kernel/include/net/sctp/constants.h, branch linux-6.18.y

sctp: Convert cookie authentication to use HMAC-SHA256

2025-08-20T02:36:26Z

Convert SCTP cookies to use HMAC-SHA256, instead of the previous choice of the legacy algorithms HMAC-MD5 and HMAC-SHA1. Simplify and optimize the code by using the HMAC-SHA256 library instead of crypto_shash, and by preparing the HMAC key when it is generated instead of per-operation. This doesn't break compatibility, since the cookie format is an implementation detail, not part of the SCTP protocol itself. Note that the cookie size doesn't change either. The HMAC field was already 32 bytes, even though previously at most 20 bytes were actually compared. 32 bytes exactly fits an untruncated HMAC-SHA256 value. So, although we could safely truncate the MAC to something slightly shorter, for now just keep the cookie size the same. I also considered SipHash, but that would generate only 8-byte MACs. An 8-byte MAC *might* suffice here. However, there's quite a lot of information in the SCTP cookies: more than in TCP SYN cookies. So absent an analysis that occasional forgeries of all that information is okay in SCTP, I errored on the side of caution. Remove HMAC-MD5 and HMAC-SHA1 as options, since the new HMAC-SHA256 option is just better. It's faster as well as more secure. For example, benchmarking on x86_64, cookie authentication is now nearly 3x as fast as the previous default choice and implementation of HMAC-MD5. Also just make the kernel always support cookie authentication if SCTP is supported at all, rather than making it optional in the build. (It was sort of optional before, but it didn't really work properly. E.g., a kernel with CONFIG_SCTP_COOKIE_HMAC_MD5=n still supported HMAC-MD5 cookie authentication if CONFIG_CRYPTO_HMAC and CONFIG_CRYPTO_MD5 happened to be enabled in the kconfig for other reasons.) Acked-by: Xin Long Signed-off-by: Eric Biggers Link: https://patch.msgid.link/20250818205426.30222-5-ebiggers@kernel.org Signed-off-by: Jakub Kicinski

sctp: Use HMAC-SHA1 and HMAC-SHA256 library for chunk authentication

2025-08-20T02:36:25Z

For SCTP chunk authentication, use the HMAC-SHA1 and HMAC-SHA256 library functions instead of crypto_shash. This is simpler and faster. There's no longer any need to pre-allocate 'crypto_shash' objects; the SCTP code now simply calls into the HMAC code directly. As part of this, make SCTP always support both HMAC-SHA1 and HMAC-SHA256. Previously, it only guaranteed support for HMAC-SHA1. However, HMAC-SHA256 tended to be supported too anyway, as it was supported if CONFIG_CRYPTO_SHA256 was enabled elsewhere in the kconfig. Acked-by: Xin Long Signed-off-by: Eric Biggers Link: https://patch.msgid.link/20250818205426.30222-4-ebiggers@kernel.org Signed-off-by: Jakub Kicinski

sctp: move 198 addresses from unusable to private scope

2021-07-01T18:47:13Z

The doc draft-stewart-tsvwg-sctp-ipv4-00 that restricts 198 addresses was never published. These addresses as private addresses should be allowed to use in SCTP. As Michael Tuexen suggested, this patch is to move 198 addresses from unusable to private scope. Reported-by: Sérgio Signed-off-by: Xin Long Acked-by: Marcelo Ricardo Leitner Signed-off-by: David S. Miller

sctp: add the probe timer in transport for PLPMTUD

2021-06-22T18:28:52Z

There are 3 timers described in rfc8899#section-5.1.1: PROBE_TIMER, PMTU_RAISE_TIMER, CONFIRMATION_TIMER This patches adds a 'probe_timer' in transport, and it works as either PROBE_TIMER or PMTU_RAISE_TIMER. At most time, it works as PROBE_TIMER and expires every a 'probe_interval' time to send the HB probe packet. When transport pl enters COMPLETE state, it works as PMTU_RAISE_TIMER and expires in 'probe_interval * 30' time to go back to SEARCH state and do searching again. SCTP HB is an acknowledged packet, CONFIRMATION_TIMER is not needed. The timer will start when transport pl enters BASE state and stop when it enters DISABLED state. Signed-off-by: Xin Long Acked-by: Marcelo Ricardo Leitner Signed-off-by: David S. Miller

sctp: add the constants/variables and states and some APIs for transport

2021-06-22T18:28:52Z

These are 4 constants described in rfc8899#section-5.1.2: MAX_PROBES, MIN_PLPMTU, MAX_PLPMTU, BASE_PLPMTU; And 2 variables described in rfc8899#section-5.1.3: PROBED_SIZE, PROBE_COUNT; And 5 states described in rfc8899#section-5.2: DISABLED, BASE, SEARCH, SEARCH_COMPLETE, ERROR; And these 4 APIs are used to reset/update PLPMTUD, check if PLPMTUD is enabled, and calculate the additional headers length for a transport. Note the member 'probe_high' in transport will be set to the probe size when a probe fails with this probe size in the next patches. Signed-off-by: Xin Long Acked-by: Marcelo Ricardo Leitner Signed-off-by: David S. Miller

