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-rw-r--r--print-loopback.c135
1 files changed, 135 insertions, 0 deletions
diff --git a/print-loopback.c b/print-loopback.c
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+/*
+ * Copyright (c) 2014 The TCPDUMP project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+/* \summary: Loopback Protocol printer */
+
+/*
+ * originally defined as the Ethernet Configuration Testing Protocol.
+ * specification: https://www.mit.edu/people/jhawk/ctp.pdf
+ */
+
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+#include "netdissect-stdinc.h"
+
+#define ND_LONGJMP_FROM_TCHECK
+#include "netdissect.h"
+#include "extract.h"
+#include "addrtoname.h"
+
+
+#define LOOPBACK_REPLY 1
+#define LOOPBACK_FWDDATA 2
+
+static const struct tok fcode_str[] = {
+ { LOOPBACK_REPLY, "Reply" },
+ { LOOPBACK_FWDDATA, "Forward Data" },
+ { 0, NULL }
+};
+
+static void
+loopback_message_print(netdissect_options *ndo,
+ const u_char *cp, u_int len)
+{
+ uint16_t function;
+
+ if (len < 2)
+ goto invalid;
+ /* function */
+ function = GET_LE_U_2(cp);
+ cp += 2;
+ len -= 2;
+ ND_PRINT(", %s", tok2str(fcode_str, " invalid (%u)", function));
+
+ switch (function) {
+ case LOOPBACK_REPLY:
+ if (len < 2)
+ goto invalid;
+ /* receipt number */
+ ND_PRINT(", receipt number %u", GET_LE_U_2(cp));
+ cp += 2;
+ len -= 2;
+ /* data */
+ ND_PRINT(", data (%u octets)", len);
+ ND_TCHECK_LEN(cp, len);
+ break;
+ case LOOPBACK_FWDDATA:
+ if (len < MAC_ADDR_LEN)
+ goto invalid;
+ /* forwarding address */
+ ND_PRINT(", forwarding address %s", GET_ETHERADDR_STRING(cp));
+ cp += MAC_ADDR_LEN;
+ len -= MAC_ADDR_LEN;
+ /* data */
+ ND_PRINT(", data (%u octets)", len);
+ ND_TCHECK_LEN(cp, len);
+ break;
+ default:
+ ND_TCHECK_LEN(cp, len);
+ break;
+ }
+ return;
+
+invalid:
+ nd_print_invalid(ndo);
+ ND_TCHECK_LEN(cp, len);
+}
+
+void
+loopback_print(netdissect_options *ndo,
+ const u_char *cp, u_int len)
+{
+ uint16_t skipCount;
+
+ ndo->ndo_protocol = "loopback";
+ ND_PRINT("Loopback");
+ if (len < 2)
+ goto invalid;
+ /* skipCount */
+ skipCount = GET_LE_U_2(cp);
+ cp += 2;
+ len -= 2;
+ ND_PRINT(", skipCount %u", skipCount);
+ if (skipCount % 8)
+ ND_PRINT(" (bogus)");
+ if (skipCount > len)
+ goto invalid;
+ /* the octets to skip */
+ ND_TCHECK_LEN(cp, skipCount);
+ cp += skipCount;
+ len -= skipCount;
+ /* the first message to decode */
+ loopback_message_print(ndo, cp, len);
+ return;
+
+invalid:
+ nd_print_invalid(ndo);
+ ND_TCHECK_LEN(cp, len);
+}
+