From nobody Thu Aug 29 18:51:37 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 4Wvr3p5Y29z52QW2 for ; Thu, 29 Aug 2024 18:51:50 +0000 (UTC) (envelope-from mike@sentex.net) Received: from smarthost1.sentex.ca (smarthost1.sentex.ca [IPv6:2607:f3e0:0:1::12]) (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 "smarthost1.sentex.ca", Issuer "R10" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 4Wvr3n6J5Fz458J for ; Thu, 29 Aug 2024 18:51:49 +0000 (UTC) (envelope-from mike@sentex.net) Authentication-Results: mx1.freebsd.org; dkim=none; dmarc=none; spf=pass (mx1.freebsd.org: domain of mike@sentex.net designates 2607:f3e0:0:1::12 as permitted sender) smtp.mailfrom=mike@sentex.net Received: from pyroxene2a.sentex.ca (pyroxene19.sentex.ca [199.212.134.19]) by smarthost1.sentex.ca (8.18.1/8.18.1) with ESMTPS id 47TIpbHa042853 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=FAIL) for ; Thu, 29 Aug 2024 14:51:37 -0400 (EDT) (envelope-from mike@sentex.net) Received: from [IPV6:2607:f3e0:0:4:8428:6097:7a81:e591] ([IPv6:2607:f3e0:0:4:8428:6097:7a81:e591]) by pyroxene2a.sentex.ca (8.18.1/8.15.2) with ESMTPS id 47TIpake011192 (version=TLSv1.3 cipher=TLS_AES_128_GCM_SHA256 bits=128 verify=NO) for ; Thu, 29 Aug 2024 14:51:36 -0400 (EDT) (envelope-from mike@sentex.net) Message-ID: <790fcb38-db6c-41ce-8222-8146be5dbe3b@sentex.net> Date: Thu, 29 Aug 2024 14:51:37 -0400 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 Content-Language: en-US To: FreeBSD Net From: mike tancsa Subject: dropping udp fragments with ipfw Autocrypt: addr=mike@sentex.net; keydata= xsBNBFywzOMBCACoNFpwi5MeyEREiCeHtbm6pZJI/HnO+wXdCAWtZkS49weOoVyUj5BEXRZP xflV2ib2hflX4nXqhenaNiia4iaZ9ft3I1ebd7GEbGnsWCvAnob5MvDZyStDAuRxPJK1ya/s +6rOvr+eQiXYNVvfBhrCfrtR/esSkitBGxhUkBjOti8QwzD71JVF5YaOjBAs7jZUKyLGj0kW yDg4jUndudWU7G2yc9GwpHJ9aRSUN8e/mWdIogK0v+QBHfv/dsI6zVB7YuxCC9Fx8WPwfhDH VZC4kdYCQWKXrm7yb4TiVdBh5kgvlO9q3js1yYdfR1x8mjK2bH2RSv4bV3zkNmsDCIxjABEB AAHNHW1pa2UgdGFuY3NhIDxtaWtlQHNlbnRleC5uZXQ+wsCOBBMBCAA4FiEEmuvCXT0aY6hs 4SbWeVOEFl5WrMgFAl+pQfkCGwMFCwkIBwIGFQoJCAsCBBYCAwECHgECF4AACgkQeVOEFl5W rMiN6ggAk3H5vk8QnbvGbb4sinxZt/wDetgk0AOR9NRmtTnPaW+sIJEfGBOz47Xih+f7uWJS j+uvc9Ewn2Z7n8z3ZHJlLAByLVLtcNXGoRIGJ27tevfOaNqgJHBPbFOcXCBBFTx4MYMM4iAZ cDT5vsBTSaM36JZFtHZBKkuFEItbA/N8ZQSHKdTYMIA7A3OCLGbJBqloQ8SlW4MkTzKX4u7R yefAYQ0h20x9IqC5Ju8IsYRFacVZconT16KS81IBceO42vXTN0VexbVF2rZIx3v/NT75r6Vw 