Date: Sat, 02 Nov 1996 17:47:11 -0800 From: David Greenman <dg@root.com> To: kent@lono.nosc.mil (Kent K. Kuriyama) Cc: freebsd-bugs@freebsd.org, u651rc@emh.cpf.navy.mil, kobash@lono.nosc.mil (Sidney H. Kobashigawa) Subject: Re: Illegal options in TCP header? Message-ID: <199611030147.RAA23310@root.com> In-Reply-To: Your message of "Sat, 02 Nov 1996 15:23:06 -1000." <9611030123.AA16199@lono.nosc.mil>
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>I am running FreeBSD version 2.1.0. > >I believe that FreeBSD is inserting illegal options in the TCP header >packets which it sends out during the session negotiation phase. >Shown below is a sniffer trace of the packets sent out by the >FreeBSD box to 198.22.146.10. Notice that it sends an unknown option >3 on the TCP header. > >This causes the host at 198.22.146.10 to refuse the connection (frame >2). Now granted the host at 198.22.146.10 (system type unknown) is >the first one that refuses a connection from our FreeBSD's systems >but the sniffer trace also indicates that the FreeBSD system is sending >TCP headers with illegal options. I believe that 1 is the only valid >option defined. Conforming TCP stacks are supposed to ignore options they don't understand. There are far more than just one valid option defined. Here are a few of them: #define TCPOPT_EOL 0 #define TCPOPT_NOP 1 #define TCPOPT_MAXSEG 2 #define TCPOPT_WINDOW 3 #define TCPOPT_SACK_PERMITTED 4 /* Experimental */ #define TCPOPT_SACK 5 /* Experimental */ #define TCPOPT_TIMESTAMP 8 #define TCPOLEN_TIMESTAMP 10 You may wish to try: sysctl -w net.inet.tcp.rfc1323=0 sysctl -w net.inet.tcp.rfc1644=0 ...and see if this helps the problem. -DG David Greenman Core-team/Principal Architect, The FreeBSD Project
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