github.com/waldiirawan/apm-agent-go/v2@v2.2.2/internal/apmhttputil/forwarded.go (about)

     1  // Licensed to Elasticsearch B.V. under one or more contributor
     2  // license agreements. See the NOTICE file distributed with
     3  // this work for additional information regarding copyright
     4  // ownership. Elasticsearch B.V. licenses this file to you under
     5  // the Apache License, Version 2.0 (the "License"); you may
     6  // not use this file except in compliance with the License.
     7  // You may obtain a copy of the License at
     8  //
     9  //     http://www.apache.org/licenses/LICENSE-2.0
    10  //
    11  // Unless required by applicable law or agreed to in writing,
    12  // software distributed under the License is distributed on an
    13  // "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
    14  // KIND, either express or implied.  See the License for the
    15  // specific language governing permissions and limitations
    16  // under the License.
    17  
    18  package apmhttputil
    19  
    20  import (
    21  	"strconv"
    22  	"strings"
    23  )
    24  
    25  // ForwardedHeader holds information extracted from a "Forwarded" HTTP header.
    26  type ForwardedHeader struct {
    27  	For   string
    28  	Host  string
    29  	Proto string
    30  }
    31  
    32  // ParseForwarded parses a "Forwarded" HTTP header.
    33  func ParseForwarded(f string) ForwardedHeader {
    34  	// We only consider the first value in the sequence,
    35  	// if there are multiple. Disregard everything after
    36  	// the first comma.
    37  	if comma := strings.IndexRune(f, ','); comma != -1 {
    38  		f = f[:comma]
    39  	}
    40  	var result ForwardedHeader
    41  	for f != "" {
    42  		field := f
    43  		if semi := strings.IndexRune(f, ';'); semi != -1 {
    44  			field = f[:semi]
    45  			f = f[semi+1:]
    46  		} else {
    47  			f = ""
    48  		}
    49  		eq := strings.IndexRune(field, '=')
    50  		if eq == -1 {
    51  			// Malformed field, ignore.
    52  			continue
    53  		}
    54  		key := strings.TrimSpace(field[:eq])
    55  		value := strings.TrimSpace(field[eq+1:])
    56  		if len(value) > 0 && value[0] == '"' {
    57  			var err error
    58  			value, err = strconv.Unquote(value)
    59  			if err != nil {
    60  				// Malformed, ignore
    61  				continue
    62  			}
    63  		}
    64  		switch strings.ToLower(key) {
    65  		case "for":
    66  			result.For = value
    67  		case "host":
    68  			result.Host = value
    69  		case "proto":
    70  			result.Proto = value
    71  		}
    72  	}
    73  	return result
    74  }