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>
56 lines
1.1 KiB
C
56 lines
1.1 KiB
C
#ifndef _NFNL_CTHELPER_H_
|
|
#define _NFNL_CTHELPER_H_
|
|
|
|
#define NFCT_HELPER_STATUS_DISABLED 0
|
|
#define NFCT_HELPER_STATUS_ENABLED 1
|
|
|
|
enum nfnl_acct_msg_types {
|
|
NFNL_MSG_CTHELPER_NEW,
|
|
NFNL_MSG_CTHELPER_GET,
|
|
NFNL_MSG_CTHELPER_DEL,
|
|
NFNL_MSG_CTHELPER_MAX
|
|
};
|
|
|
|
enum nfnl_cthelper_type {
|
|
NFCTH_UNSPEC,
|
|
NFCTH_NAME,
|
|
NFCTH_TUPLE,
|
|
NFCTH_QUEUE_NUM,
|
|
NFCTH_POLICY,
|
|
NFCTH_PRIV_DATA_LEN,
|
|
NFCTH_STATUS,
|
|
__NFCTH_MAX
|
|
};
|
|
#define NFCTH_MAX (__NFCTH_MAX - 1)
|
|
|
|
enum nfnl_cthelper_policy_type {
|
|
NFCTH_POLICY_SET_UNSPEC,
|
|
NFCTH_POLICY_SET_NUM,
|
|
NFCTH_POLICY_SET,
|
|
NFCTH_POLICY_SET1 = NFCTH_POLICY_SET,
|
|
NFCTH_POLICY_SET2,
|
|
NFCTH_POLICY_SET3,
|
|
NFCTH_POLICY_SET4,
|
|
__NFCTH_POLICY_SET_MAX
|
|
};
|
|
#define NFCTH_POLICY_SET_MAX (__NFCTH_POLICY_SET_MAX - 1)
|
|
|
|
enum nfnl_cthelper_pol_type {
|
|
NFCTH_POLICY_UNSPEC,
|
|
NFCTH_POLICY_NAME,
|
|
NFCTH_POLICY_EXPECT_MAX,
|
|
NFCTH_POLICY_EXPECT_TIMEOUT,
|
|
__NFCTH_POLICY_MAX
|
|
};
|
|
#define NFCTH_POLICY_MAX (__NFCTH_POLICY_MAX - 1)
|
|
|
|
enum nfnl_cthelper_tuple_type {
|
|
NFCTH_TUPLE_UNSPEC,
|
|
NFCTH_TUPLE_L3PROTONUM,
|
|
NFCTH_TUPLE_L4PROTONUM,
|
|
__NFCTH_TUPLE_MAX,
|
|
};
|
|
#define NFCTH_TUPLE_MAX (__NFCTH_TUPLE_MAX - 1)
|
|
|
|
#endif /* _NFNL_CTHELPER_H */
|