Rename dialers into network

mtglib/network/network.go

@@ -0,0 +1,112 @@
+package network
+
+import (
+	"context"
+	"fmt"
+	"math/rand"
+	"net"
+	"net/http"
+	"time"
+
+	doh "github.com/babolivier/go-doh-client"
+)
+
+type Network struct {
+	HTTP http.Client
+	DNS  doh.Resolver
+
+	dialer Dialer
+}
+
+func (d *Network) Dial(network, address string) (net.Conn, error) {
+	return d.DialContext(context.Background(), network, address)
+}
+
+func (d *Network) DialContext(ctx context.Context, network, address string) (net.Conn, error) {
+	host, port, _ := net.SplitHostPort(address)
+
+	ips, err := d.resolveIPs(network, host)
+	if err != nil {
+		return nil, fmt.Errorf("cannot resolve dns names: %w", err)
+	}
+
+	rand.Shuffle(len(ips), func(i, j int) {
+		ips[i], ips[j] = ips[j], ips[i]
+	})
+
+	for _, v := range ips {
+		if conn, err := d.dialer.DialContext(ctx, network, net.JoinHostPort(v, port)); err == nil {
+			return conn, nil
+		}
+	}
+
+	return nil, fmt.Errorf("cannot dial to %s:%s", network, address)
+}
+
+func (d *Network) resolveIPs(network, address string) ([]string, error) {
+	if net.ParseIP(address) != nil {
+		return []string{address}, nil
+	}
+
+	var ips []string
+
+	switch network {
+	case "tcp", "tcp4":
+		if recs, _, err := d.DNS.LookupA(address); err == nil {
+			for _, v := range recs {
+				ips = append(ips, v.IP4)
+			}
+		}
+	}
+
+	switch network {
+	case "tcp", "tcp6":
+		if recs, _, err := d.DNS.LookupAAAA(address); err == nil {
+			for _, v := range recs {
+				ips = append(ips, v.IP6)
+			}
+		}
+	}
+
+	if len(ips) == 0 {
+		return nil, fmt.Errorf("cannot find any ips for %s:%s", network, address)
+	}
+
+	return ips, nil
+}
+
+func NewNetwork(dialer Dialer, dohHostname string, httpTimeout time.Duration) (*Network, error) {
+	switch {
+	case httpTimeout < 0:
+		return nil, fmt.Errorf("timeout should be positive number %v", httpTimeout)
+	case httpTimeout == 0:
+		httpTimeout = DefaultHTTPTimeout
+	}
+
+	if net.ParseIP(dohHostname) == nil {
+		return nil, fmt.Errorf("hostname %s should be IP address", dohHostname)
+	}
+
+	dohHTTPClient := &http.Client{
+		Timeout: httpTimeout,
+		Transport: &http.Transport{
+			DialContext: dialer.DialContext,
+		},
+	}
+	network := &Network{
+		dialer: dialer,
+		DNS: doh.Resolver{
+			Host:       dohHostname,
+			Class:      doh.IN,
+			HTTPClient: dohHTTPClient,
+		},
+	}
+	network.HTTP = http.Client{
+		Timeout: httpTimeout,
+		Transport: &http.Transport{
+			DialContext: network.DialContext,
+		},
+	}
+
+	return network, nil
+}