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+/*
+ * 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 <stddef.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <ctype.h>
+#include <errno.h>
+#include <assert.h>
+#include <ipxe/pccrd.h>
+
+/** @file
+ *
+ * Peer Content Caching and Retrieval: Discovery Protocol [MS-PCCRD]
+ *
+ * This protocol manages to ingeniously combine the excessive
+ * verbosity of XML with a paucity of actual information. For
+ * example: even in version 2.0 of the protocol it is still not
+ * possible to discover which peers hold a specific block within a
+ * given segment.
+ *
+ * For added bonus points, version 1.0 of the protocol is specified to
+ * use a case-sensitive string comparison (for SHA2 digest values) but
+ * nothing specifies whether the strings in question should be in
+ * upper or lower case. There are example strings given in the
+ * specification, but the author skilfully manages to leave the issue
+ * unresolved by using the somewhat implausible digest value of
+ * "0200000000000000000000000000000000000000000000000000000000000000".
+ *
+ * Just in case you were thinking that the silver lining of the choice
+ * to use an XML-based protocol would be the ability to generate and
+ * process messages with standard tools, version 2.0 of the protocol
+ * places most of the critical information inside a Base64-encoded
+ * custom binary data structure. Within an XML element, naturally.
+ *
+ * I hereby announce this specification to be the 2015 winner of the
+ * prestigious "UEFI HII API" award for incompetent design.
+ */
+
+/** Discovery request format */
+#define PEERDIST_DISCOVERY_REQUEST \
+ "<?xml version=\"1.0\" encoding=\"utf-8\"?>" \
+ "<soap:Envelope " \
+ "xmlns:soap=\"http://www.w3.org/2003/05/soap-envelope\" " \
+ "xmlns:wsa=\"http://schemas.xmlsoap.org/ws/2004/08/addressing\" " \
+ "xmlns:wsd=\"http://schemas.xmlsoap.org/ws/2005/04/discovery\" " \
+ "xmlns:PeerDist=\"http://schemas.microsoft.com/p2p/" \
+ "2007/09/PeerDistributionDiscovery\">" \
+ "<soap:Header>" \
+ "<wsa:To>" \
+ "urn:schemas-xmlsoap-org:ws:2005:04:discovery" \
+ "</wsa:To>" \
+ "<wsa:Action>" \
+ "http://schemas.xmlsoap.org/ws/2005/04/discovery/Probe" \
+ "</wsa:Action>" \
+ "<wsa:MessageID>" \
+ "urn:uuid:%s" \
+ "</wsa:MessageID>" \
+ "</soap:Header>" \
+ "<soap:Body>" \
+ "<wsd:Probe>" \
+ "<wsd:Types>" \
+ "PeerDist:PeerDistData" \
+ "</wsd:Types>" \
+ "<wsd:Scopes MatchBy=\"http://schemas.xmlsoap.org/ws/" \
+ "2005/04/discovery/strcmp0\">" \
+ "%s" \
+ "</wsd:Scopes>" \
+ "</wsd:Probe>" \
+ "</soap:Body>" \
+ "</soap:Envelope>"
+
+/**
+ * Construct discovery request
+ *
+ * @v uuid Message UUID string
+ * @v id Segment identifier string
+ * @ret request Discovery request, or NULL on failure
+ *
+ * The request is dynamically allocated; the caller must eventually
+ * free() the request.
+ */
+char * peerdist_discovery_request ( const char *uuid, const char *id ) {
+ char *request;
+ int len;
+
+ /* Construct request */
+ len = asprintf ( &request, PEERDIST_DISCOVERY_REQUEST, uuid, id );
+ if ( len < 0 )
+ return NULL;
+
+ return request;
+}
+
+/**
+ * Locate discovery reply tag
+ *
+ * @v data Reply data (not NUL-terminated)
+ * @v len Length of reply data
+ * @v tag XML tag
+ * @ret found Found tag (or NULL if not found)
+ */
+static char * peerdist_discovery_reply_tag ( char *data, size_t len,
+ const char *tag ) {
+ size_t tag_len = strlen ( tag );
+
+ /* Search, allowing for the fact that the reply data is not
+ * cleanly NUL-terminated and may contain embedded NULs due to
+ * earlier parsing.
+ */
+ for ( ; len >= tag_len ; data++, len-- ) {
+ if ( strncmp ( data, tag, tag_len ) == 0 )
+ return data;
+ }
+ return NULL;
+}
+
+/**
+ * Locate discovery reply values
+ *
+ * @v data Reply data (not NUL-terminated, will be modified)
+ * @v len Length of reply data
+ * @v name XML tag name
+ * @ret values Tag values (or NULL if not found)
+ *
+ * The reply data is modified by adding NULs and moving characters as
+ * needed to produce a NUL-separated list of values, terminated with a
+ * zero-length string.
