From nobody Tue Nov 15 21:14:26 2022 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 4NBf7x34Mzz4hmZR for ; Tue, 15 Nov 2022 21:14:37 +0000 (UTC) (envelope-from tuexen@freebsd.org) Received: from drew.franken.de (drew.ipv6.franken.de [IPv6:2001:638:a02:a001:20e:cff:fe4a:feaa]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client CN "*.franken.de", Issuer "Sectigo RSA Domain Validation Secure Server CA" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 4NBf7w4ZpXz4bSV for ; Tue, 15 Nov 2022 21:14:36 +0000 (UTC) (envelope-from tuexen@freebsd.org) Authentication-Results: mx1.freebsd.org; dkim=none; spf=softfail (mx1.freebsd.org: 2001:638:a02:a001:20e:cff:fe4a:feaa is neither permitted nor denied by domain of tuexen@freebsd.org) smtp.mailfrom=tuexen@freebsd.org; dmarc=none Received: from smtpclient.apple (unknown [IPv6:2a02:8109:1140:c3d:8544:35e7:7303:ae7f]) (Authenticated sender: macmic) by drew.franken.de (Postfix) with ESMTPSA id 4158377A1B6BA for ; Tue, 15 Nov 2022 22:14:27 +0100 (CET) From: tuexen@freebsd.org Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable 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 (Mac OS X Mail 16.0 \(3731.200.110.1.12\)) Subject: ICMPv6 over lo0 Message-Id: Date: Tue, 15 Nov 2022 22:14:26 +0100 To: freebsd-net X-Mailer: Apple Mail (2.3731.200.110.1.12) X-Spam-Status: No, score=-2.9 required=5.0 tests=ALL_TRUSTED,BAYES_00 autolearn=disabled version=3.4.1 X-Spam-Checker-Version: SpamAssassin 3.4.1 (2015-04-28) on mail-n.franken.de X-Spamd-Result: default: False [-1.57 / 15.00]; NEURAL_HAM_SHORT(-1.00)[-1.000]; NEURAL_HAM_MEDIUM(-0.97)[-0.970]; MV_CASE(0.50)[]; MIME_GOOD(-0.10)[text/plain]; FROM_NO_DN(0.00)[]; MLMMJ_DEST(0.00)[freebsd-net@freebsd.org]; FROM_EQ_ENVFROM(0.00)[]; R_DKIM_NA(0.00)[]; MIME_TRACE(0.00)[0:+]; MID_RHS_MATCH_FROM(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; ASN(0.00)[asn:680, ipnet:2001:638::/32, country:DE]; ARC_NA(0.00)[]; TO_DN_ALL(0.00)[]; RCPT_COUNT_ONE(0.00)[1]; FREEFALL_USER(0.00)[tuexen]; RCVD_VIA_SMTP_AUTH(0.00)[]; RCVD_TLS_ALL(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; DMARC_NA(0.00)[freebsd.org]; PREVIOUSLY_DELIVERED(0.00)[freebsd-net@freebsd.org]; R_SPF_SOFTFAIL(0.00)[~all:c]; TO_DOM_EQ_FROM_DOM(0.00)[] X-Rspamd-Queue-Id: 4NBf7w4ZpXz4bSV X-Spamd-Bar: - X-ThisMailContainsUnwantedMimeParts: N Dear all, when using the master branch of today (or 13.1) I get when running tuexen@ampere128:~ % ping6 -c 1 -b 30000 -s 20000 ::1 PING6(20048=3D40+8+20000 bytes) ::1 --> ::1 20008 bytes from ::1, icmp_seq=3D0 hlim=3D64 time=3D0.709 ms --- ::1 ping6 statistics --- 1 packets transmitted, 1 packets received, 0.0% packet loss round-trip min/avg/max/std-dev =3D 0.709/0.709/0.709/0.000 ms which is expected. What I don't expect is: tuexen@ampere128:~ % tcpdump -i lo0 -n tcpdump: verbose output suppressed, use -v or -vv for full protocol = decode listening on lo0, link-type NULL (BSD loopback), capture size 262144 = bytes 22:06:38.835630 IP6 ::1 > ::1: frag (0|1232) ICMP6, echo request, seq 0, = length 1232 22:06:38.835639 IP6 ::1 > ::1: frag (1232|1232) 22:06:38.835641 IP6 ::1 > ::1: frag (2464|1232) 22:06:38.835641 IP6 ::1 > ::1: frag (3696|1232) 22:06:38.835642 IP6 ::1 > ::1: frag (4928|1232) 22:06:38.835642 IP6 ::1 > ::1: frag (6160|1232) 22:06:38.835643 IP6 ::1 > ::1: frag (7392|1232) 22:06:38.835644 IP6 ::1 > ::1: frag (8624|1232) 22:06:38.835644 IP6 ::1 > ::1: frag (9856|1232) 22:06:38.835645 IP6 ::1 > ::1: frag (11088|1232) 22:06:38.835645 IP6 ::1 > ::1: frag (12320|1232) 22:06:38.835646 IP6 ::1 > ::1: frag (13552|1232) 22:06:38.835647 IP6 ::1 > ::1: frag (14784|1232) 22:06:38.835647 IP6 ::1 > ::1: frag (16016|1232) 22:06:38.835648 IP6 ::1 > ::1: frag (17248|1232) 22:06:38.835648 IP6 ::1 > ::1: frag (18480|1232) 22:06:38.835649 IP6 ::1 > ::1: frag (19712|296) 22:06:38.836002 IP6 ::1 > ::1: frag (0|16336) ICMP6, echo reply, seq 0, = length 16336 22:06:38.836006 IP6 ::1 > ::1: frag (16336|3672) ^C 19 packets captured 19 packets received by filter 0 packets dropped by kernel Why is for the Echo Request an MTU of 1280 used, whereas for the = response an MTU of 16384 is used. Since tuexen@ampere128:~ % ifconfig lo0 lo0: flags=3D8049 metric 0 mtu 16384 options=3D680003 inet6 ::1 prefixlen 128 inet6 fe80::1%lo0 prefixlen 64 scopeid 0x3 inet 127.0.0.1 netmask 0xff000000 groups: lo nd6 options=3D21 is used, I would expect an MTU of 16384 also be used for the Echo = Request instead of the minimum IPv6 MTU of 1280. Is this intended? At least for me, it is not expected... Best regards Michael=