/*
* 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"
-#include <string.h>
-
+#define ND_LONGJMP_FROM_TCHECK
#include "netdissect.h"
#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_RECRS 0x0700 /* recursion count */
-#define GRE_AP 0x0080 /* acknowledgment# present */
+#include "gre.h"
static const struct tok gre_flag_values[] = {
{ GRE_CP, "checksum present"},
{ GRE_KP, "key present"},
{ GRE_SP, "sequence# present"},
{ GRE_sP, "source routing present"},
- { GRE_RECRS, "recursion count"},
{ GRE_AP, "ack present"},
{ 0, NULL }
};
+#define GRE_RECRS_MASK 0x0700 /* recursion count */
#define GRE_VERS_MASK 0x0007 /* protocol version */
/* source route entry types */
#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);
void
gre_print(netdissect_options *ndo, const u_char *bp, u_int length)
{
- u_int len = length, vers;
+ u_int vers;
ndo->ndo_protocol = "gre";
- ND_TCHECK_2(bp);
- if (len < 2)
- goto trunc;
- vers = EXTRACT_BE_U_2(bp) & GRE_VERS_MASK;
- ND_PRINT("GREv%u",vers);
-
- switch(vers) {
- case 0:
- gre_print_0(ndo, bp, len);
- break;
- case 1:
- gre_print_1(ndo, bp, len);
- break;
+ nd_print_protocol_caps(ndo);
+ ND_ICHECK_U(length, <, 2);
+ vers = GET_BE_U_2(bp) & GRE_VERS_MASK;
+ ND_PRINT("v%u",vers);
+
+ switch(vers) {
+ case 0:
+ gre_print_0(ndo, bp, length);
+ break;
+ case 1:
+ gre_print_1(ndo, bp, length);
+ break;
default:
- ND_PRINT(" ERROR: unknown-version");
- break;
- }
- return;
-
-trunc:
- nd_print_trunc(ndo);
+ ND_PRINT(" ERROR: unknown-version");
+ break;
+ }
return;
+
+invalid:
+ nd_print_invalid(ndo);
}
static void
u_int len = length;
uint16_t flags, prot;
- /* 16 bits ND_TCHECKed in gre_print() */
- flags = EXTRACT_BE_U_2(bp);
- if (ndo->ndo_vflag)
- ND_PRINT(", Flags [%s]",
- bittok2str(gre_flag_values,"none",flags));
+ ND_ICHECK_U(len, <, 2);
+ flags = GET_BE_U_2(bp);
+ if (ndo->ndo_vflag)
+ ND_PRINT(", Flags [%s]",
+ bittok2str(gre_flag_values,"none",flags));
len -= 2;
bp += 2;
- ND_TCHECK_2(bp);
- if (len < 2)
- goto trunc;
- prot = EXTRACT_BE_U_2(bp);
+ ND_ICHECK_U(len, <, 2);
+ prot = GET_BE_U_2(bp);
len -= 2;
bp += 2;
if ((flags & GRE_CP) | (flags & GRE_RP)) {
- ND_TCHECK_2(bp);
- if (len < 2)
- goto trunc;
+ uint16_t sum;
+
+ ND_ICHECK_U(len, <, 2);
+ sum = GET_BE_U_2(bp);
if (ndo->ndo_vflag)
- ND_PRINT(", sum 0x%x", EXTRACT_BE_U_2(bp));
+ ND_PRINT(", sum 0x%x", sum);
bp += 2;
len -= 2;
- ND_TCHECK_2(bp);
- if (len < 2)
- goto trunc;
- ND_PRINT(", off 0x%x", EXTRACT_BE_U_2(bp));
+ ND_ICHECK_U(len, <, 2);
+ ND_PRINT(", off 0x%x", GET_BE_U_2(bp));
bp += 2;
len -= 2;
}
if (flags & GRE_KP) {
- ND_TCHECK_4(bp);
- if (len < 4)
- goto trunc;
- ND_PRINT(", key=0x%x", EXTRACT_BE_U_4(bp));
+ uint32_t key;
+
+ ND_ICHECK_U(len, <, 4);
+ 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) {
- ND_TCHECK_4(bp);
- if (len < 4)
- goto trunc;
- ND_PRINT(", seq %u", EXTRACT_BE_U_4(bp));
+ ND_ICHECK_U(len, <, 4);
+ ND_PRINT(", seq %u", GET_BE_U_4(bp));
