diff options
Diffstat (limited to 'net/netfilter/nf_conntrack_proto_gre.c')
| -rw-r--r-- | net/netfilter/nf_conntrack_proto_gre.c | 317 |
1 files changed, 317 insertions, 0 deletions
diff --git a/net/netfilter/nf_conntrack_proto_gre.c b/net/netfilter/nf_conntrack_proto_gre.c new file mode 100644 index 000000000..728eeb0ae --- /dev/null +++ b/net/netfilter/nf_conntrack_proto_gre.c @@ -0,0 +1,317 @@ +// 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; +} + +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 */ +}; |