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https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
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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>
542 lines
14 KiB
C
542 lines
14 KiB
C
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/* (C) 1999-2001 Paul `Rusty' Russell
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* (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#include <linux/types.h>
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#include <linux/ip.h>
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#include <linux/netfilter.h>
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#include <linux/module.h>
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#include <linux/skbuff.h>
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#include <linux/icmp.h>
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#include <linux/sysctl.h>
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#include <net/route.h>
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#include <net/ip.h>
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#include <linux/netfilter_ipv4.h>
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#include <net/netfilter/nf_conntrack.h>
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#include <net/netfilter/nf_conntrack_helper.h>
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#include <net/netfilter/nf_conntrack_l4proto.h>
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#include <net/netfilter/nf_conntrack_l3proto.h>
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#include <net/netfilter/nf_conntrack_zones.h>
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#include <net/netfilter/nf_conntrack_core.h>
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#include <net/netfilter/ipv4/nf_conntrack_ipv4.h>
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#include <net/netfilter/nf_nat_helper.h>
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#include <net/netfilter/ipv4/nf_defrag_ipv4.h>
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#include <net/netfilter/nf_log.h>
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int (*nf_nat_seq_adjust_hook)(struct sk_buff *skb,
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struct nf_conn *ct,
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enum ip_conntrack_info ctinfo);
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EXPORT_SYMBOL_GPL(nf_nat_seq_adjust_hook);
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static bool ipv4_pkt_to_tuple(const struct sk_buff *skb, unsigned int nhoff,
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struct nf_conntrack_tuple *tuple)
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{
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const __be32 *ap;
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__be32 _addrs[2];
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ap = skb_header_pointer(skb, nhoff + offsetof(struct iphdr, saddr),
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sizeof(u_int32_t) * 2, _addrs);
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if (ap == NULL)
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return false;
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tuple->src.u3.ip = ap[0];
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tuple->dst.u3.ip = ap[1];
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return true;
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}
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static bool ipv4_invert_tuple(struct nf_conntrack_tuple *tuple,
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const struct nf_conntrack_tuple *orig)
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{
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tuple->src.u3.ip = orig->dst.u3.ip;
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tuple->dst.u3.ip = orig->src.u3.ip;
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return true;
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}
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static int ipv4_print_tuple(struct seq_file *s,
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const struct nf_conntrack_tuple *tuple)
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{
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return seq_printf(s, "src=%pI4 dst=%pI4 ",
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&tuple->src.u3.ip, &tuple->dst.u3.ip);
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}
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static int ipv4_get_l4proto(const struct sk_buff *skb, unsigned int nhoff,
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unsigned int *dataoff, u_int8_t *protonum)
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{
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const struct iphdr *iph;
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struct iphdr _iph;
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iph = skb_header_pointer(skb, nhoff, sizeof(_iph), &_iph);
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if (iph == NULL)
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return -NF_ACCEPT;
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/* Conntrack defragments packets, we might still see fragments
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* inside ICMP packets though. */
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if (iph->frag_off & htons(IP_OFFSET))
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return -NF_ACCEPT;
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*dataoff = nhoff + (iph->ihl << 2);
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*protonum = iph->protocol;
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/* Check bogus IP headers */
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if (*dataoff > skb->len) {
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pr_debug("nf_conntrack_ipv4: bogus IPv4 packet: "
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"nhoff %u, ihl %u, skblen %u\n",
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nhoff, iph->ihl << 2, skb->len);
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return -NF_ACCEPT;
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}
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return NF_ACCEPT;
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}
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static unsigned int ipv4_helper(unsigned int hooknum,
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struct sk_buff *skb,
