[quagga-users 14817] Re: BGP type 2 length 3302 is too large, attribute total length is 2308.

On Sat, Sep 30, 2017 at 5:45 PM, William Herrin <[email protected]> wrote:

> While we wait for the patch to be rolled out, the myriad distros to
> release it and then wait for a decade's worth of Quagga users to update
> their software, is there anything I can do to discard the malformed
> advertisement with the stupidly long AS path when I _receive_ it instead of
> flapping the BGP session every 30 seconds?
>

Howdy,

It was pointed out to me in another forum:
https://tools.ietf.org/html/rfc7606#section-7.2

"An AS_PATH is considered malformed if [...]

There is an overrun where the Path Segment Length field of the last segment
encountered would cause the Attribute Length to be exceeded.

[...]

An UPDATE message with a malformed AS_PATH attribute SHALL be handled using
the approach of "treat-as-withdraw"."

Any chance of getting a patch to Quagga that makes it comply? I tried
editing bgp_attr.c to:

      if (attr_endp > endp)
        {
          zlog (peer->log, LOG_WARNING,
                "%s: BGP type %d length %d is too large, attribute total
length is %d.  attr_endp is %p.  endp is %p", peer->host, type, length,
size, attr_endp, endp);
          if (type==2) { /* bad AS path, log and move on. */
            zlog (peer->log, LOG_WARNING,
                "%s: BGP Attribute %s, parse error - treating as
withdrawal",
                peer->host,
                LOOKUP (attr_str, type));
            return BGP_ATTR_PARSE_WITHDRAW;
          }
          bgp_notify_send (peer,
                           BGP_NOTIFY_UPDATE_ERR,
                           BGP_NOTIFY_UPDATE_ATTR_LENG_ERR);
          return BGP_ATTR_PARSE_ERROR;
        }

But that didn't get the job done so I guess there's more to it than that.

Regards,
Bill Herrin


-- 
William Herrin ................ herrin-n7Wb/xkVUn1Wk0Htik3J/[email protected]  [email protected]
Dirtside Systems ......... Web: <http://www.dirtside.com/>

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