misc/61336: traceroute doesn't work with more than 85 hops

Mike Hibler mike at cs.utah.edu
Tue Jan 13 13:50:25 PST 2004


>Number:         61336
>Category:       misc
>Synopsis:       traceroute doesn't work with more than 85 hops
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Tue Jan 13 13:50:21 PST 2004
>Closed-Date:
>Last-Modified:
>Originator:     Mike Hibler
>Release:        4.7-RELEASE
>Organization:
University of Utah
>Environment:
>Description:
Any combination of (nhops * nprobes per hop) > 255 will fail due to a sequence number placed in the packet as 8-bits but kept internally as 32-bits.  So comparison
of what comes back in the packet (8-bits) with the internal counter (32-bits) fails.
With the default of 3 probes per hop, 85 * 3 == 255.

I know, I know, who gives a .... :-)



>How-To-Repeat:
Traceroute a host 86 hops away!
>Fix:
 Ensure that the "check" performed upon reply only uses 8-bits of sequence,
as the "prepare" function does implicitly by using outdata->seq

1060c1060
<           && (*proto->check)((u_char *)icp,seq))
---
>           && (*proto->check)((u_char *)icp, (u_char)seq))
1072c1072
<                   && (*proto->check)(inner, seq))
---
>                   && (*proto->check)(inner, (u_char)seq))

>Release-Note:
>Audit-Trail:
>Unformatted:


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