There's no link-layer header on Linux ARPHRD_ATM packets; there's

[tcpdump] / print-gre.c

diff --git a/print-gre.c b/print-gre.c
index 1e801b91112123df9725efca53d4c1e2ac9a58fc..4accdfe0fe49d787b1cb014fada5e4e4d925ea68 100644 (file)
--- a/print-gre.c
+++ b/print-gre.c
@@ -24,7 +24,7 @@
 
 #ifndef lint
 static const char rcsid[] =
-    "@(#) $Header: /tcpdump/master/tcpdump/print-gre.c,v 1.9 2000-12-18 05:41:59 guy Exp $";
+    "@(#) $Header: /tcpdump/master/tcpdump/print-gre.c,v 1.13 2001-06-15 22:17:31 fenner Exp $";
 #endif
 
 #ifdef HAVE_CONFIG_H
@@ -45,38 +45,31 @@ static const char rcsid[] =
 #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;
+       u_int16_t flags;
+       u_int16_t proto;
 };
 
+/* RFC 2784 - GRE */
 #define GRE_CP         0x8000  /* Checksum Present */
-#define GRE_RP         0x4000  /* Routing Present */
+#define GRE_VER_MASK   0x0007  /* Version */
+
+/* RFC 2890 - Key and Sequence extensions to GRE */
 #define GRE_KP         0x2000  /* Key Present */
 #define GRE_SP         0x1000  /* Sequence Present */
 
+/* Legacy from RFC 1700 */
+#define GRE_RP         0x4000  /* Routing Present */
+#define GRE_sP         0x0800  /* strict source route present */
+#define GRE_RECUR_MASK 0x0700  /* Recursion Control */
+#define GRE_RECUR_SHIFT        8
+
+#define GRE_COP                (GRE_RP|GRE_CP) /* Checksum & Offset Present */
+
+/* "Enhanced GRE" from RFC2637 - PPTP */
+#define GRE_AP         0x0080  /* Ack present */
+
+#define GRE_MBZ_MASK   0x0078  /* not defined */
 
 /*
  * Deencapsulate and print a GRE-tunneled IP datagram
@@ -86,17 +79,18 @@ gre_print(const u_char *bp, u_int length)
 {
        const u_char *cp = bp + 4;
        const struct gre *gre;
-       u_short flags, proto, extracted_ethertype;
+       u_int16_t flags, proto;
+       u_short ver=0;
+       u_short extracted_ethertype;
 
        gre = (const struct gre *)bp;
 
-       if (length < GRE_SIZE) {
-               goto trunc;
-       }
+       TCHECK(gre->proto);
        flags = EXTRACT_16BITS(&gre->flags);
        proto = EXTRACT_16BITS(&gre->proto);
+       (void)printf("gre ");
 
-       if (vflag) {
+       if (flags) {
                /* Decode the flags */
                putchar('[');
                if (flags & GRE_CP)
@@ -107,20 +101,68 @@ gre_print(const u_char *bp, u_int length)
                        putchar('K');
                if (flags & GRE_SP)
                        putchar('S');
+               if (flags & GRE_sP)
+                       putchar('s');
+               if (flags & GRE_AP)
+                       putchar('A');
+               if (flags & GRE_RECUR_MASK)
+                       printf("R%x", (flags & GRE_RECUR_MASK) >> GRE_RECUR_SHIFT);
+               ver = flags & GRE_VER_MASK;
+               printf("v%u", ver);
+               
+               if (flags & GRE_MBZ_MASK)
+                       printf("!%x", flags & GRE_MBZ_MASK);
                fputs("] ", stdout);
        }
-       /* Checksum & Offset are present */
-       if ((flags & GRE_CP) | (flags & GRE_RP))
-               cp += 4;
 
+       if (flags & GRE_COP) {
+               int checksum, offset;
+
+               TCHECK2(*cp, 4);
+               checksum = EXTRACT_16BITS(cp);
+               offset = EXTRACT_16BITS(cp + 2);
+
+               if (flags & GRE_CP) {
+                       /* Checksum present */
+
+                       /* todo: check checksum */
+                       if (vflag > 1)
+                               printf("C:%04x ", checksum);
+               }
+               if (flags & GRE_RP) {
+                       /* Offset present */
+
+                       if (vflag > 1)
+                               printf("O:%04x ", offset);
+               }
+               cp += 4;        /* skip checksum and offset */
+       }
+       if (flags & GRE_KP) {
+               TCHECK2(*cp, 4);
+               if (ver == 1) {         /* PPTP */
+                       if (vflag > 1)
+                               printf("PL:%u ", EXTRACT_16BITS(cp));
+                       printf("ID:%04x ", EXTRACT_16BITS(cp+2));
+               }
+               else 
+                       printf("K:%08x ", EXTRACT_32BITS(cp));
+               cp += 4;        /* skip key */
+       }
+       if (flags & GRE_SP) {
+               TCHECK2(*cp, 4);
+               printf("S:%u ", EXTRACT_32BITS(cp));
+               cp += 4;        /* skip seq */
+       }
+       if (flags & GRE_AP && ver >= 1) {
+               TCHECK2(*cp, 4);
+               printf("A:%u ", EXTRACT_32BITS(cp));
+               cp += 4;        /* skip ack */
+       }
        /* 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;
+       TCHECK(cp[0]);
 
        length -= cp - bp;
        if (ether_encap_print(proto, cp, length, length,