Set or append to X-Forwarded-For for downstream requests

spring-cloud-netflix-core/src/main/java/org/springframework/cloud/netflix/zuul/filters/pre/PreDecorationFilter.java

@@ -107,6 +107,15 @@ public class PreDecorationFilter extends ZuulFilter {
 					if (StringUtils.hasText(route.getPrefix())) {
 						ctx.addZuulRequestHeader("X-Forwarded-Prefix", route.getPrefix());
 					}
+					String xforwardedfor = ctx.getRequest().getHeader("X-Forwarded-For");
+					String remoteAddr = ctx.getRequest().getRemoteAddr();
+					if (xforwardedfor == null) {
+						xforwardedfor = remoteAddr;
+					}
+					else if (!xforwardedfor.contains(remoteAddr)) { // Prevent duplicates
+						xforwardedfor += ", " + remoteAddr;
+					}
+					ctx.addZuulRequestHeader("X-Forwarded-For", xforwardedfor);
 				}
 			}
 		}

spring-cloud-netflix-core/src/test/java/org/springframework/cloud/netflix/zuul/filters/pre/PreDecorationFilterTests.java

@@ -85,6 +85,8 @@ public class PreDecorationFilterTests {
 		this.properties.setPrefix("/api");
 		this.properties.setStripPrefix(true);
 		this.request.setRequestURI("/api/foo/1");
+		this.request.setRemoteAddr("5.6.7.8");
+		this.request.addHeader("X-Forwarded-For", "1.2.3.4");
 		this.routeLocator.addRoute(
 				new ZuulRoute("foo", "/foo/**", "foo", null, false, null, null));
 		this.filter.run();
@@ -94,6 +96,7 @@ public class PreDecorationFilterTests {
 		assertEquals("80", ctx.getZuulRequestHeaders().get("x-forwarded-port"));
 		assertEquals("http", ctx.getZuulRequestHeaders().get("x-forwarded-proto"));
 		assertEquals("/api", ctx.getZuulRequestHeaders().get("x-forwarded-prefix"));
+		assertEquals("1.2.3.4, 5.6.7.8", ctx.getZuulRequestHeaders().get("x-forwarded-for"));
 		assertEquals("foo",
 				getHeader(ctx.getOriginResponseHeaders(), "x-zuul-serviceid"));
 	}