path: root/include/linux/netfilter/nfnetlink.h
diff options
authorPablo Neira Ayuso <pablo@netfilter.org>2012-05-13 21:44:54 +0200
committerPablo Neira Ayuso <pablo@netfilter.org>2012-06-16 15:40:02 +0200
commit12f7a505331e6b2754684b509f2ac8f0011ce644 (patch)
treeda127aa83f0fdf0fc6be32c6386a304d5087c858 /include/linux/netfilter/nfnetlink.h
parentnetfilter: ctnetlink: add CTA_HELP_INFO attribute (diff)
netfilter: add user-space connection tracking helper infrastructure
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= dst= sport=0 dport=54037 mask-src= mask-dst= sport=0 dport=65535 master-src= master-dst= sport=57127 dport=21 class=0 helper=ftp [DESTROY] 301 proto=6 src= dst= sport=0 dport=54037 mask-src= mask-dst= sport=0 dport=65535 master-src= master-dst= 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>
Diffstat (limited to 'include/linux/netfilter/nfnetlink.h')
1 files changed, 2 insertions, 1 deletions
diff --git a/include/linux/netfilter/nfnetlink.h b/include/linux/netfilter/nfnetlink.h
index a1048c1587d1..18341cdb2443 100644
--- a/include/linux/netfilter/nfnetlink.h
+++ b/include/linux/netfilter/nfnetlink.h
@@ -50,7 +50,8 @@ struct nfgenmsg {
#ifdef __KERNEL__