feat(dns): add dnscrypt and dns over tcp

common/protocols/dnscrypt/dnscrypt.go

@@ -1,3 +1,85 @@
 package dnscrypt
 
-// DNSCrypt resolver implementation
+import (
+	"fmt"
+	"time"
+
+	"github.com/afonsofrancof/sdns-proxy/common/logger"
+	"github.com/ameshkov/dnscrypt/v2"
+	"github.com/miekg/dns"
+)
+
+type Config struct {
+	ServerStamp  string
+	DNSSEC       bool
+	WriteTimeout time.Duration
+	ReadTimeout  time.Duration
+}
+
+type Client struct {
+	resolver *dnscrypt.Client
+	config   Config
+	ri       *dnscrypt.ResolverInfo
+}
+
+func New(config Config) (*Client, error) {
+	logger.Debug("Creating DNSCrypt client with stamp: %s", config.ServerStamp)
+
+	if config.ServerStamp == "" {
+		logger.Error("DNSCrypt client creation failed: empty ServerStamp")
+		return nil, fmt.Errorf("dnscrypt: ServerStamp cannot be empty")
+	}
+	if config.WriteTimeout <= 0 {
+		config.WriteTimeout = 5 * time.Second
+	}
+	if config.ReadTimeout <= 0 {
+		config.ReadTimeout = 10 * time.Second
+	}
+
+	resolver := &dnscrypt.Client{
+		Net:     "udp",
+		Timeout: config.ReadTimeout,
+	}
+
+	// Resolve the server info from the stamp
+	ri, err := resolver.Dial(config.ServerStamp)
+	if err != nil {
+		logger.Error("DNSCrypt failed to dial server: %v", err)
+		return nil, fmt.Errorf("dnscrypt: failed to dial server: %w", err)
+	}
+
+	logger.Debug("DNSCrypt client created (DNSSEC: %v)", config.DNSSEC)
+
+	return &Client{
+		resolver: resolver,
+		config:   config,
+		ri:       ri,
+	}, nil
+}
+
+func (c *Client) Close() {
+	// The dnscrypt library doesn't require explicit cleanup
+}
+
+func (c *Client) Query(msg *dns.Msg) (*dns.Msg, error) {
+	if len(msg.Question) > 0 {
+		question := msg.Question[0]
+		logger.Debug("DNSCrypt query: %s %s", question.Name, dns.TypeToString[question.Qtype])
+	}
+
+	if c.config.DNSSEC {
+		msg.SetEdns0(4096, true)
+	}
+
+	response, err := c.resolver.Exchange(msg, c.ri)
+	if err != nil {
+		logger.Error("DNSCrypt query failed: %v", err)
+		return nil, fmt.Errorf("dnscrypt: query failed: %w", err)
+	}
+
+	if len(response.Answer) > 0 {
+		logger.Debug("DNSCrypt response: %d answers", len(response.Answer))
+	}
+
+	return response, nil
+}