bp += 4;
len -= 4;
}
uint8_t sreoff;
uint8_t srelen;
- ND_TCHECK_4(bp);
- if (len < 4)
- goto trunc;
- af = EXTRACT_BE_U_2(bp);
- sreoff = EXTRACT_U_1(bp + 2);
- srelen = EXTRACT_U_1(bp + 3);
+ ND_ICHECK_U(len, <, 4);
+ af = GET_BE_U_2(bp);
+ sreoff = GET_U_1(bp + 2);
+ srelen = GET_U_1(bp + 3);
bp += 4;
len -= 4;
break;
if (!gre_sre_print(ndo, af, sreoff, srelen, bp, len))
- goto trunc;
+ goto invalid;
- if (len < srelen)
- goto trunc;
+ ND_ICHECK_U(len, <, srelen);
bp += srelen;
len -= srelen;
}
}
- if (ndo->ndo_eflag)
- ND_PRINT(", proto %s (0x%04x)",
- tok2str(ethertype_values,"unknown",prot),
- prot);
+ if (ndo->ndo_eflag)
+ ND_PRINT(", proto %s (0x%04x)",
+ tok2str(ethertype_values,"unknown",prot), prot);
- ND_PRINT(", length %u",length);
+ ND_PRINT(", length %u",length);
- if (ndo->ndo_vflag < 1)
- ND_PRINT(": "); /* put in a colon as protocol demarc */
- else
- ND_PRINT("\n\t"); /* if verbose go multiline */
+ if (ndo->ndo_vflag < 1)
+ ND_PRINT(": "); /* put in a colon as protocol demarc */
+ else
+ 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);
+ ip_print(ndo, bp, len);
break;
case ETHERTYPE_IPV6:
ip6_print(ndo, bp, len);
break;
case ETHERTYPE_MPLS:
+ case ETHERTYPE_MPLS_MULTI:
mpls_print(ndo, bp, len);
break;
case ETHERTYPE_IPX:
isoclns_print(ndo, bp, len);
break;
case ETHERTYPE_TEB:
- ether_print(ndo, bp, len, ndo->ndo_snapend - bp, NULL, NULL);
+ 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);
}
return;
-trunc:
- nd_print_trunc(ndo);
+invalid:
+ nd_print_invalid(ndo);
}
static void
u_int len = length;
uint16_t flags, prot;
- /* 16 bits ND_TCHECKed in gre_print() */
- flags = EXTRACT_BE_U_2(bp);
+ ND_ICHECK_U(len, <, 2);
+ flags = GET_BE_U_2(bp);
len -= 2;
bp += 2;
if (ndo->ndo_vflag)
- ND_PRINT(", Flags [%s]",
- bittok2str(gre_flag_values,"none",flags));
+ ND_PRINT(", Flags [%s]",
+ bittok2str(gre_flag_values,"none",flags));
- ND_TCHECK_2(bp);
- if (len < 2)
- goto trunc;
- prot = EXTRACT_BE_U_2(bp);
+ ND_ICHECK_U(len, <, 2);
+ prot = GET_BE_U_2(bp);
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_TCHECK_4(bp);
- if (len < 4)
- goto trunc;
- k = EXTRACT_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_TCHECK_4(bp);
- if (len < 4)
- goto trunc;
- ND_PRINT(", seq %u", EXTRACT_BE_U_4(bp));
+ ND_ICHECK_U(len, <, 4);
+ ND_PRINT(", seq %u", GET_BE_U_4(bp));
bp += 4;
len -= 4;
}
if (flags & GRE_AP) {
- ND_TCHECK_4(bp);
- if (len < 4)
- goto trunc;
- ND_PRINT(", ack %u", EXTRACT_BE_U_4(bp));
+ ND_ICHECK_U(len, <, 4);
+ ND_PRINT(", ack %u", GET_BE_U_4(bp));
bp += 4;
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)
- ND_PRINT(", proto %s (0x%04x)",
- tok2str(ethertype_values,"unknown",prot),
- prot);
+ if (ndo->ndo_eflag)
+ ND_PRINT(", proto %s (0x%04x)",
+ tok2str(ethertype_values,"unknown",prot), prot);
- ND_PRINT(", length %u",length);
+ ND_PRINT(", length %u",length);
- if ((flags & GRE_SP) == 0)
- return;
+ /*
+ * More non-standard EoIP behavior.
