mirror of
https://github.com/team-infusion-developers/android_kernel_samsung_msm8976.git
synced 2024-10-19 09:59:04 +00:00
128 lines
2.8 KiB
C
128 lines
2.8 KiB
C
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/* Kernel module to match TCP MSS values. */
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/* Copyright (C) 2000 Marc Boucher <marc@mbsi.ca>
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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 <net/tcp.h>
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#include <linux/netfilter_ipv4/ipt_tcpmss.h>
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#include <linux/netfilter_ipv4/ip_tables.h>
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#define TH_SYN 0x02
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("Marc Boucher <marc@mbsi.ca>");
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MODULE_DESCRIPTION("iptables TCP MSS match module");
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/* Returns 1 if the mss option is set and matched by the range, 0 otherwise */
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static inline int
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mssoption_match(u_int16_t min, u_int16_t max,
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const struct sk_buff *skb,
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int invert,
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int *hotdrop)
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{
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struct tcphdr _tcph, *th;
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/* tcp.doff is only 4 bits, ie. max 15 * 4 bytes */
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u8 _opt[15 * 4 - sizeof(_tcph)], *op;
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unsigned int i, optlen;
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/* If we don't have the whole header, drop packet. */
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th = skb_header_pointer(skb, skb->nh.iph->ihl * 4,
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sizeof(_tcph), &_tcph);
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if (th == NULL)
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goto dropit;
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/* Malformed. */
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if (th->doff*4 < sizeof(*th))
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goto dropit;
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optlen = th->doff*4 - sizeof(*th);
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if (!optlen)
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goto out;
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/* Truncated options. */
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op = skb_header_pointer(skb, skb->nh.iph->ihl * 4 + sizeof(*th),
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optlen, _opt);
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if (op == NULL)
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goto dropit;
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for (i = 0; i < optlen; ) {
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if (op[i] == TCPOPT_MSS
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&& (optlen - i) >= TCPOLEN_MSS
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&& op[i+1] == TCPOLEN_MSS) {
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u_int16_t mssval;
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mssval = (op[i+2] << 8) | op[i+3];
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return (mssval >= min && mssval <= max) ^ invert;
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}
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if (op[i] < 2) i++;
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else i += op[i+1]?:1;
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}
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out:
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return invert;
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dropit:
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*hotdrop = 1;
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return 0;
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}
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static int
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match(const struct sk_buff *skb,
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const struct net_device *in,
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const struct net_device *out,
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const void *matchinfo,
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int offset,
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int *hotdrop)
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{
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const struct ipt_tcpmss_match_info *info = matchinfo;
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return mssoption_match(info->mss_min, info->mss_max, skb,
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info->invert, hotdrop);
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}
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static int
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checkentry(const char *tablename,
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const struct ipt_ip *ip,
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void *matchinfo,
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unsigned int matchsize,
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unsigned int hook_mask)
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{
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if (matchsize != IPT_ALIGN(sizeof(struct ipt_tcpmss_match_info)))
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return 0;
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/* Must specify -p tcp */
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if (ip->proto != IPPROTO_TCP || (ip->invflags & IPT_INV_PROTO)) {
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printk("tcpmss: Only works on TCP packets\n");
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return 0;
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}
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return 1;
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}
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static struct ipt_match tcpmss_match = {
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.name = "tcpmss",
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.match = &match,
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.checkentry = &checkentry,
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.me = THIS_MODULE,
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};
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static int __init init(void)
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{
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return ipt_register_match(&tcpmss_match);
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}
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static void __exit fini(void)
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{
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ipt_unregister_match(&tcpmss_match);
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}
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module_init(init);
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module_exit(fini);
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