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ce5f51e082
tcpdump/print-dvmrp.c
Denis Ovsienko b648875d98 DVMRP: Modernize packet parsing style. 
Remove all ND_TCHECK*() instances as redundant. Remove all improvised
snapshot end guards. Make invalid packet handling uniform and always
print the reason. Merge trivial single-use helper functions into the
code that needs them. Add more length checks. Use tok2str() to print the
message type. Lose a single-use variable in print_probe().
2020-12-04 01:35:32 +00:00

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/*
* Copyright (c) 1995, 1996
* The Regents of the University of California. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that: (1) source code distributions
* retain the above copyright notice and this paragraph in its entirety, (2)
* distributions including binary code include the above copyright notice and
* this paragraph in its entirety in the documentation or other materials
* provided with the distribution, and (3) all advertising materials mentioning
* features or use of this software display the following acknowledgement:
* ``This product includes software developed by the University of California,
* Lawrence Berkeley Laboratory and its contributors.'' Neither the name of
* the University nor the names of its contributors may be used to endorse
* or promote products derived from this software without specific prior
* written permission.
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
* WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
*/
/* \summary: Distance Vector Multicast Routing Protocol printer */
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
#include "netdissect-stdinc.h"
#include "netdissect.h"
#include "extract.h"
#include "addrtoname.h"
/*
* See: RFC 1075 and draft-ietf-idmr-dvmrp-v3
*
* DVMRP message types and flag values shamelessly stolen from
* mrouted/dvmrp.h.
*/
#define DVMRP_PROBE 1 /* for finding neighbors */
#define DVMRP_REPORT 2 /* for reporting some or all routes */
#define DVMRP_ASK_NEIGHBORS 3 /* sent by mapper, asking for a list */
/* of this router's neighbors */
#define DVMRP_NEIGHBORS 4 /* response to such a request */
#define DVMRP_ASK_NEIGHBORS2 5 /* as above, want new format reply */
#define DVMRP_NEIGHBORS2 6
#define DVMRP_PRUNE 7 /* prune message */
#define DVMRP_GRAFT 8 /* graft message */
#define DVMRP_GRAFT_ACK 9 /* graft acknowledgement */
static const struct tok dvmrp_msgtype_str[] = {
{ DVMRP_PROBE, "Probe" },
{ DVMRP_REPORT, "Report" },
{ DVMRP_ASK_NEIGHBORS, "Ask-neighbors(old)" },
{ DVMRP_NEIGHBORS, "Neighbors(old)" },
{ DVMRP_ASK_NEIGHBORS2, "Ask-neighbors2" },
{ DVMRP_NEIGHBORS2, "Neighbors2" },
{ DVMRP_PRUNE, "Prune" },
{ DVMRP_GRAFT, "Graft" },
{ DVMRP_GRAFT_ACK, "Graft-ACK" },
{ 0, NULL }
};
/*
* 'flags' byte values in DVMRP_NEIGHBORS2 reply.
*/
#define DVMRP_NF_TUNNEL 0x01 /* neighbors reached via tunnel */
#define DVMRP_NF_SRCRT 0x02 /* tunnel uses IP source routing */
#define DVMRP_NF_DOWN 0x10 /* kernel state of interface */
#define DVMRP_NF_DISABLED 0x20 /* administratively disabled */
#define DVMRP_NF_QUERIER 0x40 /* I am the subnet's querier */
static void print_probe(netdissect_options *, const u_char *, u_int);
static void print_report(netdissect_options *, const u_char *, u_int);
static void print_neighbors(netdissect_options *, const u_char *, u_int);
static void print_neighbors2(netdissect_options *, const u_char *, u_int, uint8_t, uint8_t);
void
dvmrp_print(netdissect_options *ndo,
const u_char *bp, u_int len)
{
u_char type;
uint8_t major_version, minor_version;
ndo->ndo_protocol = "dvmrp";
if (len < 8) {
ND_PRINT(" [length %u < 8]", len);
goto invalid;
}
type = GET_U_1(bp + 1);
/* Skip IGMP header */
bp += 8;
len -= 8;
ND_PRINT(" %s", tok2str(dvmrp_msgtype_str, "[type %u]", type));
switch (type) {
case DVMRP_PROBE:
if (ndo->ndo_vflag) {
print_probe(ndo, bp, len);
}
break;
case DVMRP_REPORT:
if (ndo->ndo_vflag > 1) {
print_report(ndo, bp, len);
}
break;
case DVMRP_NEIGHBORS:
print_neighbors(ndo, bp, len);
break;
case DVMRP_NEIGHBORS2:
/*
* extract version from IGMP group address field
*/
bp -= 4;
major_version = GET_U_1(bp + 3);
minor_version = GET_U_1(bp + 2);
bp += 4;
print_neighbors2(ndo, bp, len, major_version, minor_version);
break;
case DVMRP_PRUNE:
ND_PRINT(" src %s grp %s", GET_IPADDR_STRING(bp), GET_IPADDR_STRING(bp + 4));
ND_PRINT(" timer ");
unsigned_relts_print(ndo, GET_BE_U_4(bp + 8));
break;
case DVMRP_GRAFT:
ND_PRINT(" src %s grp %s", GET_IPADDR_STRING(bp), GET_IPADDR_STRING(bp + 4));
break;
case DVMRP_GRAFT_ACK:
ND_PRINT(" src %s grp %s", GET_IPADDR_STRING(bp), GET_IPADDR_STRING(bp + 4));
break;
}
return;
invalid:
nd_print_invalid(ndo);
}
static void
print_report(netdissect_options *ndo,
const u_char *bp,
u_int len)
{
uint32_t mask, origin;
u_int metric, done;
u_int i, width;
while (len > 0) {
if (len < 3) {
ND_PRINT(" [length %u < 3]", len);
goto invalid;
}
mask = (uint32_t)0xff << 24 | GET_U_1(bp) << 16 |
GET_U_1(bp + 1) << 8 | GET_U_1(bp + 2);
width = 1;
if (GET_U_1(bp))
width = 2;
if (GET_U_1(bp + 1))
width = 3;
if (GET_U_1(bp + 2))
width = 4;
ND_PRINT("\n\tMask %s", intoa(htonl(mask)));
bp += 3;
len -= 3;
do {
if (len < width + 1) {
ND_PRINT("\n\t [Truncated Report]");
goto invalid;
}
origin = 0;
for (i = 0; i < width; ++i) {
origin = origin << 8 | GET_U_1(bp);
bp++;
}
for ( ; i < 4; ++i)
origin <<= 8;
metric = GET_U_1(bp);
bp++;
done = metric & 0x80;
metric &= 0x7f;
ND_PRINT("\n\t %s metric %u", intoa(htonl(origin)),
metric);
len -= width + 1;
} while (!done);
}
return;
invalid:
nd_print_invalid(ndo);
}
static void
print_probe(netdissect_options *ndo,
const u_char *bp,
u_int len)
{
if (len < 4) {
ND_PRINT(" [full length %u < 4]", len);
goto invalid;
}
ND_PRINT(ndo->ndo_vflag > 1 ? "\n\t" : " ");
ND_PRINT("genid %u", GET_BE_U_4(bp));
if (ndo->ndo_vflag < 2)
return;
bp += 4;
len -= 4;
while (len > 0) {
if (len < 4) {
ND_PRINT("[remaining length %u < 4]", len);
goto invalid;
}
ND_PRINT("\n\tneighbor %s", GET_IPADDR_STRING(bp));
bp += 4; len -= 4;
}
return;
invalid:
nd_print_invalid(ndo);
}
static void
print_neighbors(netdissect_options *ndo,
const u_char *bp,
u_int len)
{
const u_char *laddr;
u_char metric;
u_char thresh;
int ncount;
while (len > 0) {
if (len < 7) {
ND_PRINT(" [length %u < 7]", len);
goto invalid;
}
laddr = bp;
bp += 4;
metric = GET_U_1(bp);
bp++;
thresh = GET_U_1(bp);
bp++;
ncount = GET_U_1(bp);
bp++;
len -= 7;
while (--ncount >= 0) {
if (len < 4) {
ND_PRINT(" [length %u < 4]", len);
goto invalid;
}
ND_PRINT(" [%s ->", GET_IPADDR_STRING(laddr));
ND_PRINT(" %s, (%u/%u)]",
GET_IPADDR_STRING(bp), metric, thresh);
bp += 4;
len -= 4;
}
}
return;
invalid:
nd_print_invalid(ndo);
}
static void
print_neighbors2(netdissect_options *ndo,
const u_char *bp,
u_int len, uint8_t major_version,
uint8_t minor_version)
{
const u_char *laddr;
u_char metric, thresh, flags;
int ncount;
ND_PRINT(" (v %u.%u):", major_version, minor_version);
while (len > 0) {
if (len < 8) {
ND_PRINT(" [length %u < 8]", len);
goto invalid;
}
laddr = bp;
bp += 4;
metric = GET_U_1(bp);
bp++;
thresh = GET_U_1(bp);
bp++;
flags = GET_U_1(bp);
bp++;
ncount = GET_U_1(bp);
bp++;
len -= 8;
while (--ncount >= 0 && len > 0) {
if (len < 4) {
ND_PRINT(" [length %u < 4]", len);
goto invalid;
}
ND_PRINT(" [%s -> ", GET_IPADDR_STRING(laddr));
ND_PRINT("%s (%u/%u", GET_IPADDR_STRING(bp),
metric, thresh);
if (flags & DVMRP_NF_TUNNEL)
ND_PRINT("/tunnel");
if (flags & DVMRP_NF_SRCRT)
ND_PRINT("/srcrt");
if (flags & DVMRP_NF_QUERIER)
ND_PRINT("/querier");
if (flags & DVMRP_NF_DISABLED)
ND_PRINT("/disabled");
if (flags & DVMRP_NF_DOWN)
ND_PRINT("/down");
ND_PRINT(")]");
bp += 4;
len -= 4;
}
if (ncount != -1) {
ND_PRINT(" [invalid ncount]");
goto invalid;
}
}
return;
invalid:
nd_print_invalid(ndo);
}
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