| In the gstreamer plugin I want to provide a plugin property named
| ccid, where the programmer will set or get the current ccid. Is dccp
| implementation for linux already prepared to support this mechanism
| through feature negotiation (or something related via
| setsockopt/getsockopt)?
Yes it is - all the necessary code is in the test tree, but it is not
exhaustively documented so far (but all set/getsockopts are documented
in Documentation/networking/dccp.txt).
Here is a short test program to document:
/*----------------------------------------------------------------------------------------------*/
#include <err.h>
uint8_t ccid = 3, /* the CCID you want to set */
ccids[4], /* for getting the available CCIDs, should be large enough */
tx_ccid, rx_ccid;
socklen_t len = sizeof(ccids);
int sockfd = socket(AF_XXX, SOCK_DCCP, 0);
/*
* Determine which CCIDs are available on the host
*/
if (getsockopt(sockfd, SOL_DCCP, DCCP_SOCKOPT_AVAILABLE_CCIDS, &ccids, &len) < 0)
err(1, "Can not determine available CCIDs");
ccid = my_favourite_ccid;
if (!found_in_array(ccid, ccids, sizeof(ccids))
err(1, "CCID %d not supported", ccid);
/*
* The following calls need to be made before establishing the connection, i.e. before
* calling listen() or connect()
*/
if (setsockopt(sockfd, SOL_DCCP, DCCP_SOCKOPT_CCID, &ccid, sizeof(ccid)) < 0)
err(1, "Can not set CCID");
/*
Alternatively, if you want to set different CCIDs for each direction:
if (setsockopt(sockfd, SOL_DCCP, DCCP_SOCKOPT_TX_CCID, &tx_ccid, sizeof(tx_ccid)) < 0)
err(1, "Can not set TX CCID");
if (setsockopt(sockfd, SOL_DCCP, DCCP_SOCKOPT_RX_CCID, &rx_ccid, sizeof(rx_ccid)) < 0)
err(1, "Can not set RX CCID");
NOTE: In the above, single values are used. If you want choice, you can pass an ordered
array (preferred CCID first), which will then be used for feature-negotiation.
If you are negotiating with single values, it will only work when both sides pick
the same value.
*/
/*
* Once the connection is established, you can find out the results of the feature negotiation
* by calling getsocktopt() with DCCP_SOCKOPT_TX_CCID/DCCP_SOCKOPT_RX_CCID
*/
/*----------------------------------------------------------------------------------------------*/
Looking forward to the gstreamer plugin - can you please announce on the list.
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