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- /*
- * ip_conntrack_proto_gre.c - Version 3.0
- *
- * 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/)
- *
- */
- #include <linux/module.h>
- #include <linux/types.h>
- #include <linux/timer.h>
- #include <linux/netfilter.h>
- #include <linux/ip.h>
- #include <linux/in.h>
- #include <linux/list.h>
- #include <linux/seq_file.h>
- #include <linux/interrupt.h>
- static DEFINE_RWLOCK(ip_ct_gre_lock);
- #include <linux/netfilter_ipv4/ip_conntrack_protocol.h>
- #include <linux/netfilter_ipv4/ip_conntrack_helper.h>
- #include <linux/netfilter_ipv4/ip_conntrack_core.h>
- #include <linux/netfilter_ipv4/ip_conntrack_proto_gre.h>
- #include <linux/netfilter_ipv4/ip_conntrack_pptp.h>
- MODULE_LICENSE("GPL");
- MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>");
- MODULE_DESCRIPTION("netfilter connection tracking protocol helper for GRE");
- /* shamelessly stolen from ip_conntrack_proto_udp.c */
- #define GRE_TIMEOUT (30*HZ)
- #define GRE_STREAM_TIMEOUT (180*HZ)
- #if 0
- #define DEBUGP(format, args...) printk(KERN_DEBUG "%s:%s: " format, __FILE__, __FUNCTION__, ## args)
- #define DUMP_TUPLE_GRE(x) printk("%u.%u.%u.%u:0x%x -> %u.%u.%u.%u:0x%x\n", \
- NIPQUAD((x)->src.ip), ntohs((x)->src.u.gre.key), \
- NIPQUAD((x)->dst.ip), ntohs((x)->dst.u.gre.key))
- #else
- #define DEBUGP(x, args...)
- #define DUMP_TUPLE_GRE(x)
- #endif
- /* GRE KEYMAP HANDLING FUNCTIONS */
- static LIST_HEAD(gre_keymap_list);
- static inline int gre_key_cmpfn(const struct ip_ct_gre_keymap *km,
- const struct ip_conntrack_tuple *t)
- {
- return ((km->tuple.src.ip == t->src.ip) &&
- (km->tuple.dst.ip == t->dst.ip) &&
- (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 ip_conntrack_tuple *t)
- {
- struct ip_ct_gre_keymap *km;
- __be16 key = 0;
- read_lock_bh(&ip_ct_gre_lock);
- list_for_each_entry(km, &gre_keymap_list, list) {
- if (gre_key_cmpfn(km, t)) {
- key = km->tuple.src.u.gre.key;
- break;
- }
- }
- read_unlock_bh(&ip_ct_gre_lock);
- DEBUGP("lookup src key 0x%x up key for ", key);
- DUMP_TUPLE_GRE(t);
- return key;
- }
- /* add a single keymap entry, associate with specified master ct */
- int
- ip_ct_gre_keymap_add(struct ip_conntrack *ct,
- struct ip_conntrack_tuple *t, int reply)
- {
- struct ip_ct_gre_keymap **exist_km, *km;
- if (!ct->helper || strcmp(ct->helper->name, "pptp")) {
- DEBUGP("refusing to add GRE keymap to non-pptp session\n");
- return -1;
- }
- if (!reply)
- exist_km = &ct->help.ct_pptp_info.keymap_orig;
- else
- exist_km = &ct->help.ct_pptp_info.keymap_reply;
- if (*exist_km) {
- /* check whether it's a retransmission */
- list_for_each_entry(km, &gre_keymap_list, list) {
- if (gre_key_cmpfn(km, t) && km == *exist_km)
- return 0;
- }
- DEBUGP("trying to override keymap_%s for ct %p\n",
- reply? "reply":"orig", ct);
- return -EEXIST;
- }
- km = kmalloc(sizeof(*km), GFP_ATOMIC);
- if (!km)
- return -ENOMEM;
- memcpy(&km->tuple, t, sizeof(*t));
- *exist_km = km;
- DEBUGP("adding new entry %p: ", km);
- DUMP_TUPLE_GRE(&km->tuple);
- write_lock_bh(&ip_ct_gre_lock);
- list_add_tail(&km->list, &gre_keymap_list);
- write_unlock_bh(&ip_ct_gre_lock);
- return 0;
- }
- /* destroy the keymap entries associated with specified master ct */
- void ip_ct_gre_keymap_destroy(struct ip_conntrack *ct)
- {
- DEBUGP("entering for ct %p\n", ct);
- if (!ct->helper || strcmp(ct->helper->name, "pptp")) {
- DEBUGP("refusing to destroy GRE keymap to non-pptp session\n");
- return;
- }
- write_lock_bh(&ip_ct_gre_lock);
- if (ct->help.ct_pptp_info.keymap_orig) {
- DEBUGP("removing %p from list\n",
- ct->help.ct_pptp_info.keymap_orig);
- list_del(&ct->help.ct_pptp_info.keymap_orig->list);
- kfree(ct->help.ct_pptp_info.keymap_orig);
- ct->help.ct_pptp_info.keymap_orig = NULL;
- }
- if (ct->help.ct_pptp_info.keymap_reply) {
- DEBUGP("removing %p from list\n",
- ct->help.ct_pptp_info.keymap_reply);
- list_del(&ct->help.ct_pptp_info.keymap_reply->list);
- kfree(ct->help.ct_pptp_info.keymap_reply);
- ct->help.ct_pptp_info.keymap_reply = NULL;
- }
- write_unlock_bh(&ip_ct_gre_lock);
- }
- /* PUBLIC CONNTRACK PROTO HELPER FUNCTIONS */
- /* invert gre part of tuple */
- static int gre_invert_tuple(struct ip_conntrack_tuple *tuple,
- const struct ip_conntrack_tuple *orig)
- {
