These changes are the raw update to qemu-2.6.

Collission happened in the following patches:

migration: do cleanup operation after completion(738df5b9)
Bug fix.(1750c932f86)
kvmclock: add a new function to update env->tsc.(b52baab2)

The code provided by the patches was already in the upstreamed
version.

Change-Id: I3cc11841a6a76ae20887b2e245710199e1ea7f9a
Signed-off-by: José Pekkarinen <jose.pekkarinen@nokia.com>

1 files changed, 1366 insertions, 0 deletions

diff --git a/qemu/roms/ipxe/src/net/peerblk.c b/qemu/roms/ipxe/src/net/peerblk.c
new file mode 100644
index 000000000..fd7ea0893
--- /dev/null
+++ b/qemu/roms/ipxe/src/net/peerblk.c
@@ -0,0 +1,1366 @@
+/*
+ * Copyright (C) 2015 Michael Brown <mbrown@fensystems.co.uk>.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ *
+ * You can also choose to distribute this program under the terms of
+ * the Unmodified Binary Distribution Licence (as given in the file
+ * COPYING.UBDL), provided that you have satisfied its requirements.
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <errno.h>
+#include <ipxe/http.h>
+#include <ipxe/iobuf.h>
+#include <ipxe/xfer.h>
+#include <ipxe/uri.h>
+#include <ipxe/timer.h>
+#include <ipxe/profile.h>
+#include <ipxe/fault.h>
+#include <ipxe/pccrr.h>
+#include <ipxe/peerblk.h>
+
+/** @file
+ *
+ * Peer Content Caching and Retrieval (PeerDist) protocol block downloads
+ *
+ */
+
+/** PeerDist decryption chunksize
+ *
+ * This is a policy decision.
+ */
+#define PEERBLK_DECRYPT_CHUNKSIZE 2048
+
+/** PeerDist raw block download attempt initial progress timeout
+ *
+ * This is a policy decision.
+ */
+#define PEERBLK_RAW_OPEN_TIMEOUT ( 10 * TICKS_PER_SEC )
+
+/** PeerDist raw block download attempt ongoing progress timeout
+ *
+ * This is a policy decision.
+ */
+#define PEERBLK_RAW_RX_TIMEOUT ( 15 * TICKS_PER_SEC )
+
+/** PeerDist retrieval protocol block download attempt initial progress timeout
+ *
+ * This is a policy decision.
+ */
+#define PEERBLK_RETRIEVAL_OPEN_TIMEOUT ( 3 * TICKS_PER_SEC )
+
+/** PeerDist retrieval protocol block download attempt ongoing progress timeout
+ *
+ * This is a policy decision.
+ */
+#define PEERBLK_RETRIEVAL_RX_TIMEOUT ( 5 * TICKS_PER_SEC )
+
+/** PeerDist maximum number of full download attempt cycles
+ *
+ * This is the maximum number of times that we will try a full cycle
+ * of download attempts (i.e. a retrieval protocol download attempt
+ * from each discovered peer plus a raw download attempt from the
+ * origin server).
+ *
+ * This is a policy decision.
+ */
+#define PEERBLK_MAX_ATTEMPT_CYCLES 4
+
+/** PeerDist block download profiler */
+static struct profiler peerblk_download_profiler __profiler =
+	{ .name = "peerblk.download" };
+
+/** PeerDist block download attempt success profiler */
+static struct profiler peerblk_attempt_success_profiler __profiler =
+	{ .name = "peerblk.attempt.success" };
+
+/** PeerDist block download attempt failure profiler */
+static struct profiler peerblk_attempt_failure_profiler __profiler =
+	{ .name = "peerblk.attempt.failure" };
+
+/** PeerDist block download attempt timeout profiler */
+static struct profiler peerblk_attempt_timeout_profiler __profiler =
+	{ .name = "peerblk.attempt.timeout" };
+
+/** PeerDist block download discovery success profiler */
+static struct profiler peerblk_discovery_success_profiler __profiler =
+	{ .name = "peerblk.discovery.success" };
+
+/** PeerDist block download discovery timeout profiler */
+static struct profiler peerblk_discovery_timeout_profiler __profiler =
+	{ .name = "peerblk.discovery.timeout" };
+
+/**
+ * Get profiling timestamp
+ *
+ * @ret timestamp	Timestamp
+ */
+static inline __attribute__ (( always_inline )) unsigned long
+peerblk_timestamp ( void ) {
+
+	if ( PROFILING ) {
+		return currticks();
+	} else {
+		return 0;
+	}
+}
+
+/**
+ * Free PeerDist block download
+ *
+ * @v refcnt		Reference count
+ */
+static void peerblk_free ( struct refcnt *refcnt ) {
+	struct peerdist_block *peerblk =
+		container_of ( refcnt, struct peerdist_block, refcnt );
+
+	uri_put ( peerblk->uri );
+	free ( peerblk->cipherctx );
+	free ( peerblk );
+}
+
+/**
+ * Reset PeerDist block download attempt
+ *
+ * @v peerblk		PeerDist block download
+ * @v rc		Reason for reset
+ */
+static void peerblk_reset ( struct peerdist_block *peerblk, int rc ) {
+
+	/* Stop decryption process */
+	process_del ( &peerblk->process );
+
+	/* Stop timer */
+	stop_timer ( &peerblk->timer );
+
+	/* Abort any current download attempt */
+	intf_restart ( &peerblk->raw, rc );
+	intf_restart ( &peerblk->retrieval, rc );
+
+	/* Empty received data buffer */
+	xferbuf_free ( &peerblk->buffer );
+	peerblk->pos = 0;
+
+	/* Reset digest and free cipher context */
+	digest_init ( peerblk->digest, peerblk->digestctx );
+	free ( peerblk->cipherctx );
+	peerblk->cipherctx = NULL;
+	peerblk->cipher = NULL;
+
+	/* Reset trim thresholds */
+	peerblk->start = ( peerblk->trim.start - peerblk->range.start );
+	peerblk->end = ( peerblk->trim.end - peerblk->range.start );
+	assert ( peerblk->start <= peerblk->end );
+}
+
+/**
+ * Close PeerDist block download
+ *
+ * @v peerblk		PeerDist block download
+ * @v rc		Reason for close
+ */
+static void peerblk_close ( struct peerdist_block *peerblk, int rc ) {
+	unsigned long now = peerblk_timestamp();
+
+	/* Profile overall block download */
+	profile_custom ( &peerblk_download_profiler,
+			 ( now - peerblk->started ) );
+
+	/* Reset download attempt */
+	peerblk_reset ( peerblk, rc );
+
+	/* Close discovery */
+	peerdisc_close ( &peerblk->discovery );
+
+	/* Shut down all interfaces */
+	intf_shutdown ( &peerblk->retrieval, rc );
+	intf_shutdown ( &peerblk->raw, rc );
+	intf_shutdown ( &peerblk->xfer, rc );
+}
+
+/**
+ * Calculate offset within overall download
+ *
+ * @v peerblk		PeerDist block download
+ * @v pos		Position within incoming data stream
+ * @ret offset		Offset within overall download
+ */
+static inline __attribute__ (( always_inline )) size_t
+peerblk_offset ( struct peerdist_block *peerblk, size_t pos ) {
+
+	return ( ( pos - peerblk->start ) + peerblk->offset );
+}
+
+/**
+ * Deliver download attempt data block
+ *
+ * @v peerblk		PeerDist block download
+ * @v iobuf		I/O buffer
+ * @v meta		Original data transfer metadata
+ * @v pos		Position within incoming data stream
+ * @ret rc		Return status code
+ */
+static int peerblk_deliver ( struct peerdist_block *peerblk,
+			     struct io_buffer *iobuf,
+			     struct xfer_metadata *meta, size_t pos ) {
+	struct xfer_metadata xfer_meta;
+	size_t len = iob_len ( iobuf );
+	size_t start = pos;
+	size_t end = ( pos + len );
+	int rc;
+
+	/* Discard zero-length packets and packets which lie entirely
+	 * outside the trimmed range.
