mirror of
https://github.com/the-tcpdump-group/tcpdump.git
synced 2024-12-03 23:13:36 +08:00
142 lines
3.2 KiB
C
142 lines
3.2 KiB
C
/*
|
|
* 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: /tcpdump/master/tcpdump/print-gre.c,v 1.4 1999-10-07 23:47:11 mcr 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);
|
|
|
|
}
|