net: Retire DCCP socket.

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 keep DCCP netfilter modules as requested.  [3]

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]
Link: https://lore.kernel.org/netdev/Z_VQ0KlCRkqYWXa-@calendula/ #[3]
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Acked-by: Paul Moore <paul@paul-moore.com> (LSM and SELinux)
Acked-by: Casey Schaufler <casey@schaufler-ca.com>
Link: https://patch.msgid.link/20250410023921.11307-3-kuniyu@amazon.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 0 insertions, 42 deletions

diff --git a/net/core/secure_seq.c b/net/core/secure_seq.c
index 568779d5a0ef..9a3965680451 100644
--- a/net/core/secure_seq.c
+++ b/net/core/secure_seq.c
@@ -156,45 +156,3 @@ u64 secure_ipv4_port_ephemeral(__be32 saddr, __be32 daddr, __be16 dport)
 }
 EXPORT_SYMBOL_GPL(secure_ipv4_port_ephemeral);
 #endif
-
-#if IS_ENABLED(CONFIG_IP_DCCP)
-u64 secure_dccp_sequence_number(__be32 saddr, __be32 daddr,
-				__be16 sport, __be16 dport)
-{
-	u64 seq;
-	net_secret_init();
-	seq = siphash_3u32((__force u32)saddr, (__force u32)daddr,
-			   (__force u32)sport << 16 | (__force u32)dport,
-			   &net_secret);
-	seq += ktime_get_real_ns();
-	seq &= (1ull << 48) - 1;
-	return seq;
-}
-EXPORT_SYMBOL(secure_dccp_sequence_number);
-
-#if IS_ENABLED(CONFIG_IPV6)
-u64 secure_dccpv6_sequence_number(__be32 *saddr, __be32 *daddr,
-				  __be16 sport, __be16 dport)
-{
-	const struct {
-		struct in6_addr saddr;
-		struct in6_addr daddr;
-		__be16 sport;
-		__be16 dport;
-	} __aligned(SIPHASH_ALIGNMENT) combined = {
-		.saddr = *(struct in6_addr *)saddr,
-		.daddr = *(struct in6_addr *)daddr,
-		.sport = sport,
-		.dport = dport
-	};
-	u64 seq;
-	net_secret_init();
-	seq = siphash(&combined, offsetofend(typeof(combined), dport),
-		      &net_secret);
-	seq += ktime_get_real_ns();
-	seq &= (1ull << 48) - 1;
-	return seq;
-}
-EXPORT_SYMBOL(secure_dccpv6_sequence_number);
-#endif
-#endif