+	 */
+	if ( ( start >= peerblk->end ) || ( end <= peerblk->start ) ||
+	     ( len == 0 ) ) {
+		free_iob ( iobuf );
+		return 0;
+	}
+
+	/* Truncate data to within trimmed range */
+	if ( start < peerblk->start ) {
+		iob_pull ( iobuf, ( peerblk->start - start ) );
+		start = peerblk->start;
+	}
+	if ( end > peerblk->end ) {
+		iob_unput ( iobuf, ( end - peerblk->end ) );
+		end = peerblk->end;
+	}
+
+	/* Construct metadata */
+	memcpy ( &xfer_meta, meta, sizeof ( xfer_meta ) );
+	xfer_meta.flags |= XFER_FL_ABS_OFFSET;
+	xfer_meta.offset = peerblk_offset ( peerblk, start );
+
+	/* Deliver data */
+	if ( ( rc = xfer_deliver ( &peerblk->xfer, iob_disown ( iobuf ),
+				   &xfer_meta ) ) != 0 ) {
+		DBGC ( peerblk, "PEERBLK %p %d.%d could not deliver data: %s\n",
+		       peerblk, peerblk->segment, peerblk->block,
+		       strerror ( rc ) );
+		return rc;
+	}
+
+	return 0;
+}
+
+/**
+ * Finish PeerDist block download attempt
+ *
+ * @v peerblk		PeerDist block download
+ * @v rc		Reason for close
+ */
+static void peerblk_done ( struct peerdist_block *peerblk, int rc ) {
+	struct digest_algorithm *digest = peerblk->digest;
+	uint8_t hash[digest->digestsize];
+	unsigned long now = peerblk_timestamp();
+
+	/* Check for errors on completion */
+	if ( rc != 0 ) {
+		DBGC ( peerblk, "PEERBLK %p %d.%d attempt failed: %s\n",
+		       peerblk, peerblk->segment, peerblk->block,
+		       strerror ( rc ) );
+		goto err;
+	}
+
+	/* Check digest */
+	digest_final ( digest, peerblk->digestctx, hash );
+	if ( memcmp ( hash, peerblk->hash, peerblk->digestsize ) != 0 ) {
+		DBGC ( peerblk, "PEERBLK %p %d.%d digest mismatch:\n",
+		       peerblk, peerblk->segment, peerblk->block );
+		DBGC_HDA ( peerblk, 0, hash, peerblk->digestsize );
+		DBGC_HDA ( peerblk, 0, peerblk->hash, peerblk->digestsize );
+		rc = -EIO;
+		goto err;
+	}
+
+	/* Profile successful attempt */
+	profile_custom ( &peerblk_attempt_success_profiler,
+			 ( now - peerblk->attempted ) );
+
+	/* Close download */
+	peerblk_close ( peerblk, 0 );
+	return;
+
+ err:
+	/* Record failure reason and schedule a retry attempt */
+	profile_custom ( &peerblk_attempt_failure_profiler,
+			 ( now - peerblk->attempted ) );
+	peerblk_reset ( peerblk, rc );
+	peerblk->rc = rc;
+	start_timer_nodelay ( &peerblk->timer );
+}
+
+/******************************************************************************
+ *
+ * Raw block download attempts (using an HTTP range request)
+ *
+ ******************************************************************************
+ */
+
+/**
+ * Open PeerDist raw block download attempt
+ *
+ * @v peerblk		PeerDist block download
+ * @ret rc		Return status code
+ */
+static int peerblk_raw_open ( struct peerdist_block *peerblk ) {
+	struct http_request_range range;
+	int rc;
+
+	DBGC2 ( peerblk, "PEERBLK %p %d.%d attempting raw range request\n",
+		peerblk, peerblk->segment, peerblk->block );
+
+	/* Construct HTTP range */
+	memset ( &range, 0, sizeof ( range ) );
+	range.start = peerblk->range.start;
+	range.len = ( peerblk->range.end - peerblk->range.start );
+
+	/* Initiate range request to retrieve block */
+	if ( ( rc = http_open ( &peerblk->raw, &http_get, peerblk->uri,
+				&range, NULL ) ) != 0 ) {
+		DBGC ( peerblk, "PEERBLK %p %d.%d could not create range "
+		       "request: %s\n", peerblk, peerblk->segment,
+		       peerblk->block, strerror ( rc ) );
+		return rc;
+	}
+
+	/* Annul HTTP connection (for testing) if applicable.  Do not
+	 * report as an immediate error, in order to test our ability
+	 * to recover from a totally unresponsive HTTP server.
+	 */
+	if ( inject_fault ( PEERBLK_ANNUL_RATE ) )
+		intf_restart ( &peerblk->raw, 0 );
+
+	return 0;
+}
+
+/**
+ * Receive PeerDist raw data
+ *
+ * @v peerblk		PeerDist block download
+ * @v iobuf		I/O buffer
+ * @v meta		Data transfer metadata
+ * @ret rc		Return status code
+ */
+static int peerblk_raw_rx ( struct peerdist_block *peerblk,
+			    struct io_buffer *iobuf,
+			    struct xfer_metadata *meta ) {
+	size_t len = iob_len ( iobuf );
+	size_t pos = peerblk->pos;
+	size_t mid = ( ( peerblk->range.end - peerblk->range.start ) / 2 );
+	int rc;
+
+	/* Corrupt received data (for testing) if applicable */
+	inject_corruption ( PEERBLK_CORRUPT_RATE, iobuf->data, len );
+
+	/* Fail if data is delivered out of order, since the streaming
+	 * digest requires strict ordering.
