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− | [[Category: Empty articles]] | + | Libsoccr is a library that does [[TCP connection]] checkpoint and restore. |
| + | |
| + | Libsoccr resides in criu source code (<code>soccr</code> subdirectory) and consists of an API header and a static library. |
| + | |
| + | Libsoccr is available since CRIU {{criu|2.10}} release. |
| + | |
| + | == 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 == |
| + | |
| + | soccr/soccr.h declares three types: |
| + | |
| + | ; <source lang="c" inline>struct libsoccr_sk</source> |
| + | : An abstract handler returned by ''pausing'' routine that is used as an opaque identifier by the rest of the libsoccr calls |
| + | |
| + | ; <source lang="c" inline>struct libsoccr_sk_data</source> |
| + | : 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 |
| + | |
| + | ; <source lang="c" inline>struct libsoccr_addr</source> |
| + | : A structure that defines soccaddr for a socket. It's used by set/get calls described further. |
| + | |
| + | === Data internals === |
| + | |
| + | Inside the <code>libsoccr_sk_data</code> 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. |
| + | |
| + | Here are the flags that make sense: |
| + | |
| + | ; <source lang="c" inline>SOCCR_FLAGS_WINDOW == 0x1</source> |
| + | : 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 a valid value for any of these) |
| + | |
| + | == Calls == |
| + | |
| + | === Generic === |
| + | |
| + | ; <source lang="c" inline>struct libsoccr_sk *libsoccr_pause(int sk)</source> |
| + | : 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. |
| + | |
| + | ; <source lang="c" inline>void libsoccr_resume(struct libsoccr_sk *)</source> |
| + | : Resumes the socket and frees the handler. Data flow unlock may happen before this. |
| + | |
| + | ; <source lang="c" inline>void libsoccr_release(struct libsoccr_sk *)</source> |
| + | : Only releases the handler and doesn't do anything with the socket itself. Use when saving the state and willing to kill the socket -- call <code>close()</code> on descriptor and this thing on the handler. |
| + | |
| + | ; <source lang="c" inline>void libsoccr_set_log(unsigned int level, void (*fn)(unsigned int level, const char *fmt, ...))</source> |
| + | : Sets a function that will be called when libsoccr will want to print something on the screen. |
| + | |
| + | === Dump === |
| + | |
| + | ; <source lang="c" inline>int libsoccr_save(struct libsoccr_sk *sk, struct libsoccr_sk_data *data, unsigned data_size)</source> |
| + | : 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. |
| + | |
| + | ; <source lang="c" inline>char *libsoccr_get_queue_bytes(struct libsoccr_sk *sk, int queue_id, unsigned flags)</source> |
| + | : 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>flags</code> may have <code>SOCCR_MEM_EXCL</code> bit set (see below). |
| + | |
| + | ; <source lang="c" inline>union libsoccr_addr *libsoccr_get_addr(struct libsoccr_sk *sk, int self, unsigned flags)</source> (currently unimplemented and returns NULL) |
| + | : Returns address (self or peer) of the socket. The <code>flags</code> may have <code>SOCCR_MEM_EXCL</code> bit set (see below) |
| + | |
| + | === Restore === |
| + | |
| + | ; <source lang="c" inline>int libsoccr_restore(struct libsoccr_sk *sk, struct libsoccr_sk_data *data, unsigned data_size)</source> |
| + | : Restores data on a socket from the <code>data</code> structure. Should be called after the calls below, but before the "resume" one. |
| + | |
| + | ; <source lang="c" inline>int libsoccr_set_queue_bytes(struct libsoccr_sk *sk, int queue, char *buf, unsigned flags)</source> |
| + | : Puts back the contents of the respective queue. The <code>flags</code> may contain <code>SOCCR_MEM_EXCL</code>. |
| + | |
| + | ; <source lang="c" inline>int libsoccr_set_addr(struct libsoccr_sk *sk, int self, union libsoccr_addr *, unsigned flags)</source> |
| + | : Sets address (self or peer) of the socket. The <code>flags</code> may contain <code>SOCCR_MEM_EXCL</code>. |
| + | |
| + | == Flags == |
| + | Here are the flags accepted by various calls. |
| + | |
| + | ; <code>SOCCR_MEM_EXCL</code> |
| + | : Tells that the memory buffer set or get by the call is to be managed (and should be freed) by the ''receiving side''. In case of a get call the receiving side is the caller program, meaning it has to free() the buffer. In case of a set call the receiver is libsoccr, meaning libsoccr has to free() it. |
| + | |
| [[Category: Sub-projects]] | | [[Category: Sub-projects]] |
| [[Category: Sockets]] | | [[Category: Sockets]] |
| + | == Example == |
| + | |
| + | <source lang="c"> |
| + | /* Dump a tcp socket */ |
| + | |
| + | dst_let = sizeof(addr); |
| + | if (getsockname(sock, (struct sockaddr *) &addr, &dst_let)) { |
| + | pr_perror("connect"); |
| + | return -1; |
| + | } |
| + | dst_let = sizeof(addr); |
| + | if (getpeername(sock, (struct sockaddr *) &dst, &dst_let)) { |
| + | pr_perror("connect"); |
| + | return -1; |
| + | } |
| + | |
| + | so = libsoccr_pause(sock); |
| + | |
| + | dsize = libsoccr_save(so, &data, sizeof(data)); |
| + | if (dsize < 0) { |
| + | pr_perror("libsoccr_save"); |
| + | return -1; |
| + | } |
| + | close(sock); |
| + | |
| + | |
| + | /* Restore a tcp socket */ |
| + | rst = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP); |
| + | if (rst == -1) |
| + | return -1; |
| + | |
| + | |
| + | so_rst = libsoccr_pause(rst); |
| + | libsoccr_set_addr(so_rst, 1, &addr, 0); |
| + | libsoccr_set_addr(so_rst, 0, &dst, 0); |
| + | |
| + | queue = libsoccr_get_queue_bytes(so, TCP_RECV_QUEUE, SOCCR_MEM_EXCL); |
| + | libsoccr_set_queue_bytes(so_rst, TCP_RECV_QUEUE, queue, SOCCR_MEM_EXCL); |
| + | queue = libsoccr_get_queue_bytes(so, TCP_SEND_QUEUE, SOCCR_MEM_EXCL); |
| + | libsoccr_set_queue_bytes(so_rst, TCP_SEND_QUEUE, queue, SOCCR_MEM_EXCL); |
| + | |
| + | ret = libsoccr_restore(so_rst, &data, dsize); |
| + | if (ret) |
| + | return -1; |
| + | |
| + | libsoccr_resume(so_rst); |
| + | libsoccr_resume(so); |
| + | </source> |