| /* |
| * 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/slab.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)) |
| goto invalid; |
| |
| 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. */ |
| goto partial; |
| } |
| |
| 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; |
| |
| partial: |
| spin_unlock_bh(&dccp_buflock); |
| invalid: |
| *hotdrop = true; |
| 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_action_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 int dccp_mt_check(const struct xt_mtchk_param *par) |
| { |
| const struct xt_dccp_info *info = par->matchinfo; |
| |
| if (info->flags & ~XT_DCCP_VALID_FLAGS) |
| return -EINVAL; |
| if (info->invflags & ~XT_DCCP_VALID_FLAGS) |
| return -EINVAL; |
| if (info->invflags & ~info->flags) |
| return -EINVAL; |
| return 0; |
| } |
| |
| 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); |