2,257
edits
Changes
Jump to navigation
Jump to search
Line 1:
Line 1: − + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +
no edit summary
[[Category: Empty articles]]
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.
== Overview ==
To checkpoint a TCP connection one should
# ''pause'' a socket (referenced by descriptor)
# get socket data
# get contents of two queues
# (optionally) resume the socket
# close it
To restore a connection one should
# create a socket
# ''pause'' one
# restore ''unbound'' data
# bind() and/or connect() socket to whatever addresses is appropriate using standard calls
# restore ''noq'' data
# put contents of two queues
# restore remaining data
== Data types ==
In soccr/soccr.h there are two types declares
; <code>struct libsoccr_sk</code>
: It's an abstract handler returned by ''pausing'' routine that is used as an opaque identifier by the rest of the libsoccr calls
; <code>struct libsoccr_sk_data</code>
: 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
=== Data internals ===
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.
So here are the flags that make sense
; <code>SOCCR_FLAGS_WINDOW == 0x1</code>
: 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)
== Calls ==
=== Generic ===
; <code>struct libsoccr_sk *libsoccr_pause(int sk)</code>
: 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.
; <code>void libsoccr_resume(struct libsoccr_sk *)</code>
: Resumes the socket. Data flow unlock may happen before this.
; <code>void libsoccr_set_log(unsigned int level, void (*fn)(unsigned int level, const char *fmt, ...))</code>
: Sets a function that will be called when libsoccr will want to print something on the screen.
=== Dump ===
; <code>int libsoccr_get_sk_data(struct libsoccr_sk *sk, struct libsoccr_sk_data *data, unsigned data_size)</code>
: 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.
; <code>char *libsoccr_get_queue_bytes(struct libsoccr_sk *sk, int queue_id, int steal)</code>
: 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).
=== Restore ===
; <code>int libsoccr_set_sk_data_unbound(struct libsoccr_sk *sk, struct libsoccr_sk_data *data, unsigned data_size)</code>
: Restores data on a socket from the <code>data</code> structure. Should be called before bind()-ing or connect()-ing the socket.
; <code>int libsoccr_set_sk_data_noq(struct libsoccr_sk *sk, struct libsoccr_sk_data *data, unsigned data_size)</code>
: Continues restoration after bind() and/or connect(), but before the queue data restore (see below)
; <code>int libsoccr_set_sk_data(struct libsoccr_sk *sk, struct libsoccr_sk_data *data, unsigned data_size)</code>
: Completes the restoration after queues, but doesn't resume the socket.
; <code>int libsoccr_set_queue_bytes(struct libsoccr_sk *sk, struct libsoccr_sk_data *data, unsigned data_size, int queue, char *buf)</code>
: Puts back the contents of the respective queue.
[[Category: Sub-projects]]
[[Category: Sub-projects]]
[[Category: Sockets]]
[[Category: Sockets]]