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Diffstat (limited to 'contrib/tcpdump/print-gre.c')
-rw-r--r-- | contrib/tcpdump/print-gre.c | 141 |
1 files changed, 141 insertions, 0 deletions
diff --git a/contrib/tcpdump/print-gre.c b/contrib/tcpdump/print-gre.c new file mode 100644 index 0000000..dd1ac83 --- /dev/null +++ b/contrib/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: print-gre.c,v 1.4 96/12/10 23:28:23 leres 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); + +} |