cancel()
reply, err := s.resolver.Lookup(ctx, qname, qtype)
if err != nil {
slog.Error("resolution failed",
"err", err,
"qname", qname,
"qtype", dns.TypeToString[qtype],
)
m := new(dns.Msg)
m.Rcode = dns.RcodeServerFailure
m.Response = true
m.ID = req.ID
m.Question = req.Question
return m, false
}
reply.ID = req.ID
if s.cache != nil && reply.Rcode != dns.RcodeServerFailure {
key := cache.Key{Name: qname, Qtype: qtype, Class: qclass}
s.cache.Set(key, reply, 0)
}
return reply, false
}
func (s *Server) blockedResponse(req *dns.Msg) *dns.Msg {
m := new(dns.Msg)
m.Response = true
m.ID = req.ID
m.Opcode = req.Opcode
m.RecursionDesired = req.RecursionDesired
m.Question = req.Question
m.Authoritative = true
if s.blocklist.Response() == blocklist.ResponseNXDOMAIN {
m.Rcode = dns.RcodeNameError
return m
}
q := req.Question[0]
qname := q.Header().Name
qtype := dns.RRToType(q)
switch qtype {
case dns.TypeA:
m.Answer = append(m.Answer, &dns.A{
Hdr: dns.Header{Name: qname, Class: dns.ClassINET, TTL: 60},
A: rdata.A{Addr: netip.AddrFrom4([4]byte{})},
})
case dns.TypeAAAA:
m.Answer = append(m.Answer, &dns.AAAA{
Hdr: dns.Header{Name: qname, Class: dns.ClassINET, TTL: 60},
AAAA: rdata.AAAA{Addr: netip.IPv6Unspecified()},
})
}
return m
}
|
