diff options
Diffstat (limited to 'net/netfilter/nf_conntrack_proto_gre.c')
| -rw-r--r-- | net/netfilter/nf_conntrack_proto_gre.c | 305 |
1 files changed, 305 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 00000000000..ac193ce7024 --- /dev/null +++ b/net/netfilter/nf_conntrack_proto_gre.c @@ -0,0 +1,305 @@ +/* + * 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/list.h> +#include <linux/seq_file.h> +#include <linux/in.h> +#include <linux/skbuff.h> + +#include <net/netfilter/nf_conntrack_l4proto.h> +#include <net/netfilter/nf_conntrack_helper.h> +#include <net/netfilter/nf_conntrack_core.h> +#include <linux/netfilter/nf_conntrack_proto_gre.h> +#include <linux/netfilter/nf_conntrack_pptp.h> + +#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) +#else +#define DEBUGP(x, args...) +#endif + +static DEFINE_RWLOCK(nf_ct_gre_lock); +static LIST_HEAD(gre_keymap_list); + +void nf_ct_gre_keymap_flush(void) +{ + struct list_head *pos, *n; + + write_lock_bh(&nf_ct_gre_lock); + list_for_each_safe(pos, n, &gre_keymap_list) { + list_del(pos); + kfree(pos); + } + write_unlock_bh(&nf_ct_gre_lock); +} +EXPORT_SYMBOL(nf_ct_gre_keymap_flush); + +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 nf_conntrack_tuple *t) +{ + struct nf_ct_gre_keymap *km; + __be16 key = 0; + + read_lock_bh(&nf_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(&nf_ct_gre_lock); + + DEBUGP("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 nf_conn_help *help = nfct_help(ct); + struct nf_ct_gre_keymap **kmp, *km; + + BUG_ON(strcmp(help->helper->name, "pptp")); + kmp = &help->help.ct_pptp_info.keymap[dir]; + if (*kmp) { + /* check whether it's a retransmission */ + list_for_each_entry(km, &gre_keymap_list, list) { + if (gre_key_cmpfn(km, t) && km == *kmp) + return 0; + } + DEBUGP("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; + + DEBUGP("adding new entry %p: ", km); + NF_CT_DUMP_TUPLE(&km->tuple); + + write_lock_bh(&nf_ct_gre_lock); + list_add_tail(&km->list, &gre_keymap_list); + write_unlock_bh(&nf_ct_gre_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_conn_help *help = nfct_help(ct); + enum ip_conntrack_dir dir; + + DEBUGP("entering for ct %p\n", ct); + BUG_ON(strcmp(help->helper->name, "pptp")); + + write_lock_bh(&nf_ct_gre_lock); + for (dir = IP_CT_DIR_ORIGINAL; dir < IP_CT_DIR_MAX; dir++) { + if (help->help.ct_pptp_info.keymap[dir]) { + DEBUGP("removing %p from list\n", + help->help.ct_pptp_info.keymap[dir]); + list_del(&help->help.ct_pptp_info.keymap[dir]->list); + kfree(help->help.ct_pptp_info.keymap[dir]); + help->help.ct_pptp_info.keymap[dir] = NULL; + } + } + write_unlock_bh(&nf_ct_gre_lock); +} +EXPORT_SYMBOL_GPL(nf_ct_gre_keymap_destroy); + +/* PUBLIC CONNTRACK PROTO HELPER FUNCTIONS */ + +/* invert gre part of tuple */ +static int gre_invert_tuple(struct nf_conntrack_tuple *tuple, + const struct nf_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 nf_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 "nf_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 nf_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 nf_conn *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 nf_conn *ct, + const struct sk_buff *skb, + unsigned int dataoff, + enum ip_conntrack_info ctinfo, + int pf, + unsigned int hooknum) +{ + /* 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. */ + set_bit(IPS_ASSURED_BIT, &ct->status); + nf_conntrack_event_cache(IPCT_STATUS, skb); + } else + nf_ct_refresh_acct(ct, ctinfo, skb, + ct->proto.gre.timeout); + + return NF_ACCEPT; +} + +/* Called when a new connection for this protocol found. */ +static int gre_new(struct nf_conn *ct, const struct sk_buff *skb, + unsigned int dataoff) +{ + DEBUGP(": "); + NF_CT_DUMP_TUPLE(&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 nf_conn *ct) +{ + struct nf_conn *master = ct->master; + DEBUGP(" entering\n"); + + if (!master) + DEBUGP("no master !?!\n"); + else + nf_ct_gre_keymap_destroy(master); +} + +/* protocol helper struct */ +static struct nf_conntrack_l4proto nf_conntrack_l4proto_gre4 = { + .l3proto = AF_INET, + .l4proto = 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_NF_CONNTRACK_NETLINK) || \ + defined(CONFIG_NF_CONNTRACK_NETLINK_MODULE) + .tuple_to_nfattr = nf_ct_port_tuple_to_nfattr, + .nfattr_to_tuple = nf_ct_port_nfattr_to_tuple, +#endif +}; + +static int __init nf_ct_proto_gre_init(void) +{ + return nf_conntrack_l4proto_register(&nf_conntrack_l4proto_gre4); +} + +static void nf_ct_proto_gre_fini(void) +{ + nf_conntrack_l4proto_unregister(&nf_conntrack_l4proto_gre4); + nf_ct_gre_keymap_flush(); +} + +module_init(nf_ct_proto_gre_init); +module_exit(nf_ct_proto_gre_fini); + +MODULE_LICENSE("GPL"); |