- tuple->dst.u.gre.key = orig->src.u.gre.key;
- tuple->src.u.gre.key = orig->dst.u.gre.key;
- return 1;
- }
- /* gre hdr info to tuple */
- static int gre_pkt_to_tuple(const struct sk_buff *skb,
- unsigned int dataoff,
- struct ip_conntrack_tuple *tuple)
- {
- struct gre_hdr_pptp _pgrehdr, *pgrehdr;
- __be16 srckey;
- struct gre_hdr _grehdr, *grehdr;
- /* first only delinearize old RFC1701 GRE header */
- grehdr = skb_header_pointer(skb, dataoff, sizeof(_grehdr), &_grehdr);
- if (!grehdr || grehdr->version != GRE_VERSION_PPTP) {
- /* try to behave like "ip_conntrack_proto_generic" */
- tuple->src.u.all = 0;
- tuple->dst.u.all = 0;
- return 1;
- }
- /* PPTP header is variable length, only need up to the call_id field */
- pgrehdr = skb_header_pointer(skb, dataoff, 8, &_pgrehdr);
- if (!pgrehdr)
- return 1;
- if (ntohs(grehdr->protocol) != GRE_PROTOCOL_PPTP) {
- DEBUGP("GRE_VERSION_PPTP but unknown proto\n");
- return 0;
- }
- tuple->dst.u.gre.key = pgrehdr->call_id;
- srckey = gre_keymap_lookup(tuple);
- tuple->src.u.gre.key = srckey;
- return 1;
- }
- /* print gre part of tuple */
- static int gre_print_tuple(struct seq_file *s,
- const struct ip_conntrack_tuple *tuple)
- {
- return seq_printf(s, "srckey=0x%x dstkey=0x%x ",
- ntohs(tuple->src.u.gre.key),
- ntohs(tuple->dst.u.gre.key));
- }
- /* print private data for conntrack */
- static int gre_print_conntrack(struct seq_file *s,
- const struct ip_conntrack *ct)
- {
- return seq_printf(s, "timeout=%u, stream_timeout=%u ",
- (ct->proto.gre.timeout / HZ),
- (ct->proto.gre.stream_timeout / HZ));
- }
- /* Returns verdict for packet, and may modify conntrack */
- static int gre_packet(struct ip_conntrack *ct,
- const struct sk_buff *skb,
- enum ip_conntrack_info conntrackinfo)
- {
- /* If we've seen traffic both ways, this is a GRE connection.
- * Extend timeout. */
- if (ct->status & IPS_SEEN_REPLY) {
- ip_ct_refresh_acct(ct, conntrackinfo, skb,
- ct->proto.gre.stream_timeout);
- /* Also, more likely to be important, and not a probe. */
- set_bit(IPS_ASSURED_BIT, &ct->status);
- ip_conntrack_event_cache(IPCT_STATUS, skb);
- } else
- ip_ct_refresh_acct(ct, conntrackinfo, skb,
- ct->proto.gre.timeout);
- return NF_ACCEPT;
- }
- /* Called when a new connection for this protocol found. */
- static int gre_new(struct ip_conntrack *ct,
- const struct sk_buff *skb)
- {
- DEBUGP(": ");
- DUMP_TUPLE_GRE(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple);
- /* initialize to sane value. Ideally a conntrack helper
- * (e.g. in case of pptp) is increasing them */
- ct->proto.gre.stream_timeout = GRE_STREAM_TIMEOUT;
- ct->proto.gre.timeout = GRE_TIMEOUT;
- return 1;
- }
- /* Called when a conntrack entry has already been removed from the hashes
- * and is about to be deleted from memory */
- static void gre_destroy(struct ip_conntrack *ct)
- {
- struct ip_conntrack *master = ct->master;
- DEBUGP(" entering\n");
- if (!master)
- DEBUGP("no master !?!\n");
- else
- ip_ct_gre_keymap_destroy(master);
- }
- /* protocol helper struct */
- static struct ip_conntrack_protocol gre = {
- .proto = IPPROTO_GRE,
- .name = "gre",
- .pkt_to_tuple = gre_pkt_to_tuple,
- .invert_tuple = gre_invert_tuple,
- .print_tuple = gre_print_tuple,
- .print_conntrack = gre_print_conntrack,
- .packet = gre_packet,
- .new = gre_new,
- .destroy = gre_destroy,
- .me = THIS_MODULE,
- #if defined(CONFIG_IP_NF_CONNTRACK_NETLINK) || \
- defined(CONFIG_IP_NF_CONNTRACK_NETLINK_MODULE)
- .tuple_to_nfattr = ip_ct_port_tuple_to_nfattr,
- .nfattr_to_tuple = ip_ct_port_nfattr_to_tuple,
- #endif
- };
- /* ip_conntrack_proto_gre initialization */
- int __init ip_ct_proto_gre_init(void)
- {
- return ip_conntrack_protocol_register(&gre);
- }
- /* This cannot be __exit, as it is invoked from ip_conntrack_helper_pptp.c's
- * init() code on errors.
- */
- void ip_ct_proto_gre_fini(void)
- {
- struct list_head *pos, *n;
- /* delete all keymap entries */
- write_lock_bh(&ip_ct_gre_lock);
- list_for_each_safe(pos, n, &gre_keymap_list) {
- DEBUGP("deleting keymap %p at module unload time\n", pos);
- list_del(pos);
- kfree(pos);
- }
- write_unlock_bh(&ip_ct_gre_lock);
- ip_conntrack_protocol_unregister(&gre);
- }
- EXPORT_SYMBOL(ip_ct_gre_keymap_add);
- EXPORT_SYMBOL(ip_ct_gre_keymap_destroy);
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