Date: Wed, 20 Oct 2004 00:35:10 +0200 From: Max Laier <max@love2party.net> To: Andre Oppermann <andre@freebsd.org> Cc: cvs-src@freebsd.org Subject: Re: cvs commit: src/sys/sys protosw.h src/sys/kern uipc_domain.cuipc_socket2.c Message-ID: <200410200035.19752.max@love2party.net> In-Reply-To: <41758B35.D5340AEA@freebsd.org> References: <200410191513.i9JFDUbf072176@repoman.freebsd.org> <200410192329.46723.max@love2party.net> <41758B35.D5340AEA@freebsd.org>
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[-- Attachment #1 --] On Tuesday 19 October 2004 23:46, Andre Oppermann wrote: <...> > > problems. For example, in ip_icmp.c line 457 ff we have: > > > > ctlfunc = > > inetsw[ip_protox[icp->icmp_ip.ip_p]].pr_ctlinput; if (ctlfunc) > > (*ctlfunc)(code, (struct sockaddr *)&icmpsrc, > > (void *)&icp->icmp_ip); > > Ok, this one is easy to fix. I'll audit the code for any other of these > abuses. One of many, I am afraid. > > This is clearly a problem if we can remove protocols. There might be more > > places where we (temporary) cache values from the protocol array. Another > > problem might be that we check for protocol existence early and assume > > that this remains true ... > > Well, too bad if some code tries to remember this. Doesn't hurt then. > From my reading of many parts of the netinet/* code this is usually not > a problem and the code is rather well behaved. I refuse to take this > argument as reason to not have loadable protocols. "... usually ... rather ..." I really urge you, to reconsider. Many have argumented in the same way. I understand that it is nice to have this possibility, but it *does* cause *real* problems! > > I'd suggest, that you remove the possibility to remove protocols > > completely. It is very likely that there are no races with adding > > protocols - though it might take "some time" for the protocol to be fully > > useable - but the removal is critical. > > I don't think it should be a one-way street. To be able to unload > protocols is an important but seldomly used function and it's certainly not > that a crash is guarnteed. Far from it. > > > We also have to check that really all code can cope with the addition and > > properly reinitializes it's view of the protocol arrays. > > The point of the protocol arrays is precisely to have them as the only > and sole place where such information is stored. Any code that copies > any part of it to its own private structures is horribly broken by design > and must be fixed anyway! (BTW: I'm not aware of any code within netinet/* > that does this.) I mentioned one above, I am sure there are others. Some as obvious as the one above, some less so ... > > Another point: If you really want to keep the possibility to remove a > > protocol, you have to introduce some busy counter that pervents removal > > while the kernel is inside a protocol function. This has to be handled by > > the protocol itself, but it has to be taken care of somehow. > > Yes, the protocol has to be able to handle its own unloading. I have > documented that fact. If a protocol in unable to do so it should simply > refuse any unload attempts with EBUSY. Divert can be paniced with the sysctl code, btw. You have something like: lock; unlock; SYSCTL_OUT; <-- this can be made to take *some* time lock; <-- this will panic once the lock is destroyed And there are other problems. Yes, it is not a problem in the common case, but you have to account for edge cases as well! -- /"\ Best regards, | mlaier@freebsd.org \ / Max Laier | ICQ #67774661 X http://pf4freebsd.love2party.net/ | mlaier@EFnet / \ ASCII Ribbon Campaign | Against HTML Mail and News [-- Attachment #2 --] -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.6 (FreeBSD) iD8DBQBBdZanXyyEoT62BG0RAqacAJ4p7xH50oz47gf+QjkMVZd9FeSvgACfUj4e bC0+2SLN9ZjnBlbH+eoX/S0= =mwLt -----END PGP SIGNATURE-----
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