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[[Category: Empty articles]]
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Libsoccr is the library that does [[TCP connection]] checkpoint and restore. It sits in criu sources and includes an API header and a static library.
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== Overview ==
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To checkpoint a TCP connection one should
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# ''pause'' a socket (referenced by descriptor)
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# get socket data
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# get contents of two queues
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# (optionally) resume the socket
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# close it
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To restore a connection one should
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# create a socket
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# ''pause'' one
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# restore ''unbound'' data
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# bind() and/or connect() socket to whatever addresses is appropriate using standard calls
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# restore ''noq'' data
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# put contents of two queues
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# restore remaining data
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== Data types ==
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In soccr/soccr.h there are two types declares
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; <code>struct libsoccr_sk</code>
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: It's an abstract handler returned by ''pausing'' routine that is used as an opaque identifier by the rest of the libsoccr calls
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; <code>struct libsoccr_sk_data</code>
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: A structure containing a set of 32-bit values that are returned by ''getter'' and that are to be passed '''as is''' to the ''setter'' call
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=== Data internals ===
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Inside the data structure there's a special field called <code>flags</code> that gives information about the meaning of some other fields. Though it's not bad just to pass this structure as-is between libsoccr calls, doing some optimization based on flags is OK.
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So here are the flags that make sense
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; <code>SOCCR_FLAGS_WINDOW == 0x1</code>
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: When set indicates, that fields <code>snd_wl1</code>, <code>snd_wnd</code>, <code>max_window</code>, <code>rcv_wnd</code> and <code>rcv_wup</code> contain some valuable data (0 is valid value for any)
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== Calls ==
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=== Generic ===
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; <code>struct libsoccr_sk *libsoccr_pause(int sk)</code>
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: Pauses the socket and returns a handler for further operations. Any data flow for this socket ''must be blocked by the caller'' before this call.
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; <code>void libsoccr_resume(struct libsoccr_sk *)</code>
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: Resumes the socket. Data flow unlock may happen before this.
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; <code>void libsoccr_set_log(unsigned int level, void (*fn)(unsigned int level, const char *fmt, ...))</code>
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: Sets a function that will be called when libsoccr will want to print something on the screen.
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=== Dump ===
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; <code>int libsoccr_get_sk_data(struct libsoccr_sk *sk, struct libsoccr_sk_data *data, unsigned data_size)</code>
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: Fills in the <code>data</code> structure with the info get from paused socket. The <code>data_size</code> should be the size of the structure passed. The return code is the size of the structure really filled with data.
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; <code>char *libsoccr_get_queue_bytes(struct libsoccr_sk *sk, int queue_id, int steal)</code>
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: Returns a malloc()-ed array with the contents of the queue. The queue can be TCP_RECV_QUEUE or TCP_SEND_QUEUE. The amount of bytes in each is <code>data.inq_len</code> and <code>data.outq_len</code> respectively. The <code>steal</code> is a boolean value specifying whether the caller would free() the buffers himself (1) or expects the <code>_resume()</code> to do it (0).
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=== Restore ===
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; <code>int libsoccr_set_sk_data_unbound(struct libsoccr_sk *sk, struct libsoccr_sk_data *data, unsigned data_size)</code>
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: Restores data on a socket from the <code>data</code> structure. Should be called before bind()-ing or connect()-ing the socket.
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; <code>int libsoccr_set_sk_data_noq(struct libsoccr_sk *sk, struct libsoccr_sk_data *data, unsigned data_size)</code>
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: Continues restoration after bind() and/or connect(), but before the queue data restore (see below)
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; <code>int libsoccr_set_sk_data(struct libsoccr_sk *sk, struct libsoccr_sk_data *data, unsigned data_size)</code>
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: Completes the restoration after queues, but doesn't resume the socket.
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; <code>int libsoccr_set_queue_bytes(struct libsoccr_sk *sk, struct libsoccr_sk_data *data, unsigned data_size, int queue, char *buf)</code>
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: Puts back the contents of the respective queue.
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[[Category: Sub-projects]]
 
[[Category: Sub-projects]]
 
[[Category: Sockets]]
 
[[Category: Sockets]]

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