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from Ananth Suryanarayana <anantha@juniper.net>:

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add full support for 4-byte AS parsing to the bgp printer
This commit is contained in:
hannes 2007-12-07 15:54:52 +00:00
parent f3d3a1bc8f
commit 31428da165
2 changed files with 87 additions and 47 deletions
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1
CREDITS
View File

@ -14,6 +14,7 @@ Additional people who have contributed patches:
Aaron Campbell <aaron@arbor.net>
Alfredo Andres <aandres@s21sec.com>
Albert Chin <china@thewrittenword.com>
Ananth Suryanarayana <anantha@juniper.net>
Andrea Bittau <a.bittau@cs.ucl.ac.uk>
Andrew Brown <atatat@atatdot.net>
Andrew Church <andrew@users.sourceforge.net>

133
print-bgp.c
View File

@ -36,7 +36,7 @@
#ifndef lint
static const char rcsid[] _U_ =
"@(#) $Header: /tcpdump/master/tcpdump/print-bgp.c,v 1.117 2007-10-05 02:00:11 guy Exp $";
"@(#) $Header: /tcpdump/master/tcpdump/print-bgp.c,v 1.118 2007-12-07 15:54:52 hannes Exp $";
#endif
#include <tcpdump-stdinc.h>
@ -145,6 +145,8 @@ struct bgp_attr {
#define BGPTYPE_MP_REACH_NLRI 14 /* RFC2283 */
#define BGPTYPE_MP_UNREACH_NLRI 15 /* RFC2283 */
#define BGPTYPE_EXTD_COMMUNITIES 16 /* draft-ietf-idr-bgp-ext-communities */
#define BGPTYPE_AS4_PATH 17 /* RFC4893 */
#define BGPTYPE_AGGREGATOR4 18 /* RFC4893 */
#define BGPTYPE_PMSI_TUNNEL 22 /* draft-ietf-l3vpn-2547bis-mcast-bgp-02.txt */
#define BGPTYPE_ATTR_SET 128 /* draft-marques-ppvpn-ibgp */
@ -153,11 +155,13 @@ struct bgp_attr {
static struct tok bgp_attr_values[] = {
{ BGPTYPE_ORIGIN, "Origin"},
{ BGPTYPE_AS_PATH, "AS Path"},
{ BGPTYPE_AS4_PATH, "AS4 Path"},
{ BGPTYPE_NEXT_HOP, "Next Hop"},
{ BGPTYPE_MULTI_EXIT_DISC, "Multi Exit Discriminator"},
{ BGPTYPE_LOCAL_PREF, "Local Preference"},
{ BGPTYPE_ATOMIC_AGGREGATE, "Atomic Aggregate"},
{ BGPTYPE_AGGREGATOR, "Aggregator"},
{ BGPTYPE_AGGREGATOR4, "Aggregator4"},
{ BGPTYPE_COMMUNITIES, "Community"},
{ BGPTYPE_ORIGINATOR_ID, "Originator ID"},
{ BGPTYPE_CLUSTER_LIST, "Cluster List"},
@ -178,13 +182,8 @@ static struct tok bgp_attr_values[] = {
#define BGP_CONFED_AS_SEQUENCE 3 /* draft-ietf-idr-rfc3065bis-01 */
#define BGP_CONFED_AS_SET 4 /* draft-ietf-idr-rfc3065bis-01 */
static int bgp_as_path_segment_known[] = {
BGP_AS_SEQUENCE,
BGP_AS_SET,
BGP_CONFED_AS_SEQUENCE,
BGP_CONFED_AS_SET,
0
};
#define BGP_AS_SEG_TYPE_MIN BGP_AS_SET
#define BGP_AS_SEG_TYPE_MAX BGP_CONFED_AS_SET
static struct tok bgp_as_path_segment_open_values[] = {
{ BGP_AS_SEQUENCE, ""},
@ -1102,31 +1101,60 @@ trunc:
}
/*
* Check for 4-byte ASN's, as per RFC 4893.
* bgp_attr_get_as_size
*
* Try to find the size of the ASs encoded in an as-path. It is not obvious, as
* both Old speakers that do not support 4 byte AS, and the new speakers that do
* support, exchange AS-Path with the same path-attribute type value 0x02.
*/
static int
check_asnbytes(const u_char *tptr, const u_char *mptr, int asnlen)
bgp_attr_get_as_size (u_int8_t bgpa_type, const u_char *pptr, int len)
{
int *kptr;
const u_char *tptr = pptr;
while (tptr < mptr) {
TCHECK(tptr[0]);
kptr = bgp_as_path_segment_known;
while (kptr[0] != 0) {
if (kptr[0] == tptr[0])
break;
++kptr;
}
if (kptr[0] == 0)
goto trunc;
TCHECK(tptr[1]);
tptr += 2 + tptr[1] * asnlen;
}
if (tptr == mptr)
return 1;
/*
* If the path attribute is the optional AS4 path type, then we already
