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[peerdist] Add support for constructing and decoding discovery messages

Signed-off-by: Michael Brown <mcb30@ipxe.org>
tags/v1.20.1
Michael Brown 9 years ago
parent
commit
51b99d8bc8
3 changed files with 334 additions and 0 deletions
  1. 1
    0
      src/include/ipxe/errfile.h
  2. 47
    0
      src/include/ipxe/pccrd.h
  3. 286
    0
      src/net/pccrd.c

+ 1
- 0
src/include/ipxe/errfile.h View File

@@ -246,6 +246,7 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
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 #define ERRFILE_rndis			( ERRFILE_NET | 0x003d0000 )
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 #define ERRFILE_pccrc			( ERRFILE_NET | 0x003e0000 )
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 #define ERRFILE_stp			( ERRFILE_NET | 0x003f0000 )
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+#define ERRFILE_pccrd			( ERRFILE_NET | 0x00400000 )
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 #define ERRFILE_image		      ( ERRFILE_IMAGE | 0x00000000 )
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 #define ERRFILE_elf		      ( ERRFILE_IMAGE | 0x00010000 )

+ 47
- 0
src/include/ipxe/pccrd.h View File

@@ -0,0 +1,47 @@
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+#ifndef _IPXE_PCCRD_H
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+#define _IPXE_PCCRD_H
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+
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+/** @file
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+ *
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+ * Peer Content Caching and Retrieval: Discovery Protocol [MS-PCCRD]
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+ *
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+ */
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+
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+FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
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+
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+/** PeerDist discovery port */
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+#define PEERDIST_DISCOVERY_PORT 3702
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+
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+/** PeerDist discovery IPv4 address (239.255.255.250) */
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+#define PEERDIST_DISCOVERY_IPV4 \
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+	( ( 239 << 24 ) | ( 255 << 16 ) | ( 255 << 8 ) | ( 250 << 0 ) )
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+
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+/** PeerDist discovery IPv6 address (ff02::c) */
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+#define PEERDIST_DISCOVERY_IPV6 \
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+	{ 0xff, 0x02, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0xc }
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+
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+/** A PeerDist discovery reply block count */
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+struct peerdist_discovery_block_count {
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+	/** Count (as an eight-digit hex value) */
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+	char hex[8];
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+} __attribute__ (( packed ));
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+
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+/** A PeerDist discovery reply */
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+struct peerdist_discovery_reply {
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+	/** List of segment ID strings
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+	 *
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+	 * The list is terminated with a zero-length string.
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+	 */
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+	char *ids;
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+	/** List of peer locations
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+	 *
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+	 * The list is terminated with a zero-length string.
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+	 */
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+	char *locations;
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+};
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+
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+extern char * peerdist_discovery_request ( const char *uuid, const char *id );
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+extern int peerdist_discovery_reply ( char *data, size_t len,
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+				      struct peerdist_discovery_reply *reply );
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+
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+#endif /* _IPXE_PCCRD_H */

