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CO1PR11MB5153.namprd11.prod.outlook.com (2603:10b6:303:95::13) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.7698.30; Wed, 26 Jun 2024 10:10:18 +0000 Received: from MW3PR11MB4714.namprd11.prod.outlook.com ([fe80::9b77:8d77:3800:f0fd]) by MW3PR11MB4714.namprd11.prod.outlook.com ([fe80::9b77:8d77:3800:f0fd%6]) with mapi id 15.20.7698.025; Wed, 26 Jun 2024 10:10:18 +0000 Message-ID: <0fc38c1b-1a28-4818-b2cc-a661f037999d@silabs.com> Date: Wed, 26 Jun 2024 12:10:00 +0200 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1 2/2] ipv6: always accept routing headers with 0 segments left To: Alexander Aring , Kuniyuki Iwashima Cc: alex.aring@gmail.com, davem@davemloft.net, dsahern@kernel.org, edumazet@google.com, jerome.pouiller@silabs.com, kuba@kernel.org, kylian.balan@silabs.com, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, pabeni@redhat.com, Michael Richardson References: <20240624141602.206398-3-Mathis.Marion@silabs.com> 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engine=ICAP:2.0.272,Aquarius:18.0.1039,Hydra:6.0.680,FMLib:17.12.28.16 definitions=2024-06-26_04,2024-06-25_01,2024-05-17_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 adultscore=0 priorityscore=1501 mlxlogscore=999 bulkscore=0 mlxscore=0 phishscore=0 suspectscore=0 lowpriorityscore=0 clxscore=1011 malwarescore=0 spamscore=0 impostorscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2406140001 definitions=main-2406260077 On 26/06/2024 3:45 AM, Alexander Aring wrote: > Hi, > > On Tue, Jun 25, 2024 at 5:39 PM Kuniyuki Iwashima wrote: >> >> From: Mathis Marion >> Date: Mon, 24 Jun 2024 16:15:33 +0200 >>> From: Mathis Marion >>> >>> Routing headers of type 3 and 4 would be rejected even if segments left >>> was 0, in the case that they were disabled through system configuration. >>> >>> RFC 8200 section 4.4 specifies: >>> >>> If Segments Left is zero, the node must ignore the Routing header >>> and proceed to process the next header in the packet, whose type >>> is identified by the Next Header field in the Routing header. >> >> I think this part is only applied to an unrecognized Routing Type, >> so only applied when the network stack does not know the type. >> >> https://www.rfc-editor.org/rfc/rfc8200.html#section-4.4 >> >> If, while processing a received packet, a node encounters a Routing >> header with an unrecognized Routing Type value, the required behavior >> of the node depends on the value of the Segments Left field, as >> follows: >> >> If Segments Left is zero, the node must ignore the Routing header >> and proceed to process the next header in the packet, whose type >> is identified by the Next Header field in the Routing header. >> >> That's why RPL with segment length 0 was accepted before 8610c7c6e3bd. >> >> But now the kernel recognizes RPL and it's intentionally disabled >> by default with net.ipv6.conf.$DEV.rpl_seg_enabled since introduced. >> >> And SRv6 has been rejected since 1ababeba4a21f for the same reason. > > so there might be a need to have an opt-in knob to actually tell the > kernel ipv6 stack to recognize or not recognize a next header field > for users wanting to bypass certain next header fields to the user > space? > > - Alex > My point is that if a particular routing header support is disabled through system configuration, it should be treated as any unrecognized header. From my perspective, doing otherwise causes a regression every time a new routing header is supported.