427
edits
Changes
Jump to navigation
Jump to search
no edit summary
Line 39:
Line 39:
All four can be read with <code>getsockopt()</code> calls to a socket and in order to restore them the <code>TCP_REPAIR_OPTIONS</code> sockoption is introduced.
All four can be read with <code>getsockopt()</code> calls to a socket and in order to restore them the <code>TCP_REPAIR_OPTIONS</code> sockoption is introduced.
+
+== Timestamp ==
+"The sender's timestamp clock is used as a source of monotonic non-decreasing values to stamp the segments"(rfc7323). The Linux kernel uses the jiffies counter as the tcp timestamp.
+ #define tcp_time_stamp ((__u32)(jiffies))
+
+We add the TCP_TIMESTAMP options to be able to compensate a difference between jiffies counters, when a connection is migrated on another host. When a connection is dumped, criu calls getsockopt(TCP_TIMESTAMP) to get a current timestamp, then on restore it calls setsockopt(TCP_TIMESTAMP) to set this timestamp as a starting point.
== Checkpoint and restore TCP connection ==
== Checkpoint and restore TCP connection ==