add observer

resolver/plugin/http.go

@@ -0,0 +1,106 @@
+package resolver
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"net"
+	"net/http"
+
+	"github.com/go-gost/core/logger"
+	"github.com/go-gost/core/resolver"
+	ctxvalue "github.com/go-gost/x/internal/ctx"
+	"github.com/go-gost/x/internal/plugin"
+)
+
+type httpPluginRequest struct {
+	Network string `json:"network"`
+	Host    string `json:"host"`
+	Client  string `json:"client"`
+}
+
+type httpPluginResponse struct {
+	IPs []string `json:"ips"`
+	OK  bool     `json:"ok"`
+}
+
+type httpPlugin struct {
+	url    string
+	client *http.Client
+	header http.Header
+	log    logger.Logger
+}
+
+// NewHTTPPlugin creates an Resolver plugin based on HTTP.
+func NewHTTPPlugin(name string, url string, opts ...plugin.Option) resolver.Resolver {
+	var options plugin.Options
+	for _, opt := range opts {
+		opt(&options)
+	}
+
+	return &httpPlugin{
+		url:    url,
+		client: plugin.NewHTTPClient(&options),
+		header: options.Header,
+		log: logger.Default().WithFields(map[string]any{
+			"kind":     "resolver",
+			"resolver": name,
+		}),
+	}
+}
+
+func (p *httpPlugin) Resolve(ctx context.Context, network, host string, opts ...resolver.Option) (ips []net.IP, err error) {
+	p.log.Debugf("resolve %s/%s", host, network)
+
+	if p.client == nil {
+		return
+	}
+
+	rb := httpPluginRequest{
+		Network: network,
+		Host:    host,
+		Client:  string(ctxvalue.ClientIDFromContext(ctx)),
+	}
+	v, err := json.Marshal(&rb)
+	if err != nil {
+		return
+	}
+
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost, p.url, bytes.NewReader(v))
+	if err != nil {
+		return
+	}
+
+	if p.header != nil {
+		req.Header = p.header.Clone()
+	}
+	req.Header.Set("Content-Type", "application/json")
+	resp, err := p.client.Do(req)
+	if err != nil {
+		return
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		err = fmt.Errorf("%s", resp.Status)
+		return
+	}
+
+	res := httpPluginResponse{}
+	if err = json.NewDecoder(resp.Body).Decode(&res); err != nil {
+		return
+	}
+
+	if !res.OK {
+		return nil, errors.New("resolve failed")
+	}
+
+	for _, s := range res.IPs {
+		if ip := net.ParseIP(s); ip != nil {
+			ips = append(ips, ip)
+		}
+	}
+	return ips, nil
+}