+	 */
+	if ( ( rc = xfer_check_order ( meta, &peerblk->pos, len ) ) != 0 )
+		goto err;
+
+	/* Add data to digest */
+	digest_update ( peerblk->digest, peerblk->digestctx, iobuf->data, len );
+
+	/* Deliver data */
+	if ( ( rc = peerblk_deliver ( peerblk, iob_disown ( iobuf ), meta,
+				      pos ) ) != 0 )
+		goto err;
+
+	/* Extend download attempt timer */
+	start_timer_fixed ( &peerblk->timer, PEERBLK_RAW_RX_TIMEOUT );
+
+	/* Stall download attempt (for testing) if applicable */
+	if ( ( pos < mid ) && ( ( pos + len ) >= mid ) &&
+	     ( ( rc = inject_fault ( PEERBLK_STALL_RATE ) ) != 0 ) ) {
+		intf_restart ( &peerblk->raw, rc );
+	}
+
+	return 0;
+
+ err:
+	free_iob ( iobuf );
+	peerblk_done ( peerblk, rc );
+	return rc;
+}
+
+/**
+ * Close PeerDist raw block download attempt
+ *
+ * @v peerblk		PeerDist block download
+ * @v rc		Reason for close
+ */
+static void peerblk_raw_close ( struct peerdist_block *peerblk, int rc ) {
+
+	/* Restart interface */
+	intf_restart ( &peerblk->raw, rc );
+
+	/* Fail immediately if we have an error */
+	if ( rc != 0 )
+		goto done;
+
+	/* Abort download attempt (for testing) if applicable */
+	if ( ( rc = inject_fault ( PEERBLK_ABORT_RATE ) ) != 0 )
+		goto done;
+
+ done:
+	/* Complete download attempt */
+	peerblk_done ( peerblk, rc );
+}
+
+/******************************************************************************
+ *
+ * Retrieval protocol block download attempts (using HTTP POST)
+ *
+ ******************************************************************************
+ */
+
+/**
+ * Construct PeerDist retrieval protocol URI
+ *
+ * @v location		Peer location
+ * @ret uri		Retrieval URI, or NULL on error
+ */
+static struct uri * peerblk_retrieval_uri ( const char *location ) {
+	char uri_string[ 7 /* "http://" */ + strlen ( location ) +
+			 sizeof ( PEERDIST_MAGIC_PATH /* includes NUL */ ) ];
+
+	/* Construct URI string */
+	snprintf ( uri_string, sizeof ( uri_string ),
+		   ( "http://%s" PEERDIST_MAGIC_PATH ), location );
+
+	/* Parse URI string */
+	return parse_uri ( uri_string );
+}
+
+/**
+ * Open PeerDist retrieval protocol block download attempt
+ *
+ * @v peerblk		PeerDist block download
+ * @v location		Peer location
+ * @ret rc		Return status code
+ */
+static int peerblk_retrieval_open ( struct peerdist_block *peerblk,
+				    const char *location ) {
+	size_t digestsize = peerblk->digestsize;
+	peerdist_msg_getblks_t ( digestsize, 1, 0 ) req;
+	peerblk_msg_blk_t ( digestsize, 0, 0, 0 ) *rsp;
+	struct http_request_content content;
+	struct uri *uri;
+	int rc;
+
+	DBGC2 ( peerblk, "PEERBLK %p %d.%d attempting retrieval from %s\n",
+		peerblk, peerblk->segment, peerblk->block, location );
+
+	/* Construct block fetch request */
+	memset ( &req, 0, sizeof ( req ) );
+	req.getblks.hdr.version.raw = htonl ( PEERDIST_MSG_GETBLKS_VERSION );
+	req.getblks.hdr.type = htonl ( PEERDIST_MSG_GETBLKS_TYPE );
+	req.getblks.hdr.len = htonl ( sizeof ( req ) );
+	req.getblks.hdr.algorithm = htonl ( PEERDIST_MSG_AES_128_CBC );
+	req.segment.segment.digestsize = htonl ( digestsize );
+	memcpy ( req.segment.id, peerblk->id, digestsize );
+	req.ranges.ranges.count = htonl ( 1 );
+	req.ranges.range[0].first = htonl ( peerblk->block );
+	req.ranges.range[0].count = htonl ( 1 );
+
+	/* Construct POST request content */
+	memset ( &content, 0, sizeof ( content ) );
+	content.data = &req;
+	content.len = sizeof ( req );
+
+	/* Construct URI */
+	if ( ( uri = peerblk_retrieval_uri ( location ) ) == NULL ) {
+		rc = -ENOMEM;
+		goto err_uri;
+	}
+
+	/* Update trim thresholds */
+	peerblk->start += offsetof ( typeof ( *rsp ), msg.vrf );
+	peerblk->end += offsetof ( typeof ( *rsp ), msg.vrf );
+
+	/* Initiate HTTP POST to retrieve block */
+	if ( ( rc = http_open ( &peerblk->retrieval, &http_post, uri,
+				NULL, &content ) ) != 0 ) {
+		DBGC ( peerblk, "PEERBLK %p %d.%d could not create retrieval "
+		       "request: %s\n", peerblk, peerblk->segment,
+		       peerblk->block, strerror ( rc ) );
+		goto err_open;
+	}
+
+	/* Annul HTTP connection (for testing) if applicable.  Do not
+	 * report as an immediate error, in order to test our ability
+	 * to recover from a totally unresponsive HTTP server.
+	 */
+	if ( inject_fault ( PEERBLK_ANNUL_RATE ) )
+		intf_restart ( &peerblk->retrieval, 0 );
+
+ err_open:
+	uri_put ( uri );
+ err_uri:
+	return rc;
+}
+
+/**
+ * Receive PeerDist retrieval protocol data
+ *
+ * @v peerblk		PeerDist block download
+ * @v iobuf		I/O buffer
+ * @v meta		Data transfer metadata
+ * @ret rc		Return status code
+ */
+static int peerblk_retrieval_rx ( struct peerdist_block *peerblk,
+				  struct io_buffer *iobuf,
+				  struct xfer_metadata *meta ) {
+	size_t len = iob_len ( iobuf );
+	size_t start;
+	size_t end;
+	size_t before;
+	size_t after;
+	size_t cut;
+	int rc;
+
+	/* Some genius at Microsoft thought it would be a great idea
+	 * to place the AES-CBC initialisation vector *after* the
+	 * encrypted data, thereby making it logically impossible to
+	 * decrypt each packet as it arrives.
