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