Date: Mon, 7 Jul 2003 17:33:14 +0200 From: Toni Andjelkovic <toni@soth.at> To: Socketd <db@traceroute.dk> Cc: hackers@freebsd.org Subject: Re: 5 "Advanced" networking questions Message-ID: <20030707153314.GA1695@webboy.soth.at> In-Reply-To: <20030707012205.3103dfc8.db@traceroute.dk> References: <20030707012205.3103dfc8.db@traceroute.dk>
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On Mon, Jul 07 2003 (01:22:05 +0200), Socketd wrote: > 1. Reading "man blackhole" I found that net.inet.udp.blackhole=1 will > prevent traceroute. Is this only if the host is the end target? or will > it simply disable sending an ICMP packet when it get's a packet with > ttl=1? Look in sys/netinet/udp_usrreq.c. This flag operates on the UDP layer and doesn't interfere with TTLs. > 2. Does net.inet.icmp.drop_redirect drop all redirects? > Redirect datagrams for the Network. > Redirect datagrams for the Host. > Redirect datagrams for the Type of Service and Network. > Redirect datagrams for the Type of Service and Host. Look in sys/netinet/ip_icmp.c, it checks for icp->icmp_type, not icp->icmp_code, so all incoming ICMP packets with a type of ICMP_REDIRECT would be dropped. > 3. What is the difference between net.inet.ip.redirect and the above? Look in sys/netinet/ip_input.c. This is different from incoming redirects. > 4. There is a net.inet.icmp.maskrepl, but can you also disable > timestamp, echo request and information request messages the same way or > do I need a firewall for that? Look in sys/netinet/ip_icmp.c. You need to block these packets separately. > 5. In order to drop SYN-FIN packets, do I need to compile the kernel > with "options TCP_DROP_SYNFIN" or can I just use "tcp_drop_synfin="YES"" in > /etc/rc.conf? Is there a net.inet.tcp.?? I can use instead of the above > suggestions? Look in netinet/tcp_input.c. You need the kernel option "TCP_DROP_SYNFIN" in addition to tcp_drop_synfin="YES". Cheers, Toni
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