+	 *
+	 * To work around this mindless stupidity, we deliver the
+	 * ciphertext as-is and later use xfer_buffer() to obtain
+	 * access to the underlying data transfer buffer in order to
+	 * perform the decryption.
+	 *
+	 * There will be some data both before and after the bytes
+	 * corresponding to the trimmed plaintext: a MSG_BLK
+	 * header/footer, some block padding for the AES-CBC cipher,
+	 * and a possibly large quantity of unwanted ciphertext which
+	 * is excluded from the trimmed content range.  We store this
+	 * data in a local data transfer buffer.  If the amount of
+	 * data to be stored is too large, we will fail allocation and
+	 * so eventually fall back to using a range request (which
+	 * does not require this kind of temporary storage
+	 * allocation).
+	 */
+
+	/* Corrupt received data (for testing) if applicable */
+	inject_corruption ( PEERBLK_CORRUPT_RATE, iobuf->data, len );
+
+	/* Calculate start and end positions of this buffer */
+	start = peerblk->pos;
+	if ( meta->flags & XFER_FL_ABS_OFFSET )
+		start = 0;
+	start += meta->offset;
+	end = ( start + len );
+
+	/* Buffer any data before the trimmed content */
+	if ( ( start < peerblk->start ) && ( len > 0 ) ) {
+
+		/* Calculate length of data before the trimmed content */
+		before = ( peerblk->start - start );
+		if ( before > len )
+			before = len;
+
+		/* Buffer data before the trimmed content */
+		if ( ( rc = xferbuf_write ( &peerblk->buffer, start,
+					    iobuf->data, before ) ) != 0 ) {
+			DBGC ( peerblk, "PEERBLK %p %d.%d could not buffer "
+			       "data: %s\n", peerblk, peerblk->segment,
+			       peerblk->block, strerror ( rc ) );
+			goto err;
+		}
+	}
+
+	/* Buffer any data after the trimmed content */
+	if ( ( end > peerblk->end ) && ( len > 0 ) ) {
+
+		/* Calculate length of data after the trimmed content */
+		after = ( end - peerblk->end );
+		if ( after > len )
+			after = len;
+
+		/* Buffer data after the trimmed content */
+		cut = ( peerblk->end - peerblk->start );
+		if ( ( rc = xferbuf_write ( &peerblk->buffer,
+					    ( end - after - cut ),
+					    ( iobuf->data + len - after ),
+					    after ) ) != 0 ) {
+			DBGC ( peerblk, "PEERBLK %p %d.%d could not buffer "
+			       "data: %s\n", peerblk, peerblk->segment,
+			       peerblk->block, strerror ( rc ) );
+			goto err;
+		}
+	}
+
+	/* Deliver any remaining data */
+	if ( ( rc = peerblk_deliver ( peerblk, iob_disown ( iobuf ), meta,
+				      start ) ) != 0 )
+		goto err;
+
+	/* Update position */
+	peerblk->pos = end;
+
+	/* Extend download attempt timer */
+	start_timer_fixed ( &peerblk->timer, PEERBLK_RETRIEVAL_RX_TIMEOUT );
+
+	/* Stall download attempt (for testing) if applicable */
+	if ( ( start < peerblk->end ) && ( end >= peerblk->end ) &&
+	     ( ( rc = inject_fault ( PEERBLK_STALL_RATE ) ) != 0 ) ) {
+		intf_restart ( &peerblk->retrieval, rc );
+	}
+
+	return 0;
+
+ err:
+	free_iob ( iobuf );
+	peerblk_done ( peerblk, rc );
+	return rc;
+}
+
+/**
+ * Parse retrieval protocol message header
+ *
+ * @v peerblk		PeerDist block download
+ * @ret rc		Return status code
+ */
+static int peerblk_parse_header ( struct peerdist_block *peerblk ) {
+	struct {
+		struct peerdist_msg_transport_header hdr;
+		struct peerdist_msg_header msg;
+	} __attribute__ (( packed )) *msg = peerblk->buffer.data;
+	struct cipher_algorithm *cipher;
+	size_t len = peerblk->buffer.len;
+	size_t keylen = 0;
+	int rc;
+
+	/* Check message length */
+	if ( len < sizeof ( *msg ) ) {
+		DBGC ( peerblk, "PEERBLK %p %d.%d message too short for header "
+		       "(%zd bytes)\n", peerblk, peerblk->segment,
+		       peerblk->block, len );
+		return -ERANGE;
+	}
+
+	/* Check message type */
+	if ( msg->msg.type != htonl ( PEERDIST_MSG_BLK_TYPE ) ) {
+		DBGC ( peerblk, "PEERBLK %p %d.%d unexpected message type "
+		       "%#08x\n", peerblk, peerblk->segment, peerblk->block,
+		       ntohl ( msg->msg.type ) );
+		return -EPROTO;
+	}
+
+	/* Determine cipher algorithm and key length */
+	cipher = &aes_cbc_algorithm;
+	switch ( msg->msg.algorithm ) {
+	case htonl ( PEERDIST_MSG_PLAINTEXT ) :
+		cipher = NULL;
+		break;
+	case htonl ( PEERDIST_MSG_AES_128_CBC ) :
+		keylen = ( 128 / 8 );
+		break;
+	case htonl ( PEERDIST_MSG_AES_192_CBC ) :
+		keylen = ( 192 / 8 );
+		break;
+	case htonl ( PEERDIST_MSG_AES_256_CBC ) :
+		keylen = ( 256 / 8 );
+		break;
+	default:
+		DBGC ( peerblk, "PEERBLK %p %d.%d unrecognised algorithm "
+		       "%#08x\n", peerblk, peerblk->segment, peerblk->block,
+		       ntohl ( msg->msg.algorithm ) );
+		return -ENOTSUP;
+	}
+	DBGC2 ( peerblk, "PEERBLK %p %d.%d using %s with %zd-bit key\n",
+		peerblk, peerblk->segment, peerblk->block,
+		( cipher ? cipher->name : "plaintext" ), ( 8 * keylen ) );
+
+	/* Sanity check key length against maximum secret length */
+	if ( keylen > peerblk->digestsize ) {
+		DBGC ( peerblk, "PEERBLK %p %d.%d %zd-byte secret too short "
+		       "for %zd-bit key\n", peerblk, peerblk->segment,
+		       peerblk->block, peerblk->digestsize, ( 8 * keylen ) );
+		return -EPROTO;
+	}
+
+	/* Allocate cipher context.  Freeing the cipher context (on
+	 * error or otherwise) is handled by peerblk_reset().
