diff options
Diffstat (limited to 'net/netfilter/xt_dccp.c')
| -rw-r--r-- | net/netfilter/xt_dccp.c | 181 |
1 files changed, 181 insertions, 0 deletions
diff --git a/net/netfilter/xt_dccp.c b/net/netfilter/xt_dccp.c new file mode 100644 index 0000000..e5d3e86 --- /dev/null +++ b/net/netfilter/xt_dccp.c @@ -0,0 +1,181 @@ +/* + * 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("Xtables: DCCP protocol packet match"); +MODULE_ALIAS("ipt_dccp"); +MODULE_ALIAS("ip6t_dccp"); + +#define DCCHECK(cond, option, flag, invflag) (!((flag) & (option)) \ + || (!!((invflag) & (option)) ^ (cond))) + +static unsigned char *dccp_optbuf; +static DEFINE_SPINLOCK(dccp_buflock); + +static inline bool +dccp_find_option(u_int8_t option, + const struct sk_buff *skb, + unsigned int protoff, + const struct dccp_hdr *dh, + bool *hotdrop) +{ + /* tcp.doff is only 4 bits, ie. max 15 * 4 bytes */ + const 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 = true; + return false; + } + + if (!optlen) + return false; + + 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 = true; + return false; + } + + for (i = 0; i < optlen; ) { + if (op[i] == option) { + spin_unlock_bh(&dccp_buflock); + return true; + } + + if (op[i] < 2) + i++; + else + i += op[i+1]?:1; + } + + spin_unlock_bh(&dccp_buflock); + return false; +} + + +static inline bool +match_types(const struct dccp_hdr *dh, u_int16_t typemask) +{ + return typemask & (1 << dh->dccph_type); +} + +static inline bool +match_option(u_int8_t option, const struct sk_buff *skb, unsigned int protoff, + const struct dccp_hdr *dh, bool *hotdrop) +{ + return dccp_find_option(option, skb, protoff, dh, hotdrop); +} + +static bool +dccp_mt(const struct sk_buff *skb, const struct xt_match_param *par) +{ + const struct xt_dccp_info *info = par->matchinfo; + const struct dccp_hdr *dh; + struct dccp_hdr _dh; + + if (par->fragoff != 0) + return false; + + dh = skb_header_pointer(skb, par->thoff, sizeof(_dh), &_dh); + if (dh == NULL) { + *par->hotdrop = true; + return false; + } + + 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, par->thoff, dh, + par->hotdrop), + XT_DCCP_OPTION, info->flags, info->invflags); +} + +static bool dccp_mt_check(const struct xt_mtchk_param *par) +{ + const struct xt_dccp_info *info = par->matchinfo; + + return !(info->flags & ~XT_DCCP_VALID_FLAGS) + && !(info->invflags & ~XT_DCCP_VALID_FLAGS) + && !(info->invflags & ~info->flags); +} + +static struct xt_match dccp_mt_reg[] __read_mostly = { + { + .name = "dccp", + .family = NFPROTO_IPV4, + .checkentry = dccp_mt_check, + .match = dccp_mt, + .matchsize = sizeof(struct xt_dccp_info), + .proto = IPPROTO_DCCP, + .me = THIS_MODULE, + }, + { + .name = "dccp", + .family = NFPROTO_IPV6, + .checkentry = dccp_mt_check, + .match = dccp_mt, + .matchsize = sizeof(struct xt_dccp_info), + .proto = IPPROTO_DCCP, + .me = THIS_MODULE, + }, +}; + +static int __init dccp_mt_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(dccp_mt_reg, ARRAY_SIZE(dccp_mt_reg)); + if (ret) + goto out_kfree; + return ret; + +out_kfree: + kfree(dccp_optbuf); + return ret; +} + +static void __exit dccp_mt_exit(void) +{ + xt_unregister_matches(dccp_mt_reg, ARRAY_SIZE(dccp_mt_reg)); + kfree(dccp_optbuf); +} + +module_init(dccp_mt_init); +module_exit(dccp_mt_exit); |
