netdev - Re: [PATCH v1 net-next 2/4] net: Retire DCCP.

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Message-ID: <CAHC9VhQeq6RjukUUnoyoCopEOfR5VJ85yPZ1CUfTAA7LeiWJTA@mail.gmail.com>
Date: Tue, 8 Apr 2025 04:12:25 -0400
From: Paul Moore <paul@...l-moore.com>
To: Christian Göttsche <cgzones@...glemail.com>
Cc: Kuniyuki Iwashima <kuniyu@...zon.com>, selinux@...r.kernel.org, 
	linux-security-module@...r.kernel.org, 
	Casey Schaufler <casey@...aufler-ca.com>, "David S. Miller" <davem@...emloft.net>, 
	Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
	Simon Horman <horms@...nel.org>, David Ahern <dsahern@...nel.org>, 
	Neal Cardwell <ncardwell@...gle.com>, Willem de Bruijn <willemb@...gle.com>, 
	Pablo Neira Ayuso <pablo@...filter.org>, Jozsef Kadlecsik <kadlec@...filter.org>, 
	James Morris <jmorris@...ei.org>, "Serge E. Hallyn" <serge@...lyn.com>, 
	Kuniyuki Iwashima <kuni1840@...il.com>, netdev@...r.kernel.org
Subject: Re: [PATCH v1 net-next 2/4] net: Retire DCCP.

On Tue, Apr 8, 2025 at 1:22 AM Christian Göttsche
<cgzones@...glemail.com> wrote:
> Apr 8, 2025 03:35:15 Paul Moore <paul@...l-moore.com>:
> > On Mon, Apr 7, 2025 at 7:19 PM Kuniyuki Iwashima <kuniyu@...zon.com> wrote:
> >>
> >> DCCP was orphaned in 2021 by commit 054c4610bd05 ("MAINTAINERS: dccp:
> >> move Gerrit Renker to CREDITS"), which noted that the last maintainer
> >> had been inactive for five years.
> >>
> >> In recent years, it has become a playground for syzbot, and most changes
> >> to DCCP have been odd bug fixes triggered by syzbot.  Apart from that,
> >> the only changes have been driven by treewide or networking API updates
> >> or adjustments related to TCP.
> >>
> >> Thus, in 2023, we announced we would remove DCCP in 2025 via commit
> >> b144fcaf46d4 ("dccp: Print deprecation notice.").
> >>
> >> Since then, only one individual has contacted the netdev mailing list. [0]
> >>
> >> There is ongoing research for Multipath DCCP.  The repository is hosted
> >> on GitHub [1], and development is not taking place through the upstream
> >> community.  While the repository is published under the GPLv2 license,
> >> the scheduling part remains proprietary, with a LICENSE file [2] stating:
> >>
> >>   "This is not Open Source software."
> >>
> >> The researcher mentioned a plan to address the licensing issue, upstream
> >> the patches, and step up as a maintainer, but there has been no further
> >> communication since then.
> >>
> >> Maintaining DCCP for a decade without any real users has become a burden.
> >>
> >> Therefore, it's time to remove it.
> >>
> >> Removing DCCP will also provide significant benefits to TCP.  It allows
> >> us to freely reorganize the layout of struct inet_connection_sock, which
> >> is currently shared with DCCP, and optimize it to reduce the number of
> >> cachelines accessed in the TCP fast path.
> >>
> >> Note that we leave uAPI headers alone for userspace programs.
> >>
> >> Link: https://lore.kernel.org/netdev/20230710182253.81446-1-kuniyu@amazon.com/T/#u #[0]
> >> Link: https://github.com/telekom/mp-dccp #[1]
> >> Link: https://github.com/telekom/mp-dccp/blob/mpdccp_v03_k5.10/net/dccp/non_gpl_scheduler/LICENSE #[2]
> >> Signed-off-by: Kuniyuki Iwashima <kuniyu@...zon.com>
> >
> > Adding the LSM and SELinux lists for obvious reasons, as well as Casey
> > directly since he maintains Smack and I don't see him on the To/CC
> > line.
> >
> > For those that weren't on the original posting, the lore link is below:
> > https://lore.kernel.org/all/20250407231823.95927-1-kuniyu@amazon.com
> >
> >> diff --git a/security/selinux/include/classmap.h b/security/selinux/include/classmap.h
> >> index 04a9b480885e..5665aa5e7853 100644
> >> --- a/security/selinux/include/classmap.h
> >> +++ b/security/selinux/include/classmap.h
> >> @@ -127,8 +127,6 @@ const struct security_class_mapping secclass_map[] = {
> >>         { "key",
> >>           { "view", "read", "write", "search", "link", "setattr", "create",
> >>             NULL } },
> >> -       { "dccp_socket",
> >> -         { COMMON_SOCK_PERMS, "node_bind", "name_connect", NULL } },
> >>         { "memprotect", { "mmap_zero", NULL } },
> >>         { "peer", { "recv", NULL } },
> >>         { "capability2", { COMMON_CAP2_PERMS, NULL } },
> >
> > A quick question for the rest of the SELinux folks: the DCCP code is
> > going away, so we won't be performing any of the access checks listed
> > above, and there will be no way to get a "dccp_socket" object, but do
> > we want to preserve the class/perms simply to quiet the warning when
> > loading existing policies?
>
> Isn't the kernel just warning about missing clssses/permissions? If policies still define dccp_socket I think the kernel treats it as user space class, like dbus.

Ah yes, my apologies, I mixed up the "... not defined in policy"
warning in my mind.  Thanks for setting me straight :)

Anyway, this looks fine to me.

Acked-by: Paul Moore <paul@...l-moore.com> (LSM and SELinux)

-- 
paul-moore.com