+	 */
+	peerblk->cipher = cipher;
+	assert ( peerblk->cipherctx == NULL );
+	peerblk->cipherctx = malloc ( cipher->ctxsize );
+	if ( ! peerblk->cipherctx )
+		return -ENOMEM;
+
+	/* Initialise cipher */
+	if ( ( rc = cipher_setkey ( cipher, peerblk->cipherctx, peerblk->secret,
+				    keylen ) ) != 0 ) {
+		DBGC ( peerblk, "PEERBLK %p %d.%d could not set key: %s\n",
+		       peerblk, peerblk->segment, peerblk->block,
+		       strerror ( rc ) );
+		return rc;
+	}
+
+	return 0;
+}
+
+/**
+ * Parse retrieval protocol message segment and block details
+ *
+ * @v peerblk		PeerDist block download
+ * @v buf_len		Length of buffered data to fill in
+ * @ret rc		Return status code
+ */
+static int peerblk_parse_block ( struct peerdist_block *peerblk,
+				 size_t *buf_len ) {
+	size_t digestsize = peerblk->digestsize;
+	peerblk_msg_blk_t ( digestsize, 0, 0, 0 ) *msg = peerblk->buffer.data;
+	size_t len = peerblk->buffer.len;
+	size_t data_len;
+	size_t total;
+
+	/* Check message length */
+	if ( len < offsetof ( typeof ( *msg ), msg.block.data ) ) {
+		DBGC ( peerblk, "PEERBLK %p %d.%d message too short for "
+		       "zero-length data (%zd bytes)\n", peerblk,
+		       peerblk->segment, peerblk->block, len );
+		return -ERANGE;
+	}
+
+	/* Check digest size */
+	if ( ntohl ( msg->msg.segment.segment.digestsize ) != digestsize ) {
+		DBGC ( peerblk, "PEERBLK %p %d.%d incorrect digest size %d\n",
+		       peerblk, peerblk->segment, peerblk->block,
+		       ntohl ( msg->msg.segment.segment.digestsize ) );
+		return -EPROTO;
+	}
+
+	/* Check segment ID */
+	if ( memcmp ( msg->msg.segment.id, peerblk->id, digestsize ) != 0 ) {
+		DBGC ( peerblk, "PEERBLK %p %d.%d segment ID mismatch\n",
+		       peerblk, peerblk->segment, peerblk->block );
+		return -EPROTO;
+	}
+
+	/* Check block ID */
+	if ( ntohl ( msg->msg.index ) != peerblk->block ) {
+		DBGC ( peerblk, "PEERBLK %p %d.%d block ID mismatch (got %d)\n",
+		       peerblk, peerblk->segment, peerblk->block,
+		       ntohl ( msg->msg.index ) );
+		return -EPROTO;
+	}
+
+	/* Check for missing blocks */
+	data_len = be32_to_cpu ( msg->msg.block.block.len );
+	if ( ! data_len ) {
+		DBGC ( peerblk, "PEERBLK %p %d.%d block not found\n",
+		       peerblk, peerblk->segment, peerblk->block );
+		return -ENOENT;
+	}
+
+	/* Check for underlength blocks */
+	if ( data_len < ( peerblk->range.end - peerblk->range.start ) ) {
+		DBGC ( peerblk, "PEERBLK %p %d.%d underlength block (%zd "
+		       "bytes)\n", peerblk, peerblk->segment, peerblk->block,
+		       data_len );
+		return -ERANGE;
+	}
+
+	/* Calculate buffered data length (i.e. excluding data which
+	 * was delivered to the final data transfer buffer).
+	 */
+	*buf_len = ( data_len - ( peerblk->end - peerblk->start ) );
+
+	/* Describe data before the trimmed content */
+	peerblk->decrypt[PEERBLK_BEFORE].xferbuf = &peerblk->buffer;
+	peerblk->decrypt[PEERBLK_BEFORE].offset =
+		offsetof ( typeof ( *msg ), msg.block.data );
+	peerblk->decrypt[PEERBLK_BEFORE].len =
+		( peerblk->start -
+		  offsetof ( typeof ( *msg ), msg.block.data ) );
+	total = peerblk->decrypt[PEERBLK_BEFORE].len;
+
+	/* Describe data within the trimmed content */
+	peerblk->decrypt[PEERBLK_DURING].offset =
+		peerblk_offset ( peerblk, peerblk->start );
+	peerblk->decrypt[PEERBLK_DURING].len =
+		( peerblk->end - peerblk->start );
+	total += peerblk->decrypt[PEERBLK_DURING].len;
+
+	/* Describe data after the trimmed content */
+	peerblk->decrypt[PEERBLK_AFTER].xferbuf = &peerblk->buffer;
+	peerblk->decrypt[PEERBLK_AFTER].offset = peerblk->start;
+	peerblk->decrypt[PEERBLK_AFTER].len =
+		( offsetof ( typeof ( *msg ), msg.block.data )
+		  + *buf_len - peerblk->start );
+	total += peerblk->decrypt[PEERBLK_AFTER].len;
+
+	/* Sanity check */
+	assert ( total == be32_to_cpu ( msg->msg.block.block.len ) );
+
+	/* Initialise cipher and digest lengths */
+	peerblk->cipher_remaining = total;
+	peerblk->digest_remaining =
+		( peerblk->range.end - peerblk->range.start );
+	assert ( peerblk->cipher_remaining >= peerblk->digest_remaining );
+
+	return 0;
+}
+
+/**
+ * Parse retrieval protocol message useless details
+ *
+ * @v peerblk		PeerDist block download
+ * @v buf_len		Length of buffered data
+ * @v vrf_len		Length of uselessness to fill in
+ * @ret rc		Return status code
+ */
+static int peerblk_parse_useless ( struct peerdist_block *peerblk,
+				   size_t buf_len, size_t *vrf_len ) {
+	size_t digestsize = peerblk->digestsize;
+	peerblk_msg_blk_t ( digestsize, buf_len, 0, 0 ) *msg =
+		peerblk->buffer.data;
+	size_t len = peerblk->buffer.len;
+
+	/* Check message length */
+	if ( len < offsetof ( typeof ( *msg ), msg.vrf.data ) ) {
+		DBGC ( peerblk, "PEERBLK %p %d.%d message too short for "
+		       "zero-length uselessness (%zd bytes)\n", peerblk,
+		       peerblk->segment, peerblk->block, len );
+		return -ERANGE;
+	}
+
+	/* Extract length of uselessness */
+	*vrf_len = be32_to_cpu ( msg->msg.vrf.vrf.len );
+
+	return 0;
+}
+
+/**
+ * Parse retrieval protocol message initialisation vector details
+ *
+ * @v peerblk		PeerDist block download
+ * @v buf_len		Length of buffered data
+ * @v vrf_len		Length of uselessness
+ * @ret rc		Return status code
+ */
