From: Aydın Mercan <aydin@isc.org>
Date: Thu, 11 Jun 2026 13:38:27 +0000 (+0300)
Subject: ignore 0-byte reads in the TCP read callback
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=20d3ef1643b2b5ab4ea2bdd115bb025c11fc33b0;p=thirdparty%2Fbind9.git

ignore 0-byte reads in the TCP read callback

Callbacks for libuv stream reads do not signal zero-length reads as a
failure signal but rather as EAGAIN/EWOULDBLOCK. This can trigger an
assertion when a zero-length read is pushed onto a PROXYv2 endpoint that
has not yet processed the headers as it expects a non-NULL region of
positive length.
---

diff --git a/lib/isc/netmgr/tcp.c b/lib/isc/netmgr/tcp.c
index 9d50d98e1a..9ec8a7f3b5 100644
--- a/lib/isc/netmgr/tcp.c
+++ b/lib/isc/netmgr/tcp.c
@@ -778,7 +778,10 @@ isc__nm_tcp_read_cb(uv_stream_t *stream, ssize_t nread, const uv_buf_t *buf) {
 		goto free;
 	}
 
-	if (nread < 0) {
+	if (nread == 0) {
+		/* EAGAIN/EWOULDBLOCK: no data yet, not an error on libuv. */
+		goto free;
+	} else if (nread < 0) {
 		if (nread != UV_EOF) {
 			isc__nm_incstats(sock, STATID_RECVFAIL);
 		}
@@ -837,7 +840,7 @@ isc__nm_tcp_read_cb(uv_stream_t *stream, ssize_t nread, const uv_buf_t *buf) {
 	}
 
 free:
-	if (nread < 0) {
+	if (nread <= 0) {
 		/*
 		 * The buffer may be a null buffer on error.
 		 */