BUG/MEDIUM: stconn: Don't perform L7 retries with large buffer

L7 retries are buggy when a large buffer is used on the request channel. A
memcpy is used to copy data from the request buffer into the L7 buffer. The
L7 buffer is for now always a standard buffer. So if a larger buffer is
used, this leads to a buffer overflow and crash the process.

The Best way to fix the issue is to disable L7 retries when a large buffer
was allocated for the request channel. In that case, we don't want to
allocate an extra large buffer.

No backport needed.

Author: capflam

src/stconn.c

@@ -1493,7 +1493,7 @@ int sc_conn_send(struct stconn *sc)
 			 * disable the l7 retries by setting
 			 * l7_conn_retries to 0.
 			 */
-			if (s->txn->req.msg_state != HTTP_MSG_DONE)
+			if (s->txn->req.msg_state != HTTP_MSG_DONE || b_is_large(&oc->buf))
 				s->txn->flags &= ~TX_L7_RETRY;
 			else {
 				if (b_alloc(&s->txn->l7_buffer, DB_UNLIKELY) == NULL)