+ */
+ if (prot != GRE_MIKROTIK_EOIP && (flags & GRE_SP) == 0)
+ return;
- if (ndo->ndo_vflag < 1)
- ND_PRINT(": "); /* put in a colon as protocol demarc */
- else
- ND_PRINT("\n\t"); /* if verbose go multiline */
+ if (ndo->ndo_vflag < 1)
+ ND_PRINT(": "); /* put in a colon as protocol demarc */
+ else
+ ND_PRINT("\n\t"); /* if verbose go multiline */
switch (prot) {
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;
}
return;
-trunc:
- nd_print_trunc(ndo);
+invalid:
+ nd_print_invalid(ndo);
}
static int
gre_sre_print(netdissect_options *ndo, uint16_t af, uint8_t sreoff,
- uint8_t srelen, const u_char *bp, u_int len)
+ uint8_t srelen, const u_char *bp, u_int len)
{
int ret;
static int
gre_sre_ip_print(netdissect_options *ndo, uint8_t sreoff, uint8_t srelen,
- const u_char *bp, u_int len)
+ const u_char *bp, u_int len)
{
const u_char *up = bp;
char buf[INET_ADDRSTRLEN];
if (sreoff & 3) {
ND_PRINT(", badoffset=%u", sreoff);
- return (1);
+ goto invalid;
}
if (srelen & 3) {
ND_PRINT(", badlength=%u", srelen);
- return (1);
+ goto invalid;
}
if (sreoff >= srelen) {
ND_PRINT(", badoff/len=%u/%u", sreoff, srelen);
- return (1);
+ goto invalid;
}
while (srelen != 0) {
- if (!ND_TTEST_4(bp))
- return (0);
- if (len < 4)
- return (0);
+ ND_ICHECK_U(len, <, 4);
+ ND_TCHECK_LEN(bp, sizeof(nd_ipv4));
addrtostr(bp, buf, sizeof(buf));
ND_PRINT(" %s%s",
- ((bp - up) == sreoff) ? "*" : "", buf);
+ ((bp - up) == sreoff) ? "*" : "", buf);
bp += 4;
len -= 4;
srelen -= 4;
}
- return (1);
+ return 1;
+
+invalid:
+ return 0;
}
static int
gre_sre_asn_print(netdissect_options *ndo, uint8_t sreoff, uint8_t srelen,
- const u_char *bp, u_int len)
+ const u_char *bp, u_int len)
{
const u_char *up = bp;
if (sreoff & 1) {
ND_PRINT(", badoffset=%u", sreoff);
- return (1);
+ goto invalid;
}
if (srelen & 1) {
ND_PRINT(", badlength=%u", srelen);
- return (1);
+ goto invalid;
}
if (sreoff >= srelen) {
ND_PRINT(", badoff/len=%u/%u", sreoff, srelen);
- return (1);
+ goto invalid;
}
while (srelen != 0) {
- if (!ND_TTEST_2(bp))
- return (0);
- if (len < 2)
- return (0);
+ ND_ICHECK_U(len, <, 2);
ND_PRINT(" %s%x",
- ((bp - up) == sreoff) ? "*" : "",
- EXTRACT_BE_U_2(bp));
+ ((bp - up) == sreoff) ? "*" : "", GET_BE_U_2(bp));
bp += 2;
len -= 2;
srelen -= 2;
}
- return (1);
+ return 1;
+
+invalid:
+ return 0;
}
projects / tcpdump / blobdiff