From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from Chamillionaire.breakpoint.cc (Chamillionaire.breakpoint.cc [193.142.43.52]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5640B5F for ; Thu, 25 Mar 2021 14:45:30 +0000 (UTC) Received: from fw by Chamillionaire.breakpoint.cc with local (Exim 4.92) (envelope-from ) id 1lPREm-0002vD-5E; Thu, 25 Mar 2021 15:45:28 +0100 Date: Thu, 25 Mar 2021 15:45:28 +0100 From: Florian Westphal To: Paolo Abeni Cc: Florian Westphal , mptcp@lists.linux.dev, mptcp@lists.01.org Subject: Re: [MPTCP] [RFC PATCH mptcp-next v2 1/8] mptcp: add skeleton to sync msk socket options to subflows Message-ID: <20210325144528.GB8998@breakpoint.cc> References: <20210324131546.13730-1-fw@strlen.de> <20210324131546.13730-2-fw@strlen.de> <85febbb1c0b4dc7b73861fabdc846194f468f127.camel@redhat.com> <20210324200148.GL22603@breakpoint.cc> <2ee15b0397e7653f8d8cfd74d53398a6a5f0c19c.camel@redhat.com> <20210325124904.GB26567@breakpoint.cc> <205a6dd33129312123ca863a8bab4aca23dad96b.camel@redhat.com> <20210325140603.GA8998@breakpoint.cc> <027b859a6f5dd1f03ad6d1c56376dc19d5d2af5b.camel@redhat.com> X-Mailing-List: mptcp@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <027b859a6f5dd1f03ad6d1c56376dc19d5d2af5b.camel@redhat.com> User-Agent: Mutt/1.10.1 (2018-07-13) Paolo Abeni wrote: > On Thu, 2021-03-25 at 15:06 +0100, Florian Westphal wrote: > > Sorry, I am not following. > > > > The ssk (s2 msk->first) has ssk->seq 1, s2 msk has 2, so this would be > > synced again on completion. > > > > I don't understand how s1 and s2 are related. > > This is too complicated for me :( > > s1 is an msk listener socket. It will get 2 setsockopt() syscall, so > s1->sockopt_seq == 2. > > Even s2->sockopt_seq == 2, as you noted. > > If we copy msk->sockopt_seq into ssk->sockopt_seq, any additional MPJ > subflow joining s2 created after the above syscalls sequence, will > get sockopt_seq == 2, (inherited by s1->sockopt_seq), so will not be > synched, even if synchronization will be needed. > > Not sure if the above is less confusing ?!? I would expect the new join ssk to have a 0 sequence number. > > > Instead, if we set sockopt_seq to some socket status related value > > > after every setsockopt(), s2->sockopt_seq and s1->sockopt_seq will be > > > different and we will sync later MPJ subflows. > > > > What is a 'socket status related value'? > > I mean something that changes when 'sk->sk_state' changes. Even plain > 'sk->sk_state'. So instead of sync if msk->seq != ssk->seq we sync if sk->sk_state != ssk->sk_state? I don't understand how that works. We might try to discuss this in the meeting, perhaps that would help?