kernel/git/stable/linux.git/net/dccp/ccids/ccid2.h, branch master

net: Retire DCCP socket.

2025-04-12T01:58:10+00:00

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 Acked-by: Paul Moore (LSM and SELinux) Acked-by: Casey Schaufler Link: https://patch.msgid.link/20250410023921.11307-3-kuniyu@amazon.com Signed-off-by: Jakub Kicinski

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 61

2019-05-24T15:36:45+00:00

Based on 1 normalized pattern(s): this program is free software you can redistribute it and or modify it under the terms of the gnu general public license as published by the free software foundation either version 2 of the license or at your option any later version this program is distributed in the hope that it will be useful but without any warranty without even the implied warranty of merchantability or fitness for a particular purpose see the gnu general public license for more details you should have received a copy of the gnu general public license along with this program if not write to the free software foundation inc 675 mass ave cambridge ma 02139 usa extracted by the scancode license scanner the SPDX license identifier GPL-2.0-or-later has been chosen to replace the boilerplate/reference in 441 file(s). Signed-off-by: Thomas Gleixner Reviewed-by: Michael Ellerman (powerpc) Reviewed-by: Richard Fontana Reviewed-by: Allison Randal Reviewed-by: Kate Stewart Cc: linux-spdx@vger.kernel.org Link: https://lkml.kernel.org/r/20190520071858.739733335@linutronix.de Signed-off-by: Greg Kroah-Hartman

net: dccp: Convert timers to use timer_setup()

2017-10-25T03:59:19+00:00

In preparation for unconditionally passing the struct timer_list pointer to all timer callbacks, switch to using the new timer_setup() and from_timer() to pass the timer pointer explicitly. Adds a pointer back to the sock. Cc: Gerrit Renker Cc: "David S. Miller" Cc: Soheil Hassas Yeganeh Cc: Hannes Frederic Sowa Cc: Eric Dumazet Cc: dccp@vger.kernel.org Cc: netdev@vger.kernel.org Signed-off-by: Kees Cook Signed-off-by: David S. Miller

dccp: do not use tcp_time_stamp

2017-05-17T20:06:01+00:00

Use our own macro instead of abusing tcp_time_stamp Signed-off-by: Eric Dumazet Acked-by: Soheil Hassas Yeganeh Signed-off-by: David S. Miller

dccp ccid-2: prevent cwnd > Sequence Window

2011-08-01T13:52:35+00:00

Add a check to prevent CCID-2 from increasing the cwnd greater than the Sequence Window. When the congestion window becomes bigger than the Sequence Window, CCID-2 will attempt to keep more data in the network than the DCCP Sequence Window code considers possible. This results in the Sequence Window code issuing a Sync, thereby inducing needless overhead. Further, if this occurs at the sender, CCID-2 will never detect the problem because the Acks it receives will indicate no losses. I have seen this cause a drop of 1/3rd in throughput for a connection. Also add code to adjust the Sequence Window to be about 5 times the number of packets in the network (RFC 4340, 7.5.2) and to adjust the Ack Ratio so that the remote Sequence Window will hold about 5 times the number of packets in the network. This allows the congestion window to increase correctly without being limited by the Sequence Window. Signed-off-by: Samuel Jero Acked-by: Gerrit Renker

dccp ccid-2: Perform congestion-window validation

2011-07-04T18:37:49+00:00

CCID-2's cwnd increases like TCP during slow-start, which has implications for * the local Sequence Window value (should be > cwnd), * the Ack Ratio value. Hence an exponential growth, if it does not reflect the actual network conditions, can quickly lead to instability. This patch adds congestion-window validation (RFC2861) to CCID-2: * cwnd is constrained if the sender is application limited; * cwnd is reduced after a long idle period, as suggested in the '90 paper by Van Jacobson, in RFC 2581 (sec. 4.1); * cwnd is never reduced below the RFC 3390 initial window. As marked in the comments, the code is actually almost a direct copy of the TCP congestion-window-validation algorithms. By continuing this work, it may in future be possible to use the TCP code (not possible at the moment). The mechanism can be turned off using a module parameter. Sampling of the currently-used window (moving-maximum) is however done constantly; this is used to determine the expected window, which can be exploited to regulate DCCP's Sequence Window value. This patch also sets slow-start-after-idle (RFC 4341, 5.1), i.e. it behaves like TCP when net.ipv4.tcp_slow_start_after_idle = 1. Signed-off-by: Gerrit Renker

dccp ccid-2: Use existing function to test for data packets

2011-07-04T18:37:40+00:00

This replaces a switch statement with a test, using the equivalent function dccp_data_packet(skb). It also doubles the range of the field `rx_num_data_pkts' by changing the type from `int' to `u32', avoiding signed/unsigned comparison with the u16 field `dccps_r_ack_ratio'. Signed-off-by: Gerrit Renker

dccp ccid-2: move rfc 3390 function into header file

2011-07-04T18:37:30+00:00

This moves CCID-2's initial window function into the header file, since several parts throughout the CCID-2 code need to call it (CCID-2 still uses RFC 3390). Signed-off-by: Gerrit Renker Acked-by: Leandro Melo de Sales

dccp ccid-2: Separate option parsing from CCID processing

2010-11-15T06:12:01+00:00

This patch replaces an almost identical replication of code: large parts of dccp_parse_options() re-appeared as ccid2_ackvector() in ccid2.c. Apart from the duplication, this caused two more problems: 1. CCIDs should not need to be concerned with parsing header options; 2. one can not assume that Ack Vectors appear as a contiguous area within an skb, it is legal to insert other options and/or padding in between. The current code would throw an error and stop reading in such a case. Since Ack Vectors provide CCID-specific information, they are now processed by the CCID directly, separating this functionality from the main DCCP code. Signed-off-by: Gerrit Renker

dccp ccid-2: Stop polling

2010-10-28T17:27:01+00:00

This updates CCID-2 to use the CCID dequeuing mechanism, converting from previous continuous-polling to a now event-driven mechanism. Signed-off-by: Gerrit Renker Signed-off-by: David S. Miller