0FlXVB1lXOHKydRA2NeleS4NEG2vWqy/9Boj0itMfNDlOhkrA/0DcCurMpnpbM7ATQRcsMzk AQgA1Dpo/xWS66MaOJLwA28sKNMwkEk1Yjs+okOXDOu1F+0qvgE8sVmrOOPvvWr4axtKRSG1 t2QUiZ/ZkW/x/+t0nrM39EANV1VncuQZ1ceIiwTJFqGZQ8kb0+BNkwuNVFHRgXm1qzAJweEt RdsCMohB+H7BL5LGCVG5JaU0lqFU9pFP40HxEbyzxjsZgSE8LwkI6wcu0BLv6K6cLm0EiHPO l5G8kgRi38PS7/6s3R8QDsEtbGsYy6O82k3zSLIjuDBwA9GRaeigGppTxzAHVjf5o9KKu4O7 gC2KKVHPegbXS+GK7DU0fjzX57H5bZ6komE5eY4p3oWT/CwVPSGfPs8jOwARAQABwsB2BBgB CAAgFiEEmuvCXT0aY6hs4SbWeVOEFl5WrMgFAl+pQfkCGwwACgkQeVOEFl5WrMiVqwf9GwU8 c6cylknZX8QwlsVudTC8xr/L17JA84wf03k3d4wxP7bqy5AYy7jboZMbgWXngAE/HPQU95NM aukysSnknzoIpC96XZJ0okLBXVS6Y0ylZQ+HrbIhMpuQPoDweoF5F9wKrsHRoDaUK1VR706X rwm4HUzh7Jk+auuMYfuCh0FVlFBEuiJWMLhg/5WCmcRfiuB6F59ZcUQrwLEZeNhF2XJV4KwB Tlg7HCWO/sy1foE5noaMyACjAtAQE9p5kGYaj+DuRhPdWUTsHNuqrhikzIZd2rrcMid+ktb0 NvtvswzMO059z1YGMtGSqQ4srCArju+XHIdTFdiIYbd7+jeehg== Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.86 X-Spamd-Bar: --- X-Spamd-Result: default: False [-3.36 / 15.00]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_MEDIUM(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.97)[-0.974]; R_SPF_ALLOW(-0.20)[+ip6:2607:f3e0::/32]; MIME_GOOD(-0.10)[text/plain]; RCVD_IN_DNSWL_LOW(-0.10)[199.212.134.19:received]; XM_UA_NO_VERSION(0.01)[]; TO_DN_ALL(0.00)[]; RCPT_COUNT_ONE(0.00)[1]; FREEFALL_USER(0.00)[mike]; ASN(0.00)[asn:11647, ipnet:2607:f3e0::/32, country:CA]; MIME_TRACE(0.00)[0:+]; MID_RHS_MATCH_FROM(0.00)[]; R_DKIM_NA(0.00)[]; MLMMJ_DEST(0.00)[freebsd-net@freebsd.org]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; ARC_NA(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; PREVIOUSLY_DELIVERED(0.00)[freebsd-net@freebsd.org]; TO_MATCH_ENVRCPT_ALL(0.00)[]; DMARC_NA(0.00)[sentex.net]; RCVD_TLS_ALL(0.00)[] X-Rspamd-Queue-Id: 4Wvr3n6J5Fz458J I was working on some firewall rules to drop large UDP fragment attacks and noticed there is no easy way to drop fragments based on port ? e.g. if someone sends a UDP packet of 1400 bytes, I can drop it with TARGET=192.168.1.1 ipfw add 5 deny log udp from any 53 to $TARGET But if that packet is say 2000 bytes and is fragmented, the fragment passes through. I have to add a subsequent rule ipfw add 10 deny log udp from any to $TARGET fragment But this would kill all UDP fragments.  If the host has some other UDP application that needs to deal with fragmented packets, is there a way to get around that and only drop packets with a certain port in the first fragment ?     ---Mike