net/http: don't hang if RemoteAddr() blocks
The PROXY protocol is supported by several proxy servers such as haproxy
and Amazon ELB. This protocol allows services running behind a proxy to
learn the remote address of the actual client connecting to the proxy,
by including a single textual line at the beginning of the TCP
connection.
http://www.haproxy.org/download/1.5/doc/proxy-protocol.txt
There are several Go libraries for this protocol (such as
https://github.com/armon/go-proxyproto), which operate by wrapping a
net.Conn with an implementation whose RemoteAddr method reads the
protocol line before returning. This means that RemoteAddr is a blocking
call.
Before this change, http.Serve called RemoteAddr from the main Accepting
goroutine, not from the per-connection goroutine. This meant that it
would not Accept another connection until RemoteAddr returned, which is
not appropriate if RemoteAddr needs to do a blocking read from the
socket first.
Fixes #12943.
Change-Id: I1a242169e6e4aafd118b794e7c8ac45d0d573421
Reviewed-on: https://go-review.googlesource.com/15835
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
diff --git a/src/net/http/serve_test.go b/src/net/http/serve_test.go
index 7840742..11a0a9e 100644
--- a/src/net/http/serve_test.go
+++ b/src/net/http/serve_test.go
@@ -755,6 +755,107 @@
}
}
+type blockingRemoteAddrListener struct {
+ net.Listener
+ conns chan<- net.Conn
+}
+
+func (l *blockingRemoteAddrListener) Accept() (net.Conn, error) {
+ c, err := l.Listener.Accept()
+ if err != nil {
+ return nil, err
+ }
+ brac := &blockingRemoteAddrConn{
+ Conn: c,
+ addrs: make(chan net.Addr, 1),
+ }
+ l.conns <- brac
+ return brac, nil
+}
+
+type blockingRemoteAddrConn struct {
+ net.Conn
+ addrs chan net.Addr
+}
+
+func (c *blockingRemoteAddrConn) RemoteAddr() net.Addr {
+ return <-c.addrs
+}
+
+// Issue 12943
+func TestServerAllowsBlockingRemoteAddr(t *testing.T) {
+ defer afterTest(t)
+ ts := httptest.NewUnstartedServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+ fmt.Fprintf(w, "RA:%s", r.RemoteAddr)
+ }))
+ conns := make(chan net.Conn)
+ ts.Listener = &blockingRemoteAddrListener{
+ Listener: ts.Listener,
+ conns: conns,
+ }
+ ts.Start()
+ defer ts.Close()
+
+ tr := &Transport{DisableKeepAlives: true}
+ defer tr.CloseIdleConnections()
+ c := &Client{Transport: tr, Timeout: time.Second}
+
+ fetch := func(response chan string) {
+ resp, err := c.Get(ts.URL)
+ if err != nil {
+ t.Error(err)
+ response <- ""
+ return
+ }
+ defer resp.Body.Close()
+ body, err := ioutil.ReadAll(resp.Body)
+ if err != nil {
+ t.Error(err)
+ response <- ""
+ return
+ }
+ response <- string(body)
+ }
+
+ // Start a request. The server will block on getting conn.RemoteAddr.
+ response1c := make(chan string, 1)
+ go fetch(response1c)
+
+ // Wait for the server to accept it; grab the connection.
+ conn1 := <-conns
+
+ // Start another request and grab its connection
+ response2c := make(chan string, 1)
+ go fetch(response2c)
+ var conn2 net.Conn
+
+ select {
+ case conn2 = <-conns:
+ case <-time.After(time.Second):
+ t.Fatal("Second Accept didn't happen")
+ }
+
+ // Send a response on connection 2.
+ conn2.(*blockingRemoteAddrConn).addrs <- &net.TCPAddr{
+ IP: net.ParseIP("12.12.12.12"), Port: 12}
+
+ // ... and see it
+ response2 := <-response2c
+ if g, e := response2, "RA:12.12.12.12:12"; g != e {
+ t.Fatalf("response 2 addr = %q; want %q", g, e)
+ }
+
+ // Finish the first response.
+ conn1.(*blockingRemoteAddrConn).addrs <- &net.TCPAddr{
+ IP: net.ParseIP("21.21.21.21"), Port: 21}
+
+ // ... and see it
+ response1 := <-response1c
+ if g, e := response1, "RA:21.21.21.21:21"; g != e {
+ t.Fatalf("response 1 addr = %q; want %q", g, e)
+ }
+}
+
func TestChunkedResponseHeaders(t *testing.T) {
defer afterTest(t)
log.SetOutput(ioutil.Discard) // is noisy otherwise
diff --git a/src/net/http/server.go b/src/net/http/server.go
index 0bdc9b6..ae62e07 100644
--- a/src/net/http/server.go
+++ b/src/net/http/server.go
@@ -470,7 +470,6 @@
// Create new connection from rwc.
func (srv *Server) newConn(rwc net.Conn) (c *conn, err error) {
c = new(conn)
- c.remoteAddr = rwc.RemoteAddr().String()
c.server = srv
c.rwc = rwc
c.w = rwc
@@ -1290,6 +1289,7 @@
// Serve a new connection.
func (c *conn) serve() {
+ c.remoteAddr = c.rwc.RemoteAddr().String()
origConn := c.rwc // copy it before it's set nil on Close or Hijack
defer func() {
if err := recover(); err != nil {
