From nobody Wed Jun 04 16:36:39 2025 X-Original-To: questions@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 4bCCsW1Yrrz5xGwm; Wed, 04 Jun 2025 16:37:03 +0000 (UTC) (envelope-from dch@skunkwerks.at) Received: from fout-b3-smtp.messagingengine.com (fout-b3-smtp.messagingengine.com [202.12.124.146]) (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 did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 4bCCsV3pM5z3w23; Wed, 04 Jun 2025 16:37:02 +0000 (UTC) (envelope-from dch@skunkwerks.at) Authentication-Results: mx1.freebsd.org; none Received: from phl-compute-02.internal (phl-compute-02.phl.internal [10.202.2.42]) by mailfout.stl.internal (Postfix) with ESMTP id E9199114007E; Wed, 4 Jun 2025 12:37:00 -0400 (EDT) Received: from phl-imap-16 ([10.202.2.88]) by phl-compute-02.internal (MEProxy); Wed, 04 Jun 2025 12:37:01 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=skunkwerks.at; h=cc:cc:content-transfer-encoding:content-type:content-type :date:date:from:from:in-reply-to:in-reply-to:message-id :mime-version:references:reply-to:subject:subject:to:to; s=fm2; t=1749055020; x=1749141420; bh=q/8gR0QxRt6qSeHuBWw4lLxPA3GHs3Id j/kmVLtCnd8=; b=qsnPrnisHroNGTjsUTEt4hsw7UKj0FAlwHamFDAeNu5Lmw38 zA+Nlny6ErEBF1sUzpulWgrXN7nVROA8OQB00/Yvb4eSCsVlirtL6EgeQj4fcpxW NLKIiSv24ARwrInMvZUhVl7mdJbusTuf2Ym0/0pBulrZFLcDsmms/9N88Klm3CxY KDtHGCkfu/skk7BSFngf7jb0Lt2JYqto+DT1c6OuKa+cy5qyoTcsrgM2rte54TCp 8/20xDTFY7J0xRphA5dHED4b/UNwvGF8HgRcgtZ+Xjx+UEeqTFcN7VWeO/XXVgpq DvsHeihrjkY6pszirU9N/LnZqLP77+jxc9Hx3g== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=cc:cc:content-transfer-encoding :content-type:content-type:date:date:feedback-id:feedback-id :from:from:in-reply-to:in-reply-to:message-id:mime-version :references:reply-to:subject:subject:to:to:x-me-proxy :x-me-sender:x-me-sender:x-sasl-enc; s=fm1; t=1749055020; x= 1749141420; bh=q/8gR0QxRt6qSeHuBWw4lLxPA3GHs3Idj/kmVLtCnd8=; b=R VqRNPBadNTNZrvOAE6XvPMh1K+y5e45oAlUWzncJkLMF8zPrqkaTwJlmBNs2ip3m vK5cbBzI7m++jwy/qvfZS6LPQxAEeVup9Ey8eyMHehX/09ogGYx1taRfY1RceJv6 aKQFhZZDaQGCqinxI4m8FQlVBxmAVT6PxAOLiPNJsgZSO3oAwSH6i7TQMJ2T5zMC PwdB5W+hD7CJ/+3ERdns/J8hFo+ShF6XDJUtKbMS1y+ofc9JAKxbMJr4pyGVj6Kh gym3R4lRzel6wGsMdvBu00MhX6N+ya8rxuu8rR/12Tyk/zUvGai3jjOV3PYUggNo c6285FPCqJLWmpbIbEDRA== X-ME-Sender: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgeeffedrtddugddvgedtucetufdoteggodetrfdotf fvucfrrhhofhhilhgvmecuhfgrshhtofgrihhlpdggtfgfnhhsuhgsshgtrhhisggvpdfu rfetoffkrfgpnffqhgenuceurghilhhouhhtmecufedttdenucesvcftvggtihhpihgvnh htshculddquddttddmnecujfgurhepofggfffhvfevkfgjfhfutgfgsehtqhertdertdej necuhfhrohhmpedfffgrvhgvucevohhtthhlvghhuhgsvghrfdcuoegutghhsehskhhunh hkfigvrhhkshdrrghtqeenucggtffrrghtthgvrhhnpefhudelueevleehfeekuddvhfet gfdvffdvvedtiedukeeuveeftedutdeuvdefteenucevlhhushhtvghrufhiiigvpedtne curfgrrhgrmhepmhgrihhlfhhrohhmpegutghhsehskhhunhhkfigvrhhkshdrrghtpdhn sggprhgtphhtthhopeefpdhmohguvgepshhmthhpohhuthdprhgtphhtthhopegthhhrih hssegtrhgvthgrfhhorhgtvgdrghhrpdhrtghpthhtohepfhhrvggvsghsugdqnhgvthes fhhrvggvsghsugdrohhrghdprhgtphhtthhopehquhgvshhtihhonhhssehfrhgvvggssh gurdhorhhg X-ME-Proxy: Feedback-ID: ic0e84090:Fastmail Received: by mailuser.phl.internal (Postfix, from userid 501) id DDFBD2CC0081; Wed, 4 Jun 2025 12:36:59 -0400 (EDT) X-Mailer: MessagingEngine.com Webmail Interface List-Id: User questions List-Archive: https://lists.freebsd.org/archives/freebsd-questions List-Help: List-Post: List-Subscribe: List-Unsubscribe: X-BeenThere: freebsd-questions@freebsd.org Sender: owner-freebsd-questions@FreeBSD.org MIME-Version: 1.0 X-ThreadId: T6c5d219d11e80eeb Date: Wed, 04 Jun 2025 18:36:39 +0200 From: "Dave Cottlehuber" To: "Christos Chatzaras" , questions@freebsd.org Cc: freebsd-net Message-Id: In-Reply-To: <9728060D-2C02-426B-BACE-F2D2F651A62F@cretaforce.gr> References: <9728060D-2C02-426B-BACE-F2D2F651A62F@cretaforce.gr> Subject: Re: Problem with net.inet.tcp.path_mtu_discovery=1 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 4bCCsV3pM5z3w23 X-Spamd-Bar: ---- X-Rspamd-Pre-Result: action=no action; module=replies; Message is reply to one we originated X-Spamd-Result: default: False [-4.00 / 15.00]; REPLY(-4.00)[]; ASN(0.00)[asn:151847, ipnet:202.12.124.0/24, country:AU] On Wed, 4 Jun 2025, at 16:36, Christos Chatzaras wrote: > Hello, > > I manage some servers hosting websites. What does tcpdump/wireshark show for traffic, particularly icmp? Wiresha= rk is very helpful in explaining some issues. What is the actual MTU on the working net vs the failing one? Is there a local MTU where the failing websites start working again? see ping(8) and use -v -D -s =E2=80=A6. together to find a working MTU a= nd cross check with tcpdump to find where things seem to break. On a recent cloud environment I needed to add =E2=80=98 set reassemble y= es no-df=E2=80=99 to my pf.conf to address MTU issues between VNET jails= and the internet. Happy hunting Dave