From nobody Mon Jul 08 06:17:06 2024 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 4WHYnB31qCz5R4M7 for ; Mon, 08 Jul 2024 06:17:18 +0000 (UTC) (envelope-from ml@netfence.it) Received: from soth.netfence.it (mailserver.netfence.it [78.134.96.152]) (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 "mailserver.netfence.it", Issuer "R11" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 4WHYn92vjVz40Z6 for ; Mon, 8 Jul 2024 06:17:17 +0000 (UTC) (envelope-from ml@netfence.it) Authentication-Results: mx1.freebsd.org; dkim=none; dmarc=pass (policy=none) header.from=netfence.it; spf=pass (mx1.freebsd.org: domain of ml@netfence.it designates 78.134.96.152 as permitted sender) smtp.mailfrom=ml@netfence.it Received: from [10.1.2.18] (mailserver.netfence.it [78.134.96.152]) (authenticated bits=0) by soth.netfence.it (8.18.1/8.17.2) with ESMTPSA id 4686H6ch006954 (version=TLSv1.3 cipher=TLS_AES_128_GCM_SHA256 bits=128 verify=NO); Mon, 8 Jul 2024 08:17:07 +0200 (CEST) (envelope-from ml@netfence.it) X-Authentication-Warning: soth.netfence.it: Host mailserver.netfence.it [78.134.96.152] claimed to be [10.1.2.18] Message-ID: <44769ec1-7523-49c7-a64d-181530c90a0d@netfence.it> Date: Mon, 8 Jul 2024 08:17:06 +0200 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 User-Agent: Mozilla Thunderbird Subject: Re: OpenVPN suddenly working one way only Content-Language: en-US To: "Patrick M. Hausen" Cc: "freebsd-net@freebsd.org" References: <202407061502.466F28cR033040@gndrsh.dnsmgr.net> From: Andrea Venturoli In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.86 X-Spamd-Bar: --- X-Spamd-Result: default: False [-3.77 / 15.00]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_MEDIUM(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.98)[-0.977]; DMARC_POLICY_ALLOW(-0.50)[netfence.it,none]; R_SPF_ALLOW(-0.20)[+ip4:78.134.96.152]; MIME_GOOD(-0.10)[text/plain]; XM_UA_NO_VERSION(0.01)[]; TO_DN_SOME(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; TO_DN_EQ_ADDR_SOME(0.00)[]; MIME_TRACE(0.00)[0:+]; ASN(0.00)[asn:35612, ipnet:78.134.0.0/17, country:IT]; RCVD_COUNT_ONE(0.00)[1]; RCVD_TLS_ALL(0.00)[]; MID_RHS_MATCH_FROM(0.00)[]; R_DKIM_NA(0.00)[]; FROM_HAS_DN(0.00)[]; HAS_XAW(0.00)[]; RCPT_COUNT_TWO(0.00)[2]; FROM_EQ_ENVFROM(0.00)[]; MLMMJ_DEST(0.00)[freebsd-net@freebsd.org]; TO_MATCH_ENVRCPT_SOME(0.00)[]; ARC_NA(0.00)[] X-Rspamd-Queue-Id: 4WHYn92vjVz40Z6 On 7/6/24 18:13, Patrick M. Hausen wrote: Hello. >> It's almost surely due to a problem with the UDP packets that implement the VPN: again, according to tcpdump they go out host B, but never reach host A. > > Is it remotely possible that one of the ISPs blocks these UDP packets as part > of an automatic "DoS protection" mechanism? Of course I cannot exclude it with 100% confidence. That said: _ host A has about 10 VPNs, only one is misbehaving, so I guess it's not ISP A; _ host B has an enterprise-grade contract, so they should not firewall anything; another one of the above VPNs connects to a different host which has the same type of contract with the same ISP and it works. Maybe it's the ISP or someone in between... I have no control over this. I'd like to exclude any local issue, about which I might actually do something. bye & Thanks av.