xtables-monitor

XTABLES-MONITOR(8)              iptables 1.8.4              XTABLES-MONITOR(8)

NAME
       xtables-monitor -- show changes to rule set and trace-events

SYNOPSIS
       xtables-monitor [-t] [-e] [-4||-6]

DESCRIPTION
       xtables-monitor  is  used  to monitor changes to the ruleset or to show
       rule evaluation events for packets tagged using the TRACE target.  xta-
       bles-monitor will run until the user aborts execution, typically by us-
       ing CTRL-C.

OPTIONS
       -e, --event

       Watch for updates to the rule set.
              Updates include creation of new tables, chains and rules and the
              name of the program that caused the rule update.

       -t, --trace
              Watch  for  trace  events  generated  by  packets that have been
              tagged using the TRACE target.

       -4     Restrict output to IPv4.

       -6     Restrict output to IPv6.

EXAMPLE OUTPUT
       xtables-monitor --trace

               1 TRACE: 2 fc475095 raw:PREROUTING:rule:0x3:CONTINUE -4 -t  raw
              -A PREROUTING -p icmp -j TRACE
               2       PACKET:       0       fc475095      IN=lo      LL=0x304
              0000000000000000000000000800 SRC=127.0.0.1 DST=127.0.0.1  LEN=84
              TOS=0x0 TTL=64 ID=38349DF
               3 TRACE: 2 fc475095 raw:PREROUTING:return:
               4 TRACE: 2 fc475095 raw:PREROUTING:policy:ACCEPT
               5 TRACE: 2 fc475095 filter:INPUT:return:
               6 TRACE: 2 fc475095 filter:INPUT:policy:DROP
               7  TRACE: 2 0df9d3d8 raw:PREROUTING:rule:0x3:CONTINUE -4 -t raw
              -A PREROUTING -p icmp -j TRACE

       The first line shows a packet entering rule set evaluation.  The proto-
       col  number  is  shown (AF_INET in this case), then a packet identifier
       number that allows to correlate messages coming from rule  set  evalua-
       tion  of  this  packet.   After  this, the rule that was matched by the
       packet is shown.  This is the TRACE rule that turns on  tracing  events
       for this packet.

       The  second line dumps information about the packet. Incoming interface
       and packet headers such as source and destination addresses are shown.

       The third line shows that the packet completed traversal of the raw ta-
       ble  PREROUTING chain, and is returning, followed by use the chain pol-
       icy to make accept/drop decision (the example shows  accept  being  ap-
       plied).   The  fifth line shows that the packet leaves the filter INPUT
       chain, i.e., no rules in the filter  tables  INPUT  chain  matched  the
       packet.  It then got DROPPED by the policy of the INPUT table, as shown
       by line six.  The last line shows another packet arriving -- the packet
       id is different.

       When  using  the TRACE target, it is usually a good idea to only select
       packets that are relevant, for example via
       iptables -t raw -A PREROUTING -p tcp --dport 80 --syn -m limit --limit 1/s -j TRACE

       xtables-monitor --event
                1 EVENT: nft: NEW table: table filter ip flags 0 use 4  handle
              444
                2  EVENT:  # nft: ip filter INPUT use 2 type filter hook input
              prio 0 policy drop packets 0 bytes 0
                3 EVENT: # nft: ip filter FORWARD use 0 type filter hook  for-
              ward prio 0 policy accept packets 0 bytes 0
                4 EVENT: # nft: ip filter OUTPUT use 0 type filter hook output
              prio 0 policy accept packets 0 bytes 0
                5 EVENT: -4 -t filter -N TCP
                6 EVENT: -4 -t filter -A TCP -s 192.168.0.0/16 -p tcp  -m  tcp
              --dport 22 -j ACCEPT
                7  EVENT:  -4  -t  filter  -A TCP -p tcp -m multiport --dports
              80,443 -j ACCEPT
                8 EVENT: -4 -t filter -A INPUT -p tcp -j TCP
                9 EVENT: -4 -t filter -A  INPUT  -m  conntrack  --ctstate  RE-
              LATED,ESTABLISHED -j ACCEPT
               10 NEWGEN: GENID=13904 PID=25167 NAME=iptables-nftables-restore

       This  example shows event monitoring.  Line one shows creation of a ta-
       ble (filter in this case), followed by three base hooks INPUT,  FORWARD
       and  OUTPUT.   The  iptables-nftables  tools all create tables and base
       chains automatically when needed, so this is expected when a table  was
       not  yet initialized or when it is re-created from scratch by iptables-
       nftables-restore.  Line five shows a new user-defined chain (TCP) being
       added, followed by addition a few rules. the last line shows that a new
       ruleset generation has become active, i.e., the rule  set  changes  are
       now active.  This also lists the process id and the programs name.

LIMITATIONS
       xtables-monitor  only  works  with rules added using iptables-nftables,
       rules added using iptables-legacy cannot be monitored.

BUGS
       Should be reported or by  sending  email  to  netfilter-devel@vger.ker-
       nel.org or by filing a report on https://bugzilla.netfilter.org/.

SEE ALSO
       iptables(8), xtables(8), nft(8)

iptables 1.8.4                                              XTABLES-MONITOR(8)