10 More Discussions You Might Find Interesting
1. Cybersecurity
Hello,
on a PC with Debian 8 I try to use a Bash script with Netfilter rules so that only traffic goes in and out that is wanted. For that I set all 3 default policies to "drop". The machine uses DHCP to get its IP, gateway and DNS. And I never checked so I was quite surprised that my... (1 Reply)
Discussion started by: SInt
1 Replies
2. AIX
Hello all,
planning to secure AIX sever by disabling insecure protocols/cipher suites; got the below requirements from secuirty team.
1.configure the server to disable support for DES and IDEA cipher suites
2.disable insecure TLS/SSL protocol support
Configure the server to... (4 Replies)
Discussion started by: Kumar7997
4 Replies
3. IP Networking
hello forum members,
What are L2 and L3 Protocols and can u brief me a bit little ie to gain a
basic knowledge.
Thanks & Regards
Rajkumar g (1 Reply)
Discussion started by: rajkumar_g
1 Replies
4. Linux
HI,
Is the Netfilter and IPtables same?
Thanks & Regards
Arun (1 Reply)
Discussion started by: Arun.Kakarla
1 Replies
5. IP Networking
OK Guys I need help.
I'm interest in P2p , can you recommend some books or sites about it
thx in advance (0 Replies)
Discussion started by: aobai
0 Replies
6. UNIX for Dummies Questions & Answers
I need suggestions for what to use.
I need all my users to be able to share files and be able to search into all their files.
I also need to control how much bandwidth they use so my network doesn't overload.
I can't have my users searching/downloading directly from each other which is my... (5 Replies)
Discussion started by: GoranX
5 Replies
7. IP Networking
what method would I use to determine which IP protocols network (0 Replies)
Discussion started by: mar mar
0 Replies
8. Programming
Hi everybody,
I have to write a module for matching in netfilter , extending the netfilter but I'm facing some problems can somebody guide me in that. I know that I need to write matching module working in kernel space and a program in userspace. I went through the HOWTO on netfilter-hacking but... (0 Replies)
Discussion started by: Trusted Penguin
0 Replies
9. UNIX for Dummies Questions & Answers
What protocol would be the best to use on a network with nt and unix servers and windows me clients?
Can SMB protocol be used to implement large networks?
What protocol can be used to make remote file systems appear as if they are local?
Quite a few questions I know, any help would be... (1 Reply)
Discussion started by: jnash
1 Replies
10. UNIX for Dummies Questions & Answers
Which network protocol is used by UNIX systems to make remote file systems appear as if they are local? (2 Replies)
Discussion started by: OLLERTON
2 Replies
CONNTRACK(8) CONNTRACK(8)
NAME
conntrack - command line interface for netfilter connection tracking
SYNOPSIS
conntrack -L [table] [options] [-z]
conntrack -G [table] parameters
conntrack -D [table] parameters
conntrack -I [table] parameters
conntrack -U [table] parameters
conntrack -E [table] [options]
conntrack -F [table]
conntrack -C [table]
conntrack -S
DESCRIPTION
conntrack provides a full featured userspace interface to the netfilter connection tracking system that is intended to replace the old
/proc/net/ip_conntrack interface. This tool can be used to search, list, inspect and maintain the connection tracking subsystem of the
Linux kernel. Using conntrack , you can dump a list of all (or a filtered selection of) currently tracked connections, delete connections
from the state table, and even add new ones.
In addition, you can also monitor connection tracking events, e.g. show an event message (one line) per newly established connection.
TABLES
The connection tracking subsystem maintains two internal tables:
conntrack:
This is the default table. It contains a list of all currently tracked connections through the system. If you don't use connection
tracking exemptions (NOTRACK iptables target), this means all connections that go through the system.
expect:
This is the table of expectations. Connection tracking expectations are the mechanism used to "expect" RELATED connections to
existing ones. Expectations are generally used by "connection tracking helpers" (sometimes called application level gateways
[ALGs]) for more complex protocols such as FTP, SIP, H.323.
OPTIONS
The options recognized by conntrack can be divided into several different groups.
