gre: add support for MikroTik Ethernet-over-IP hack.

More from OpenBSD's tcpdump.

diff --git a/print-gre.c b/print-gre.c
index 3355005acd30d9dbe6e2a17e9cc7cd4df6289a84..30bb6c212a54d8c425463da3d72c0b30312cf8fa 100644 (file)
--- a/print-gre.c
+++ b/print-gre.c
@@ -86,6 +86,7 @@ static const struct tok gre_flag_values[] = {
  */
 #define GRE_CDP                        0x2000  /* Cisco Discovery Protocol */
 #define GRE_NHRP               0x2001  /* Next Hop Resolution Protocol */
+#define GRE_MIKROTIK_EOIP      0x6400  /* MikroTik RouterBoard Ethernet over IP (EoIP) */
 #define GRE_ERSPAN_III         0x22eb
 #define GRE_WCCP               0x883e  /* Web Cache C* Protocol */
 #define GRE_ERSPAN_I_II                0x88be
@@ -348,6 +349,31 @@ gre_print_1(netdissect_options *ndo, const u_char *bp, u_int length)
        len -= 2;
        bp += 2;
 
+       /*
+        * This version is used for two purposes:
+        *
+        *  RFC 2637 PPTP;
+        *  Some Mikrotik Ethernet-over-IP hack.
+        */
+       switch (prot) {
+       case GRE_MIKROTIK_EOIP:
+               /*
+                * The MikroTik hack uses only the key field, and uses it
+                * for its own purposes.  If anything other than the version
+                * and K bit are set, report an error and give up.
+                */
+               if ((flags & ~GRE_VERS_MASK) != GRE_KP) {
+                       ND_PRINT(" unknown-eoip-flags-%04x!", flags);
+                       return;
+               }
+               break;
+       default:
+               /*
+                * XXX - what should we do if it's not ETHERTYPE_PPP?
+                */
+               break;
+       }
+
        if (flags & GRE_KP) {
                /* Skip payload length? */
                ND_ICHECK_U(len, <, 2);
@@ -356,7 +382,11 @@ gre_print_1(netdissect_options *ndo, const u_char *bp, u_int length)
                bp += 2;
 
                ND_ICHECK_U(len, <, 2);
-               ND_PRINT(", call %u", GET_BE_U_2(bp));
+               if (prot == GRE_MIKROTIK_EOIP) {
+                       /* Non-standard */
+                       ND_PRINT(", tunnel-id %u", GET_BE_U_2(bp));
+               } else
+                       ND_PRINT(", call %u", GET_BE_U_2(bp));
                len -= 2;
                bp += 2;
        } else
@@ -376,7 +406,10 @@ gre_print_1(netdissect_options *ndo, const u_char *bp, u_int length)
                len -= 4;
        }
 
-       if ((flags & GRE_SP) == 0)
+       /*
+        * More non-standard EoIP behavior.
+        */
+       if (prot != GRE_MIKROTIK_EOIP && (flags & GRE_SP) == 0)
                ND_PRINT(", no-payload");
 
        if (ndo->ndo_eflag)
@@ -385,7 +418,10 @@ gre_print_1(netdissect_options *ndo, const u_char *bp, u_int length)
 
        ND_PRINT(", length %u",length);
 
-       if ((flags & GRE_SP) == 0)
+       /*
+        * More non-standard EoIP behavior.
+        */
+       if (prot != GRE_MIKROTIK_EOIP && (flags & GRE_SP) == 0)
                return;
 
        if (ndo->ndo_vflag < 1)
@@ -397,6 +433,13 @@ gre_print_1(netdissect_options *ndo, const u_char *bp, u_int length)
        case ETHERTYPE_PPP:
                ppp_print(ndo, bp, len);
                break;
+       case GRE_MIKROTIK_EOIP:
+               /* MikroTik RouterBoard Ethernet over IP (EoIP) */
+               if (len == 0)
+                       ND_PRINT("keepalive");
+               else
+                       ether_print(ndo, bp, len, ND_BYTES_AVAILABLE_AFTER(bp), NULL, NULL);
+               break;
        default:
                ND_PRINT("gre-proto-0x%x", prot);
                break;