Add support for custom DNS resolvers

go.mod

 )
 
 require (
+	github.com/ncruces/go-dns v1.3.2
 	github.com/pelletier/go-toml/v2 v2.2.4
 	github.com/pires/go-proxyproto v0.11.0
 	github.com/things-go/go-socks5 v0.1.0

go.sum

 github.com/miekg/dns v1.1.51/go.mod h1:2Z9d3CP1LQWihRZUf29mQ19yDThaI4DAYzte2CaQW5c=
 github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822 h1:C3w9PqII01/Oq1c1nUAm88MOHcQC9l5mIlSMApZMrHA=
 github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822/go.mod h1:+n7T8mK8HuQTcFwEeznm/DIxMOiR9yIdICNftLE1DvQ=
+github.com/ncruces/go-dns v1.3.2 h1:kBLuUZBgkQ4qF4WDXZRQ4rG0Gk6sLVJQ5tESkWrxUa0=
+github.com/ncruces/go-dns v1.3.2/go.mod h1:tuzixNY8PY/M7yUzcvRbUaeLs3ifIdydpi5H2bfRU+s=
 github.com/panjf2000/ants/v2 v2.11.5 h1:a7LMnMEeux/ebqTux140tRiaqcFTV0q2bEHF03nl6Rg=
 github.com/panjf2000/ants/v2 v2.11.5/go.mod h1:8u92CYMUc6gyvTIw8Ru7Mt7+/ESnJahz5EVtqfrilek=
 github.com/patrickmn/go-cache v2.1.0+incompatible h1:HRMgzkcYKYpi3C8ajMPV8OFXaaRUnok+kx1WdO15EQc=

network/v2/dns.go

+package network
+
+import (
+	"context"
+	"fmt"
+	"net"
+	"net/url"
+	"time"
+
+	"github.com/ncruces/go-dns"
+)
+
+var dnsCacheOptions = []dns.CacheOption{
+	dns.MaxCacheEntries(dns.DefaultMaxCacheEntries),
+	dns.MaxCacheTTL(time.Hour),
+	dns.NegativeCache(false),
+}
+
+func GetDNS(u *url.URL) (*net.Resolver, error) {
+	if u == nil {
+		return dns.NewCachingResolver(nil, dnsCacheOptions...), nil
+	}
+
+	switch u.Scheme {
+	case "tls":
+		return dns.NewDoTResolver(u.Host, dns.DoTCache(dnsCacheOptions...))
+	case "https":
+		if u.Path == "" {
+			u.Path = "/dns-query"
+		}
+
+		return dns.NewDoHResolver(u.String(), dns.DoHCache(dnsCacheOptions...))
+	case "udp", "":
+	default:
+		return nil, fmt.Errorf("unsupported DNS %v", u)
+	}
+
+	port := u.Port()
+	if port == "" {
+		port = "53"
+	}
+
+	hostport := net.JoinHostPort(u.Hostname(), port)
+	dialer := &net.Dialer{}
+	resolver := &net.Resolver{
+		PreferGo: true,
+		Dial: func(ctx context.Context, network, address string) (net.Conn, error) {
+			return dialer.DialContext(ctx, "udp", hostport)
+		},
+	}
+
+	return dns.NewCachingResolver(resolver, dnsCacheOptions...), nil
+}

network/v2/dns_test.go

+package network_test
+
+import (
+	"context"
+	"net"
+	"net/url"
+	"testing"
+	"time"
+
+	"github.com/9seconds/mtg/v2/network/v2"
+	"github.com/stretchr/testify/require"
+	"github.com/stretchr/testify/suite"
+)
+
+type DNSTestSuite struct {
+	suite.Suite
+}
+
+func (suite *DNSTestSuite) TestDefault() {
+	resolver, err := network.GetDNS(nil)
+	suite.NoError(err)
+	suite.doTest(resolver)
+}
+
+func (suite *DNSTestSuite) TestDoH() {
+	for _, addr := range []string{"1.1.1.1", "cloudflare-dns.com"} {
+		suite.Run(addr, func() {
+			u, err := url.Parse("https://" + addr)
+			require.NoError(suite.T(), err)
+
+			resolver, err := network.GetDNS(u)
+			suite.NoError(err)
+			suite.doTest(resolver)
+		})
+	}
+}
+
+func (suite *DNSTestSuite) TestDoT() {
+	u, err := url.Parse("tls://dns.google")
+	require.NoError(suite.T(), err)
+
+	resolver, err := network.GetDNS(u)
+	suite.NoError(err)
+	suite.doTest(resolver)
+}
+
+func (suite *DNSTestSuite) TestUDP() {
+	u, err := url.Parse("8.8.8.8")
+	require.NoError(suite.T(), err)
+
+	resolver, err := network.GetDNS(u)
+	suite.NoError(err)
+	suite.doTest(resolver)
+}
+
+func (suite *DNSTestSuite) doTest(resolver *net.Resolver) {
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+
+	ips, err := resolver.LookupIP(ctx, "ip4", "dns.google")
+	suite.NoError(err)
+	suite.Greater(len(ips), 0)
+}
+
+func TestGetDNS(t *testing.T) {
+	t.Parallel()
+	suite.Run(t, &DNSTestSuite{})
+}