github.com/google/martian/v3@v3.3.3/header/forwarded_modifier.go (about) 1 // Copyright 2015 Google Inc. All rights reserved. 2 // 3 // Licensed under the Apache License, Version 2.0 (the "License"); 4 // you may not use this file except in compliance with the License. 5 // You may obtain a copy of the License at 6 // 7 // http://www.apache.org/licenses/LICENSE-2.0 8 // 9 // Unless required by applicable law or agreed to in writing, software 10 // distributed under the License is distributed on an "AS IS" BASIS, 11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 // See the License for the specific language governing permissions and 13 // limitations under the License. 14 15 package header 16 17 import ( 18 "net" 19 "net/http" 20 21 "github.com/google/martian/v3" 22 ) 23 24 // NewForwardedModifier sets the X-Forwarded-For, X-Forwarded-Proto, 25 // X-Forwarded-Host, and X-Forwarded-Url headers. 26 // 27 // If X-Forwarded-For is already present, the client IP is appended to 28 // the existing value. X-Forwarded-Proto, X-Forwarded-Host, and 29 // X-Forwarded-Url are preserved if already present. 30 // 31 // TODO: Support "Forwarded" header. 32 // see: http://tools.ietf.org/html/rfc7239 33 func NewForwardedModifier() martian.RequestModifier { 34 return martian.RequestModifierFunc( 35 func(req *http.Request) error { 36 if v := req.Header.Get("X-Forwarded-Proto"); v == "" { 37 req.Header.Set("X-Forwarded-Proto", req.URL.Scheme) 38 } 39 if v := req.Header.Get("X-Forwarded-Host"); v == "" { 40 req.Header.Set("X-Forwarded-Host", req.Host) 41 } 42 if v := req.Header.Get("X-Forwarded-Url"); v == "" { 43 req.Header.Set("X-Forwarded-Url", req.URL.String()) 44 } 45 46 xff, _, err := net.SplitHostPort(req.RemoteAddr) 47 if err != nil { 48 xff = req.RemoteAddr 49 } 50 51 if v := req.Header.Get("X-Forwarded-For"); v != "" { 52 xff = v + ", " + xff 53 } 54 55 req.Header.Set("X-Forwarded-For", xff) 56 57 return nil 58 }) 59 }