[netfilter-cvslog] r4306 - branches/netfilter-ha/linux-2.6-actact/ct_sync

[laforge at netfilter.org]

Author: laforge at netfilter.org
Date: 2005-09-25 17:27:30 +0200 (Sun, 25 Sep 2005)
New Revision: 4306

Added:
   branches/netfilter-ha/linux-2.6-actact/ct_sync/actact.txt
   branches/netfilter-ha/linux-2.6-actact/ct_sync/locking.txt
Log:
some thoughts on locking and active-active


Added: branches/netfilter-ha/linux-2.6-actact/ct_sync/actact.txt
===================================================================
--- branches/netfilter-ha/linux-2.6-actact/ct_sync/actact.txt	2005-09-25 15:26:59 UTC (rev 4305)
+++ branches/netfilter-ha/linux-2.6-actact/ct_sync/actact.txt	2005-09-25 15:27:30 UTC (rev 4306)
@@ -0,0 +1,53 @@
+terminology:
+
+ct_sync
+	the connection tracking synchronization code
+
+ct_sync instance
+	one instance of ct_sync
+
+ct_sync node
+	a node running one or more ct_sync instances
+
+ct_sync cluster
+	all ct_sync instances participating in one multicast group
+
+ct_sync peer 
+	a remote ct_sync instance within the same cluster
+
+active ct_sync instance
+	a ct_sync instance that actively participates in packet forwarding
+
+passive ct_sync instance
+	a ct_sync instance that only passively listens for state updates by it's peers.
+
+eligible passive ct_sync instance
+	a ct_sync instance that is fully synchronized with it's peers and thus
+	eligible to become active
+
+
+data structuring:
+
+
+per-instance data:
+	name of instance
+	multicast group
+	syncdevice
+	whether we're in sync with all peers and thus eligible for becoming active
+	tunable parameters such as send_burst, recv_burst
+	cmarkbit of which local conntracks participate in this cluster
+	protocol handle
+	group of three threads and their waitqueues
+	sysfs attributes
+	
+	
+	
+per-peer data structure:
+	incoming side:
+		last received seqno
+		whether we requested initsync or not
+		whether we requested retransmit or not
+	outgoing side:
+		last sent seqno
+		whether we've been requested to give initsync
+		whether we've been requested to retransmit

Added: branches/netfilter-ha/linux-2.6-actact/ct_sync/locking.txt
===================================================================
--- branches/netfilter-ha/linux-2.6-actact/ct_sync/locking.txt	2005-09-25 15:26:59 UTC (rev 4305)
+++ branches/netfilter-ha/linux-2.6-actact/ct_sync/locking.txt	2005-09-25 15:27:30 UTC (rev 4306)
@@ -0,0 +1,27 @@
+thoughts about locking
+
+1. ct_sync_instances list:
+
+- the list is traversed from
+	- bottom half context via hook functions l2drop/notrack (read)
+		- iterates over list to find all syncdev_ifindex
+	- bottom half context via conntrack notifiers (read)
+		- interates over list to find protoh
+	- userspace context via /sys/netfilter/ct_sync/instances/control (write)
+		- activate/deactivate
+		- create/destroy
+	- kernel thread context from the three ct_sync kernel threads (read)
+		- interates over list to send pending packets for each 
+		  instance
+		- can sleep while dealing with one item in the list
+- result
+	- writing control accesses very rare event
+	- majority of accesses are read-only
+	- some read accesses may inevitably sleep
+	- majority of accesses from process context
+
+2. locking of cts_buff structure
+
+2.a send path
+
+-