peerdist.c File Reference

Peer Content Caching and Retrieval (PeerDist) protocol. More...

#include <stdio.h>
#include <ipxe/http.h>
#include <ipxe/settings.h>
#include <ipxe/peermux.h>

Go to the source code of this file.

Functions
	FILE_LICENCE (GPL2_OR_LATER_OR_UBDL)
static int	http_peerdist_supported (struct http_transaction *http)
	Check whether or not to support PeerDist encoding for this request. More...
static int	http_format_p2p_peerdist (struct http_transaction *http, char *buf, size_t len)
	Format HTTP "X-P2P-PeerDist" header. More...
static int	http_format_p2p_peerdistex (struct http_transaction *http, char *buf, size_t len)
	Format HTTP "X-P2P-PeerDistEx" header. More...
static int	http_peerdist_init (struct http_transaction *http)
	Initialise PeerDist content encoding. More...
const struct setting peerdist_setting	__setting (SETTING_MISC, peerdist)
	PeerDist enabled setting. More...
static int	apply_peerdist_settings (void)
	Apply PeerDist settings. More...

Variables
static long	peerdist_enabled = 1
	PeerDist is globally enabled. More...
struct http_request_header http_request_p2p_peerdist	__http_request_header
	HTTP "X-P2P-PeerDist" header. More...
struct http_content_encoding peerdist_encoding	__http_content_encoding
	PeerDist HTTP content encoding. More...
struct settings_applicator peerdist_applicator	__settings_applicator
	PeerDist settings applicator. More...

Detailed Description

Peer Content Caching and Retrieval (PeerDist) protocol.

This is quite possibly the ugliest protocol I have ever had the misfortune to encounter, and I've encountered multicast TFTP.

Definition in file peerdist.c.

Function Documentation

FILE_LICENCE()

FILE_LICENCE

(

GPL2_OR_LATER_OR_UBDL

)

http_peerdist_supported()

static int http_peerdist_supported ( struct http_transaction *  http )

static

Check whether or not to support PeerDist encoding for this request.

Parameters

http	HTTP transaction

Return values

supported

PeerDist encoding is supported for this request

Definition at line 48 of file peerdist.c.

                                                                     {

        /* Allow PeerDist to be globally enabled/disabled */
        if ( ! peerdist_enabled )
                return 0;

        /* Support PeerDist encoding only if we can directly access an
         * underlying data transfer buffer.  Direct access is required
         * in order to support decryption of data received via the
         * retrieval protocol (which provides the AES initialisation
         * vector only after all of the encrypted data has been
         * received).
         *
         * This test simultaneously ensures that we do not attempt to
         * use PeerDist encoding on a request which is itself a
         * PeerDist individual block download, since the individual
         * block downloads do not themselves provide direct access to
         * an underlying data transfer buffer.
         */
        return ( xfer_buffer ( &http->xfer ) != NULL );
}

References NULL, peerdist_enabled, and http_transaction::xfer.

Referenced by http_format_p2p_peerdist(), and http_format_p2p_peerdistex().

http_format_p2p_peerdist()

static int http_format_p2p_peerdist ( struct http_transaction *  http, char *  buf, size_t  len  )

static

Format HTTP "X-P2P-PeerDist" header.

Parameters

http	HTTP transaction
buf	Buffer
len	Length of buffer

Return values

len	Length of header value, or negative error

Definition at line 78 of file peerdist.c.

                                                              {
        int supported = http_peerdist_supported ( http );
        int missing;

        /* PeerDist wants us to inform the server whenever we make a
         * request for data that was missing from local peers
         * (presumably for statistical purposes only).  We use the
         * heuristic of assuming that the combination of "this request
         * may not itself use PeerDist content encoding" and "this is
         * a range request" probably indicates that we are making a
         * PeerDist block raw range request for missing data.
         */
        missing = ( http->request.range.len && ( ! supported ) );

        /* Omit header if PeerDist encoding is not supported and we
         * are not reporting a missing data request.
         */
        if ( ! ( supported || missing ) )
                return 0;

        /* Construct header */
        return snprintf ( buf, len, "Version=1.1%s",
                          ( missing ? ", MissingDataRequest=true" : "" ) );
}

References http_peerdist_supported(), len, http_request_range::len, http_request::range, http_transaction::request, snprintf(), and supported.

http_format_p2p_peerdistex()

static int http_format_p2p_peerdistex ( struct http_transaction *  http, char *  buf, size_t  len  )

static

Format HTTP "X-P2P-PeerDistEx" header.

Parameters

http	HTTP transaction
buf	Buffer
len	Length of buffer

Return values

len	Length of header value, or negative error

Definition at line 118 of file peerdist.c.

                                                                {
        int supported = http_peerdist_supported ( http );

        /* Omit header if PeerDist encoding is not supported */
        if ( ! supported )
                return 0;

        /* Construct header */
        return snprintf ( buf, len, ( "MinContentInformation=1.0, "
                                      "MaxContentInformation=2.0" ) );
}

References http_peerdist_supported(), len, snprintf(), and supported.

http_peerdist_init()

static int http_peerdist_init ( struct http_transaction *  http )

static

Initialise PeerDist content encoding.

Parameters

http	HTTP transaction

Return values

rc	Return status code

Definition at line 143 of file peerdist.c.

                                                                {

        return peermux_filter ( &http->content, &http->transfer, http->uri );
}

References http_transaction::content, peermux_filter(), http_transaction::transfer, and http_transaction::uri.

__setting()

const struct setting peerdist_setting __setting	(	SETTING_MISC	,
		peerdist
	)

PeerDist enabled setting.

apply_peerdist_settings()

static int apply_peerdist_settings ( void  )

static

Apply PeerDist settings.

Return values

rc	Return status code

Definition at line 167 of file peerdist.c.

                                            {

        /* Fetch global PeerDist enabled setting */
        if ( fetch_int_setting ( NULL, &peerdist_setting,
                                 &peerdist_enabled ) < 0 ) {
                peerdist_enabled = 1;
        }
        DBGC ( &peerdist_enabled, "PEERDIST is %s\n",
               ( peerdist_enabled ? "enabled" : "disabled" ) );

        return 0;
}

References DBGC, fetch_int_setting(), NULL, and peerdist_enabled.

Variable Documentation

peerdist_enabled

long peerdist_enabled = 1

static

PeerDist is globally enabled.

Definition at line 40 of file peerdist.c.

Referenced by apply_peerdist_settings(), and http_peerdist_supported().

__http_request_header

struct http_request_header http_request_p2p_peerdistex __http_request_header

Initial value:

= {
        .name = "X-P2P-PeerDist",
        .format = http_format_p2p_peerdist,
}

HTTP "X-P2P-PeerDist" header.

Definition at line 105 of file peerdist.c.

__http_content_encoding

struct http_content_encoding peerdist_encoding __http_content_encoding

Initial value:

= {
        .name = "peerdist",
        .supported = http_peerdist_supported,
        .init = http_peerdist_init,
}

PeerDist HTTP content encoding.

Definition at line 149 of file peerdist.c.

__settings_applicator

struct settings_applicator peerdist_applicator __settings_applicator

Initial value:

= {
        .apply = apply_peerdist_settings,
}

PeerDist settings applicator.

Definition at line 181 of file peerdist.c.