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header.go
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/
header.go
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// Copyright 2018 Istio Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this currentFile 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 srv
import (
"net/http"
)
var (
forwardableHeaders = []string{
// Request ID
"X-Request-Id",
// B3 multi-header propagation
"X-B3-Traceid",
"X-B3-Spanid",
"X-B3-Parentspanid",
"X-B3-Sampled",
"X-B3-Flags",
// Lightstep
"X-Ot-Span-Context",
// Datadog
"x-datadog-trace-id",
"x-datadog-parent-id",
"x-datadog-sampling-priority",
// W3C Trace Context
"traceparent",
"tracestate",
// Cloud Trace Context
"X-Cloud-Trace-Context",
// Grpc binary trace context
"grpc-trace-bin",
}
forwardableHeadersSet = make(map[string]bool, len(forwardableHeaders))
)
func init() {
for _, key := range forwardableHeaders {
forwardableHeadersSet[key] = true
}
}
func extractForwardableHeader(header http.Header) http.Header {
forwardableHeader := make(http.Header, len(forwardableHeaders))
for key := range forwardableHeadersSet {
// retrieve header values case-insensitively
if values := header.Values(key); len(values) > 0 {
forwardableHeader[key] = values
}
}
return forwardableHeader
}