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const struct net_device *in,
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const struct net_device *out,
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int (*okfn)(struct sk_buff *))
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{
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struct nf_conn *ct;
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enum ip_conntrack_info ctinfo;
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const struct nf_conn_help *help;
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const struct nf_conntrack_helper *helper;
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unsigned int ret;
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/* This is where we call the helper: as the packet goes out. */
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ct = nf_ct_get(skb, &ctinfo);
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if (!ct || ctinfo == IP_CT_RELATED_REPLY)
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return NF_ACCEPT;
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help = nfct_help(ct);
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if (!help)
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return NF_ACCEPT;
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/* rcu_read_lock()ed by nf_hook_slow */
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helper = rcu_dereference(help->helper);
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if (!helper)
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return NF_ACCEPT;
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ret = helper->help(skb, skb_network_offset(skb) + ip_hdrlen(skb),
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ct, ctinfo);
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if (ret != NF_ACCEPT && (ret & NF_VERDICT_MASK) != NF_QUEUE) {
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nf_log_packet(NFPROTO_IPV4, hooknum, skb, in, out, NULL,
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"nf_ct_%s: dropping packet", helper->name);
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}
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return ret;
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}
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static unsigned int ipv4_confirm(unsigned int hooknum,
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struct sk_buff *skb,
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const struct net_device *in,
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const struct net_device *out,
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int (*okfn)(struct sk_buff *))
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{
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struct nf_conn *ct;
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enum ip_conntrack_info ctinfo;
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ct = nf_ct_get(skb, &ctinfo);
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if (!ct || ctinfo == IP_CT_RELATED_REPLY)
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goto out;
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/* adjust seqs for loopback traffic only in outgoing direction */
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if (test_bit(IPS_SEQ_ADJUST_BIT, &ct->status) &&
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!nf_is_loopback_packet(skb)) {
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typeof(nf_nat_seq_adjust_hook) seq_adjust;
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seq_adjust = rcu_dereference(nf_nat_seq_adjust_hook);
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if (!seq_adjust || !seq_adjust(skb, ct, ctinfo)) {
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NF_CT_STAT_INC_ATOMIC(nf_ct_net(ct), drop);
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return NF_DROP;
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}
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}
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out:
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/* We've seen it coming out the other side: confirm it */
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return nf_conntrack_confirm(skb);
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}
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static unsigned int ipv4_conntrack_in(unsigned int hooknum,
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struct sk_buff *skb,
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const struct net_device *in,
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const struct net_device *out,
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int (*okfn)(struct sk_buff *))
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{
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return nf_conntrack_in(dev_net(in), PF_INET, hooknum, skb);
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}
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static unsigned int ipv4_conntrack_local(unsigned int hooknum,
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struct sk_buff *skb,
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const struct net_device *in,
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const struct net_device *out,
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int (*okfn)(struct sk_buff *))
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{
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/* root is playing with raw sockets. */
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if (skb->len < sizeof(struct iphdr) ||
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ip_hdrlen(skb) < sizeof(struct iphdr))
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return NF_ACCEPT;
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return nf_conntrack_in(dev_net(out), PF_INET, hooknum, skb);
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}
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/* Connection tracking may drop packets, but never alters them, so
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make it the first hook. */
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static struct nf_hook_ops ipv4_conntrack_ops[] __read_mostly = {
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{
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.hook = ipv4_conntrack_in,
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.owner = THIS_MODULE,
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.pf = NFPROTO_IPV4,
