Update GRE printer from RFC 2784 (GRE), 2890 (Key and Sequence extensions).

Handle PPTP's GRE extension (RFC 2637)
Print the seq, ack, key fields if -vv

diff --git a/print-gre.c b/print-gre.c
index 1e801b91112123df9725efca53d4c1e2ac9a58fc..cf2ba469265932a148842f644770fafa6e1be99a 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 1.10 2001-02-03 20:21:28 fenner Exp $";
 #endif
 
 #ifdef HAVE_CONFIG_H
@@ -72,14 +72,29 @@ struct gre {
        }     gre_void4;
 };
 
+/* 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
+
+/* "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
+ *
+ * XXX PPTP needs to interpret the "key" field...
  */
 void
 gre_print(const u_char *bp, u_int length)
@@ -90,13 +105,11 @@ gre_print(const u_char *bp, u_int length)
 
        gre = (const struct gre *)bp;
 
-       if (length < GRE_SIZE) {
-               goto trunc;
-       }
+       TCHECK(gre->proto);
        flags = EXTRACT_16BITS(&gre->flags);
        proto = EXTRACT_16BITS(&gre->proto);
 
-       if (vflag) {
+       if (flags) {
                /* Decode the flags */
                putchar('[');
                if (flags & GRE_CP)
@@ -107,6 +120,16 @@ 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);
+               if (flags & GRE_VER_MASK)
+                       printf("v%x", flags & GRE_VER_MASK);
+               if (flags & GRE_MBZ_MASK)
+                       printf("!%x", flags & GRE_MBZ_MASK);
                fputs("] ", stdout);
        }
        /* Checksum & Offset are present */
@@ -117,10 +140,26 @@ gre_print(const u_char *bp, u_int length)
        if (flags & GRE_RP)
                return;
 
-       if (flags & GRE_KP)
-               cp += 4;
-       if (flags & GRE_SP)
-               cp += 4;
+       if (flags & GRE_KP) {
+               TCHECK2(*cp, 4);
+               if (vflag > 1)
+                       printf("K:%08x ", EXTRACT_32BITS(cp));
+               cp += 4;        /* skip key */
+       }
+       if (flags & GRE_SP) {
+               TCHECK2(*cp, 4);
+               if (vflag > 1)
+                       printf("S:%08x ", EXTRACT_32BITS(cp));
+               cp += 4;        /* skip seq */
+       }
+       if (flags & GRE_AP && (flags & GRE_VER_MASK) >= 1) {
+               TCHECK2(*cp, 4);
+               if (vflag > 1)
+                       printf("A:%08x ", EXTRACT_32BITS(cp));
+               cp += 4;        /* skip ack */
+       }
+
+       TCHECK(cp[0]);
 
        length -= cp - bp;
        if (ether_encap_print(proto, cp, length, length,