![Jan Engelhardt](/assets/img/avatar_default.png)
The function signatures for Xtables extensions have grown over time. It involves a lot of typing/replication, and also a bit of stack space even if they are not used. Realize an NFWS2008 idea and pack them into structs. The skb remains outside of the struct so gcc can continue to apply its optimizations. This patch does this for match extensions' match functions. A few ambiguities have also been addressed. The "offset" parameter for example has been renamed to "fragoff" (there are so many different offsets already) and "protoff" to "thoff" (there is more than just one protocol here, so clarify). Signed-off-by: Jan Engelhardt <jengelh@medozas.de> Signed-off-by: Patrick McHardy <kaber@trash.net>
185 lines
4.5 KiB
C
185 lines
4.5 KiB
C
/*
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* iptables module for DCCP protocol header matching
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*
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* (C) 2005 by Harald Welte <laforge@netfilter.org>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#include <linux/module.h>
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#include <linux/skbuff.h>
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#include <linux/spinlock.h>
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#include <net/ip.h>
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#include <linux/dccp.h>
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#include <linux/netfilter/x_tables.h>
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#include <linux/netfilter/xt_dccp.h>
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#include <linux/netfilter_ipv4/ip_tables.h>
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#include <linux/netfilter_ipv6/ip6_tables.h>
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
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MODULE_DESCRIPTION("Xtables: DCCP protocol packet match");
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MODULE_ALIAS("ipt_dccp");
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MODULE_ALIAS("ip6t_dccp");
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#define DCCHECK(cond, option, flag, invflag) (!((flag) & (option)) \
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|| (!!((invflag) & (option)) ^ (cond)))
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static unsigned char *dccp_optbuf;
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static DEFINE_SPINLOCK(dccp_buflock);
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static inline bool
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dccp_find_option(u_int8_t option,
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const struct sk_buff *skb,
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unsigned int protoff,
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const struct dccp_hdr *dh,
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bool *hotdrop)
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{
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/* tcp.doff is only 4 bits, ie. max 15 * 4 bytes */
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const unsigned char *op;
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unsigned int optoff = __dccp_hdr_len(dh);
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unsigned int optlen = dh->dccph_doff*4 - __dccp_hdr_len(dh);
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unsigned int i;
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if (dh->dccph_doff * 4 < __dccp_hdr_len(dh)) {
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*hotdrop = true;
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return false;
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}
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if (!optlen)
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return false;
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spin_lock_bh(&dccp_buflock);
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op = skb_header_pointer(skb, protoff + optoff, optlen, dccp_optbuf);
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if (op == NULL) {
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/* If we don't have the whole header, drop packet. */
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spin_unlock_bh(&dccp_buflock);
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*hotdrop = true;
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return false;
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}
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for (i = 0; i < optlen; ) {
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if (op[i] == option) {
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spin_unlock_bh(&dccp_buflock);
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return true;
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}
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if (op[i] < 2)
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i++;
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else
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i += op[i+1]?:1;
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}
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spin_unlock_bh(&dccp_buflock);
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return false;
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}
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static inline bool
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match_types(const struct dccp_hdr *dh, u_int16_t typemask)
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{
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return typemask & (1 << dh->dccph_type);
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}
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static inline bool
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match_option(u_int8_t option, const struct sk_buff *skb, unsigned int protoff,
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const struct dccp_hdr *dh, bool *hotdrop)
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{
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return dccp_find_option(option, skb, protoff, dh, hotdrop);
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}
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static bool
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dccp_mt(const struct sk_buff *skb, const struct xt_match_param *par)
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{
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const struct xt_dccp_info *info = par->matchinfo;
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const struct dccp_hdr *dh;
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struct dccp_hdr _dh;
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if (par->fragoff != 0)
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return false;
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dh = skb_header_pointer(skb, par->thoff, sizeof(_dh), &_dh);
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if (dh == NULL) {
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*par->hotdrop = true;
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return false;
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}
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return DCCHECK(ntohs(dh->dccph_sport) >= info->spts[0]
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&& ntohs(dh->dccph_sport) <= info->spts[1],
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XT_DCCP_SRC_PORTS, info->flags, info->invflags)
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&& DCCHECK(ntohs(dh->dccph_dport) >= info->dpts[0]
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&& ntohs(dh->dccph_dport) <= info->dpts[1],
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XT_DCCP_DEST_PORTS, info->flags, info->invflags)
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&& DCCHECK(match_types(dh, info->typemask),
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XT_DCCP_TYPE, info->flags, info->invflags)
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&& DCCHECK(match_option(info->option, skb, par->thoff, dh,
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par->hotdrop),
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XT_DCCP_OPTION, info->flags, info->invflags);
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}
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static bool
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dccp_mt_check(const char *tablename, const void *inf,
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const struct xt_match *match, void *matchinfo,
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unsigned int hook_mask)
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{
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const struct xt_dccp_info *info = matchinfo;
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return !(info->flags & ~XT_DCCP_VALID_FLAGS)
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&& !(info->invflags & ~XT_DCCP_VALID_FLAGS)
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&& !(info->invflags & ~info->flags);
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}
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static struct xt_match dccp_mt_reg[] __read_mostly = {
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{
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.name = "dccp",
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.family = NFPROTO_IPV4,
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.checkentry = dccp_mt_check,
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.match = dccp_mt,
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.matchsize = sizeof(struct xt_dccp_info),
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.proto = IPPROTO_DCCP,
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.me = THIS_MODULE,
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},
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{
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.name = "dccp",
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.family = NFPROTO_IPV6,
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.checkentry = dccp_mt_check,
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.match = dccp_mt,
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.matchsize = sizeof(struct xt_dccp_info),
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.proto = IPPROTO_DCCP,
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.me = THIS_MODULE,
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},
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};
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static int __init dccp_mt_init(void)
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{
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int ret;
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/* doff is 8 bits, so the maximum option size is (4*256). Don't put
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* this in BSS since DaveM is worried about locked TLB's for kernel
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* BSS. */
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dccp_optbuf = kmalloc(256 * 4, GFP_KERNEL);
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if (!dccp_optbuf)
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return -ENOMEM;
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ret = xt_register_matches(dccp_mt_reg, ARRAY_SIZE(dccp_mt_reg));
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if (ret)
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goto out_kfree;
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return ret;
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out_kfree:
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kfree(dccp_optbuf);
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return ret;
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}
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static void __exit dccp_mt_exit(void)
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{
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xt_unregister_matches(dccp_mt_reg, ARRAY_SIZE(dccp_mt_reg));
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kfree(dccp_optbuf);
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}
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module_init(dccp_mt_init);
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module_exit(dccp_mt_exit);
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