COMMANDS
These options specify the particular operation to perform. Only one of them can be specified at any given time.
-L --dump
List connection tracking or expectation table
-G, --get
Search for and show a particular (matching) entry in the given table.
-D, --delete
Delete an entry from the given table.
-I, --create
Create a new entry from the given table.
-U, --update
Update an entry from the given table.
-E, --event
Display a real-time event log.
-F, --flush
Flush the whole given table
-C, --count
Show the table counter.
-S, --stats
Show the in-kernel connection tracking system statistics.
PARAMETERS
-z, --zero
Atomically zero counters after reading them. This option is only valid in combination with the "-L, --dump" command options.
-o, --output [extended,xml,timestamp,id,ktimestamp]
Display output in a certain format. With the extended output option, this tool displays the layer 3 information. With ktimestamp, it
displays the in-kernel timestamp available since 2.6.38 (you can enable it via echo 1 > /proc/sys/net/netfilter/nf_conntrack_time-
stamp).
-e, --event-mask [ALL|NEW|UPDATES|DESTROY][,...]
Set the bitmask of events that are to be generated by the in-kernel ctnetlink event code. Using this parameter, you can reduce the
event messages generated by the kernel to those types to those that you are actually interested in. This option can only be used in
conjunction with "-E, --event".
-b, --buffer-size value (in bytes)
Set the Netlink socket buffer size. This option is useful if the command line tool reports ENOBUFS errors. If you do not pass this
option, the default value available at /proc/sys/net/core/rmem_default is used. The tool reports this problem if your process is too
slow to handle all the event messages or, in other words, if the amount of events are big enough to overrun the socket buffer. Note
that using a big buffer reduces the chances to hit ENOBUFS, however, this results in more memory consumption. This option can only
be used in conjunction with "-E, --event".
FILTER PARAMETERS
-s, --orig-src IP_ADDRESS
Match only entries whose source address in the original direction equals the one specified as argument.
-d, --orig-dst IP_ADDRESS
Match only entries whose destination address in the original direction equals the one specified as argument.
-r, --reply-src IP_ADDRESS
Match only entries whose source address in the reply direction equals the one specified as argument.
-q, --reply-dst IP_ADDRESS
Match only entries whose destination address in the reply direction equals the one specified as argument.
-p, --proto PROTO
Specify layer four (TCP, UDP, ...) protocol.
-f, --family PROTO
Specify layer three (ipv4, ipv6) protocol This option is only required in conjunction with "-L, --dump". If this option is not
passed, the default layer 3 protocol will be IPv4.
-t, --timeout TIMEOUT
Specify the timeout.
-m, --mark MARK[/MASK]
Specify the conntrack mark. Optionally, a mask value can be specified. In "--update" mode, this mask specifies the bits that
should be zeroed before XORing the MARK value into the ctmark. Otherwise, the mask is logically ANDed with the existing mark before
the comparision. In "--create" mode, the mask is ignored.
-c, --secmark SECMARK
Specify the conntrack selinux security mark.
-u, --status [ASSURED|SEEN_REPLY|FIXED_TIMEOUT|EXPECTED|UNSET][,...]
Specify the conntrack status.
-n, --src-nat
Filter source NAT connections.
-g, --dst-nat
Filter destination NAT connections.
-j, --any-nat
Filter any NAT connections.
-w, --zone
Filter by conntrack zone. See iptables CT target for more information.
--tuple-src IP_ADDRESS
Specify the tuple source address of an expectation.
--tuple-dst IP_ADDRESS
Specify the tuple destination address of an expectation.
--mask-src IP_ADDRESS
Specify the source address mask of an expectation.
--mask-dst IP_ADDRESS
Specify the destination address mask of an expectation.
