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Miller" , andy.rudoff@intel.com References: <20210122150638.210444-1-willy@infradead.org> <20210125153650.18c84b1a@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> <23fc3de2-7541-04c9-a56f-4006a7dc773f@oracle.com> <20210129110605.54df8409@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> <20210129120250.269c366d@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> <20210129121837.467280fb@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> From: Shoaib Rao Message-ID: Date: Fri, 29 Jan 2021 12:44:44 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.6.1 In-Reply-To: <20210129121837.467280fb@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-Originating-IP: [2606:b400:8301:1010::16aa] X-ClientProxiedBy: CH2PR14CA0007.namprd14.prod.outlook.com (2603:10b6:610:60::17) To SJ0PR10MB4494.namprd10.prod.outlook.com (2603:10b6:a03:2d4::12) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from [IPv6:2606:b400:400:7446:8000::12a8] (2606:b400:8301:1010::16aa) by CH2PR14CA0007.namprd14.prod.outlook.com (2603:10b6:610:60::17) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3805.16 via Frontend Transport; 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Let's >> look at the code of unix_stream_sendmsg() It does the following (sent is >> initialized to zero) > Okay. Let me try again. AFAICS your code makes it so that data sent > with MSG_OOB is treated like any other data. It just sends a signal. Correct. > So you're hijacking the MSG_OOB to send a signal, because OOB also > sends a signal. Correct. > But there is nothing OOB about the data itself. Correct. > So > I'm asking you to make sure that there is no data in the message. Yes I can do that. > That way when someone wants _actual_ OOB data on UNIX sockets they > can implement it without breaking backwards compatibility of the > kernel uAPI. I see what you are trying to achieve. However it may not work. Let's assume that __actual__ OOB data has been implemented. An application sends a zero length message with MSG_OOB, after that it sends some data (not suppose to be OOB data). How is the receiver going to differentiate if the data an OOB or not. We could use a different flag (MSG_SIGURG) or implement the _actual_ OOB data semantics (If anyone is interested in it). MSG_SIGURG could be a generic flag that just sends SIGURG irrespective of the length of the data. Shoaib > >> while (sent < len) { >>                 size = len - sent; >> <..> >> >> } >> >>         if (msg->msg_flags & MSG_OOB) >>                 sk_send_sigurg(other); >> >> Before the patch there was a check above the while loop that checked the >> flag and returned and error, that has been removed.