* know, that ASs must be encoded in 4 byte format.
*/
if (bgpa_type == BGPTYPE_AS4_PATH) {
return 4;
}
/*
* Let us assume that ASs are of 2 bytes in size, and check if the AS-Path
* TLV is good. If not, ask the caller to try with AS encoded as 4 bytes
* each.
*/
while (tptr < pptr + len) {
TCHECK(tptr[0]);
/*
* If we do not find a valid segment type, our guess might be wrong.
*/
if (tptr[0] < BGP_AS_SEG_TYPE_MIN || tptr[0] > BGP_AS_SEG_TYPE_MAX) {
goto trunc;
}
TCHECK(tptr[1]);
tptr += 2 + tptr[1] * 2;
}
/*
* If we correctly reached end of the AS path attribute data content,
* then most likely ASs were indeed encoded as 2 bytes.
*/
if (tptr == pptr + len) {
return 2;
}
trunc:
return 0;
/*
* We can come here, either we did not have enough data, or if we
* try to decode 4 byte ASs in 2 byte format. Either way, return 4,
* so that calller can try to decode each AS as of 4 bytes. If indeed
* there was not enough data, it will crib and end the parse anyways.
*/
return 4;
}
static int
@ -1144,7 +1172,7 @@ bgp_attr_print(const struct bgp_attr *attr, const u_char *pptr, int len)
const u_char *tptr;
char buf[MAXHOSTNAMELEN + 100];
char tokbuf[TOKBUFSIZE];
int asn4bytes;
int as_size;
tptr = pptr;
tlen=len;
@ -1162,6 +1190,11 @@ bgp_attr_print(const struct bgp_attr *attr, const u_char *pptr, int len)
}
break;
/*
* Process AS4 byte path and AS2 byte path attributes here.
*/
case BGPTYPE_AS4_PATH:
case BGPTYPE_AS_PATH:
if (len % 2) {
printf("invalid len");
@ -1172,36 +1205,33 @@ bgp_attr_print(const struct bgp_attr *attr, const u_char *pptr, int len)
break;
}
asn4bytes = 0;
if (!check_asnbytes(tptr, pptr+len, 2) &&
check_asnbytes(tptr, pptr+len, 4))
asn4bytes = 1;
/*
* BGP updates exchanged between New speakers that support 4
* byte AS, ASs are always encoded in 4 bytes. There is no
* definitive way to find this, just by the packet's
* contents. So, check for packet's TLV's sanity assuming
* 2 bytes first, and it does not pass, assume that ASs are
* encoded in 4 bytes format and move on.
*/
as_size = bgp_attr_get_as_size(attr->bgpa_type, pptr, len);
while (tptr < pptr + len) {
TCHECK(tptr[0]);
printf("%s", tok2strbuf(bgp_as_path_segment_open_values,
"?", tptr[0],
tokbuf, sizeof(tokbuf)));
TCHECK(tptr[1]);
if (asn4bytes == 0) {
for (i = 0; i < tptr[1] * 2; i += 2) {
TCHECK2(tptr[2 + i], 2);
printf("%u ", EXTRACT_16BITS(&tptr[2 + i]));
}
} else {
for (i = 0; i < tptr[1] * 4; i += 4) {
TCHECK2(tptr[2 + i], 4);
printf("%u.%u ", EXTRACT_16BITS(&tptr[2 + i]), EXTRACT_16BITS(&tptr[4 + i]));
}
for (i = 0; i < tptr[1] * as_size; i += as_size) {
TCHECK2(tptr[2 + i], as_size);
printf("%u ",
as_size == 2 ? EXTRACT_16BITS(&tptr[2 + i]) :
EXTRACT_32BITS(&tptr[2 + i]));
}
TCHECK(tptr[0]);
printf("%s", tok2strbuf(bgp_as_path_segment_close_values,
"?", tptr[0],
tokbuf, sizeof(tokbuf)));
TCHECK(tptr[1]);
if (asn4bytes == 0)
tptr += 2 + tptr[1] * 2;
else
tptr += 2 + tptr[1] * 4;
tptr += 2 + tptr[1] * as_size;
}
break;
case BGPTYPE_NEXT_HOP:
@ -1234,6 +1264,15 @@ bgp_attr_print(const struct bgp_attr *attr, const u_char *pptr, int len)
printf(" AS #%u, origin %s", EXTRACT_16BITS(tptr),
getname(tptr + 2));
break;
case BGPTYPE_AGGREGATOR4:
if (len != 8) {
printf("invalid len");
break;
}
TCHECK2(tptr[0], 8);
printf(" AS #%u, origin %s", EXTRACT_32BITS(tptr),
getname(tptr + 4));
break;
case BGPTYPE_COMMUNITIES:
if (len % 4) {
printf("invalid len");