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package gateway
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import (
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	"context"
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	"fmt"
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	"net"
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	"net/http"
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	"net/http/httputil"
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	"net/url"
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	"go.miragespace.co/specter/spec/protocol"
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	"go.miragespace.co/specter/spec/rpc"
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	"go.miragespace.co/specter/spec/transport"
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	"go.uber.org/zap"
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)
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const (
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	internalProxyNodeAddress = "x-internal-proxy-node-address"
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	internalProxyForwarded   = "x-internal-proxy-forwarded"
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)
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func (g *Gateway) getInternalProxyHandler() func(http.Handler) http.Handler {
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	targetURL := &url.URL{
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		Scheme: "http",
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		Host:   g.RootDomains[0],
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	}
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	proxy := &httputil.ReverseProxy{}
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	proxy.Transport = &http.Transport{
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		DisableKeepAlives:   true,
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		MaxIdleConnsPerHost: -1,
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		DialContext: func(ctx context.Context, network, addr string) (conn net.Conn, err error) {
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			defer func() {
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				if pr := recover(); pr != nil {
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					err = fmt.Errorf("internalDialer panic: %v", pr)
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				}
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			}()
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			target := rpc.GetNode(ctx)
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			if target == nil {
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				return nil, transport.ErrNoDirect
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			}
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			return g.TunnelServer.DialInternal(ctx, target)
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		},
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	}
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	proxy.Rewrite = func(preq *httputil.ProxyRequest) {
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		preq.SetURL(targetURL)
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		preq.Out.Host = preq.Out.URL.Host
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		preq.SetXForwarded()
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		preq.Out.Header.Set(internalProxyForwarded, "true")
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		preq.Out.Header.Del(internalProxyNodeAddress)
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	}
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	proxy.ErrorHandler = func(w http.ResponseWriter, r *http.Request, err error) {
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		w.WriteHeader(http.StatusBadGateway)
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		fmt.Fprintf(w, "error proxying internal request: %v", err)
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	}
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	return func(h http.Handler) http.Handler {
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		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
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			var (
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				forwarded     = r.Header.Get(internalProxyForwarded) != ""
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				targetAddress = r.Header.Get(internalProxyNodeAddress)
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			)
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			if forwarded || targetAddress == "" {
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				h.ServeHTTP(w, r)
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				return
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			}
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			target := &protocol.Node{
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				Address: targetAddress,
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			}
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			r = r.WithContext(rpc.WithNode(r.Context(), target))
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			g.Logger.Debug("Proxying internal request", zap.Object("target", target))
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			proxy.ServeHTTP(w, r)
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		})
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	}
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}