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.hooknum = NF_INET_PRE_ROUTING,
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.priority = NF_IP_PRI_CONNTRACK,
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},
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{
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.hook = ipv4_conntrack_local,
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.owner = THIS_MODULE,
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.pf = NFPROTO_IPV4,
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.hooknum = NF_INET_LOCAL_OUT,
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.priority = NF_IP_PRI_CONNTRACK,
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},
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{
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.hook = ipv4_helper,
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.owner = THIS_MODULE,
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.pf = NFPROTO_IPV4,
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.hooknum = NF_INET_POST_ROUTING,
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.priority = NF_IP_PRI_CONNTRACK_HELPER,
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},
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{
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.hook = ipv4_confirm,
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.owner = THIS_MODULE,
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.pf = NFPROTO_IPV4,
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.hooknum = NF_INET_POST_ROUTING,
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.priority = NF_IP_PRI_CONNTRACK_CONFIRM,
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},
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{
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.hook = ipv4_helper,
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.owner = THIS_MODULE,
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.pf = NFPROTO_IPV4,
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.hooknum = NF_INET_LOCAL_IN,
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.priority = NF_IP_PRI_CONNTRACK_HELPER,
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},
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{
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.hook = ipv4_confirm,
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.owner = THIS_MODULE,
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.pf = NFPROTO_IPV4,
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.hooknum = NF_INET_LOCAL_IN,
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.priority = NF_IP_PRI_CONNTRACK_CONFIRM,
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},
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};
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#if defined(CONFIG_SYSCTL) && defined(CONFIG_NF_CONNTRACK_PROC_COMPAT)
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static int log_invalid_proto_min = 0;
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static int log_invalid_proto_max = 255;
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static ctl_table ip_ct_sysctl_table[] = {
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{
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.procname = "ip_conntrack_max",
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.maxlen = sizeof(int),
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.mode = 0644,
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.proc_handler = proc_dointvec,
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},
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{
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.procname = "ip_conntrack_count",
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.maxlen = sizeof(int),
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.mode = 0444,
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.proc_handler = proc_dointvec,
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},
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{
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.procname = "ip_conntrack_buckets",
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.maxlen = sizeof(unsigned int),
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.mode = 0444,
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.proc_handler = proc_dointvec,
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},
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{
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.procname = "ip_conntrack_checksum",
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.maxlen = sizeof(int),
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.mode = 0644,
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.proc_handler = proc_dointvec,
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},
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{
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.procname = "ip_conntrack_log_invalid",
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.maxlen = sizeof(unsigned int),
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.mode = 0644,
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.proc_handler = proc_dointvec_minmax,
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.extra1 = &log_invalid_proto_min,
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.extra2 = &log_invalid_proto_max,
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},
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{ }
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};
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#endif /* CONFIG_SYSCTL && CONFIG_NF_CONNTRACK_PROC_COMPAT */
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/* Fast function for those who don't want to parse /proc (and I don't
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blame them). */
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/* Reversing the socket's dst/src point of view gives us the reply
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mapping. */
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static int
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getorigdst(struct sock *sk, int optval, void __user *user, int *len)
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{
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const struct inet_sock *inet = inet_sk(sk);
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const struct nf_conntrack_tuple_hash *h;
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struct nf_conntrack_tuple tuple;
