Introduce http->failed to mark struct http's suffering from trouble.

Usually, (probably always) this means failure to get workspace for
modifications of the http.

The intent is that this flag will have the same "latching" behaviour
as error handling in VSB's:  Once set, it stays set and nobody
reads or writes the struct http any more.

Setting the flag causes a SLT_Error message.

Rewrite http_CollectHdr() to respect failed and optimize it
slightly while were here.

bin/varnishd/cache/cache.h

@@ -202,6 +202,7 @@ struct http {
 	uint16_t		status;
 	uint8_t			protover;
 	uint8_t			conds;		/* If-* headers present */
+	uint8_t			failed;		/* usually: ws-alloc failed */
 };
 
 /*--------------------------------------------------------------------

bin/varnishd/cache/cache_http.c

@@ -92,6 +92,15 @@ http_VSL_log(const struct http *hp)
 			http_VSLH(hp, u);
 }
 
+/*--------------------------------------------------------------------*/
+
+static void
+http_fail(struct http *hp)
+{
+	VSLb(hp->vsl, SLT_Error, "out of workspace");
+	hp->failed = 1;
+}
+
 /*--------------------------------------------------------------------*/
 /* List of canonical HTTP response code names from RFC2616 */
 
@@ -146,12 +155,17 @@ HTTP_Setup(struct http *hp, struct ws *ws, struct vsl_log *vsl,
     enum VSL_tag_e  whence)
 {
 	http_Teardown(hp);
+	hp->nhd = HTTP_HDR_FIRST;
 	hp->logtag = whence;
 	hp->ws = ws;
 	hp->vsl = vsl;
 }
 
-/*--------------------------------------------------------------------*/
+/*--------------------------------------------------------------------
+ * http_Teardown() is a safety feature, we use it to zap all http
+ * structs once we're done with them, to minimize the risk that
+ * old stale pointers exist to no longer valid stuff.
+ */
 
 void
 http_Teardown(struct http *hp)
@@ -162,7 +176,6 @@ http_Teardown(struct http *hp)
 	memset(&hp->nhd, 0, sizeof *hp - offsetof(struct http, nhd));
 	memset(hp->hd, 0, sizeof *hp->hd * hp->shd);
 	memset(hp->hdf, 0, sizeof *hp->hdf * hp->shd);
-	hp->nhd = HTTP_HDR_FIRST;
 }
 
 /*--------------------------------------------------------------------*/
@@ -181,6 +194,26 @@ http_IsHdr(const txt *hh, const char *hdr)
 	return (!strncasecmp(hdr, hh->b, l));
 }
 
+/*--------------------------------------------------------------------*/
+
+static unsigned
+http_findhdr(const struct http *hp, unsigned l, const char *hdr)
+{
+	unsigned u;
+
+	for (u = HTTP_HDR_FIRST; u < hp->nhd; u++) {
+		Tcheck(hp->hd[u]);
+		if (hp->hd[u].e < hp->hd[u].b + l + 1)
+			continue;
+		if (hp->hd[u].b[l] != ':')
+			continue;
+		if (strncasecmp(hdr, hp->hd[u].b, l))
+			continue;
+		return (u);
+	}
+	return (0);
+}
+
 /*--------------------------------------------------------------------
  * This function collapses multiple headerlines of the same name.
  * The lines are joined with a comma, according to [rfc2616, 4.2bot, p32]
@@ -189,16 +222,25 @@ http_IsHdr(const txt *hh, const char *hdr)
 void
 http_CollectHdr(struct http *hp, const char *hdr)
 {
-	unsigned u, v, ml, f = 0, x;
+	unsigned u, l, ml, f, x, d;
 	char *b = NULL, *e = NULL;
 
-	for (u = HTTP_HDR_FIRST; u < hp->nhd; u++) {
-		while (u < hp->nhd && http_IsHdr(&hp->hd[u], hdr)) {
+	if (hp->failed)
+		return;
+	l = hdr[0];
+	assert(l == strlen(hdr + 1));
+	assert(hdr[l] == ':');
+	f = http_findhdr(hp, l - 1, hdr + 1);
+	if (f == 0)
+		return;
+
+	for (d = u = f + 1; u < hp->nhd; u++) {
 		Tcheck(hp->hd[u]);
-			if (f == 0) {
-				/* Found first header, just record the fact */
-				f = u;
-				break;
+		if (!http_IsHdr(&hp->hd[u], hdr)) {
+			if (d != u)
+				hp->hd[d] = hp->hd[u];
+			d++;
+			continue;
 		}
 		if (b == NULL) {
 			/* Found second header, start our collection */
@@ -206,11 +248,13 @@ http_CollectHdr(struct http *hp, const char *hdr)
 			b = hp->ws->f;
 			e = b + ml;
 			x = Tlen(hp->hd[f]);
-				if (b + x < e) {
+			if (b + x >= e) {
+				http_fail(hp);
+				WS_Release(hp->ws, 0);
+				return;
+			}
 			memcpy(b, hp->hd[f].b, x);
 			b += x;
-				} else
-					b = e;
 		}
 
 		AN(b);
@@ -219,27 +263,19 @@ http_CollectHdr(struct http *hp, const char *hdr)
 		/* Append the Nth header we found */
 		if (b < e)
 			*b++ = ',';
-			x = Tlen(hp->hd[u]) - *hdr;
-			if (b + x < e) {
+		x = Tlen(hp->hd[u]) - l;
+		if (b + x >= e) {
+			http_fail(hp);
+			WS_Release(hp->ws, 0);
+			return;
+		}
 		memcpy(b, hp->hd[u].b + *hdr, x);
 		b += x;
-			} else
-				b = e;
-
-			/* Shift remaining headers up one slot */
-			for (v = u; v < hp->nhd - 1; v++)
-				hp->hd[v] = hp->hd[v + 1];
-			hp->nhd--;
-		}
-
 	}
 	if (b == NULL)
 		return;
+	hp->nhd = (uint16_t)d;
 	AN(e);
-	if (b >= e) {
-		WS_Release(hp->ws, 0);
-		return;
-	}
 	*b = '\0';
 	hp->hd[f].b = hp->ws->f;
 	hp->hd[f].e = b;
@@ -248,24 +284,6 @@ http_CollectHdr(struct http *hp, const char *hdr)
 
 /*--------------------------------------------------------------------*/
 
-static unsigned
-http_findhdr(const struct http *hp, unsigned l, const char *hdr)
-{
-	unsigned u;
-
-	for (u = HTTP_HDR_FIRST; u < hp->nhd; u++) {
-		Tcheck(hp->hd[u]);
-		if (hp->hd[u].e < hp->hd[u].b + l + 1)
-			continue;
-		if (hp->hd[u].b[l] != ':')
-			continue;
-		if (strncasecmp(hdr, hp->hd[u].b, l))
-			continue;
-		return (u);
-	}
-	return (0);
-}
-
 int
 http_GetHdr(const struct http *hp, const char *hdr, char **ptr)
 {