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some more formatting
When set the queue to repair as described above, one can call recv or send syscalls on a repaired socket. Both calls
When set the queue to repair as described above, one can call recv or send syscalls on a repaired socket. Both calls
result on peeking or poking data from/to the respective queue. This sounds funny, but yes, for repaired socket one
result on peeking or poking data from/to the respective queue. This sounds funny, but yes, for repaired socket one
can receve the outgoing and send the incoming queues. Using the MSG_PEEK flag for recv is required.
can receve the outgoing and send the incoming queues. Using the <code>MSG_PEEK</code> flag for <code>recv()</code> is required.
=== Options ===
=== Options ===
* tstamp -- whether timestamps on packets are supported
* tstamp -- whether timestamps on packets are supported
All four can be read with getsockopt calls to a socket and in order to restore them the TCP_REPAIR_OPTIONS sockoption
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.
is introduced.
== Checkpoint and restore TCP connection ==
== Checkpoint and restore TCP connection ==
state and restores it back letting the protocol resurrect the data sequence.
state and restores it back letting the protocol resurrect the data sequence.
One thing to note here -- while the socket is closed between dump and restore the connection should be "locked", i.e.
One thing to note here — while the socket is closed between dump and restore the connection should be "locked", i.e.
no packets from peer should enter the stack, otherwise the RST will be sent by a kernel. In order to do so a simple
no packets from peer should enter the stack, otherwise the RST will be sent by a kernel. In order to do so a simple
netfilter rule is configured that drops all the packets from peer to a socket we're dealing with. This rule sits
netfilter rule is configured that drops all the packets from peer to a socket we're dealing with. This rule sits
criu restore one.
criu restore one.
That said, the command line option --tcp-established should be used when calling criu to explicitly state, that the
That said, the command line option <code>--tcp-established</code> should be used when calling criu to explicitly state, that the
caller is aware of this "transitional" state of the netfilter.
caller is aware of this "transitional" state of the netfilter.