Treat NULL elements of string assignment as empty string line1 proto fields.

Refuse assignment of empty strings to line1 proto fields, issue VSL
record LostHdr.

line1 proto fields are request, url, proto and response. status is
numeric and not affected.

Fixes: #781



git-svn-id: http://www.varnish-cache.org/svn/trunk/varnish-cache@5224 d4fa192b-c00b-0410-8231-f00ffab90ce4

bin/varnishd/cache_vrt.c

@@ -161,12 +161,12 @@ vrt_build_string(struct ws *ws, const char *h, const char *p, va_list ap)
 		b++;
 	}
 	while (p != vrt_magic_string_end && b < e) {
-		if (p == NULL)
-			p = "(null)";
-		x = strlen(p);
-		if (b + x < e)
-			memcpy(b, p, x);
-		b += x;
+		if (p != NULL) {
+			x = strlen(p);
+			if (b + x < e)
+				memcpy(b, p, x);
+			b += x;
+		}
 		p = va_arg(ap, const char *);
 	}
 	if (b < e)
@@ -247,10 +247,10 @@ vrt_do_string(struct worker *w, int fd, struct http *hp, int fld,
 {
 	char *b;
 
-	AN(p);
+	// AN(p);
 	AN(hp);
 	b = vrt_assemble_string(hp, NULL, p, ap);
-	if (b == NULL) {
+	if (b == NULL || *b == '\0') {
 		WSL(w, SLT_LostHeader, fd, err);
 	} else {
 		http_SetH(hp, fld, b);
@@ -264,7 +264,6 @@ VRT_l_##obj##_##hdr(const struct sess *sp, const char *p, ...)	\
 {								\
 	va_list ap;						\
 								\
-	AN(p);							\
 	va_start(ap, p);					\
 	vrt_do_string(sp->wrk, sp->fd,				\
 	    http, fld, #obj "." #hdr, p, ap);			\

bin/varnishtest/tests/r00781.vtc

+# $Id$
+
+test "NULL assignment to line1 fields."
+
+server s1 {
+	rxreq
+	txresp  -bodylen 10
+} -start
+
+varnish v1 -vcl+backend {
+	sub vcl_recv {
+		set req.url = req.http.foo;
+	}
+	sub vcl_miss {
+		set bereq.url = req.http.foo;
+	}
+} -start
+
+client c1 {
+	txreq 
+	rxresp
+} -run