1 files changed, 112 insertions, 0 deletions
diff --git a/hcdns/server.go b/hcdns/server.go
new file mode 100644
index 0000000..ce7894b
--- /dev/null
+++ b/hcdns/server.go
@@ -0,0 +1,112 @@
+package hcdns
+
+import (
+	"database/sql"
+	"fmt"
+	"git.hatecomputers.club/hatecomputers/hatecomputers.club/args"
+	"git.hatecomputers.club/hatecomputers/hatecomputers.club/database"
+	"github.com/miekg/dns"
+	"log"
+)
+
+const MAX_RECURSION = 15
+
+func resolveInternalCNAMEs(dbConn *sql.DB, domain string, qtype uint16, maxDepth int) ([]dns.RR, error) {
+	internalCnames, err := database.FindDNSRecords(dbConn, domain, "CNAME")
+	if err != nil {
+		return nil, err
+	}
+
+	var answers []dns.RR
+	for _, record := range internalCnames {
+		cname, err := dns.NewRR(fmt.Sprintf("%s %d IN CNAME %s", record.Name, record.TTL, record.Content))
+		if err != nil {
+			log.Println(err)
+			return nil, err
+		}
+		answers = append(answers, cname)
+
+		cnameRecursive, err := resolveDNS(dbConn, record.Content, qtype, maxDepth-1)
+		if err != nil {
+			log.Println(err)
+			return nil, err
+		}
+		answers = append(answers, cnameRecursive...)
+	}
+
+	qtypeName := dns.TypeToString[qtype]
+	if qtypeName == "" {
+		return nil, fmt.Errorf("invalid query type %d", qtype)
+	}
+
+	typeDnsRecords, err := database.FindDNSRecords(dbConn, domain, qtypeName)
+	if err != nil {
+		return nil, err
+	}
+	for _, record := range typeDnsRecords {
+		answer, err := dns.NewRR(fmt.Sprintf("%s %d IN %s %s", record.Name, record.TTL, qtypeName, record.Content))
+		if err != nil {
+			return nil, err
+		}
+		answers = append(answers, answer)
+	}
+
+	return answers, nil
+}
+
+func resolveDNS(dbConn *sql.DB, domain string, qtype uint16, maxDepth int) ([]dns.RR, error) {
+	if maxDepth == 0 {
+		return nil, fmt.Errorf("too much recursion")
+	}
+
+	answers, err := resolveInternalCNAMEs(dbConn, domain, qtype, maxDepth)
+	if err != nil {
+		return nil, err
+	}
+
+	return answers, nil
+}
+
+type DnsHandler struct {
+	DnsResolvers []string
+	DbConn       *sql.DB
+}
+
+func (h *DnsHandler) ServeDNS(w dns.ResponseWriter, r *dns.Msg) {
+	msg := new(dns.Msg)
+	msg.SetReply(r)
+	msg.Authoritative = true
+
+	for _, question := range r.Question {
+		answers, err := resolveDNS(h.DbConn, question.Name, question.Qtype, MAX_RECURSION)
+		if err != nil {
+			fmt.Println(err)
+			msg.SetRcode(r, dns.RcodeServerFailure)
+			w.WriteMsg(msg)
+			return
+		}
+		msg.Answer = append(msg.Answer, answers...)
+	}
+
+	if len(msg.Answer) == 0 {
+		msg.SetRcode(r, dns.RcodeNameError)
+	}
+
+	log.Println(msg.Answer)
+	w.WriteMsg(msg)
+}
+
+func MakeServer(argv *args.Arguments, dbConn *sql.DB) *dns.Server {
+	handler := &DnsHandler{
+		DbConn: dbConn,
+	}
+	addr := fmt.Sprintf(":%d", argv.DnsPort)
+
+	return &dns.Server{
+		Addr:      addr,
+		Net:       "udp",
+		Handler:   handler,
+		UDPSize:   65535,
+		ReusePort: true,
+	}
+}