// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Connection tracking protocol helper module for GRE.
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*
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* GRE is a generic encapsulation protocol, which is generally not very
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* suited for NAT, as it has no protocol-specific part as port numbers.
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*
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* It has an optional key field, which may help us distinguishing two
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* connections between the same two hosts.
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*
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* GRE is defined in RFC 1701 and RFC 1702, as well as RFC 2784
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*
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* PPTP is built on top of a modified version of GRE, and has a mandatory
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* field called "CallID", which serves us for the same purpose as the key
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* field in plain GRE.
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*
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* Documentation about PPTP can be found in RFC 2637
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*
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* (C) 2000-2005 by Harald Welte <laforge@gnumonks.org>
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*
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* Development of this code funded by Astaro AG (http://www.astaro.com/)
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*
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* (C) 2006-2012 Patrick McHardy <kaber@trash.net>
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*/
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#include <linux/module.h>
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#include <linux/types.h>
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#include <linux/timer.h>
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#include <linux/list.h>
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#include <linux/seq_file.h>
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#include <linux/in.h>
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#include <linux/netdevice.h>
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#include <linux/skbuff.h>
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#include <linux/slab.h>
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#include <net/dst.h>
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#include <net/net_namespace.h>
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#include <net/netns/generic.h>
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#include <net/netfilter/nf_conntrack_l4proto.h>
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#include <net/netfilter/nf_conntrack_helper.h>
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#include <net/netfilter/nf_conntrack_core.h>
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#include <net/netfilter/nf_conntrack_timeout.h>
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#include <linux/netfilter/nf_conntrack_proto_gre.h>
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#include <linux/netfilter/nf_conntrack_pptp.h>
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static const unsigned int gre_timeouts[GRE_CT_MAX] = {
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[GRE_CT_UNREPLIED] = 30*HZ,
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[GRE_CT_REPLIED] = 180*HZ,
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};
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/* used when expectation is added */
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static DEFINE_SPINLOCK(keymap_lock);
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static inline struct nf_gre_net *gre_pernet(struct net *net)
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{
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return &net->ct.nf_ct_proto.gre;
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}
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void nf_ct_gre_keymap_flush(struct net *net)
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{
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struct nf_gre_net *net_gre = gre_pernet(net);
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struct nf_ct_gre_keymap *km, *tmp;
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spin_lock_bh(&keymap_lock);
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list_for_each_entry_safe(km, tmp, &net_gre->keymap_list, list) {
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list_del_rcu(&km->list);
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kfree_rcu(km, rcu);
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}
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spin_unlock_bh(&keymap_lock);
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}
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static inline int gre_key_cmpfn(const struct nf_ct_gre_keymap *km,
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const struct nf_conntrack_tuple *t)
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{
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return km->tuple.src.l3num == t->src.l3num &&
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!memcmp(&km->tuple.src.u3, &t->src.u3, sizeof(t->src.u3)) &&
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!memcmp(&km->tuple.dst.u3, &t->dst.u3, sizeof(t->dst.u3)) &&
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km->tuple.dst.protonum == t->dst.protonum &&
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km->tuple.dst.u.all == t->dst.u.all;
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}
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/* look up the source key for a given tuple */
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static __be16 gre_keymap_lookup(struct net *net, struct nf_conntrack_tuple *t)
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{
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struct nf_gre_net *net_gre = gre_pernet(net);
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struct nf_ct_gre_keymap *km;
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__be16 key = 0;
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list_for_each_entry_rcu(km, &net_gre->keymap_list, list) {
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if (gre_key_cmpfn(km, t)) {
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key = km->tuple.src.u.gre.key;
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break;
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}
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}
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pr_debug("lookup src key 0x%x for ", key);
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nf_ct_dump_tuple(t);
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return key;
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}
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/* add a single keymap entry, associate with specified master ct */
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int nf_ct_gre_keymap_add(struct nf_conn *ct, enum ip_conntrack_dir dir,
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struct nf_conntrack_tuple *t)
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{
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struct net *net = nf_ct_net(ct);
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struct nf_gre_net *net_gre = gre_pernet(net);
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struct nf_ct_pptp_master *ct_pptp_info = nfct_help_data(ct);
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struct nf_ct_gre_keymap **kmp, *km;
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kmp = &ct_pptp_info->keymap[dir];
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if (*kmp) {
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/* check whether it's a retransmission */
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list_for_each_entry_rcu(km, &net_gre->keymap_list, list) {