PROTOCOL FILTER PARAMETERS
TCP-specific fields:
--sport, --orig-port-src PORT
Source port in original direction
--dport, --orig-port-dst PORT
Destination port in original direction
--reply-port-src PORT
Source port in reply direction
--reply-port-dst PORT
Destination port in reply direction
--state [NONE | SYN_SENT | SYN_RECV | ESTABLISHED | FIN_WAIT | CLOSE_WAIT | LAST_ACK | TIME_WAIT | CLOSE | LISTEN]
TCP state
UDP-specific fields:
--sport, --orig-port-src PORT
Source port in original direction
--dport, --orig-port-dst PORT
Destination port in original direction
--reply-port-src PORT
Source port in reply direction
--reply-port-dst PORT
Destination port in reply direction
ICMP-specific fields:
--icmp-type TYPE
ICMP Type. Has to be specified numerically.
--icmp-code CODE
ICMP Code. Has to be specified numerically.
--icmp-id ID
ICMP Id. Has to be specified numerically (non-mandatory)
UDPlite-specific fields:
--sport, --orig-port-src PORT
Source port in original direction
--dport, --orig-port-dst PORT
Destination port in original direction
--reply-port-src PORT
Source port in reply direction
--reply-port-dst PORT
Destination port in reply direction
SCTP-specific fields:
--sport, --orig-port-src PORT
Source port in original direction
--dport, --orig-port-dst PORT
Destination port in original direction
--reply-port-src PORT
Source port in reply direction
--reply-port-dst PORT
Destination port in reply direction
--state [NONE | CLOSED | COOKIE_WAIT | COOKIE_ECHOED | ESTABLISHED | SHUTDOWN_SENT | SHUTDOWN_RECD | SHUTDOWN_ACK_SENT]
SCTP state
--orig-vtag value
Verification tag (32-bits value) in the original direction
--reply-vtag value
Verification tag (32-bits value) in the reply direction
DCCP-specific fields (needs Linux >= 2.6.30):
--sport, --orig-port-src PORT
Source port in original direction
--dport, --orig-port-dst PORT
Destination port in original direction
--reply-port-src PORT
Source port in reply direction
--reply-port-dst PORT
Destination port in reply direction
--state [NONE | REQUEST | RESPOND | PARTOPEN | OPEN | CLOSEREQ | CLOSING | TIMEWAIT]
DCCP state --role [client | server] Role that the original conntrack tuple is tracking
GRE-specific fields:
--srckey, --orig-key-src KEY
Source key in original direction (in hexadecimal or decimal)
--dstkey, --orig-key-dst KEY
Destination key in original direction (in hexadecimal or decimal)
--reply-key-src KEY
Source key in reply direction (in hexadecimal or decimal)
--reply-key-dst KEY
Destination key in reply direction (in hexadecimal or decimal)
DIAGNOSTICS
The exit code is 0 for correct function. Errors which appear to be caused by invalid command line parameters cause an exit code of
2. Any other errors cause an exit code of 1.
EXAMPLES
conntrack -L
Show the connection tracking table in /proc/net/ip_conntrack format
conntrack -L -o extended
Show the connection tracking table in /proc/net/nf_conntrack format
conntrack -L -o xml
Show the connection tracking table in XML
conntrack -L -f ipv6 -o extended
Only dump IPv6 connections in /proc/net/nf_conntrack format
conntrack -L --src-nat
Show source NAT connections
conntrack -E -o timestamp
Show connection events together with the timestamp
conntrack -D -s 1.2.3.4
Delete all flow whose source address is 1.2.3.4
conntrack -U -s 1.2.3.4 -m 1
Set connmark to 1 of all the flows whose source address is 1.2.3.4
BUGS
Please, report them to netfilter-devel@vger.kernel.org or file a bug in Netfilter's bugzilla (https://bugzilla.netfilter.org).
SEE ALSO
iptables(8)
See http://conntrack-tools.netfilter.org
AUTHORS
Jay Schulist, Patrick McHardy, Harald Welte and Pablo Neira Ayuso wrote the kernel-level "ctnetlink" interface that is used by the con-
ntrack tool.
Pablo Neira Ayuso wrote and maintain the conntrack tool, Harald Welte added support for conntrack based accounting counters.
Man page written by Harald Welte <laforge@netfilter.org> and Pablo Neira Ayuso <pablo@netfilter.org>.
Jul 5, 2010 CONNTRACK(8)