Don't send Content-Length on 304 responses.

It seems that browser writers also have trouble figuring out that
twisted logic in HTTP/1.1.

Fixes:	#1404
Spotted by:	Scoof

bin/varnishd/cache/cache_http1_deliver.c

@@ -207,6 +207,10 @@ V1D_Deliver(struct req *req)
 		/* In ESI mode, we can't know the aggregate length */
 		req->res_mode &= ~RES_LEN;
 		req->res_mode |= RES_ESI;
+	} else if (req->resp->status == 304) {
+		req->res_mode &= ~RES_LEN;
+		http_Unset(req->resp, H_Content_Length);
+		req->wantbody = 0;
 	} else if (req->obj->objcore->busyobj == NULL) {
 		/* XXX: Not happy with this convoluted test */
 		req->res_mode |= RES_LEN;
@@ -284,9 +288,6 @@ V1D_Deliver(struct req *req)
 	if (!(req->res_mode & RES_ESI_CHILD))
 		req->acct_req.hdrbytes += HTTP1_Write(req->wrk, req->resp, 1);
 
-	if (!req->wantbody)
-		req->res_mode &= ~RES_CHUNKED;
-
 	if (req->res_mode & RES_CHUNKED)
 		WRW_Chunked(req->wrk);
 

bin/varnishd/cache/cache_req_fsm.c

@@ -146,12 +146,10 @@ cnt_deliver(struct worker *wrk, struct req *req)
 	assert(wrk->handling == VCL_RET_DELIVER);
 
 	if (!(req->obj->objcore->flags & OC_F_PASS)
+	    && req->esi_level == 0
 	    && req->obj->response == 200
-	    && req->http->conds && RFC2616_Do_Cond(req)) {
-		req->wantbody = 0;
+	    && req->http->conds && RFC2616_Do_Cond(req))
 		http_SetResp(req->resp, "HTTP/1.1", 304, "Not Modified");
-		// http_Unset(req->resp, H_Content_Length);
-	}
 
 	V1D_Deliver(req);
 

bin/varnishtest/tests/r01404.vtc

+varnishtest "Test that 304 does not send Content-Length"
+
+server s1 {
+	rxreq
+	txresp -hdr "ETag: foo" -body "11111\n"
+} -start
+
+varnish v1 -vcl+backend {
+	sub vcl_backend_response {
+		set beresp.do_stream = true;
+	}
+} -start
+
+client c1 {
+	txreq -hdr "If-None-Match: foo"
+	rxresp -no_obj
+	expect resp.status == 304
+	expect resp.http.Content-Length == <undef>
+}  -run