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if (gre_key_cmpfn(km, t) && km == *kmp)
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return 0;
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}
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pr_debug("trying to override keymap_%s for ct %p\n",
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dir == IP_CT_DIR_REPLY ? "reply" : "orig", ct);
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return -EEXIST;
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}
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km = kmalloc(sizeof(*km), GFP_ATOMIC);
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if (!km)
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return -ENOMEM;
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memcpy(&km->tuple, t, sizeof(*t));
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*kmp = km;
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pr_debug("adding new entry %p: ", km);
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nf_ct_dump_tuple(&km->tuple);
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spin_lock_bh(&keymap_lock);
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list_add_tail(&km->list, &net_gre->keymap_list);
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spin_unlock_bh(&keymap_lock);
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return 0;
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}
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EXPORT_SYMBOL_GPL(nf_ct_gre_keymap_add);
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/* destroy the keymap entries associated with specified master ct */
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void nf_ct_gre_keymap_destroy(struct nf_conn *ct)
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{
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struct nf_ct_pptp_master *ct_pptp_info = nfct_help_data(ct);
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enum ip_conntrack_dir dir;
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pr_debug("entering for ct %p\n", ct);
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spin_lock_bh(&keymap_lock);
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for (dir = IP_CT_DIR_ORIGINAL; dir < IP_CT_DIR_MAX; dir++) {
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if (ct_pptp_info->keymap[dir]) {
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pr_debug("removing %p from list\n",
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ct_pptp_info->keymap[dir]);
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list_del_rcu(&ct_pptp_info->keymap[dir]->list);
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kfree_rcu(ct_pptp_info->keymap[dir], rcu);
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ct_pptp_info->keymap[dir] = NULL;
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}
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}
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spin_unlock_bh(&keymap_lock);
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}
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EXPORT_SYMBOL_GPL(nf_ct_gre_keymap_destroy);
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/* PUBLIC CONNTRACK PROTO HELPER FUNCTIONS */
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/* gre hdr info to tuple */
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bool gre_pkt_to_tuple(const struct sk_buff *skb, unsigned int dataoff,
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struct net *net, struct nf_conntrack_tuple *tuple)
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{
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const struct pptp_gre_header *pgrehdr;
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struct pptp_gre_header _pgrehdr;
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__be16 srckey;
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const struct gre_base_hdr *grehdr;
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struct gre_base_hdr _grehdr;
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/* first only delinearize old RFC1701 GRE header */
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grehdr = skb_header_pointer(skb, dataoff, sizeof(_grehdr), &_grehdr);
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if (!grehdr || (grehdr->flags & GRE_VERSION) != GRE_VERSION_1) {
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/* try to behave like "nf_conntrack_proto_generic" */
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tuple->src.u.all = 0;
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tuple->dst.u.all = 0;
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return true;
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}
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/* PPTP header is variable length, only need up to the call_id field */
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pgrehdr = skb_header_pointer(skb, dataoff, 8, &_pgrehdr);
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if (!pgrehdr)
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return true;
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if (grehdr->protocol != GRE_PROTO_PPP) {
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pr_debug("Unsupported GRE proto(0x%x)\n", ntohs(grehdr->protocol));
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return false;
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}
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tuple->dst.u.gre.key = pgrehdr->call_id;
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srckey = gre_keymap_lookup(net, tuple);
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tuple->src.u.gre.key = srckey;
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return true;
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}
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#ifdef CONFIG_NF_CONNTRACK_PROCFS
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/* print private data for conntrack */
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static void gre_print_conntrack(struct seq_file *s, struct nf_conn *ct)
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{
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seq_printf(s, "timeout=%u, stream_timeout=%u ",
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(ct->proto.gre.timeout / HZ),
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(ct->proto.gre.stream_timeout / HZ));
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}
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#endif
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static unsigned int *gre_get_timeouts(struct net *net)
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{
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return gre_pernet(net)->timeouts;
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}
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/* Returns verdict for packet, and may modify conntrack */
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int nf_conntrack_gre_packet(struct nf_conn *ct,
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struct sk_buff *skb,
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unsigned int dataoff,
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enum ip_conntrack_info ctinfo,
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const struct nf_hook_state *state)
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{
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if (!nf_ct_is_confirmed(ct)) {
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unsigned int *timeouts = nf_ct_timeout_lookup(ct);
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if (!timeouts)
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timeouts = gre_get_timeouts(nf_ct_net(ct));
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/* initialize to sane value. Ideally a conntrack helper
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* (e.g. in case of pptp) is increasing them */
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ct->proto.gre.stream_timeout = timeouts[GRE_CT_REPLIED];
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ct->proto.gre.timeout = timeouts[GRE_CT_UNREPLIED];
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}
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/* If we've seen traffic both ways, this is a GRE connection.
