TCP connection - Revision history

Kir: use template:opt

2021-08-08T15:31:35Z

use template:opt

2021-08-08T12:43:21Z

2019-03-11T18:39:11Z

Grammar fixes

2017-11-21T09:19:50Z

TCP_SYN_SENT

2017-08-07T19:12:31Z

2017-07-13T12:57:32Z

2016-12-05T07:04:58Z

2016-12-05T06:38:17Z

Timestamp

2016-12-05T06:36:02Z

2016-09-21T18:48:14Z

separate see also / external links a la wikipedia; add link to simple tcp pair

@@ Line 56: / Line 56: @@
 netfilter rule is configured that drops all the packets from peer to a socket we're dealing with. This rule sits
 in the host netfilter tables after the criu dump command finishes and it should be there when you issue the
-criu restore one. The locking method can be specified using the [https://criu.org/index.php?title=CLI/opt/--network-lock <code>--network-lock</code>]option.
+criu restore one. The locking method can be specified using the {{opt|--network-lock}} option.
 Another thing to note is -- on restore there should be available the IP address, that was used by the connection.
@@ Line 62: / Line 62: @@
 IP address should be copied too.
-That said, the command line option <code>--tcp-established</code> should be used when calling criu to explicitly state, that the
+That said, the command line option {{opt|--tcp-established}} should be used when calling criu to explicitly state, that the
 caller is aware of this "transitional" state of the netfilter.

@@ Line 56: / Line 56: @@
 netfilter rule is configured that drops all the packets from peer to a socket we're dealing with. This rule sits
 in the host netfilter tables after the criu dump command finishes and it should be there when you issue the
-criu restore one.
+criu restore one. The locking method can be specified using the [https://criu.org/index.php?title=CLI/opt/--network-lock <code>--network-lock</code>]option.
 Another thing to note is -- on restore there should be available the IP address, that was used by the connection.

@@ Line 5: / Line 5: @@
 The <code>TCP_REPAIR</code> socket option was added to the kernel 3.5 to help with C/R for TCP sockets.
-When this option is used, a socket is switched into a special mode, in which any action performed on it
+When this option is used, the socket is switched into a special mode, in which any action performed on it
 does not result in anything defined by an appropriate protocol actions, but rather directly puts the socket
-into a state, in which the socket is expected to be at the end of the successfully finished operation.
+into the state that the socket is expected to be in at the end of a successfully finished operation.
 For example, calling <code>connect()</code> on a repaired socket just changes its state to <code>ESTABLISHED</code>,

@@ Line 71: / Line 71: @@
 == States ==
 === TCP_SYN_SENT ===
-There is only one difference with TCP_ESTABLISHED, we have to restore a socket and disable the repair mode before calling <code>conenct()</code>. The kernel will send a one syn-sent packet with the same initial sequence number and sets the TCP_SYN_SENT state for the socket.
+There is only one difference with TCP_ESTABLISHED, we have to restore a socket and disable the repair mode before calling <code>connect()</code>. The kernel will send a one syn-sent packet with the same initial sequence number and sets the TCP_SYN_SENT state for the socket.
 === Half-closed sockets ===

@@ Line 79: / Line 79: @@
 * [[Simple TCP pair]]
 * [[TCP repair TODO]]
 == External links ==

@@ Line 68: / Line 68: @@
 per-connection iptables rules the "network-lock"/"network-unlock" [[action scripts]] are called so that the user
 could isolate the whole netns from network. Typically this is done by downing the respective veth pair end.
 == See also ==

@@ Line 42: / Line 42: @@
 == 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.
-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.
+<code>#define tcp_time_stamp          ((__u32)(jiffies))</code>
 == Checkpoint and restore TCP connection ==

← Older revision		Revision as of 06:36, 5 December 2016
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 ==

@@ Line 62: / Line 62: @@
 could isolate the whole netns from network. Typically this is done by downing the respective veth pair end.
-== More info ==
+== See also ==
 * http://lwn.net/Articles/495304/
 [[Category:Under the hood]]
 [[Category:Sockets]]