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- /*
- * iptables module for DCCP protocol header matching
- *
- * (C) 2005 by Harald Welte <laforge@netfilter.org>
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License version 2 as
- * published by the Free Software Foundation.
- */
- #include <linux/module.h>
- #include <linux/skbuff.h>
- #include <linux/spinlock.h>
- #include <net/ip.h>
- #include <linux/dccp.h>
- #include <linux/netfilter/x_tables.h>
- #include <linux/netfilter/xt_dccp.h>
- #include <linux/netfilter_ipv4/ip_tables.h>
- #include <linux/netfilter_ipv6/ip6_tables.h>
- MODULE_LICENSE("GPL");
- MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
- MODULE_DESCRIPTION("Match for DCCP protocol packets");
- MODULE_ALIAS("ipt_dccp");
- #define DCCHECK(cond, option, flag, invflag) (!((flag) & (option)) \
- || (!!((invflag) & (option)) ^ (cond)))
- static unsigned char *dccp_optbuf;
- static DEFINE_SPINLOCK(dccp_buflock);
- static inline int
- dccp_find_option(u_int8_t option,
- const struct sk_buff *skb,
- unsigned int protoff,
- const struct dccp_hdr *dh,
- int *hotdrop)
- {
- /* tcp.doff is only 4 bits, ie. max 15 * 4 bytes */
- unsigned char *op;
- unsigned int optoff = __dccp_hdr_len(dh);
- unsigned int optlen = dh->dccph_doff*4 - __dccp_hdr_len(dh);
- unsigned int i;
- if (dh->dccph_doff * 4 < __dccp_hdr_len(dh)) {
- *hotdrop = 1;
- return 0;
- }
- if (!optlen)
- return 0;
- spin_lock_bh(&dccp_buflock);
- op = skb_header_pointer(skb, protoff + optoff, optlen, dccp_optbuf);
- if (op == NULL) {
- /* If we don't have the whole header, drop packet. */
- spin_unlock_bh(&dccp_buflock);
- *hotdrop = 1;
- return 0;
- }
- for (i = 0; i < optlen; ) {
- if (op[i] == option) {
- spin_unlock_bh(&dccp_buflock);
- return 1;
- }
- if (op[i] < 2)
- i++;
- else
- i += op[i+1]?:1;
- }
- spin_unlock_bh(&dccp_buflock);
- return 0;
- }
- static inline int
- match_types(const struct dccp_hdr *dh, u_int16_t typemask)
- {
- return (typemask & (1 << dh->dccph_type));
- }
- static inline int
- match_option(u_int8_t option, const struct sk_buff *skb, unsigned int protoff,
- const struct dccp_hdr *dh, int *hotdrop)
- {
- return dccp_find_option(option, skb, protoff, dh, hotdrop);
- }
- static int
- match(const struct sk_buff *skb,
- const struct net_device *in,
- const struct net_device *out,
- const struct xt_match *match,
- const void *matchinfo,
- int offset,
- unsigned int protoff,
- int *hotdrop)
- {
- const struct xt_dccp_info *info = matchinfo;
- struct dccp_hdr _dh, *dh;
- if (offset)
- return 0;
- dh = skb_header_pointer(skb, protoff, sizeof(_dh), &_dh);
- if (dh == NULL) {
- *hotdrop = 1;
- return 0;
- }
- return DCCHECK(((ntohs(dh->dccph_sport) >= info->spts[0])
- && (ntohs(dh->dccph_sport) <= info->spts[1])),
- XT_DCCP_SRC_PORTS, info->flags, info->invflags)
- && DCCHECK(((ntohs(dh->dccph_dport) >= info->dpts[0])
- && (ntohs(dh->dccph_dport) <= info->dpts[1])),
- XT_DCCP_DEST_PORTS, info->flags, info->invflags)
- && DCCHECK(match_types(dh, info->typemask),
- XT_DCCP_TYPE, info->flags, info->invflags)
- && DCCHECK(match_option(info->option, skb, protoff, dh,
- hotdrop),
- XT_DCCP_OPTION, info->flags, info->invflags);
- }
- static int
- checkentry(const char *tablename,
- const void *inf,
- const struct xt_match *match,
- void *matchinfo,
- unsigned int hook_mask)
- {
- const struct xt_dccp_info *info = matchinfo;
- return !(info->flags & ~XT_DCCP_VALID_FLAGS)
- && !(info->invflags & ~XT_DCCP_VALID_FLAGS)
- && !(info->invflags & ~info->flags);
- }
- static struct xt_match xt_dccp_match[] = {
- {
- .name = "dccp",
- .family = AF_INET,
- .checkentry = checkentry,
- .match = match,
- .matchsize = sizeof(struct xt_dccp_info),
- .proto = IPPROTO_DCCP,
- .me = THIS_MODULE,
- },
- {
- .name = "dccp",
- .family = AF_INET6,
- .checkentry = checkentry,
- .match = match,
- .matchsize = sizeof(struct xt_dccp_info),
- .proto = IPPROTO_DCCP,
- .me = THIS_MODULE,
- },
- };
- static int __init xt_dccp_init(void)
- {
- int ret;
- /* doff is 8 bits, so the maximum option size is (4*256). Don't put
- * this in BSS since DaveM is worried about locked TLB's for kernel
- * BSS. */
- dccp_optbuf = kmalloc(256 * 4, GFP_KERNEL);
- if (!dccp_optbuf)
- return -ENOMEM;
- ret = xt_register_matches(xt_dccp_match, ARRAY_SIZE(xt_dccp_match));
- if (ret)
- goto out_kfree;
- return ret;
- out_kfree:
- kfree(dccp_optbuf);
- return ret;
- }
- static void __exit xt_dccp_fini(void)
- {
- xt_unregister_matches(xt_dccp_match, ARRAY_SIZE(xt_dccp_match));
- kfree(dccp_optbuf);
- }
- module_init(xt_dccp_init);
- module_exit(xt_dccp_fini);
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