+static int peerblk_parse_iv ( struct peerdist_block *peerblk, size_t buf_len,
+			      size_t vrf_len ) {
+	size_t digestsize = peerblk->digestsize;
+	size_t blksize = peerblk->cipher->blocksize;
+	peerblk_msg_blk_t ( digestsize, buf_len, vrf_len, blksize ) *msg =
+		peerblk->buffer.data;
+	size_t len = peerblk->buffer.len;
+
+	/* Check message length */
+	if ( len < sizeof ( *msg ) ) {
+		DBGC ( peerblk, "PEERBLK %p %d.%d message too short for "
+		       "initialisation vector (%zd bytes)\n", peerblk,
+		       peerblk->segment, peerblk->block, len );
+		return -ERANGE;
+	}
+
+	/* Check initialisation vector size */
+	if ( ntohl ( msg->msg.iv.iv.blksize ) != blksize ) {
+		DBGC ( peerblk, "PEERBLK %p %d.%d incorrect IV size %d\n",
+		       peerblk, peerblk->segment, peerblk->block,
+		       ntohl ( msg->msg.iv.iv.blksize ) );
+		return -EPROTO;
+	}
+
+	/* Set initialisation vector */
+	cipher_setiv ( peerblk->cipher, peerblk->cipherctx, msg->msg.iv.data );
+
+	return 0;
+}
+
+/**
+ * Read from decryption buffers
+ *
+ * @v peerblk		PeerDist block download
+ * @v data		Data buffer
+ * @v len		Length to read
+ * @ret rc		Return status code
+ */
+static int peerblk_decrypt_read ( struct peerdist_block *peerblk,
+				  void *data, size_t len ) {
+	struct peerdist_block_decrypt *decrypt = peerblk->decrypt;
+	size_t frag_len;
+	int rc;
+
+	/* Read from each decryption buffer in turn */
+	for ( ; len ; decrypt++, data += frag_len, len -= frag_len ) {
+
+		/* Calculate length to use from this buffer */
+		frag_len = decrypt->len;
+		if ( frag_len > len )
+			frag_len = len;
+		if ( ! frag_len )
+			continue;
+
+		/* Read from this buffer */
+		if ( ( rc = xferbuf_read ( decrypt->xferbuf, decrypt->offset,
+					   data, frag_len ) ) != 0 )
+			return rc;
+	}
+
+	return 0;
+}
+
+/**
+ * Write to decryption buffers and update offsets and lengths
+ *
+ * @v peerblk		PeerDist block download
+ * @v data		Data buffer
+ * @v len		Length to read
+ * @ret rc		Return status code
+ */
+static int peerblk_decrypt_write ( struct peerdist_block *peerblk,
+				   const void *data, size_t len ) {
+	struct peerdist_block_decrypt *decrypt = peerblk->decrypt;
+	size_t frag_len;
+	int rc;
+
+	/* Write to each decryption buffer in turn */
+	for ( ; len ; decrypt++, data += frag_len, len -= frag_len ) {
+
+		/* Calculate length to use from this buffer */
+		frag_len = decrypt->len;
+		if ( frag_len > len )
+			frag_len = len;
+		if ( ! frag_len )
+			continue;
+
+		/* Write to this buffer */
+		if ( ( rc = xferbuf_write ( decrypt->xferbuf, decrypt->offset,
+					    data, frag_len ) ) != 0 )
+			return rc;
+
+		/* Update offset and length */
+		decrypt->offset += frag_len;
+		decrypt->len -= frag_len;
+	}
+
+	return 0;
+}
+
+/**
+ * Decrypt one chunk of PeerDist retrieval protocol data
+ *
+ * @v peerblk		PeerDist block download
+ */
+static void peerblk_decrypt ( struct peerdist_block *peerblk ) {
+	struct cipher_algorithm *cipher = peerblk->cipher;
+	struct digest_algorithm *digest = peerblk->digest;
+	struct xfer_buffer *xferbuf;
+	size_t cipher_len;
+	size_t digest_len;
+	void *data;
+	int rc;
+
+	/* Sanity check */
+	assert ( ( PEERBLK_DECRYPT_CHUNKSIZE % cipher->blocksize ) == 0 );
+
+	/* Get the underlying data transfer buffer */
+	xferbuf = xfer_buffer ( &peerblk->xfer );
+	if ( ! xferbuf ) {
+		DBGC ( peerblk, "PEERBLK %p %d.%d has no underlying data "
+		       "transfer buffer\n", peerblk, peerblk->segment,
+		       peerblk->block );
+		rc = -ENOTSUP;
+		goto err_xfer_buffer;
+	}
+	peerblk->decrypt[PEERBLK_DURING].xferbuf = xferbuf;
+
+	/* Calculate cipher and digest lengths */
+	cipher_len = PEERBLK_DECRYPT_CHUNKSIZE;
+	if ( cipher_len > peerblk->cipher_remaining )
+		cipher_len = peerblk->cipher_remaining;
+	digest_len = cipher_len;
+	if ( digest_len > peerblk->digest_remaining )
+		digest_len = peerblk->digest_remaining;
+	assert ( ( cipher_len & ( cipher->blocksize - 1 ) ) == 0 );
+
+	/* Allocate temporary data buffer */
+	data = malloc ( cipher_len );
+	if ( ! data ) {
+		rc = -ENOMEM;
+		goto err_alloc_data;
+	}
+
+	/* Read ciphertext */
+	if ( ( rc = peerblk_decrypt_read ( peerblk, data, cipher_len ) ) != 0 ){
+		DBGC ( peerblk, "PEERBLK %p %d.%d could not read ciphertext: "
+		       "%s\n", peerblk, peerblk->segment, peerblk->block,
+		       strerror ( rc ) );
+		goto err_read;
+	}
+
+	/* Decrypt data */
+	cipher_decrypt ( cipher, peerblk->cipherctx, data, data, cipher_len );
+
+	/* Add data to digest */
+	digest_update ( digest, peerblk->digestctx, data, digest_len );
+
+	/* Write plaintext */
+	if ( ( rc = peerblk_decrypt_write ( peerblk, data, cipher_len ) ) != 0){
+		DBGC ( peerblk, "PEERBLK %p %d.%d could not write plaintext: "
+		       "%s\n", peerblk, peerblk->segment, peerblk->block,
+		       strerror ( rc ) );
+		goto err_write;
+	}
+
+	/* Consume input */
+	peerblk->cipher_remaining -= cipher_len;
+	peerblk->digest_remaining -= digest_len;
+
+	/* Free temporary data buffer */
+	free ( data );
+
+	/* Continue processing until all input is consumed */
+	if ( peerblk->cipher_remaining )
+		return;
+
+	/* Complete download attempt */
+	peerblk_done ( peerblk, 0 );
+	return;
+
+ err_write:
+ err_read:
+	free ( data );
+ err_alloc_data:
+ err_xfer_buffer:
+	peerblk_done ( peerblk, rc );
+}
+
+/**
+ * Close PeerDist retrieval protocol block download attempt
+ *
+ * @v peerblk		PeerDist block download
+ * @v rc		Reason for close
+ */
+static void peerblk_retrieval_close ( struct peerdist_block *peerblk, int rc ) {
+	size_t buf_len;
+	size_t vrf_len;
+
+	/* Restart interface */
+	intf_restart ( &peerblk->retrieval, rc );
+
+	/* Fail immediately if we have an error */
+	if ( rc != 0 )
+		goto done;
+
+	/* Abort download attempt (for testing) if applicable */
+	if ( ( rc = inject_fault ( PEERBLK_ABORT_RATE ) ) != 0 )
+		goto done;
+
+	/* Parse message header */
+	if ( ( rc = peerblk_parse_header ( peerblk ) ) != 0 )
+		goto done;
+
+	/* Parse message segment and block details */
+	if ( ( rc = peerblk_parse_block ( peerblk, &buf_len ) ) != 0 )
+		goto done;
+
+	/* If the block was plaintext, then there is nothing more to do */
+	if ( ! peerblk->cipher )
+		goto done;
+
+	/* Parse message useless details */
+	if ( ( rc = peerblk_parse_useless ( peerblk, buf_len, &vrf_len ) ) != 0)
+		goto done;
+
+	/* Parse message initialisation vector details */
+	if ( ( rc = peerblk_parse_iv ( peerblk, buf_len, vrf_len ) ) != 0 )
+		goto done;
+
+	/* Fail if decryption length is not aligned to the cipher block size */
+	if ( peerblk->cipher_remaining & ( peerblk->cipher->blocksize - 1 ) ) {
+		DBGC ( peerblk, "PEERBLK %p %d.%d unaligned data length %zd\n",
+		       peerblk, peerblk->segment, peerblk->block,
+		       peerblk->cipher_remaining );
+		rc = -EPROTO;
+		goto done;
+	}
+
+	/* Stop the download attempt timer: there is no point in
+	 * timing out while decrypting.
+	 */
+	stop_timer ( &peerblk->timer );
+
+	/* Start decryption process */
+	process_add ( &peerblk->process );
+	return;
+
+ done:
+	/* Complete download attempt */
+	peerblk_done ( peerblk, rc );
+}
+
+/******************************************************************************
+ *
+ * Retry policy
+ *
+ ******************************************************************************
+ */
+
+/**
+ * Handle PeerDist retry timer expiry
+ *
+ * @v timer		Retry timer
+ * @v over		Failure indicator
+ */
+static void peerblk_expired ( struct retry_timer *timer, int over __unused ) {
+	struct peerdist_block *peerblk =
+		container_of ( timer, struct peerdist_block, timer );
+	struct peerdisc_segment *segment = peerblk->discovery.segment;
+	struct peerdisc_peer *head;
+	unsigned long now = peerblk_timestamp();
+	const char *location;
+	int rc;
+
+	/* Profile discovery timeout, if applicable */
+	if ( ( peerblk->peer == NULL ) && ( timer->timeout != 0 ) ) {
+		profile_custom ( &peerblk_discovery_timeout_profiler,
+				 ( now - peerblk->started ) );
+		DBGC ( peerblk, "PEERBLK %p %d.%d discovery timed out after "
+		       "%ld ticks\n", peerblk, peerblk->segment,
+		       peerblk->block, timer->timeout );
+	}
+
+	/* Profile download timeout, if applicable */
+	if ( ( peerblk->peer != NULL ) && ( timer->timeout != 0 ) ) {
+		profile_custom ( &peerblk_attempt_timeout_profiler,
+				 ( now - peerblk->attempted ) );
+		DBGC ( peerblk, "PEERBLK %p %d.%d timed out after %ld ticks\n",
+		       peerblk, peerblk->segment, peerblk->block,
+		       timer->timeout );
+	}
+
+	/* Abort any current download attempt */
+	peerblk_reset ( peerblk, -ETIMEDOUT );
+
+	/* Record attempt start time */
+	peerblk->attempted = now;
+
+	/* If we have exceeded our maximum number of attempt cycles
+	 * (each cycle comprising a retrieval protocol download from
+	 * each peer in the list followed by a raw download from the
+	 * origin server), then abort the overall download.
+	 */
+	head = list_entry ( &segment->peers, struct peerdisc_peer, list );
+	if ( ( peerblk->peer == head ) &&
+	     ( ++peerblk->cycles >= PEERBLK_MAX_ATTEMPT_CYCLES ) ) {
+		rc = peerblk->rc;
+		assert ( rc != 0 );
+		goto err;
+	}
+
+	/* If we have not yet made any download attempts, then move to
+	 * the start of the peer list.
+	 */
+	if ( peerblk->peer == NULL )
+		peerblk->peer = head;
+
+	/* Attempt retrieval protocol download from next usable peer */
+	list_for_each_entry_continue ( peerblk->peer, &segment->peers, list ) {
+
+		/* Attempt retrieval protocol download from this peer */
+		location = peerblk->peer->location;
+		if ( ( rc = peerblk_retrieval_open ( peerblk,
+						     location ) ) != 0 ) {
+			/* Non-fatal: continue to try next peer */
+			continue;
+		}
+
+		/* Start download attempt timer */
+		peerblk->rc = -ETIMEDOUT;
+		start_timer_fixed ( &peerblk->timer,
+				    PEERBLK_RETRIEVAL_OPEN_TIMEOUT );
+		return;
+	}
+
+	/* Attempt raw download */
+	if ( ( rc = peerblk_raw_open ( peerblk ) ) != 0 )
+		goto err;
+
+	/* Start download attempt timer */
+	peerblk->rc = -ETIMEDOUT;
+	start_timer_fixed ( &peerblk->timer, PEERBLK_RAW_OPEN_TIMEOUT );
+	return;
+
+ err:
+	peerblk_close ( peerblk, rc );
+}
+
+/**
+ * Handle PeerDist peer discovery
+ *
+ * @v discovery		PeerDist discovery client
+ */
+static void peerblk_discovered ( struct peerdisc_client *discovery ) {
+	struct peerdist_block *peerblk =
+		container_of ( discovery, struct peerdist_block, discovery );
+	unsigned long now = peerblk_timestamp();
+
+	/* Do nothing unless we are still waiting for the initial
+	 * discovery timeout.