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* Extend timeout. */
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if (ct->status & IPS_SEEN_REPLY) {
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nf_ct_refresh_acct(ct, ctinfo, skb,
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ct->proto.gre.stream_timeout);
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/* Also, more likely to be important, and not a probe. */
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if (!test_and_set_bit(IPS_ASSURED_BIT, &ct->status))
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nf_conntrack_event_cache(IPCT_ASSURED, ct);
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} else
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nf_ct_refresh_acct(ct, ctinfo, skb,
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ct->proto.gre.timeout);
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return NF_ACCEPT;
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}
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#ifdef CONFIG_NF_CONNTRACK_TIMEOUT
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#include <linux/netfilter/nfnetlink.h>
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#include <linux/netfilter/nfnetlink_cttimeout.h>
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static int gre_timeout_nlattr_to_obj(struct nlattr *tb[],
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struct net *net, void *data)
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{
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unsigned int *timeouts = data;
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struct nf_gre_net *net_gre = gre_pernet(net);
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if (!timeouts)
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timeouts = gre_get_timeouts(net);
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/* set default timeouts for GRE. */
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timeouts[GRE_CT_UNREPLIED] = net_gre->timeouts[GRE_CT_UNREPLIED];
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timeouts[GRE_CT_REPLIED] = net_gre->timeouts[GRE_CT_REPLIED];
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if (tb[CTA_TIMEOUT_GRE_UNREPLIED]) {
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timeouts[GRE_CT_UNREPLIED] =
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ntohl(nla_get_be32(tb[CTA_TIMEOUT_GRE_UNREPLIED])) * HZ;
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}
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if (tb[CTA_TIMEOUT_GRE_REPLIED]) {
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timeouts[GRE_CT_REPLIED] =
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ntohl(nla_get_be32(tb[CTA_TIMEOUT_GRE_REPLIED])) * HZ;
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}
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return 0;
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}
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static int
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gre_timeout_obj_to_nlattr(struct sk_buff *skb, const void *data)
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{
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const unsigned int *timeouts = data;
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if (nla_put_be32(skb, CTA_TIMEOUT_GRE_UNREPLIED,
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htonl(timeouts[GRE_CT_UNREPLIED] / HZ)) ||
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nla_put_be32(skb, CTA_TIMEOUT_GRE_REPLIED,
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htonl(timeouts[GRE_CT_REPLIED] / HZ)))
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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 -ENOSPC;
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}
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static const struct nla_policy
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gre_timeout_nla_policy[CTA_TIMEOUT_GRE_MAX+1] = {
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[CTA_TIMEOUT_GRE_UNREPLIED] = { .type = NLA_U32 },
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[CTA_TIMEOUT_GRE_REPLIED] = { .type = NLA_U32 },
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};
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#endif /* CONFIG_NF_CONNTRACK_TIMEOUT */
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void nf_conntrack_gre_init_net(struct net *net)
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{
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struct nf_gre_net *net_gre = gre_pernet(net);
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int i;
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INIT_LIST_HEAD(&net_gre->keymap_list);
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for (i = 0; i < GRE_CT_MAX; i++)
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net_gre->timeouts[i] = gre_timeouts[i];
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}
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/* protocol helper struct */
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const struct nf_conntrack_l4proto nf_conntrack_l4proto_gre = {
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.l4proto = IPPROTO_GRE,
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#ifdef CONFIG_NF_CONNTRACK_PROCFS
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.print_conntrack = gre_print_conntrack,
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#endif
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#if IS_ENABLED(CONFIG_NF_CT_NETLINK)
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.tuple_to_nlattr = nf_ct_port_tuple_to_nlattr,
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.nlattr_tuple_size = nf_ct_port_nlattr_tuple_size,
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.nlattr_to_tuple = nf_ct_port_nlattr_to_tuple,
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.nla_policy = nf_ct_port_nla_policy,
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#endif
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#ifdef CONFIG_NF_CONNTRACK_TIMEOUT
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.ctnl_timeout = {
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.nlattr_to_obj = gre_timeout_nlattr_to_obj,
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.obj_to_nlattr = gre_timeout_obj_to_nlattr,
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.nlattr_max = CTA_TIMEOUT_GRE_MAX,
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.obj_size = sizeof(unsigned int) * GRE_CT_MAX,
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.nla_policy = gre_timeout_nla_policy,
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},
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#endif /* CONFIG_NF_CONNTRACK_TIMEOUT */
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};
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