/* $NetBSD: print-gre.c,v 1.1.1.1 1997/10/03 17:24:21 christos Exp $ */ /* * 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 * * 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. */ #include #ifndef lint #if 0 static const char rcsid[] = "@(#) Header: print-gre.c,v 1.4 96/12/10 23:28:23 leres Exp "; #else __RCSID("$NetBSD: print-gre.c,v 1.1.1.1 1997/10/03 17:24:21 christos Exp $"); #endif #endif #include #include #include #include #include #include #include #include #include #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); }