[6.0] 2ac6b4dec Don't mess with C-L when responding to HEAD

[Dridi Boukelmoune]

commit 2ac6b4dece07758892b858ccf049b5941add21d5
Author: Guillaume Quintard <guillaume at varnish-software.com>
Date:   Thu Aug 16 19:22:52 2018 -0700

    Don't mess with C-L when responding to HEAD

diff --git a/bin/varnishd/cache/cache_req_fsm.c b/bin/varnishd/cache/cache_req_fsm.c
index 17c9899c7..07447bee6 100644
--- a/bin/varnishd/cache/cache_req_fsm.c
+++ b/bin/varnishd/cache/cache_req_fsm.c
@@ -342,7 +342,7 @@ cnt_transmit(struct worker *wrk, struct req *req)
 	struct boc *boc;
 	const char *r;
 	uint16_t status;
-	int err, sendbody;
+	int err, sendbody, head;
 	intmax_t clval;
 
 	CHECK_OBJ_NOTNULL(wrk, WORKER_MAGIC);
@@ -364,7 +364,8 @@ cnt_transmit(struct worker *wrk, struct req *req)
 
 	/* RFC 7230, 3.3.3 */
 	status = http_GetStatus(req->resp);
-	if (!strcmp(req->http0->hd[HTTP_HDR_METHOD].b, "HEAD")) {
+	head = !strcmp(req->http0->hd[HTTP_HDR_METHOD].b, "HEAD");
+	if (head) {
 		if (req->objcore->flags & OC_F_PASS)
 			sendbody = -1;
 		else
@@ -396,8 +397,8 @@ cnt_transmit(struct worker *wrk, struct req *req)
 		}
 	}
 
-	if (sendbody < 0) {
-		/* Don't touch pass+HEAD C-L */
+	if (sendbody < 0 || head) {
+		/* Don't touch HEAD C-L */
 		sendbody = 0;
 	} else if (clval >= 0 && clval == req->resp_len) {
 		/* Reuse C-L header */
diff --git a/bin/varnishtest/tests/b00065.vtc b/bin/varnishtest/tests/b00065.vtc
new file mode 100644
index 000000000..c8df453bf
--- /dev/null
+++ b/bin/varnishtest/tests/b00065.vtc
@@ -0,0 +1,20 @@
+varnishtest "Test that C-L on HEAD request aren't nuked"
+
+server s1 {
+	rxreq
+	txresp -nolen -hdr "content-length: 17"
+	expect req.method == "HEAD"
+} -start
+
+varnish v1 -vcl+backend {
+	sub vcl_backend_fetch {
+		set bereq.method = "HEAD";
+	}
+} -start
+
+client c1 {
+	txreq -req HEAD -hdr "connection: close"
+	rxresphdrs
+	expect resp.http.content-length == 17
+	expect_close
+} -run