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memset(&tuple, 0, sizeof(tuple));
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tuple.src.u3.ip = inet->inet_rcv_saddr;
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tuple.src.u.tcp.port = inet->inet_sport;
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tuple.dst.u3.ip = inet->inet_daddr;
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tuple.dst.u.tcp.port = inet->inet_dport;
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tuple.src.l3num = PF_INET;
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tuple.dst.protonum = sk->sk_protocol;
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/* We only do TCP and SCTP at the moment: is there a better way? */
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if (sk->sk_protocol != IPPROTO_TCP && sk->sk_protocol != IPPROTO_SCTP) {
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pr_debug("SO_ORIGINAL_DST: Not a TCP/SCTP socket\n");
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return -ENOPROTOOPT;
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}
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if ((unsigned int) *len < sizeof(struct sockaddr_in)) {
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pr_debug("SO_ORIGINAL_DST: len %d not %Zu\n",
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*len, sizeof(struct sockaddr_in));
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return -EINVAL;
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}
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h = nf_conntrack_find_get(sock_net(sk), NF_CT_DEFAULT_ZONE, &tuple);
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if (h) {
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struct sockaddr_in sin;
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struct nf_conn *ct = nf_ct_tuplehash_to_ctrack(h);
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sin.sin_family = AF_INET;
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sin.sin_port = ct->tuplehash[IP_CT_DIR_ORIGINAL]
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.tuple.dst.u.tcp.port;
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sin.sin_addr.s_addr = ct->tuplehash[IP_CT_DIR_ORIGINAL]
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.tuple.dst.u3.ip;
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memset(sin.sin_zero, 0, sizeof(sin.sin_zero));
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pr_debug("SO_ORIGINAL_DST: %pI4 %u\n",
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&sin.sin_addr.s_addr, ntohs(sin.sin_port));
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nf_ct_put(ct);
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if (copy_to_user(user, &sin, sizeof(sin)) != 0)
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return -EFAULT;
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else
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return 0;
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}
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pr_debug("SO_ORIGINAL_DST: Can't find %pI4/%u-%pI4/%u.\n",
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&tuple.src.u3.ip, ntohs(tuple.src.u.tcp.port),
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&tuple.dst.u3.ip, ntohs(tuple.dst.u.tcp.port));
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return -ENOENT;
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}
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#if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
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#include <linux/netfilter/nfnetlink.h>
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#include <linux/netfilter/nfnetlink_conntrack.h>
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static int ipv4_tuple_to_nlattr(struct sk_buff *skb,
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const struct nf_conntrack_tuple *tuple)
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{
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if (nla_put_be32(skb, CTA_IP_V4_SRC, tuple->src.u3.ip) ||
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nla_put_be32(skb, CTA_IP_V4_DST, tuple->dst.u3.ip))
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goto nla_put_failure;
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return 0;
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nla_put_failure:
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return -1;
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}
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static const struct nla_policy ipv4_nla_policy[CTA_IP_MAX+1] = {
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[CTA_IP_V4_SRC] = { .type = NLA_U32 },
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[CTA_IP_V4_DST] = { .type = NLA_U32 },
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};
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static int ipv4_nlattr_to_tuple(struct nlattr *tb[],
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struct nf_conntrack_tuple *t)
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{
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if (!tb[CTA_IP_V4_SRC] || !tb[CTA_IP_V4_DST])
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return -EINVAL;
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t->src.u3.ip = nla_get_be32(tb[CTA_IP_V4_SRC]);
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t->dst.u3.ip = nla_get_be32(tb[CTA_IP_V4_DST]);
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return 0;
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}
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static int ipv4_nlattr_tuple_size(void)
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{
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return nla_policy_len(ipv4_nla_policy, CTA_IP_MAX + 1);
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}
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#endif
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static struct nf_sockopt_ops so_getorigdst = {
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.pf = PF_INET,
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.get_optmin = SO_ORIGINAL_DST,
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.get_optmax = SO_ORIGINAL_DST+1,
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.get = &getorigdst,
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.owner = THIS_MODULE,
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};
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static int ipv4_init_net(struct net *net)
