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package microvm
import ( "context" "errors" "io" "log/slog" "net/http" "net/http/httputil" "net/url" "strings")
// httpUploadBackend reverse-proxies guest binary-cache upload traffic to an// http(s) upload cache such as ncps.type httpUploadBackend struct { handler http.Handler}
func newHTTPUploadProxyBackend(target *url.URL, readUpstreams []CacheUpstream, logger *slog.Logger) *httpUploadBackend { return &httpUploadBackend{handler: uploadProxyHandler(target, readUpstreams, logger)}}
func (b *httpUploadBackend) ServeHTTP(w http.ResponseWriter, r *http.Request) { b.handler.ServeHTTP(w, r)}
func (b *httpUploadBackend) Close() error { return nil }
func uploadProxyHandler(target *url.URL, readUpstreams []CacheUpstream, logger *slog.Logger) http.Handler { rp := httputil.NewSingleHostReverseProxy(target) rp.ErrorLog = slog.NewLogLogger(logger.Handler(), slog.LevelError)
origDirector := rp.Director rp.Director = func(req *http.Request) { origDirector(req) // ensure host matches target req.Host = target.Host // the transport doesn't turn URL userinfo into basic auth, only // http.Client does, so do it ourselves if user := target.User; user != nil { password, _ := user.Password() req.SetBasicAuth(user.Username(), password) } }
// before uploading, nix copy asks the destination whether it already has each // path by GET/HEAD-ing <hash>.narinfo and skips the ones it does. we answer // that check across the upload target *and* the read caches: if any of them // already serves the path there is no point uploading it (the guest would // just substitute it from there anyway). narinfoUpstreams := append([]CacheUpstream{{url: target}}, readUpstreams...) exists := newNarinfoExistenceTransport(narinfoUpstreams, logger)
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) { if isNarinfoExistenceCheck(r) { serveNarinfoExistence(w, r, exists, logger) return } rp.ServeHTTP(w, r) })}
func newNarinfoExistenceTransport(upstreams []CacheUpstream, logger *slog.Logger) http.RoundTripper { return ¶llelRacingTransport{ upstreams: upstreams, underlying: proxyTransport, guardedUnderlying: guardedProxyTransport, logger: logger, }}
func isNarinfoExistenceCheck(r *http.Request) bool { if r.Method != http.MethodGet && r.Method != http.MethodHead { return false } return strings.HasSuffix(r.URL.Path, ".narinfo")}
func serveNarinfoExistence(w http.ResponseWriter, r *http.Request, exists http.RoundTripper, logger *slog.Logger) { probe := r.Clone(r.Context()) probe.RequestURI = ""
resp, err := exists.RoundTrip(probe) if err != nil { logger.Warn("upload proxy narinfo check failed, treating as not present", "path", r.URL.Path, "error", err) w.WriteHeader(http.StatusNotFound) return } defer resp.Body.Close()
for key, values := range resp.Header { for _, value := range values { w.Header().Add(key, value) } } w.WriteHeader(resp.StatusCode) if _, err := io.Copy(w, resp.Body); err != nil && !errors.Is(err, context.Canceled) { logger.Warn("upload proxy narinfo copy failed", "path", r.URL.Path, "error", err) }}