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Diffstat (limited to 'Documentation/networking/xfrm_sync.txt')
| -rw-r--r-- | Documentation/networking/xfrm_sync.txt | 169 |
1 files changed, 0 insertions, 169 deletions
diff --git a/Documentation/networking/xfrm_sync.txt b/Documentation/networking/xfrm_sync.txt deleted file mode 100644 index 8d88e0f2ec49..000000000000 --- a/Documentation/networking/xfrm_sync.txt +++ /dev/null @@ -1,169 +0,0 @@ - -The sync patches work is based on initial patches from -Krisztian <hidden@balabit.hu> and others and additional patches -from Jamal <hadi@cyberus.ca>. - -The end goal for syncing is to be able to insert attributes + generate -events so that the SA can be safely moved from one machine to another -for HA purposes. -The idea is to synchronize the SA so that the takeover machine can do -the processing of the SA as accurate as possible if it has access to it. - -We already have the ability to generate SA add/del/upd events. -These patches add ability to sync and have accurate lifetime byte (to -ensure proper decay of SAs) and replay counters to avoid replay attacks -with as minimal loss at failover time. -This way a backup stays as closely up-to-date as an active member. - -Because the above items change for every packet the SA receives, -it is possible for a lot of the events to be generated. -For this reason, we also add a nagle-like algorithm to restrict -the events. i.e we are going to set thresholds to say "let me -know if the replay sequence threshold is reached or 10 secs have passed" -These thresholds are set system-wide via sysctls or can be updated -per SA. - -The identified items that need to be synchronized are: -- the lifetime byte counter -note that: lifetime time limit is not important if you assume the failover -machine is known ahead of time since the decay of the time countdown -is not driven by packet arrival. -- the replay sequence for both inbound and outbound - -1) Message Structure ----------------------- - -nlmsghdr:aevent_id:optional-TLVs. - -The netlink message types are: - -XFRM_MSG_NEWAE and XFRM_MSG_GETAE. - -A XFRM_MSG_GETAE does not have TLVs. -A XFRM_MSG_NEWAE will have at least two TLVs (as is -discussed further below). - -aevent_id structure looks like: - - struct xfrm_aevent_id { - struct xfrm_usersa_id sa_id; - xfrm_address_t saddr; - __u32 flags; - __u32 reqid; - }; - -The unique SA is identified by the combination of xfrm_usersa_id, -reqid and saddr. - -flags are used to indicate different things. The possible -flags are: - XFRM_AE_RTHR=1, /* replay threshold*/ - XFRM_AE_RVAL=2, /* replay value */ - XFRM_AE_LVAL=4, /* lifetime value */ - XFRM_AE_ETHR=8, /* expiry timer threshold */ - XFRM_AE_CR=16, /* Event cause is replay update */ - XFRM_AE_CE=32, /* Event cause is timer expiry */ - XFRM_AE_CU=64, /* Event cause is policy update */ - -How these flags are used is dependent on the direction of the -message (kernel<->user) as well the cause (config, query or event). -This is described below in the different messages. - -The pid will be set appropriately in netlink to recognize direction -(0 to the kernel and pid = processid that created the event -when going from kernel to user space) - -A program needs to subscribe to multicast group XFRMNLGRP_AEVENTS -to get notified of these events. - -2) TLVS reflect the different parameters: ------------------------------------------ - -a) byte value (XFRMA_LTIME_VAL) -This TLV carries the running/current counter for byte lifetime since -last event. - -b)replay value (XFRMA_REPLAY_VAL) -This TLV carries the running/current counter for replay sequence since -last event. - -c)replay threshold (XFRMA_REPLAY_THRESH) -This TLV carries the threshold being used by the kernel to trigger events -when the replay sequence is exceeded. - -d) expiry timer (XFRMA_ETIMER_THRESH) -This is a timer value in milliseconds which is used as the nagle -value to rate limit the events. - -3) Default configurations for the parameters: ----------------------------------------------- - -By default these events should be turned off unless there is -at least one listener registered to listen to the multicast -group XFRMNLGRP_AEVENTS. - -Programs installing SAs will need to specify the two thresholds, however, -in order to not change existing applications such as racoon -we also provide default threshold values for these different parameters -in case they are not specified. - -the two sysctls/proc entries are: -a) /proc/sys/net/core/sysctl_xfrm_aevent_etime -used to provide default values for the XFRMA_ETIMER_THRESH in incremental -units of time of 100ms. The default is 10 (1 second) - -b) /proc/sys/net/core/sysctl_xfrm_aevent_rseqth -used to provide default values for XFRMA_REPLAY_THRESH parameter -in incremental packet count. The default is two packets. - -4) Message types ----------------- - -a) XFRM_MSG_GETAE issued by user-->kernel. -XFRM_MSG_GETAE does not carry any TLVs. -The response is a XFRM_MSG_NEWAE which is formatted based on what -XFRM_MSG_GETAE queried for. -The response will always have XFRMA_LTIME_VAL and XFRMA_REPLAY_VAL TLVs. -*if XFRM_AE_RTHR flag is set, then XFRMA_REPLAY_THRESH is also retrieved -*if XFRM_AE_ETHR flag is set, then XFRMA_ETIMER_THRESH is also retrieved - -b) XFRM_MSG_NEWAE is issued by either user space to configure -or kernel to announce events or respond to a XFRM_MSG_GETAE. - -i) user --> kernel to configure a specific SA. -any of the values or threshold parameters can be updated by passing the -appropriate TLV. -A response is issued back to the sender in user space to indicate success -or failure. -In the case of success, additionally an event with -XFRM_MSG_NEWAE is also issued to any listeners as described in iii). - -ii) kernel->user direction as a response to XFRM_MSG_GETAE -The response will always have XFRMA_LTIME_VAL and XFRMA_REPLAY_VAL TLVs. -The threshold TLVs will be included if explicitly requested in -the XFRM_MSG_GETAE message. - -iii) kernel->user to report as event if someone sets any values or -thresholds for an SA using XFRM_MSG_NEWAE (as described in #i above). -In such a case XFRM_AE_CU flag is set to inform the user that -the change happened as a result of an update. -The message will always have XFRMA_LTIME_VAL and XFRMA_REPLAY_VAL TLVs. - -iv) kernel->user to report event when replay threshold or a timeout -is exceeded. -In such a case either XFRM_AE_CR (replay exceeded) or XFRM_AE_CE (timeout -happened) is set to inform the user what happened. -Note the two flags are mutually exclusive. -The message will always have XFRMA_LTIME_VAL and XFRMA_REPLAY_VAL TLVs. - -Exceptions to threshold settings --------------------------------- - -If you have an SA that is getting hit by traffic in bursts such that -there is a period where the timer threshold expires with no packets -seen, then an odd behavior is seen as follows: -The first packet arrival after a timer expiry will trigger a timeout -event; i.e we don't wait for a timeout period or a packet threshold -to be reached. This is done for simplicity and efficiency reasons. - --JHS |