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{
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#if defined(CONFIG_SYSCTL) && defined(CONFIG_NF_CONNTRACK_PROC_COMPAT)
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struct nf_ip_net *in = &net->ct.nf_ct_proto;
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in->ctl_table = kmemdup(ip_ct_sysctl_table,
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sizeof(ip_ct_sysctl_table),
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GFP_KERNEL);
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if (!in->ctl_table)
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return -ENOMEM;
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in->ctl_table[0].data = &nf_conntrack_max;
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in->ctl_table[1].data = &net->ct.count;
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in->ctl_table[2].data = &net->ct.htable_size;
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in->ctl_table[3].data = &net->ct.sysctl_checksum;
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in->ctl_table[4].data = &net->ct.sysctl_log_invalid;
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#endif
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return 0;
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}
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struct nf_conntrack_l3proto nf_conntrack_l3proto_ipv4 __read_mostly = {
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.l3proto = PF_INET,
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.name = "ipv4",
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.pkt_to_tuple = ipv4_pkt_to_tuple,
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.invert_tuple = ipv4_invert_tuple,
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.print_tuple = ipv4_print_tuple,
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.get_l4proto = ipv4_get_l4proto,
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#if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
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.tuple_to_nlattr = ipv4_tuple_to_nlattr,
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.nlattr_tuple_size = ipv4_nlattr_tuple_size,
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.nlattr_to_tuple = ipv4_nlattr_to_tuple,
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.nla_policy = ipv4_nla_policy,
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#endif
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#if defined(CONFIG_SYSCTL) && defined(CONFIG_NF_CONNTRACK_PROC_COMPAT)
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.ctl_table_path = "net/ipv4/netfilter",
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#endif
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.init_net = ipv4_init_net,
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.me = THIS_MODULE,
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};
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|
|
|
module_param_call(hashsize, nf_conntrack_set_hashsize, param_get_uint,
|
|
&nf_conntrack_htable_size, 0600);
|
|
|
|
MODULE_ALIAS("nf_conntrack-" __stringify(AF_INET));
|
|
MODULE_ALIAS("ip_conntrack");
|
|
MODULE_LICENSE("GPL");
|
|
|
|
static int ipv4_net_init(struct net *net)
|
|
{
|
|
int ret = 0;
|
|
|
|
ret = nf_conntrack_l4proto_register(net,
|
|
&nf_conntrack_l4proto_tcp4);
|
|
if (ret < 0) {
|
|
pr_err("nf_conntrack_l4proto_tcp4 :protocol register failed\n");
|
|
goto out_tcp;
|
|
}
|
|
ret = nf_conntrack_l4proto_register(net,
|
|
&nf_conntrack_l4proto_udp4);
|
|
if (ret < 0) {
|
|
pr_err("nf_conntrack_l4proto_udp4 :protocol register failed\n");
|
|
goto out_udp;
|
|
}
|
|
ret = nf_conntrack_l4proto_register(net,
|
|
&nf_conntrack_l4proto_icmp);
|
|
if (ret < 0) {
|
|
pr_err("nf_conntrack_l4proto_icmp4 :protocol register failed\n");
|
|
goto out_icmp;
|
|
}
|
|
ret = nf_conntrack_l3proto_register(net,
|
|
&nf_conntrack_l3proto_ipv4);
|
|
if (ret < 0) {
|
|
pr_err("nf_conntrack_l3proto_ipv4 :protocol register failed\n");
|
|
goto out_ipv4;
|
|
}
|
|
return 0;
|
|
out_ipv4:
|
|
nf_conntrack_l4proto_unregister(net,
|
|
&nf_conntrack_l4proto_icmp);
|
|
out_icmp:
|
|
nf_conntrack_l4proto_unregister(net,
|
|
&nf_conntrack_l4proto_udp4);
|
|
out_udp:
|
|
nf_conntrack_l4proto_unregister(net,
|
|
&nf_conntrack_l4proto_tcp4);
|
|
out_tcp:
|
|
return ret;
|
|
}
|
|
|
|
static void ipv4_net_exit(struct net *net)
|
|
{
|
|
nf_conntrack_l3proto_unregister(net,
|
|
&nf_conntrack_l3proto_ipv4);
|
|
nf_conntrack_l4proto_unregister(net,
|
|
&nf_conntrack_l4proto_icmp);
|
|
nf_conntrack_l4proto_unregister(net,
|
|
&nf_conntrack_l4proto_udp4);
|
|
nf_conntrack_l4proto_unregister(net,
|
|
&nf_conntrack_l4proto_tcp4);
|
|
}
|
|
|
|
static struct pernet_operations ipv4_net_ops = {
|
|
.init = ipv4_net_init,
|
|
.exit = ipv4_net_exit,
|
|
};
|
|
|
|
static int __init nf_conntrack_l3proto_ipv4_init(void)
|
|
{
|
|
int ret = 0;
|
|
|
|
need_conntrack();
|
|
nf_defrag_ipv4_enable();
|
|
|
|
ret = nf_register_sockopt(&so_getorigdst);
|
|
if (ret < 0) {
|
|
printk(KERN_ERR "Unable to register netfilter socket option\n");
|
|
return ret;
|
|
}
|
|
|
|
ret = register_pernet_subsys(&ipv4_net_ops);
|
|
if (ret < 0) {
|
|
pr_err("nf_conntrack_ipv4: can't register pernet ops\n");
|
|
goto cleanup_sockopt;
|
|
}
|
|
|
|
ret = nf_register_hooks(ipv4_conntrack_ops,
|
|
ARRAY_SIZE(ipv4_conntrack_ops));
|
|
if (ret < 0) {
|
|
pr_err("nf_conntrack_ipv4: can't register hooks.\n");
|
|
goto cleanup_pernet;
|
|
}
|
|
#if defined(CONFIG_PROC_FS) && defined(CONFIG_NF_CONNTRACK_PROC_COMPAT)
|
|
ret = nf_conntrack_ipv4_compat_init();
|
|
if (ret < 0)
|
|
goto cleanup_hooks;
|
|
#endif
|
|
return ret;
|
|
#if defined(CONFIG_PROC_FS) && defined(CONFIG_NF_CONNTRACK_PROC_COMPAT)
|
|
cleanup_hooks:
|
|
nf_unregister_hooks(ipv4_conntrack_ops, ARRAY_SIZE(ipv4_conntrack_ops));
|
|
#endif
|
|
cleanup_pernet:
|
|
unregister_pernet_subsys(&ipv4_net_ops);
|
|
cleanup_sockopt:
|
|
nf_unregister_sockopt(&so_getorigdst);
|
|
return ret;
|
|
}
|
|
|
|
static void __exit nf_conntrack_l3proto_ipv4_fini(void)
|
|
{
|
|
synchronize_net();
|
|
#if defined(CONFIG_PROC_FS) && defined(CONFIG_NF_CONNTRACK_PROC_COMPAT)
|
|
nf_conntrack_ipv4_compat_fini();
|
|
#endif
|
|
nf_unregister_hooks(ipv4_conntrack_ops, ARRAY_SIZE(ipv4_conntrack_ops));
|
|
unregister_pernet_subsys(&ipv4_net_ops);
|
|
nf_unregister_sockopt(&so_getorigdst);
|
|
}
|
|
|
|
module_init(nf_conntrack_l3proto_ipv4_init);
|
|
module_exit(nf_conntrack_l3proto_ipv4_fini);
|
|
|
|
void need_ipv4_conntrack(void)
|
|
{
|
|
return;
|
|
}
|
|
EXPORT_SYMBOL_GPL(need_ipv4_conntrack);
|