Log X-Forwarded-For IPs when UNIX domain sockets are in use

Closes #183

internal/upstream/upstream.go

@@ -56,7 +56,11 @@ func (u *upstream) configureURLPrefix() {
 }
 
 func (u *upstream) ServeHTTP(ow http.ResponseWriter, r *http.Request) {
-	// Automatic quasi-intelligent X-Forwarded-For parsing
+	// Unix domain sockets have a remote addr of @. This will make the
+	// xff package lookup the X-Forwarded-For address if available.
+	if r.RemoteAddr == "@" {
+		r.RemoteAddr = "127.0.0.1:0"
+	}
 	r.RemoteAddr = xff.GetRemoteAddr(r)
 
 	w := helper.NewStatsCollectingResponseWriter(ow)

internal/upstream/upstream_test.go

+package upstream
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"gitlab.com/gitlab-org/gitlab-workhorse/internal/config"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+// This test doesn't actually listen for a connection so there may be
+// some error spew that can be ignored.
+func TestXForwardedForHeaders(t *testing.T) {
+	testCases := []struct {
+		initial   string
+		forwarded string
+		expected  string
+	}{
+		{initial: "@", forwarded: "", expected: "127.0.0.1:0"},
+		{initial: "@", forwarded: "18.245.0.1", expected: "18.245.0.1:0"},
+		{initial: "@", forwarded: "127.0.0.1", expected: "127.0.0.1:0"},
+		{initial: "@", forwarded: "192.168.0.1", expected: "127.0.0.1:0"},
+		{initial: "192.168.1.1:0", forwarded: "", expected: "192.168.1.1:0"},
+		{initial: "192.168.1.1:0", forwarded: "18.245.0.1", expected: "18.245.0.1:0"},
+	}
+
+	for _, tc := range testCases {
+		req, err := http.NewRequest("POST", "unix:///tmp/test.socket/info/refs", nil)
+		require.NoError(t, err)
+
+		req.RemoteAddr = tc.initial
+
+		if tc.forwarded != "" {
+			req.Header.Add("X-Forwarded-For", tc.forwarded)
+		}
+
+		config := config.Config{}
+		u := NewUpstream(config)
+
+		resp := httptest.NewRecorder()
+		u.ServeHTTP(resp, req)
+
+		assert.Equal(t, tc.expected, req.RemoteAddr)
+	}
+}