Resubmit as v2 RFC to get some feedback before net-next opens up again. Only minor changes (see below).
This patchset introduces a generic framework for handling TCP-options. TCP-options like TCP_MD5 and SMC are rather rare use-cases, but their implementation is rather intrusive to the TCP-stack. Other, more recent TCP extensions like TCP-crypt, MPTCP or TCP-AO would make this situation even worse. This new framework allows to add these TCP-options in a modular way. Writing, reading and acting upon these options is done through callbacks that get registered to a TCP-socket. A TCP-socket has a list of "extra" TCP-options that it will use. We make TCP-SMC and TCP-MD5SIG adopt this new framework. As can be seen, there is now no more TCP-SMC code in the TCP-files and the TCP-MD5 code has been reduced to a bare minimum. This patchset is admittedly rather big, but we wanted to show where the framework will lead to and what it enables. Suggestions as to how to better structure the patchset is appreciated. There is still work to be done to more efficiently check for extra TCP options in performance-sensitive code paths. A rate-limited static key would nearly eliminate overhead if no extra TCP options are in use system-wide, or a flag in a likely-hot cache line could work well. For now we opted for a simple if (unlikely(!hlist_empty(...)) check. Feedback is very welcome! Thanks, Mat & Christoph Changelog: === v1 -> v2: * Some minor fixes thanks to the buildbot when certain configs are disabled (Patch 5 and 12) * Add spdx-header in the new files (Patch 11) * Added Ivan Delande to the CC-list as he did some TCP-MD5 changes in the past. Christoph Paasch (13): tcp: Write options after the header has been fully done tcp: Pass sock and skb to tcp_options_write tcp: Allow tcp_fast_parse_options to drop segments tcp_smc: Make smc_parse_options return 1 on success tcp_smc: Make SMC use TCP extra-option framework tcp_md5: Don't pass along md5-key tcp_md5: Detect key inside tcp_v4_send_ack instead of passing it as an argument tcp_md5: Detect key inside tcp_v6_send_response instead of passing it as an argument tcp_md5: Check for TCP_MD5 after TCP Timestamps in tcp_established_options tcp_md5: Move TCP-MD5 code out of TCP itself tcp_md5: Use tcp_extra_options in output path tcp_md5: Cleanup TCP-code tcp_md5: Use TCP extra-options on the input path Mat Martineau (1): tcp: Register handlers for extra TCP options drivers/infiniband/hw/cxgb4/cm.c | 2 +- include/linux/inet_diag.h | 1 + include/linux/tcp.h | 43 +- include/linux/tcp_md5.h | 40 ++ include/net/inet_sock.h | 3 +- include/net/tcp.h | 213 +++--- net/ipv4/Makefile | 1 + net/ipv4/syncookies.c | 6 +- net/ipv4/tcp.c | 391 ++++++++--- net/ipv4/tcp_diag.c | 81 +-- net/ipv4/tcp_input.c | 137 ++-- net/ipv4/tcp_ipv4.c | 556 ++-------------- net/ipv4/tcp_md5.c | 1359 ++++++++++++++++++++++++++++++++++++++ net/ipv4/tcp_minisocks.c | 75 +-- net/ipv4/tcp_output.c | 182 +---- net/ipv6/syncookies.c | 6 +- net/ipv6/tcp_ipv6.c | 390 ++--------- net/smc/af_smc.c | 190 +++++- 18 files changed, 2228 insertions(+), 1448 deletions(-) create mode 100644 include/linux/tcp_md5.h create mode 100644 net/ipv4/tcp_md5.c -- 2.16.1