From nobody Wed Jun 21 18:03:01 2023 X-Original-To: freebsd-net@mlmmj.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mlmmj.nyi.freebsd.org (Postfix) with ESMTP id 4QmWZ154sBz4ggYR; Wed, 21 Jun 2023 18:02:49 +0000 (UTC) (envelope-from fbsd@www.zefox.net) Received: from www.zefox.net (www.zefox.net [50.1.20.27]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256 client-signature RSA-PSS (2048 bits) client-digest SHA256) (Client CN "www.zefox.com", Issuer "www.zefox.com" (not verified)) by mx1.freebsd.org (Postfix) with ESMTPS id 4QmWZ0701jz46J0; Wed, 21 Jun 2023 18:02:48 +0000 (UTC) (envelope-from fbsd@www.zefox.net) Authentication-Results: mx1.freebsd.org; none Received: from www.zefox.net (localhost [127.0.0.1]) by www.zefox.net (8.17.1/8.15.2) with ESMTPS id 35LI31mI056579 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NO); Wed, 21 Jun 2023 11:03:02 -0700 (PDT) (envelope-from fbsd@www.zefox.net) Received: (from fbsd@localhost) by www.zefox.net (8.17.1/8.15.2/Submit) id 35LI31ow056578; Wed, 21 Jun 2023 11:03:01 -0700 (PDT) (envelope-from fbsd) Date: Wed, 21 Jun 2023 11:03:01 -0700 From: bob prohaska To: Mark Millard Cc: freebsd-net@freebsd.org, freebsd-arm@freebsd.org Subject: Re: -current dropping ssh connections Message-ID: References: List-Id: Networking and TCP/IP with FreeBSD List-Archive: https://lists.freebsd.org/archives/freebsd-net List-Help: List-Post: List-Subscribe: List-Unsubscribe: Sender: owner-freebsd-net@freebsd.org MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: 4QmWZ0701jz46J0 X-Spamd-Bar: ---- X-Spamd-Result: default: False [-4.00 / 15.00]; REPLY(-4.00)[]; ASN(0.00)[asn:7065, ipnet:50.1.16.0/20, country:US] X-Rspamd-Pre-Result: action=no action; module=replies; Message is reply to one we originated X-ThisMailContainsUnwantedMimeParts: N On Wed, Jun 21, 2023 at 10:45:25AM -0700, Mark Millard wrote: > On Jun 21, 2023, at 10:24, bob prohaska wrote: > > > I've got a Pi4 running -current that seems to selectively drop ssh connections. > > Only when the ssh has text streaming over it? Even when it > is idle? Any other types of context differences that lead > to observable differences of some type related to the > disconnects (vs. lack of them)? I can't detect any consistent pattern. For a while I thought load on the sshd-host end made a difference, but the latest disconnect was on an idle system with serial console output the only traffic on the dropped connection. > > Connections running a shell seem to stay up, but a session running tip to a > > usb-serial adapter (FTDI TTL232R-3V3) seems go away within a few hours. > > The way that reads, ssh to a shell and then running tip in > that shell would stay up. (Does it?) tip is being run > without ssh running a shell? May be more detail about the > two contexts of establishing the connection is needed here? > No, other way 'round. In both cases an ssh connection was made which started a shell. In one a tip session was started, which seems prone to dropping. In the other an active shell (typically running buildworld, or maybe idle) kept running. This makes me think (perhaps wrongly) that tip is involved with the disconnection. Both shells are started as a regular user and then su-d to root. I'm fairly confident this isn't a client-side or NAT problem, simply because there are a dozen or so other ssh sessions running from the ssh client to the various Pi2/3/4 hosts in my collection which stay up basically until they're taken down deliberately. I seem to (vaguely) recall a discussion of ssh problems over NAT some months ago, something about tolerating misssing ts (timestamps?). Is that still possible? Thanks for writing! bob prohaska