+	 */
+	if ( ( peerblk->peer != NULL ) || ( peerblk->timer.timeout == 0 ) )
+		return;
+
+	/* Schedule an immediate retry */
+	start_timer_nodelay ( &peerblk->timer );
+
+	/* Profile discovery success */
+	profile_custom ( &peerblk_discovery_success_profiler,
+			 ( now - peerblk->started ) );
+}
+
+/******************************************************************************
+ *
+ * Opener
+ *
+ ******************************************************************************
+ */
+
+/** PeerDist block download data transfer interface operations */
+static struct interface_operation peerblk_xfer_operations[] = {
+	INTF_OP ( intf_close, struct peerdist_block *, peerblk_close ),
+};
+
+/** PeerDist block download data transfer interface descriptor */
+static struct interface_descriptor peerblk_xfer_desc =
+	INTF_DESC ( struct peerdist_block, xfer, peerblk_xfer_operations );
+
+/** PeerDist block download raw data interface operations */
+static struct interface_operation peerblk_raw_operations[] = {
+	INTF_OP ( xfer_deliver, struct peerdist_block *, peerblk_raw_rx ),
+	INTF_OP ( intf_close, struct peerdist_block *, peerblk_raw_close ),
+};
+
+/** PeerDist block download raw data interface descriptor */
+static struct interface_descriptor peerblk_raw_desc =
+	INTF_DESC ( struct peerdist_block, raw, peerblk_raw_operations );
+
+/** PeerDist block download retrieval protocol interface operations */
+static struct interface_operation peerblk_retrieval_operations[] = {
+	INTF_OP ( xfer_deliver, struct peerdist_block *, peerblk_retrieval_rx ),
+	INTF_OP ( intf_close, struct peerdist_block *, peerblk_retrieval_close),
+};
+
+/** PeerDist block download retrieval protocol interface descriptor */
+static struct interface_descriptor peerblk_retrieval_desc =
+	INTF_DESC ( struct peerdist_block, retrieval,
+		    peerblk_retrieval_operations );
+
+/** PeerDist block download decryption process descriptor */
+static struct process_descriptor peerblk_process_desc =
+	PROC_DESC ( struct peerdist_block, process, peerblk_decrypt );
+
+/** PeerDist block download discovery operations */
+static struct peerdisc_client_operations peerblk_discovery_operations = {
+	.discovered = peerblk_discovered,
+};
+
+/**
+ * Open PeerDist block download
+ *
+ * @v xfer		Data transfer interface
+ * @v uri		Original URI
+ * @v info		Content information block
+ * @ret rc		Return status code
+ */
+int peerblk_open ( struct interface *xfer, struct uri *uri,
+		   struct peerdist_info_block *block ) {
+	const struct peerdist_info_segment *segment = block->segment;
+	const struct peerdist_info *info = segment->info;
+	struct digest_algorithm *digest = info->digest;
+	struct peerdist_block *peerblk;
+	unsigned long timeout;
+	size_t digestsize;
+	int rc;
+
+	/* Allocate and initialise structure */
+	peerblk = zalloc ( sizeof ( *peerblk ) + digest->ctxsize );
+	if ( ! peerblk ) {
+		rc = -ENOMEM;
+		goto err_alloc;
+	}
+	ref_init ( &peerblk->refcnt, peerblk_free );
+	intf_init ( &peerblk->xfer, &peerblk_xfer_desc, &peerblk->refcnt );
+	intf_init ( &peerblk->raw, &peerblk_raw_desc, &peerblk->refcnt );
+	intf_init ( &peerblk->retrieval, &peerblk_retrieval_desc,
+		    &peerblk->refcnt );
+	peerblk->uri = uri_get ( uri );
+	memcpy ( &peerblk->range, &block->range, sizeof ( peerblk->range ) );
+	memcpy ( &peerblk->trim, &block->trim, sizeof ( peerblk->trim ) );
+	peerblk->offset = ( block->trim.start - info->trim.start );
+	peerblk->digest = info->digest;
+	peerblk->digestsize = digestsize = info->digestsize;
+	peerblk->digestctx = ( ( ( void * ) peerblk ) + sizeof ( *peerblk ) );
+	peerblk->segment = segment->index;
+	memcpy ( peerblk->id, segment->id, sizeof ( peerblk->id ) );
+	memcpy ( peerblk->secret, segment->secret, sizeof ( peerblk->secret ) );
+	peerblk->block = block->index;
+	memcpy ( peerblk->hash, block->hash, sizeof ( peerblk->hash ) );
+	xferbuf_malloc_init ( &peerblk->buffer );
+	process_init_stopped ( &peerblk->process, &peerblk_process_desc,
+			       &peerblk->refcnt );
+	peerdisc_init ( &peerblk->discovery, &peerblk_discovery_operations );
+	timer_init ( &peerblk->timer, peerblk_expired, &peerblk->refcnt );
+	DBGC2 ( peerblk, "PEERBLK %p %d.%d id %02x%02x%02x%02x%02x..."
+		"%02x%02x%02x [%08zx,%08zx)", peerblk, peerblk->segment,
+		peerblk->block, peerblk->id[0], peerblk->id[1], peerblk->id[2],
+		peerblk->id[3], peerblk->id[4], peerblk->id[ digestsize - 3 ],
+		peerblk->id[ digestsize - 2 ], peerblk->id[ digestsize - 1 ],
+		peerblk->range.start, peerblk->range.end );
+	if ( ( peerblk->trim.start != peerblk->range.start ) ||
+	     ( peerblk->trim.end != peerblk->range.end ) ) {
+		DBGC2 ( peerblk, " covers [%08zx,%08zx)",
+			peerblk->trim.start, peerblk->trim.end );
+	}
+	DBGC2 ( peerblk, "\n" );
+
+	/* Open discovery */
+	if ( ( rc = peerdisc_open ( &peerblk->discovery, peerblk->id,
+				    peerblk->digestsize ) ) != 0 )
+		goto err_open_discovery;
+
+	/* Schedule a retry attempt either immediately (if we already
+	 * have some peers) or after the discovery timeout.
+	 */
+	timeout = ( list_empty ( &peerblk->discovery.segment->peers ) ?
+		    ( peerdisc_timeout_secs * TICKS_PER_SEC ) : 0 );
+	start_timer_fixed ( &peerblk->timer, timeout );
+
+	/* Record start time */
+	peerblk->started = peerblk_timestamp();
+
+	/* Attach to parent interface, mortalise self, and return */
+	intf_plug_plug ( xfer, &peerblk->xfer );
+	ref_put ( &peerblk->refcnt );
+	return 0;
+
+ err_open_discovery:
+	peerblk_close ( peerblk, rc );
+ err_alloc:
+	return rc;
+}