From: Aram Sargsyan <aram@isc.org>
Date: Tue, 22 Aug 2023 12:10:40 +0000 (+0000)
Subject: Handle cases when buf_size is zero
X-Git-Tag: v9.19.17~31^2~1
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=9a271371d32b7c0ff769cd9310af8beab471a3c9;p=thirdparty%2Fbind9.git

Handle cases when buf_size is zero

The isc_dnsstream_assembler_incoming() inline function expects that
when 'buf_size' is zero, then 'buf' must be NULL. The expectation is
not correct, because those values come from the libuv read callback,
and its documentation notes[1] that 'nread' ('buf_size' here) might
be 0, which does not indicate an error or EOF, but is equivalent to
EAGAIN or EWOULDBLOCK under read(2).

Change the isc_dnsstream_assembler_incoming() inline function to
remove the invalid expectation.

[1] https://docs.libuv.org/en/v1.x/stream.html#c.uv_read_cb
---

diff --git a/lib/isc/include/isc/dnsstream.h b/lib/isc/include/isc/dnsstream.h
index 1e6a26b0869..88e361331a7 100644
--- a/lib/isc/include/isc/dnsstream.h
+++ b/lib/isc/include/isc/dnsstream.h
@@ -491,13 +491,9 @@ isc_dnsstream_assembler_incoming(isc_dnsstream_assembler_t *restrict dnsasm,
 	REQUIRE(dnsasm != NULL);
 	INSIST(!dnsasm->calling_cb);
 
-	if (buf_size == 0) {
-		INSIST(buf == NULL);
-	} else {
+	if (buf != NULL && buf_size > 0) {
 		size_t remaining;
 
-		INSIST(buf != NULL);
-
 		remaining = isc_buffer_remaininglength(&dnsasm->dnsbuf);
 
 		if (remaining == 0) {
@@ -525,7 +521,7 @@ isc_dnsstream_assembler_incoming(isc_dnsstream_assembler_t *restrict dnsasm,
 			 * when receiving the next batch of data.
 			 */
 			return;
-		} else if (remaining == 1 && buf_size > 0) {
+		} else if (remaining == 1) {
 			/* Mostly the same case as above, but we have incomplete
 			 * message length in the buffer and received at least
 			 * one byte to complete it.