Bug#1117631: openssh: Connection sharing is very sluggish.
Package: src:openssh
Version: 1:10.1p1-1
Severity: serious
Tags: upstream fixed-upstream patch
control: forwarded -1 https://bugzilla.mindrot.org/show_bug.cgi?id=3872
Since the 10.1p1 connection sharing (ssh -M, ControlMaster yes) is very
sluggish. It turns to be a openssh regression that is already fixed as
of commit beae06f56e0d0 ("upstream: don't reuse c->isatty for signalling
that the remote channel") in the portable tree. Please find attached the
patch.
Since I have it almost always enabled, especially for long distance
connection, I can't use it. Hence the severity.
Sebastian
>From beae06f56e0d0a66ca535896149d5fb0b2e8a1b4 Mon Sep 17 00:00:00 2001
From: "djm@openbsd.org" <djm@openbsd.org>
Date: Tue, 7 Oct 2025 08:02:32 +0000
Subject: [PATCH] upstream: don't reuse c->isatty for signalling that the
remote channel
has a tty attached as this causes side effects, e.g. in channel_handle_rfd().
bz3872
ok markus@
OpenBSD-Commit-ID: 4cd8a9f641498ca6089442e59bad0fd3dcbe85f8
---
channels.c | 9 +++++----
channels.h | 3 ++-
2 files changed, 7 insertions(+), 5 deletions(-)
diff --git a/channels.c b/channels.c
index f1d7bcf345b19..80014ff341fad 100644
--- a/channels.c
+++ b/channels.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: channels.c,v 1.451 2025/09/25 06:33:19 djm Exp $ */
+/* $OpenBSD: channels.c,v 1.452 2025/10/07 08:02:32 djm Exp $ */
/*
* Author: Tatu Ylonen <ylo@cs.hut.fi>
* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -362,7 +362,7 @@ channel_classify(struct ssh *ssh, Channel *c)
{
struct ssh_channels *sc = ssh->chanctxt;
const char *type = c->xctype == NULL ? c->ctype : c->xctype;
- const char *classifier = c->isatty ?
+ const char *classifier = (c->isatty || c->remote_has_tty) ?
sc->bulk_classifier_tty : sc->bulk_classifier_notty;
c->bulk = type != NULL && match_pattern_list(type, classifier, 0) == 1;
@@ -566,7 +566,7 @@ channel_new(struct ssh *ssh, char *ctype, int type, int rfd, int wfd, int efd,
void
channel_set_tty(struct ssh *ssh, Channel *c)
{
- c->isatty = 1;
+ c->remote_has_tty = 1;
channel_classify(ssh, c);
}
@@ -1078,7 +1078,8 @@ channel_format_status(const Channel *c)
c->rfd, c->wfd, c->efd, c->sock, c->ctl_chan,
c->have_ctl_child_id ? "c" : "nc", c->ctl_child_id,
c->io_want, c->io_ready,
- c->isatty ? "T" : "", c->bulk ? "B" : "I");
+ c->isatty ? "T" : (c->remote_has_tty ? "RT" : ""),
+ c->bulk ? "B" : "I");
return ret;
}
diff --git a/channels.h b/channels.h
index df7c7f364d225..7456541f8ce3a 100644
--- a/channels.h
+++ b/channels.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: channels.h,v 1.161 2025/09/25 06:33:19 djm Exp $ */
+/* $OpenBSD: channels.h,v 1.162 2025/10/07 08:02:32 djm Exp $ */
/*
* Author: Tatu Ylonen <ylo@cs.hut.fi>
@@ -145,6 +145,7 @@ struct Channel {
int ctl_chan; /* control channel (multiplexed connections) */
uint32_t ctl_child_id; /* child session for mux controllers */
int have_ctl_child_id;/* non-zero if ctl_child_id is valid */
+ int remote_has_tty; /* remote side has a tty */
int isatty; /* rfd is a tty */
#ifdef _AIX
int wfd_isatty; /* wfd is a tty */
--
2.51.0
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