+ *
+ * This is not supposed to be a full XML parser; it's supposed to
+ * include just enough functionality to allow PeerDist discovery to
+ * work with existing implementations.
+ */
+static char * peerdist_discovery_reply_values ( char *data, size_t len,
+ const char *name ) {
+ char buf[ 2 /* "</" */ + strlen ( name ) + 1 /* ">" */ + 1 /* NUL */ ];
+ char *open;
+ char *close;
+ char *start;
+ char *end;
+ char *in;
+ char *out;
+ char c;
+
+ /* Locate opening tag */
+ snprintf ( buf, sizeof ( buf ), "<%s>", name );
+ open = peerdist_discovery_reply_tag ( data, len, buf );
+ if ( ! open )
+ return NULL;
+ start = ( open + strlen ( buf ) );
+ len -= ( start - data );
+ data = start;
+
+ /* Locate closing tag */
+ snprintf ( buf, sizeof ( buf ), "</%s>", name );
+ close = peerdist_discovery_reply_tag ( data, len, buf );
+ if ( ! close )
+ return NULL;
+ assert ( close >= open );
+ end = close;
+
+ /* Strip initial whitespace, convert other whitespace
+ * sequences to single NULs, add terminating pair of NULs.
+ * This will probably overwrite part of the closing tag.
+ */
+ for ( in = start, out = start ; in < end ; in++ ) {
+ c = *in;
+ if ( isspace ( c ) ) {
+ if ( ( out > start ) && ( out[-1] != '\0' ) )
+ *(out++) = '\0';
+ } else {
+ *(out++) = c;
+ }
+ }
+ *(out++) = '\0';
+ *(out++) = '\0';
+ assert ( out < ( close + strlen ( buf ) ) );
+
+ return start;
+}
+
+/**
+ * Parse discovery reply
+ *
+ * @v data Reply data (not NUL-terminated, will be modified)
+ * @v len Length of reply data
+ * @v reply Discovery reply to fill in
+ * @ret rc Return status code
+ *
+ * The discovery reply includes pointers to strings within the
+ * modified reply data.
+ */
+int peerdist_discovery_reply ( char *data, size_t len,
+ struct peerdist_discovery_reply *reply ) {
+ static const struct peerdist_discovery_block_count zcount = {
+ .hex = "00000000",
+ };
+ struct peerdist_discovery_block_count *count;
+ unsigned int max;
+ unsigned int i;
+ char *scopes;
+ char *xaddrs;
+ char *blockcount;
+ char *in;
+ char *out;
+ size_t skip;
+
+ /* Find <wsd:Scopes> tag */
+ scopes = peerdist_discovery_reply_values ( data, len, "wsd:Scopes" );
+ if ( ! scopes ) {
+ DBGC ( reply, "PCCRD %p missing <wsd:Scopes> tag\n", reply );
+ return -ENOENT;
+ }
+
+ /* Find <wsd:XAddrs> tag */
+ xaddrs = peerdist_discovery_reply_values ( data, len, "wsd:XAddrs" );
+ if ( ! xaddrs ) {
+ DBGC ( reply, "PCCRD %p missing <wsd:XAddrs> tag\n", reply );
+ return -ENOENT;
+ }
+
+ /* Find <PeerDist:BlockCount> tag */
+ blockcount = peerdist_discovery_reply_values ( data, len,
+ "PeerDist:BlockCount" );
+ if ( ! blockcount ) {
+ DBGC ( reply, "PCCRD %p missing <PeerDist:BlockCount> tag\n",
+ reply );
+ return -ENOENT;
+ }
+
+ /* Determine maximum number of segments (according to number
+ * of entries in the block count list).
+ */
+ max = ( strlen ( blockcount ) / sizeof ( *count ) );
+ count = container_of ( blockcount,
+ struct peerdist_discovery_block_count, hex[0] );
+
+ /* Eliminate any segments with a zero block count */
+ for ( i = 0, in = scopes, out = scopes ; *in ; i++, in += skip ) {
+
+ /* Fail if we have overrun the maximum number of segments */
+ if ( i >= max ) {
+ DBGC ( reply, "PCCRD %p too many segment IDs\n",
+ reply );
+ return -EPROTO;
+ }
+
+ /* Delete segment if block count is zero */
+ skip = ( strlen ( in ) + 1 /* NUL */ );
+ if ( memcmp ( count[i].hex, zcount.hex,
+ sizeof ( zcount.hex ) ) == 0 )
+ continue;
+ strcpy ( out, in );
+ out += skip;
+ }
+ out[0] = '\0'; /* Ensure list is terminated with a zero-length string */
+
+ /* Fill in discovery reply */
+ reply->ids = scopes;
+ reply->locations = xaddrs;
+
+ return 0;
+}
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