X-Git-Url: https://git.tcpdump.org/tcpdump/blobdiff_plain/ef5323efe6c03aaa50eac0949bf95999b91fe05b..HEAD:/print-gre.c

diff --git a/print-gre.c b/print-gre.c
index 136fb69d..1d545b3f 100644
--- a/print-gre.c
+++ b/print-gre.c
@@ -30,12 +30,21 @@
 
 /*
  * netdissect printer for GRE - Generic Routing Encapsulation
- * RFC1701 (GRE), RFC1702 (GRE IPv4), and RFC2637 (Enhanced GRE)
+ * RFC 1701 (GRE), RFC 1702 (GRE IPv4), RFC 2637 (PPTP, which
+ * has an extended form of GRE), RFC 2784 (revised GRE, with
+ * R, K, S, and s bits and Recur and Offset fields now reserved
+ * in the header, and no optional Key or Sequence number in the
+ * header), and RFC 2890 (proposal to add back the K and S bits
+ * and the optional Key and Sequence number).
+ *
+ * The RFC 2637 PPTP GRE repurposes the Key field to hold a
+ * 16-bit Payload Length and a 16-bit Call ID.
+ *
+ * RFC 7637 (NVGRE) repurposes the Key field to hold a 24-bit
+ * Virtual Subnet ID (VSID) and an 8-bit FlowID.
  */
 
-#ifdef HAVE_CONFIG_H
 #include <config.h>
-#endif
 
 #include "netdissect-stdinc.h"
 
@@ -44,14 +53,7 @@
 #include "addrtostr.h"
 #include "extract.h"
 #include "ethertype.h"
-
-
-#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	GRE_sP		0x0800		/* source routing */
-#define	GRE_AP		0x0080		/* acknowledgment# present */
+#include "gre.h"
 
 static const struct tok gre_flag_values[] = {
     { GRE_CP, "checksum present"},
@@ -70,6 +72,26 @@ static const struct tok gre_flag_values[] = {
 #define	GRESRE_IP	0x0800		/* IP */
 #define	GRESRE_ASN	0xfffe		/* ASN */
 
+/*
+ * Ethertype values used for GRE (but not elsewhere?).
+ */
+#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
+
+struct wccp_redirect {
+	nd_uint8_t	flags;
+#define WCCP_T			(1 << 7)
+#define WCCP_A			(1 << 6)
+#define WCCP_U			(1 << 5)
+	nd_uint8_t	ServiceId;
+	nd_uint8_t	AltBucket;
+	nd_uint8_t	PriBucket;
+};
+
 static void gre_print_0(netdissect_options *, const u_char *, u_int);
 static void gre_print_1(netdissect_options *, const u_char *, u_int);
 static int gre_sre_print(netdissect_options *, uint16_t, uint8_t, uint8_t, const u_char *, u_int);
@@ -141,10 +163,21 @@ gre_print_0(netdissect_options *ndo, const u_char *bp, u_int length)
 	}
 
 	if (flags & GRE_KP) {
+		uint32_t key;
+
 		ND_ICHECK_U(len, <, 4);
-		ND_PRINT(", key=0x%x", GET_BE_U_4(bp));
+		key = GET_BE_U_4(bp);
 		bp += 4;
 		len -= 4;
+
+		/*
+		 * OpenBSD shows this as both a 32-bit
+		 * (decimal) key value and a VSID+FlowID
+		 * pair, with the VSID in decimal and
+		 * the FlowID in hex, as key=<Key>|<VSID>+<FlowID>,
+		 * in case this is NVGRE.
+		 */
+		ND_PRINT(", key=0x%x", key);
 	}
 
 	if (flags & GRE_SP) {
@@ -191,6 +224,59 @@ gre_print_0(netdissect_options *ndo, const u_char *bp, u_int length)
 		ND_PRINT("\n\t"); /* if verbose go multiline */
 
