序
本文主要研究一下spring cloud gateway的ForwardedHeadersFilter
GatewayAutoConfiguration
spring-cloud-gateway-core-2.0.0.RC1-sources.jar!/org/springframework/cloud/gateway/config/GatewayAutoConfiguration.java
@Configuration
@ConditionalOnProperty(name = "spring.cloud.gateway.enabled", matchIfMissing = true)
@EnableConfigurationProperties
@AutoConfigureBefore(HttpHandlerAutoConfiguration.class)
@AutoConfigureAfter({GatewayLoadBalancerClientAutoConfiguration.class, GatewayClassPathWarningAutoConfiguration.class})
@ConditionalOnClass(DispatcherHandler.class)
public class GatewayAutoConfiguration {
//......
@Bean
@ConditionalOnProperty(name = "spring.cloud.gateway.forwarded.enabled", matchIfMissing = true)
public ForwardedHeadersFilter forwardedHeadersFilter() {
return new ForwardedHeadersFilter();
}
//......
}
ForwardedHeadersFilter
spring-cloud-gateway-core-2.0.0.RC1-sources.jar!/org/springframework/cloud/gateway/filter/headers/ForwardedHeadersFilter.java
public class ForwardedHeadersFilter implements HttpHeadersFilter, Ordered {
public static final String FORWARDED_HEADER = "Forwarded";
@Override
public int getOrder() {
return 0;
}
@Override
public HttpHeaders filter(HttpHeaders input, ServerWebExchange exchange) {
ServerHttpRequest request = exchange.getRequest();
HttpHeaders original = input;
HttpHeaders updated = new HttpHeaders();
// copy all headers except Forwarded
original.entrySet().stream()
.filter(entry -> !entry.getKey().toLowerCase().equalsIgnoreCase(FORWARDED_HEADER))
.forEach(entry -> updated.addAll(entry.getKey(), entry.getValue()));
List<Forwarded> forwardeds = parse(original.get(FORWARDED_HEADER));
for (Forwarded f : forwardeds) {
updated.add(FORWARDED_HEADER, f.toString());
}
//TODO: add new forwarded
URI uri = request.getURI();
String host = original.getFirst(HttpHeaders.HOST);
Forwarded forwarded = new Forwarded()
.put("host", host)
.put("proto", uri.getScheme());
InetSocketAddress remoteAddress = request.getRemoteAddress();
if (remoteAddress != null) {
String forValue = remoteAddress.getAddress().getHostAddress();
int port = remoteAddress.getPort();
if (port >= 0) {
forValue = forValue + ":" + port;
}
forwarded.put("for", forValue);
}
// TODO: support by?
updated.add(FORWARDED_HEADER, forwarded.toHeaderValue());
return updated;
}
/* for testing */ static List<Forwarded> parse(List<String> values) {
ArrayList<Forwarded> forwardeds = new ArrayList<>();
if (CollectionUtils.isEmpty(values)) {
return forwardeds;
}
for (String value : values) {
Forwarded forwarded = parse(value);
forwardeds.add(forwarded);
}
return forwardeds;
}
/* for testing */ static Forwarded parse(String value) {
String[] pairs = StringUtils.tokenizeToStringArray(value, ";");
LinkedCaseInsensitiveMap<String> result = splitIntoCaseInsensitiveMap(pairs);
if (result == null) return null;
Forwarded forwarded = new Forwarded(result);
return forwarded;
}
@Nullable
/* for testing */ static LinkedCaseInsensitiveMap<String> splitIntoCaseInsensitiveMap(String[] pairs) {
if (ObjectUtils.isEmpty(pairs)) {
return null;
}
LinkedCaseInsensitiveMap<String> result = new LinkedCaseInsensitiveMap<>();
for (String element : pairs) {
String[] splittedElement = StringUtils.split(element, "=");
if (splittedElement == null) {
continue;
}
result.put(splittedElement[0].trim(), splittedElement[1].trim());
}
return result;
}
}
这个filter首先拷贝了请求的header，然后将请求中的Forwarded提取出来，解析成一个个Forwarded对象，添加到新的HttpHeaders中。除此之外，还补充了一个转发信息的Forwarded(
host,proto,for)
Forwarded
语法
Forwarded: by=<identifier>; for=<identifier>; host=<host>; proto=<http|https>
- by=<identifier> 该请求进入到代理服务器的接口。
- for=<identifier> 发起请求的客户端以及代理链中的一系列的代理服务器。
- host=<host> 代理接收到的 Host首部的信息。
- proto=<http|https> 表示发起请求时采用的何种协议（通常是 "http" 或者 "https"）。
实例
Forwarded: for=192.0.2.60; proto=http; by=203.0.113.43
Forwarded: proto=http;host="localhost:10000";for="0:0:0:0:0:0:0:1:56443"
对象
static class Forwarded {
private static final char EQUALS = '=';
private static final char SEMICOLON = ';';
private final Map<String, String> values;
public Forwarded() {
this.values = new HashMap<>();
}
public Forwarded(Map<String, String> values) {
this.values = values;
}
public Forwarded put(String key, String value) {
this.values.put(key, quoteIfNeeded(value));
return this;
}
private String quoteIfNeeded(String s) {
if (s.contains(":")) { //TODO: broaded quote
return "\""+s+"\"";
}
return s;
}
public String get(String key) {
return this.values.get(key);
}
/* for testing */ Map<String, String> getValues() {
return this.values;
}
@Override
public String toString() {
return "Forwarded{" +
"values=" + this.values +
'}';
}
public String toHeaderValue() {
StringBuilder builder = new StringBuilder();
for (Map.Entry<String, String> entry : this.values.entrySet()) {
if (builder.length() > 0) {
builder.append(SEMICOLON);
}
builder.append(entry.getKey())
.append(EQUALS)
.append(entry.getValue());
}
return builder.toString();
}
}
小结
RFC 7239(June 2014)提出了一个标准化的Forwarded头部，来携带反向代理的基本信息，用于替代X-Forwarded系列及X-Real-IP等非标准化的头部。而ForwardedHeadersFilter便是提供了Forwarded头部的转发支持，目前经过gateway的请求会带上一个转发信息的Forwarded(host,proto,for)。