+ 286
- 0
src/net/pccrd.c View File

@@ -0,0 +1,286 @@
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+/*
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+ * Copyright (C) 2015 Michael Brown <mbrown@fensystems.co.uk>.
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+ *
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+ * This program is free software; you can redistribute it and/or
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+ * modify it under the terms of the GNU General Public License as
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+ * published by the Free Software Foundation; either version 2 of the
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+ * License, or (at your option) any later version.
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+ *
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+ * This program is distributed in the hope that it will be useful, but
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+ * WITHOUT ANY WARRANTY; without even the implied warranty of
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+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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+ * General Public License for more details.
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+ *
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+ * You should have received a copy of the GNU General Public License
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+ * along with this program; if not, write to the Free Software
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+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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+ * 02110-1301, USA.
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+ *
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+ * You can also choose to distribute this program under the terms of
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+ * the Unmodified Binary Distribution Licence (as given in the file
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+ * COPYING.UBDL), provided that you have satisfied its requirements.
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+ */
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+
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+FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
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+
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+#include <stddef.h>
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+#include <stdlib.h>
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+#include <stdio.h>
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+#include <string.h>
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+#include <ctype.h>
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+#include <errno.h>
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+#include <assert.h>
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+#include <ipxe/pccrd.h>
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+
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+/** @file
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+ *
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+ * Peer Content Caching and Retrieval: Discovery Protocol [MS-PCCRD]
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+ *
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+ * This protocol manages to ingeniously combine the excessive
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+ * verbosity of XML with a paucity of actual information.  For
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+ * example: even in version 2.0 of the protocol it is still not
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+ * possible to discover which peers hold a specific block within a
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+ * given segment.
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+ *
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+ * For added bonus points, version 1.0 of the protocol is specified to
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+ * use a case-sensitive string comparison (for SHA2 digest values) but
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+ * nothing specifies whether the strings in question should be in
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+ * upper or lower case.  There are example strings given in the
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+ * specification, but the author skilfully manages to leave the issue
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+ * unresolved by using the somewhat implausible digest value of
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+ * "0200000000000000000000000000000000000000000000000000000000000000".
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+ *
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+ * Just in case you were thinking that the silver lining of the choice
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+ * to use an XML-based protocol would be the ability to generate and
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+ * process messages with standard tools, version 2.0 of the protocol
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+ * places most of the critical information inside a Base64-encoded
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+ * custom binary data structure.  Within an XML element, naturally.
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+ *
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+ * I hereby announce this specification to be the 2015 winner of the
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+ * prestigious "UEFI HII API" award for incompetent design.
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+ */
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+
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+/** Discovery request format */
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+#define PEERDIST_DISCOVERY_REQUEST					      \
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+	"<?xml version=\"1.0\" encoding=\"utf-8\"?>"			      \
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+	"<soap:Envelope "						      \
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+	    "xmlns:soap=\"http://www.w3.org/2003/05/soap-envelope\" "	      \
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+	    "xmlns:wsa=\"http://schemas.xmlsoap.org/ws/2004/08/addressing\" " \
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+	    "xmlns:wsd=\"http://schemas.xmlsoap.org/ws/2005/04/discovery\" "  \
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+	    "xmlns:PeerDist=\"http://schemas.microsoft.com/p2p/"	      \
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+			     "2007/09/PeerDistributionDiscovery\">"	      \
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+	  "<soap:Header>"						      \
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+	    "<wsa:To>"							      \
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+	      "urn:schemas-xmlsoap-org:ws:2005:04:discovery"		      \
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+	    "</wsa:To>"							      \
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+	    "<wsa:Action>"						      \
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+	      "http://schemas.xmlsoap.org/ws/2005/04/discovery/Probe"	      \
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+	    "</wsa:Action>"						      \
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+	    "<wsa:MessageID>"						      \
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+	      "urn:uuid:%s"						      \
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+	    "</wsa:MessageID>"						      \
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+	  "</soap:Header>"						      \
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+	  "<soap:Body>"							      \
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+	    "<wsd:Probe>"						      \
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+	      "<wsd:Types>"						      \
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+		"PeerDist:PeerDistData"					      \
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+	      "</wsd:Types>"						      \
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+	      "<wsd:Scopes MatchBy=\"http://schemas.xmlsoap.org/ws/"	      \
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+				    "2005/04/discovery/strcmp0\">"	      \
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+		"%s"							      \
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+	      "</wsd:Scopes>"						      \
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+	    "</wsd:Probe>"						      \
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+	  "</soap:Body>"						      \
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+	"</soap:Envelope>"
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+
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+/**
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+ * Construct discovery request
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+ *
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+ * @v uuid		Message UUID string
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+ * @v id		Segment identifier string
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+ * @ret request		Discovery request, or NULL on failure
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+ *
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+ * The request is dynamically allocated; the caller must eventually
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+ * free() the request.
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+ */
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+char * peerdist_discovery_request ( const char *uuid, const char *id ) {
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+	char *request;
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+	int len;
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+
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+	/* Construct request */
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+	len = asprintf ( &request, PEERDIST_DISCOVERY_REQUEST, uuid, id );
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+	if ( len < 0 )
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+		return NULL;
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+
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+	return request;
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+}
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+
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+/**
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+ * Locate discovery reply tag
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+ *
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+ * @v data		Reply data (not NUL-terminated)
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+ * @v len		Length of reply data
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+ * @v tag		XML tag
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+ * @ret found		Found tag (or NULL if not found)
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+ */
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+static char * peerdist_discovery_reply_tag ( char *data, size_t len,
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+					     const char *tag ) {
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+	size_t tag_len = strlen ( tag );
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+
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+	/* Search, allowing for the fact that the reply data is not
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+	 * cleanly NUL-terminated and may contain embedded NULs due to
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+	 * earlier parsing.
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+	 */
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+	for ( ; len >= tag_len ; data++, len-- ) {
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+		if ( strncmp ( data, tag, tag_len ) == 0 )
