Subject: Re: bin/34733
To: None <gnats-admin@netbsd.org, netbsd-bugs@netbsd.org,>
From: Brian A. Seklecki <bseklecki@collaborativefusion.com>
List: netbsd-bugs
Date: 12/19/2006 20:15:05
The following reply was made to PR bin/34733; it has been noted by GNATS.

From: "Brian A. Seklecki" <bseklecki@collaborativefusion.com>
To: gnats-bugs@NetBSD.org
Cc: gnats-admin@netbsd.org, netbsd-bugs@netbsd.org
Subject: Re: bin/34733
Date: Tue, 19 Dec 2006 15:12:14 -0500

 Right; this is on a profiled system w/ :
 
 mk.conf(5)
 USE_INET6=no
 MKINET6=no
 NO_INET6=yes
 
 So the problem only surfaces because the 96byte Snaplen is required for
 both IPv6 _and_ CARP, and since CARP can work in IPv4-only environments,
 it is a rare bug, but almost certainly warrants either:
 
 -) run-time instead of compile-time checks
 -) changing the default snaplen globally 
 
 ...which doesn't seem like it'll have an detrimental performance impact
 other than extremely high volume ipv4-only sites (which are probably
 using libpcap/tcpdump from pkgsrc anyway)
 
 ~BAS
 
 > 
 >  src/dist/tcpdump/interface.h has:
 >  
 >  /*
 >   * The default snapshot length.  This value allows most printers to print
 >   * useful information while keeping the amount of unwanted data down.
 >   */
 >  #ifndef INET6
 >  #define DEFAULT_SNAPLEN 68      /* ether + IPv4 + TCP + 14 */
 >  #else
 >  #define DEFAULT_SNAPLEN 96      /* ether + IPv6 + TCP + 22 */
 >  #endif
 >  
 >  I wonder where the problem is.
 >  INET6 is defined in src/usr.sbin/tcpdump/Makefile
 >  
 >  Do you have USE_INET6=no??
 >  
 > 
 > 
 > 
 > 
 > 
 > 
 -- 
 Brian A. Seklecki <bseklecki@collaborativefusion.com>
 Collaborative Fusion, Inc.