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1 files changed, 141 insertions, 0 deletions

diff --git a/usr.sbin/tcpdump/print-gre.c b/usr.sbin/tcpdump/print-gre.c
new file mode 100644
index 00000000000..df5214ff34d
--- /dev/null
+++ b/usr.sbin/tcpdump/print-gre.c
@@ -0,0 +1,141 @@
+/*
+ * Copyright (c) 1996
+ *      The Regents of the University of California.  All rights reserved.
+ *
+ * Redistribution and use in source and binary forms are permitted
+ * provided that the above copyright notice and this paragraph are
+ * duplicated in all such forms and that any documentation,
+ * advertising materials, and other materials related to such
+ * distribution and use acknowledge that the software was developed
+ * by the University of California, Lawrence Berkeley Laboratory,
+ * Berkeley, CA.  The name of the University may not be used to
+ * endorse or promote products derived from this software without
+ * specific prior written permission.
+ * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
+ * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
+ *
+ * Initial contribution from John Hawkinson <jhawk@bbnplanet.com>
+ *
+ * This module implements support for decoding GRE (Generic Routing
+ * Encapsulation) tunnels; they're documented in RFC1701 and RFC1702.
+ * This code only supports the IP encapsulation thereof.
+ */
+
+#ifndef lint
+static const char rcsid[] =
+    "@(#) $Header: /home/cvs/src/usr.sbin/tcpdump/print-gre.c,v 1.1 1996/12/12 16:22:37 bitblt Exp $";
+#endif
+
+#include <sys/param.h>
+#include <sys/time.h>
+#include <sys/uio.h>
+#include <sys/socket.h>
+
+#include <netinet/in.h>
+#include <netinet/in_systm.h>
+#include <netinet/ip.h>
+
+#include <netdb.h>
+#include <stdio.h>
+
+#include "interface.h"
+#include "addrtoname.h"
+#include "extract.h"		/* must come after interface.h */
+
+#define GRE_SIZE (20)
+
+struct gre {
+	u_short flags;
+	u_short proto;
+	union {
+		struct gre_ckof {
+			u_short cksum;
+			u_short offset;
+		}        gre_ckof;
+		u_int32_t key;
+		u_int32_t seq;
+	}     gre_void1;
+	union {
+		u_int32_t key;
+		u_int32_t seq;
+		u_int32_t routing;
+	}     gre_void2;
+	union {
+		u_int32_t seq;
+		u_int32_t routing;
+	}     gre_void3;
+	union {
+		u_int32_t routing;
+	}     gre_void4;
+};
+
+#define GRE_CP		0x8000	/* Checksum Present */
+#define GRE_RP		0x4000	/* Routing Present */
+#define GRE_KP		0x2000	/* Key Present */
+#define GRE_SP		0x1000	/* Sequence Present */
+
+
+#define GREPROTO_IP	0x0800
+
+
+/*
+ * Deencapsulate and print a GRE-tunneled IP datagram
+ */
+void
+gre_print(const u_char *bp, u_int length)
+{
+	const u_char *cp = bp + 4;
+	const struct gre *gre;
+	u_short flags, proto;
+
+	gre = (const struct gre *)bp;
+
+	if (length < GRE_SIZE) {
+		goto trunc;
+	}
+	flags = EXTRACT_16BITS(&gre->flags);
+	proto = EXTRACT_16BITS(&gre->proto);
+
+	if (vflag) {
+		/* Decode the flags */
+		putchar('[');
+		if (flags & GRE_CP)
+			putchar('C');
+		if (flags & GRE_RP)
+			putchar('R');
+		if (flags & GRE_KP)
+			putchar('K');
+		if (flags & GRE_SP)
+			putchar('S');
+		fputs("] ", stdout);
+	}
+	/* Checksum & Offset are present */
+	if ((flags & GRE_CP) | (flags & GRE_RP))
+		cp += 4;
+
+	/* We don't support routing fields (variable length) now. Punt. */
+	if (flags & GRE_RP)
+		return;
+
+	if (flags & GRE_KP)
+		cp += 4;
+	if (flags & GRE_SP)
+		cp += 4;
+
+	switch (proto) {
+
+	case GREPROTO_IP:
+		ip_print(cp, length - ((cp - bp) / sizeof(u_char)));
+		break;
+
+	default:
+		printf("gre-proto-0x%04X", proto);
+		break;
+	}
+	return;
+
+trunc:
+	fputs("[|gre]", stdout);
+
+}