sctp: add probe_interval in sysctl and sock/asoc/transport

2021-06-22T18:28:51Z

PLPMTUD can be enabled by doing 'sysctl -w net.sctp.probe_interval=n'. 'n' is the interval for PLPMTUD probe timer in milliseconds, and it can't be less than 5000 if it's not 0. All asoc/transport's PLPMTUD in a new socket will be enabled by default. Signed-off-by: Xin Long Acked-by: Marcelo Ricardo Leitner Signed-off-by: David S. Miller

sctp: create udp4 sock and add its encap_rcv

2020-10-30T22:23:52Z

This patch is to add the functions to create/release udp4 sock, and set the sock's encap_rcv to process the incoming udp encap sctp packets. In sctp_udp_rcv(), as we can see, all we need to do is fix the transport header for sctp_rcv(), then it would implement the part of rfc6951#section-5.4: "When an encapsulated packet is received, the UDP header is removed. Then, the generic lookup is performed, as done by an SCTP stack whenever a packet is received, to find the association for the received SCTP packet" Note that these functions will be called in the last patch of this patchset when enabling this feature. v1->v2: - Add pr_err() when fails to create udp v4 sock. v2->v3: - Add 'select NET_UDP_TUNNEL' in sctp Kconfig. v3->v4: - No change. v4->v5: - Change to set udp_port to 0 by default. Signed-off-by: Xin Long Acked-by: Marcelo Ricardo Leitner Signed-off-by: Jakub Kicinski

sctp: Don't advertise IPv4 addresses if ipv6only is set on the socket

2020-06-25T23:11:33Z

If a socket is set ipv6only, it will still send IPv4 addresses in the INIT and INIT_ACK packets. This potentially misleads the peer into using them, which then would cause association termination. The fix is to not add IPv4 addresses to ipv6only sockets. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Reported-by: Corey Minyard Signed-off-by: Marcelo Ricardo Leitner Tested-by: Corey Minyard Signed-off-by: David S. Miller

sctp: add support for Primary Path Switchover

2019-11-08T22:18:32Z

This is a new feature defined in section 5 of rfc7829: "Primary Path Switchover". By introducing a new tunable parameter: Primary.Switchover.Max.Retrans (PSMR) The primary path will be changed to another active path when the path error counter on the old primary path exceeds PSMR, so that "the SCTP sender is allowed to continue data transmission on a new working path even when the old primary destination address becomes active again". This patch is to add this tunable parameter, 'ps_retrans' per netns, sock, asoc and transport. It also allows a user to change ps_retrans per netns by sysctl, and ps_retrans per sock/asoc/transport will be initialized with it. The check will be done in sctp_do_8_2_transport_strike() when this feature is enabled. Note this feature is disabled by initializing 'ps_retrans' per netns as 0xffff by default, and its value can't be less than 'pf_retrans' when changing by sysctl. v3->v4: - add define SCTP_PS_RETRANS_MAX 0xffff, and use it on extra2 of sysctl 'ps_retrans'. - add a new entry for ps_retrans on ip-sysctl.txt. Signed-off-by: Xin Long Acked-by: Neil Horman Signed-off-by: David S. Miller

sctp: add pf_expose per netns and sock and asoc

2019-11-08T22:18:32Z

As said in rfc7829, section 3, point 12: The SCTP stack SHOULD expose the PF state of its destination addresses to the ULP as well as provide the means to notify the ULP of state transitions of its destination addresses from active to PF, and vice versa. However, it is recommended that an SCTP stack implementing SCTP-PF also allows for the ULP to be kept ignorant of the PF state of its destinations and the associated state transitions, thus allowing for retention of the simpler state transition model of [RFC4960] in the ULP. Not only does it allow to expose the PF state to ULP, but also allow to ignore sctp-pf to ULP. So this patch is to add pf_expose per netns, sock and asoc. And in sctp_assoc_control_transport(), ulp_notify will be set to false if asoc->expose is not 'enabled' in next patch. It also allows a user to change pf_expose per netns by sysctl, and pf_expose per sock and asoc will be initialized with it. Note that pf_expose also works for SCTP_GET_PEER_ADDR_INFO sockopt, to not allow a user to query the state of a sctp-pf peer address when pf_expose is 'disabled', as said in section 7.3. v1->v2: - Fix a build warning noticed by Nathan Chancellor. v2->v3: - set pf_expose to UNUSED by default to keep compatible with old applications. v3->v4: - add a new entry for pf_expose on ip-sysctl.txt, as Marcelo suggested. - change this patch to 1/5, and move sctp_assoc_control_transport change into 2/5, as Marcelo suggested. - use SCTP_PF_EXPOSE_UNSET instead of SCTP_PF_EXPOSE_UNUSED, and set SCTP_PF_EXPOSE_UNSET to 0 in enum, as Marcelo suggested. Signed-off-by: Xin Long Acked-by: Neil Horman Signed-off-by: David S. Miller