Re: tcpdump: decode Large BGP Communities

[Stuart Henderson]

On 2016/10/12 18:44, Job Snijders wrote:
> This patch adds support to tcpdump(8) to decode Large BGP
> Communities in human readable form.
> 
> Example:
> 
>   [ snip ] BGP (UPDATE: (Path attributes: (ORIGIN[T] IGP)
>   (AS_PATH[T] 65000)
>   (NEXT_HOP[T] pxtr-2.meerval.net)
>   (COMMUNITIES[OT] 666:666 2914:0)
>   (LARGE_COMMUNITIES[OT] 2914:0:666 2914:4294927296:123))
>   (NLRI: 9.9.9.10/32)) (DF) (ttl 63, id 2806, len 138)
> 
> Kind regards,
> 
> Job

OK sthen@.


> 
> Index: src/usr.sbin/tcpdump/print-bgp.c
> ===
> RCS file: /cvs/src/usr.sbin/tcpdump/print-bgp.c,v
> retrieving revision 1.18
> diff -u -p -u -r1.18 print-bgp.c
> --- src/usr.sbin/tcpdump/print-bgp.c  20 Oct 2015 11:29:07 -  1.18
> +++ src/usr.sbin/tcpdump/print-bgp.c  12 Oct 2016 16:09:51 -
> @@ -134,6 +134,7 @@ struct bgp_attr {
>  #define BGPTYPE_EXTD_COMMUNITIES 16  /* RFC4360 */
>  #define BGPTYPE_AS4_PATH 17  /* RFC4893 */
>  #define BGPTYPE_AGGREGATOR4  18  /* RFC4893 */
> +#define BGPTYPE_LARGE_COMMUNITIES30  /* 
> draft-ietf-idr-large-community */
>  
>  #define BGP_AS_SET 1
>  #define BGP_AS_SEQUENCE2
> @@ -265,7 +266,8 @@ static const char *bgpattr_type[] = {
>   "MULTI_EXIT_DISC", "LOCAL_PREF", "ATOMIC_AGGREGATE", "AGGREGATOR",
>   "COMMUNITIES", "ORIGINATOR_ID", "CLUSTER_LIST", "DPA",
>   "ADVERTISERS", "RCID_PATH", "MP_REACH_NLRI", "MP_UNREACH_NLRI",
> - "EXTD_COMMUNITIES", "AS4_PATH", "AGGREGATOR4",
> + "EXTD_COMMUNITIES", "AS4_PATH", "AGGREGATOR4", NULL, NULL, NULL,
> + NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, "LARGE_COMMUNITIES",
>  };
>  #define bgp_attr_type(x) \
>   num_or_str(bgpattr_type, \
> @@ -544,6 +546,21 @@ bgp_attr_print(const struct bgp_attr *at
>   }
>   tlen -= 4;
>   p += 4;
> + }
> + break;
> + case BGPTYPE_LARGE_COMMUNITIES:
> + if (len == 0 || len % 12) {
> + printf(" invalid len");
> + break;
> + }
> + while (tlen>0) {
> + TCHECK2(p[0], 12);
> + printf(" %u:%u:%u",
> + EXTRACT_32BITS(p),
> + EXTRACT_32BITS(p + 4),
> + EXTRACT_32BITS(p + 8));
> + tlen -= 12;
> + p += 12;
>   }
>   break;
>   case BGPTYPE_ORIGINATOR_ID:
> 

tcpdump: decode Large BGP Communities

[Job Snijders]

This patch adds support to tcpdump(8) to decode Large BGP
Communities in human readable form.

Example:

[ snip ] BGP (UPDATE: (Path attributes: (ORIGIN[T] IGP)
(AS_PATH[T] 65000)
(NEXT_HOP[T] pxtr-2.meerval.net)
(COMMUNITIES[OT] 666:666 2914:0)
(LARGE_COMMUNITIES[OT] 2914:0:666 2914:4294927296:123))
(NLRI: 9.9.9.10/32)) (DF) (ttl 63, id 2806, len 138)

Kind regards,

Job


Index: src/usr.sbin/tcpdump/print-bgp.c
===
RCS file: /cvs/src/usr.sbin/tcpdump/print-bgp.c,v
retrieving revision 1.18
diff -u -p -u -r1.18 print-bgp.c
--- src/usr.sbin/tcpdump/print-bgp.c20 Oct 2015 11:29:07 -  1.18
+++ src/usr.sbin/tcpdump/print-bgp.c12 Oct 2016 16:09:51 -
@@ -134,6 +134,7 @@ struct bgp_attr {
 #define BGPTYPE_EXTD_COMMUNITIES   16  /* RFC4360 */
 #define BGPTYPE_AS4_PATH   17  /* RFC4893 */
 #define BGPTYPE_AGGREGATOR418  /* RFC4893 */
+#define BGPTYPE_LARGE_COMMUNITIES  30  /* 
draft-ietf-idr-large-community */
 
 #define BGP_AS_SET 1
 #define BGP_AS_SEQUENCE2
@@ -265,7 +266,8 @@ static const char *bgpattr_type[] = {
"MULTI_EXIT_DISC", "LOCAL_PREF", "ATOMIC_AGGREGATE", "AGGREGATOR",
"COMMUNITIES", "ORIGINATOR_ID", "CLUSTER_LIST", "DPA",
"ADVERTISERS", "RCID_PATH", "MP_REACH_NLRI", "MP_UNREACH_NLRI",
-   "EXTD_COMMUNITIES", "AS4_PATH", "AGGREGATOR4",
+   "EXTD_COMMUNITIES", "AS4_PATH", "AGGREGATOR4", NULL, NULL, NULL,
+   NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, "LARGE_COMMUNITIES",
 };
 #define bgp_attr_type(x) \
num_or_str(bgpattr_type, \
@@ -544,6 +546,21 @@ bgp_attr_print(const struct bgp_attr *at
}
tlen -= 4;
p += 4;
+   }
+   break;
+   case BGPTYPE_LARGE_COMMUNITIES:
+   if (len == 0 || len % 12) {
+   printf(" invalid len");
+   break;
+   }
+   while (tlen>0) {
+   TCHECK2(p[0], 12);
+   printf(" %u:%u:%u",
+   EXTRACT_32BITS(p),
+   EXTRACT_32BITS(p + 4),
+   EXTRACT_32BITS(p + 8));
+   tlen -= 12;
+   p += 12;
}
break;
case BGPTYPE_ORIGINATOR_ID: