12f7a50533
There are good reasons to supports helpers in user-space instead:
* Rapid connection tracking helper development, as developing code
in user-space is usually faster.
* Reliability: A buggy helper does not crash the kernel. Moreover,
we can monitor the helper process and restart it in case of problems.
* Security: Avoid complex string matching and mangling in kernel-space
running in privileged mode. Going further, we can even think about
running user-space helpers as a non-root process.
* Extensibility: It allows the development of very specific helpers (most
likely non-standard proprietary protocols) that are very likely not to be
accepted for mainline inclusion in the form of kernel-space connection
tracking helpers.
This patch adds the infrastructure to allow the implementation of
user-space conntrack helpers by means of the new nfnetlink subsystem
`nfnetlink_cthelper' and the existing queueing infrastructure
(nfnetlink_queue).
I had to add the new hook NF_IP6_PRI_CONNTRACK_HELPER to register
ipv[4|6]_helper which results from splitting ipv[4|6]_confirm into
two pieces. This change is required not to break NAT sequence
adjustment and conntrack confirmation for traffic that is enqueued
to our user-space conntrack helpers.
Basic operation, in a few steps:
1) Register user-space helper by means of `nfct':
nfct helper add ftp inet tcp
[ It must be a valid existing helper supported by conntrack-tools ]
2) Add rules to enable the FTP user-space helper which is
used to track traffic going to TCP port 21.
For locally generated packets:
iptables -I OUTPUT -t raw -p tcp --dport 21 -j CT --helper ftp
For non-locally generated packets:
iptables -I PREROUTING -t raw -p tcp --dport 21 -j CT --helper ftp
3) Run the test conntrackd in helper mode (see example files under
doc/helper/conntrackd.conf
conntrackd
4) Generate FTP traffic going, if everything is OK, then conntrackd
should create expectations (you can check that with `conntrack':
conntrack -E expect
[NEW] 301 proto=6 src=192.168.1.136 dst=130.89.148.12 sport=0 dport=54037 mask-src=255.255.255.255 mask-dst=255.255.255.255 sport=0 dport=65535 master-src=192.168.1.136 master-dst=130.89.148.12 sport=57127 dport=21 class=0 helper=ftp
[DESTROY] 301 proto=6 src=192.168.1.136 dst=130.89.148.12 sport=0 dport=54037 mask-src=255.255.255.255 mask-dst=255.255.255.255 sport=0 dport=65535 master-src=192.168.1.136 master-dst=130.89.148.12 sport=57127 dport=21 class=0 helper=ftp
This confirms that our test helper is receiving packets including the
conntrack information, and adding expectations in kernel-space.
The user-space helper can also store its private tracking information
in the conntrack structure in the kernel via the CTA_HELP_INFO. The
kernel will consider this a binary blob whose layout is unknown. This
information will be included in the information that is transfered
to user-space via glue code that integrates nfnetlink_queue and
ctnetlink.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
79 lines
1.9 KiB
Makefile
79 lines
1.9 KiB
Makefile
header-y += ipset/
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header-y += nf_conntrack_common.h
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header-y += nf_conntrack_ftp.h
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header-y += nf_conntrack_sctp.h
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header-y += nf_conntrack_tcp.h
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header-y += nf_conntrack_tuple_common.h
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header-y += nf_nat.h
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header-y += nfnetlink.h
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header-y += nfnetlink_acct.h
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header-y += nfnetlink_compat.h
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header-y += nfnetlink_conntrack.h
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header-y += nfnetlink_cthelper.h
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header-y += nfnetlink_cttimeout.h
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header-y += nfnetlink_log.h
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header-y += nfnetlink_queue.h
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header-y += x_tables.h
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header-y += xt_AUDIT.h
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header-y += xt_CHECKSUM.h
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header-y += xt_CLASSIFY.h
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header-y += xt_CONNMARK.h
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header-y += xt_CONNSECMARK.h
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header-y += xt_CT.h
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header-y += xt_DSCP.h
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header-y += xt_IDLETIMER.h
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header-y += xt_LED.h
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header-y += xt_LOG.h
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header-y += xt_MARK.h
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header-y += xt_nfacct.h
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header-y += xt_NFLOG.h
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header-y += xt_NFQUEUE.h
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header-y += xt_RATEEST.h
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header-y += xt_SECMARK.h
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header-y += xt_TCPMSS.h
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header-y += xt_TCPOPTSTRIP.h
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header-y += xt_TEE.h
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header-y += xt_TPROXY.h
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header-y += xt_addrtype.h
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header-y += xt_cluster.h
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header-y += xt_comment.h
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header-y += xt_connbytes.h
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header-y += xt_connlimit.h
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header-y += xt_connmark.h
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header-y += xt_conntrack.h
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header-y += xt_cpu.h
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header-y += xt_dccp.h
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header-y += xt_devgroup.h
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header-y += xt_dscp.h
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header-y += xt_ecn.h
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header-y += xt_esp.h
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header-y += xt_hashlimit.h
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header-y += xt_helper.h
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header-y += xt_iprange.h
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header-y += xt_ipvs.h
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header-y += xt_length.h
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header-y += xt_limit.h
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header-y += xt_mac.h
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header-y += xt_mark.h
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header-y += xt_multiport.h
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header-y += xt_osf.h
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header-y += xt_owner.h
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header-y += xt_physdev.h
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header-y += xt_pkttype.h
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header-y += xt_policy.h
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header-y += xt_quota.h
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header-y += xt_rateest.h
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header-y += xt_realm.h
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header-y += xt_recent.h
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header-y += xt_set.h
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header-y += xt_sctp.h
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header-y += xt_socket.h
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header-y += xt_state.h
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header-y += xt_statistic.h
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header-y += xt_string.h
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header-y += xt_tcpmss.h
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header-y += xt_tcpudp.h
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header-y += xt_time.h
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header-y += xt_u32.h
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