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+			return data;
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+	}
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+	return NULL;
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+}
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+
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+/**
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+ * Locate discovery reply values
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+ *
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+ * @v data		Reply data (not NUL-terminated, will be modified)
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+ * @v len		Length of reply data
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+ * @v name		XML tag name
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+ * @ret values		Tag values (or NULL if not found)
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+ *
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+ * The reply data is modified by adding NULs and moving characters as
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+ * needed to produce a NUL-separated list of values, terminated with a
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+ * zero-length string.
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+ *
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+ * This is not supposed to be a full XML parser; it's supposed to
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+ * include just enough functionality to allow PeerDist discovery to
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+ * work with existing implementations.
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+ */
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+static char * peerdist_discovery_reply_values ( char *data, size_t len,
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+						const char *name ) {
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+	char buf[ 2 /* "</" */ + strlen ( name ) + 1 /* ">" */ + 1 /* NUL */ ];
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+	char *open;
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+	char *close;
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+	char *start;
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+	char *end;
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+	char *in;
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+	char *out;
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+	char c;
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+
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+	/* Locate opening tag */
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+	snprintf ( buf, sizeof ( buf ), "<%s>", name );
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+	open = peerdist_discovery_reply_tag ( data, len, buf );
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+	if ( ! open )
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+		return NULL;
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+	start = ( open + strlen ( buf ) );
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+	len -= ( start - data );
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+	data = start;
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+
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+	/* Locate closing tag */
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+	snprintf ( buf, sizeof ( buf ), "</%s>", name );
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+	close = peerdist_discovery_reply_tag ( data, len, buf );
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+	if ( ! close )
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+		return NULL;
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+	assert ( close >= open );
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+	end = close;
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+
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+	/* Strip initial whitespace, convert other whitespace
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+	 * sequences to single NULs, add terminating pair of NULs.
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+	 * This will probably overwrite part of the closing tag.
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+	 */
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+	for ( in = start, out = start ; in < end ; in++ ) {
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+		c = *in;
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+		if ( isspace ( c ) ) {
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+			if ( ( out > start ) && ( out[-1] != '\0' ) )
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+				*(out++) = '\0';
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+		} else {
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+			*(out++) = c;
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+		}
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+	}
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+	*(out++) = '\0';
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+	*(out++) = '\0';
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+	assert ( out < ( close + strlen ( buf ) ) );
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+
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+	return start;
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+}
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+
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+/**
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+ * Parse discovery reply
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+ *
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+ * @v data		Reply data (not NUL-terminated, will be modified)
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+ * @v len		Length of reply data
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+ * @v reply		Discovery reply to fill in
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+ * @ret rc		Return status code
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+ *
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+ * The discovery reply includes pointers to strings within the
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+ * modified reply data.
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+ */
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+int peerdist_discovery_reply ( char *data, size_t len,
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+			       struct peerdist_discovery_reply *reply ) {
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+	static const struct peerdist_discovery_block_count zcount = {
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+		.hex = "00000000",
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+	};
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+	struct peerdist_discovery_block_count *count;
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+	unsigned int max;
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+	unsigned int i;
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+	char *scopes;
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+	char *xaddrs;
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+	char *blockcount;
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+	char *in;
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+	char *out;
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+	size_t skip;
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+
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+	/* Find <wsd:Scopes> tag */
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+	scopes = peerdist_discovery_reply_values ( data, len, "wsd:Scopes" );
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+	if ( ! scopes ) {
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+		DBGC ( reply, "PCCRD %p missing <wsd:Scopes> tag\n", reply );
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+		return -ENOENT;
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+	}
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+
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+	/* Find <wsd:XAddrs> tag */
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+	xaddrs = peerdist_discovery_reply_values ( data, len, "wsd:XAddrs" );
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+	if ( ! xaddrs ) {
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+		DBGC ( reply, "PCCRD %p missing <wsd:XAddrs> tag\n", reply );
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+		return -ENOENT;
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+	}
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+
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+	/* Find <PeerDist:BlockCount> tag */
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+	blockcount = peerdist_discovery_reply_values ( data, len,
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+						       "PeerDist:BlockCount" );
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+	if ( ! blockcount ) {
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+		DBGC ( reply, "PCCRD %p missing <PeerDist:BlockCount> tag\n",
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+		       reply );
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+		return -ENOENT;
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+	}
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+
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+	/* Determine maximum number of segments (according to number
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+	 * of entries in the block count list).
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+	 */
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+	max = ( strlen ( blockcount ) / sizeof ( *count ) );
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+	count = container_of ( blockcount,
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+			       struct peerdist_discovery_block_count, hex[0] );
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+
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+	/* Eliminate any segments with a zero block count */
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+	for ( i = 0, in = scopes, out = scopes ; *in ; i++, in += skip ) {
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+
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+		/* Fail if we have overrun the maximum number of segments */
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+		if ( i >= max ) {
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+			DBGC ( reply, "PCCRD %p too many segment IDs\n",
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+			       reply );
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+			return -EPROTO;
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+		}
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+
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+		/* Delete segment if block count is zero */
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+		skip = ( strlen ( in ) + 1 /* NUL */ );
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+		if ( memcmp ( count[i].hex, zcount.hex,
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+			      sizeof ( zcount.hex ) ) == 0 )
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+			continue;
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+		strcpy ( out, in );
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+		out += skip;
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+	}
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+	out[0] = '\0'; /* Ensure list is terminated with a zero-length string */
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+
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+	/* Fill in discovery reply */
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+	reply->ids = scopes;
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+	reply->locations = xaddrs;
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+
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+	return 0;
286
+}

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