 	switch (prot) {
+	case 0x0000:
+		/*
+		 * 0x0000 is reserved, but Cisco, at least, appears to
+		 * use it for keep-alives; see, for example,
+		 * https://www.cisco.com/c/en/us/support/docs/ip/generic-routing-encapsulation-gre/118370-technote-gre-00.html#anc1
+		 */
+		ND_PRINT("keep-alive");
+		break;
+	case GRE_WCCP:
+		/*
+		 * This is a bit weird.
+		 *
+		 * This may either just mean "IPv4" or it may mean
+		 * "IPv4 preceded by a WCCP redirect header".  We
+		 * check to see if the first octet looks like the
+		 * beginning of an IPv4 header and, if not, dissect
+		 * it "IPv4 preceded by a WCCP redirect header",
+		 * otherwise we dissect it as just IPv4.
+		 *
+		 * See "Packet redirection" in draft-forster-wrec-wccp-v1-00,
+		 * section 4.12 "Traffic Forwarding" in
+		 * draft-wilson-wrec-wccp-v2-01, and section 3.12.1
+		 * "Forwarding using GRE Encapsulation" in
+		 * draft-param-wccp-v2rev1-01.
+		 */
+		ND_PRINT("wccp ");
+
+		ND_ICHECK_U(len, <, 1);
+		if (GET_U_1(bp) >> 4 != 4) {
+			/*
+			 * First octet isn't 0x4*, so it's not IPv4.
+			 */
+			const struct wccp_redirect *wccp;
+			uint8_t wccp_flags;
+
+			ND_ICHECK_ZU(len, <, sizeof(*wccp));
+			wccp = (const struct wccp_redirect *)bp;
+			wccp_flags = GET_U_1(wccp->flags);
+
+			ND_PRINT("T:%c A:%c U:%c SId:%u Alt:%u Pri:%u",
+			    (wccp_flags & WCCP_T) ? '1' : '0',
+			    (wccp_flags & WCCP_A) ? '1' : '0',
+			    (wccp_flags & WCCP_U) ? '1' : '0',
+			    GET_U_1(wccp->ServiceId),
+			    GET_U_1(wccp->AltBucket),
+			    GET_U_1(wccp->PriBucket));
+
+			bp += sizeof(*wccp);
+			len -= sizeof(*wccp);
+
+			ND_PRINT(": ");
+		}
+		/* FALLTHROUGH */
 	case ETHERTYPE_IP:
 		ip_print(ndo, bp, len);
 		break;
@@ -198,6 +284,7 @@ gre_print_0(netdissect_options *ndo, const u_char *bp, u_int length)
 		ip6_print(ndo, bp, len);
 		break;
 	case ETHERTYPE_MPLS:
+	case ETHERTYPE_MPLS_MULTI:
 		mpls_print(ndo, bp, len);
 		break;
 	case ETHERTYPE_IPX:
@@ -212,6 +299,21 @@ gre_print_0(netdissect_options *ndo, const u_char *bp, u_int length)
 	case ETHERTYPE_TEB:
 		ether_print(ndo, bp, len, ND_BYTES_AVAILABLE_AFTER(bp), NULL, NULL);
 		break;
+	case ETHERTYPE_NSH:
+		nsh_print(ndo, bp, len);
+		break;
+	case GRE_ERSPAN_I_II:
+		erspan_i_ii_print(ndo, flags, bp, len);
+		break;
+	case GRE_ERSPAN_III:
+		erspan_iii_print(ndo, bp, len);
+		break;
+	case GRE_CDP:
+		cdp_print(ndo, bp, len);
+		break;
+	case GRE_NHRP:
+		nhrp_print(ndo, bp, len);
+		break;
 	default:
 		ND_PRINT("gre-proto-0x%x", prot);
 	}
@@ -241,16 +343,48 @@ 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) {
-		uint32_t k;
+		/* Skip payload length? */
+		ND_ICHECK_U(len, <, 2);
+		ND_TCHECK_2(bp);
+		len -= 2;
+		bp += 2;
 
-		ND_ICHECK_U(len, <, 4);
-		k = GET_BE_U_4(bp);
-		ND_PRINT(", call %u", k & 0xffff);
-		len -= 4;
-		bp += 4;
-	}
+		ND_ICHECK_U(len, <, 2);
+		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
+		ND_PRINT(", (ERROR: K flag not set)");
 
 	if (flags & GRE_SP) {
 		ND_ICHECK_U(len, <, 4);
@@ -266,7 +400,10 @@ 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)
@@ -275,7 +412,10 @@ 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)
@@ -287,6 +427,13 @@ 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;