From a923896c997b48bb6c39600b3704b532397c4628 Mon Sep 17 00:00:00 2001
From: Martin Polden <mpolden@mpolden.no>
Date: Wed, 25 Dec 2019 14:29:05 +0100
Subject: Implement REST API for inspecting logs

---
 http/http.go | 128 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 128 insertions(+)
 create mode 100644 http/http.go

(limited to 'http/http.go')

diff --git a/http/http.go b/http/http.go
new file mode 100644
index 0000000..2b0c5cc
--- /dev/null
+++ b/http/http.go
@@ -0,0 +1,128 @@
+package http
+
+import (
+	"context"
+	"encoding/json"
+	"net"
+	"net/http"
+	"time"
+
+	"github.com/mpolden/zdns/dns"
+	"github.com/mpolden/zdns/log"
+)
+
+// A Server defines paramaters for running an HTTP server. The HTTP server serves an API for inspecting cache contents
+// and request log.
+type Server struct {
+	server *http.Server
+	logger *log.Logger
+}
+
+type logEntry struct {
+	Time       string `json:"time"`
+	RemoteAddr net.IP `json:"remote_addr"`
+	Qtype      string `json:"type"`
+	Question   string `json:"question"`
+	Answer     string `json:"answer"`
+}
+
+type httpError struct {
+	err     error
+	Status  int    `json:"status"`
+	Message string `json:"message"`
+}
+
+// NewServer creates a new HTTP server, serving logs from the given logger and listening on listenAddr.
+func NewServer(logger *log.Logger, listenAddr string) *Server {
+	server := &http.Server{Addr: listenAddr}
+	s := &Server{logger: logger, server: server}
+	s.server.Handler = s.handler()
+	return s
+}
+
+func (s *Server) handler() http.Handler {
+	mux := http.NewServeMux()
+	mux.Handle("/log/v1/", appHandler(s.logHandler))
+	//mux.Handle("/cache/v1")
+	mux.Handle("/", appHandler(notFoundHandler))
+	return requestFilter(mux)
+}
+
+type appHandler func(http.ResponseWriter, *http.Request) (interface{}, *httpError)
+
+func (fn appHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	data, e := fn(w, r)
+	if e != nil { // e is *Error, not os.Error.
+		if e.Message == "" {
+			e.Message = e.err.Error()
+		}
+		out, err := json.Marshal(e)
+		if err != nil {
+			panic(err)
+		}
+		w.WriteHeader(e.Status)
+		w.Write(out)
+	} else if data != nil {
+		out, err := json.Marshal(data)
+		if err != nil {
+			panic(err)
+		}
+		w.Write(out)
+	}
+}
+
+func requestFilter(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+		next.ServeHTTP(w, r)
+	})
+}
+
+func notFoundHandler(w http.ResponseWriter, r *http.Request) (interface{}, *httpError) {
+	return nil, &httpError{
+		Status:  http.StatusNotFound,
+		Message: "Resource not found",
+	}
+}
+
+func (s *Server) logHandler(w http.ResponseWriter, r *http.Request) (interface{}, *httpError) {
+	logEntries, err := s.logger.Get(100)
+	if err != nil {
+		return nil, &httpError{
+			err:    err,
+			Status: http.StatusInternalServerError,
+		}
+	}
+	entries := make([]logEntry, 0, len(logEntries))
+	for _, entry := range logEntries {
+		dnsType := ""
+		switch entry.Qtype {
+		case dns.TypeA:
+			dnsType = "A"
+		case dns.TypeAAAA:
+			dnsType = "AAAA"
+		}
+		e := logEntry{
+			Time:       entry.Time.UTC().Format(time.RFC3339),
+			RemoteAddr: entry.RemoteAddr,
+			Qtype:      dnsType,
+			Question:   entry.Question,
+			Answer:     entry.Answer,
+		}
+		entries = append(entries, e)
+	}
+	return entries, nil
+}
+
+// Close shuts down the HTTP server.
+func (s *Server) Close() error { return s.server.Shutdown(context.Background()) }
+
+// ListenAndServe starts the HTTP server listening on the configured address.
+func (s *Server) ListenAndServe() error {
+	s.logger.Printf("http server listening on http://%s", s.server.Addr)
+	err := s.server.ListenAndServe()
+	if err == http.ErrServerClosed {
+		return nil // Do not treat server closing as an error
+	}
+	return err
+}
-- 
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