TCP packet with RST flag not carrying DSCP

10 More Discussions You Might Find Interesting

1. Solaris

XSCF, SP and Dscp - confused.

Hi all, I understand SP is a separate processor use for management purposes. I understand XSCF is the management facility (similar to IDRAC, ILOM etc). I understand that we can create multiple domains in a SPARC machine (something like VM) and we can install OS in it. I am able to use...

2. UNIX for Dummies Questions & Answers

Get the id with specify flag

.... means multi line ddd,bug fgdrg dfdfsdfdfsd fsdfdfdfd fdfdsfdsfsd ....... flag2 ...... aaa,bug sfsfsfsfs dfdfsdfdfsd fsdfdfdfd fdfdsfdsfsd ...... flag1 ...... ddd,bug fgdrg dfdfsdfdfsd

3. Solaris

WakeOnLan, tcp packet

I'd like to use SPARC Solaris10 to 'wake up' an old PC on same LAN. what is the simplest way of doing it? (preferably without installing new software) thanks.

4. Solaris

Too much TCP retransmitted and TCP duplicate on server Oracle Solaris 10

I have problem with oracle solaris 10 running on oracle sparc T4-2 server. Os information: 5.10 Generic_150400-03 sun4v sparc sun4v Output from tcpstat.d script TCP bytes: out outRetrans in inDup inUnorder 6833763 7300 98884 0...

5. AIX

Packet loss coming with big packet size ping

6. Shell Programming and Scripting

User switching without carrying over LC_CTYPE env variable

I am using Solaris8, userA's shell '/usr/ace/prog/sdshell', AppuserB's shell '/bin/ksh'. serverT:/home/userA>LC_CTYPE=iso_8859_1; export LC_CTYPE; vtemp='userA variable'; export vtemp serverT:/home/userA>echo "LC_CTYPE=$LC_CTYPE, vtemp=$vtemp"; LC_CTYPE=iso_8859_1, vtemp=userA...

7. UNIX for Dummies Questions & Answers

'h' flag in du

Hey, all! Why is the "human readable" flag changing the behavior of du? And while I'm at it, can you make du only look at files, not directories. I often find myself wanting to find the largest file(s) in a dir or vol. Using 'find' itself, it seems you have to at least be able to guess the size of...

8. IP Networking

TCP Packet size

Hi! I'm writing an application (using BSD sockets on a Linux host) which communicates over TCP/IP with an embedded device. This embedded device has an old and real slow integrated circuit (Epson S1S6000) which handles all of the TCP/IP communication for it. Problem is, this circuit (S1S6000)...

9. Programming

Changing source port number of a TCP client packet

Hi all, I need to change the source port number of an outgoing TCP packet. First I have to bind the socket to a particular port(suppose 9001) but when I send the TCP packet I want to change the source port number lets say to 9002 still letting the socket to be bound to the same old port (9001)....

10. Red Hat

Fedora 9 lands carrying OpenJDK 6 and more for developers

Dev Fu focuses on the fresh and free OpenJDK 6 in Fedora 9 (Sulphur) because this is great news for developers. Especially developers who want to use the best software because it’s free and it doesn’t suck. However, there is much more of interest for developers than just OpenJDK: Developers...

LEARN ABOUT FREEBSD

blackhole

BLACKHOLE(4)						   BSD Kernel Interfaces Manual 					      BLACKHOLE(4)

NAME

     blackhole -- a sysctl(8) MIB for manipulating behaviour in respect of refused TCP or UDP connection attempts

SYNOPSIS

     sysctl net.inet.tcp.blackhole[=[0 | 1 | 2]]
     sysctl net.inet.udp.blackhole[=[0 | 1]]

DESCRIPTION

     The blackhole sysctl(8) MIB is used to control system behaviour when connection requests are received on TCP or UDP ports where there is no
     socket listening.

     Normal behaviour, when a TCP SYN segment is received on a port where there is no socket accepting connections, is for the system to return a
     RST segment, and drop the connection.  The connecting system will see this as a ``Connection refused''.  By setting the TCP blackhole MIB to
     a numeric value of one, the incoming SYN segment is merely dropped, and no RST is sent, making the system appear as a blackhole.  By setting
     the MIB value to two, any segment arriving on a closed port is dropped without returning a RST.  This provides some degree of protection
     against stealth port scans.

     In the UDP instance, enabling blackhole behaviour turns off the sending of an ICMP port unreachable message in response to a UDP datagram
     which arrives on a port where there is no socket listening.  It must be noted that this behaviour will prevent remote systems from running
     traceroute(8) to a system.

     The blackhole behaviour is useful to slow down anyone who is port scanning a system, attempting to detect vulnerable services on a system.
     It could potentially also slow down someone who is attempting a denial of service attack.

WARNING

     The TCP and UDP blackhole features should not be regarded as a replacement for firewall solutions.  Better security would consist of the
     blackhole sysctl(8) MIB used in conjunction with one of the available firewall packages.

     This mechanism is not a substitute for securing a system.	It should be used together with other security mechanisms.

SEE ALSO

     ip(4), tcp(4), udp(4), ipf(8), ipfw(8), pfctl(8), sysctl(8)

HISTORY

     The TCP and UDP blackhole MIBs first appeared in FreeBSD 4.0.

AUTHORS

     Geoffrey M. Rehmet

BSD
								  January 1, 2007							       BSD

IP Networking