1 files changed, 107 insertions, 0 deletions
diff --git a/http.go b/http.go
new file mode 100644
index 0000000..423c9a9
--- /dev/null
+++ b/http.go
@@ -0,0 +1,107 @@
+// Copyright 2017 Google Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package tcpproxy
+
+import (
+	"bufio"
+	"bytes"
+	"net/http"
+)
+
+// AddHTTPHostRoute appends a route to the ipPort listener that says
+// if the incoming HTTP/1.x Host header name is httpHost, the
+// connection is given to dest. If it doesn't match, rule processing
+// continues for any additional routes on ipPort.
+//
+// The ipPort is any valid net.Listen TCP address.
+func (p *Proxy) AddHTTPHostRoute(ipPort, httpHost string, dest Target) {
+	p.addRoute(ipPort, httpHostMatch(httpHost), dest)
+}
+
+type httpHostMatch string
+
+func (host httpHostMatch) match(br *bufio.Reader) bool {
+	return httpHostHeader(br) == string(host)
+}
+
+// httpHostHeader returns the HTTP Host header from br without
+// consuming any of its bytes. It returns "" if it can't find one.
+func httpHostHeader(br *bufio.Reader) string {
+	const maxPeek = 4 << 10
+	peekSize := 0
+	for {
+		peekSize++
+		if peekSize > maxPeek {
+			b, _ := br.Peek(br.Buffered())
+			return httpHostHeaderFromBytes(b)
+		}
+		b, err := br.Peek(peekSize)
+		if n := br.Buffered(); n > peekSize {
+			b, _ = br.Peek(n)
+			peekSize = n
+		}
+		if len(b) > 0 {
+			if b[0] < 'A' || b[0] > 'Z' {
+				// Doesn't look like an HTTP verb
+				// (GET, POST, etc).
+				return ""
+			}
+			if bytes.Index(b, crlfcrlf) != -1 || bytes.Index(b, lflf) != -1 {
+				req, err := http.ReadRequest(bufio.NewReader(bytes.NewReader(b)))
+				if err != nil {
+					return ""
+				}
+				if len(req.Header["Host"]) > 1 {
+					// TODO(bradfitz): what does
+					// ReadRequest do if there are
+					// multiple Host headers?
+					return ""
+				}
+				return req.Host
+			}
+		}
+		if err != nil {
+			return httpHostHeaderFromBytes(b)
+		}
+	}
+}
+
+var (
+	lfHostColon = []byte("\nHost:")
+	lfhostColon = []byte("\nhost:")
+	crlf        = []byte("\r\n")
+	lf          = []byte("\n")
+	crlfcrlf    = []byte("\r\n\r\n")
+	lflf        = []byte("\n\n")
+)
+
+func httpHostHeaderFromBytes(b []byte) string {
+	if i := bytes.Index(b, lfHostColon); i != -1 {
+		return string(bytes.TrimSpace(untilEOL(b[i+len(lfHostColon):])))
+	}
+	if i := bytes.Index(b, lfhostColon); i != -1 {
+		return string(bytes.TrimSpace(untilEOL(b[i+len(lfhostColon):])))
+	}
+	return ""
+}
+
+// untilEOL returns v, truncated before the first '\n' byte, if any.
+// The returned slice may include a '\r' at the end.
+func untilEOL(v []byte) []byte {
+	if i := bytes.IndexByte(v, '\n'); i != -1 {
+		return v[:i]
+	}
+	return v
+}