diff options
author | Linus Torvalds <torvalds@ppc970.osdl.org> | 2005-04-16 15:20:36 -0700 |
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committer | Linus Torvalds <torvalds@ppc970.osdl.org> | 2005-04-16 15:20:36 -0700 |
commit | 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch) | |
tree | 0bba044c4ce775e45a88a51686b5d9f90697ea9d /net/ipv4/netfilter/ipt_tcpmss.c |
Linux-2.6.12-rc2
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
Diffstat (limited to 'net/ipv4/netfilter/ipt_tcpmss.c')
-rw-r--r-- | net/ipv4/netfilter/ipt_tcpmss.c | 127 |
1 files changed, 127 insertions, 0 deletions
diff --git a/net/ipv4/netfilter/ipt_tcpmss.c b/net/ipv4/netfilter/ipt_tcpmss.c new file mode 100644 index 00000000000..4dc9b16ab4a --- /dev/null +++ b/net/ipv4/netfilter/ipt_tcpmss.c @@ -0,0 +1,127 @@ +/* Kernel module to match TCP MSS values. */ + +/* Copyright (C) 2000 Marc Boucher <marc@mbsi.ca> + * + * 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 <net/tcp.h> + +#include <linux/netfilter_ipv4/ipt_tcpmss.h> +#include <linux/netfilter_ipv4/ip_tables.h> + +#define TH_SYN 0x02 + +MODULE_LICENSE("GPL"); +MODULE_AUTHOR("Marc Boucher <marc@mbsi.ca>"); +MODULE_DESCRIPTION("iptables TCP MSS match module"); + +/* Returns 1 if the mss option is set and matched by the range, 0 otherwise */ +static inline int +mssoption_match(u_int16_t min, u_int16_t max, + const struct sk_buff *skb, + int invert, + int *hotdrop) +{ + struct tcphdr _tcph, *th; + /* tcp.doff is only 4 bits, ie. max 15 * 4 bytes */ + u8 _opt[15 * 4 - sizeof(_tcph)], *op; + unsigned int i, optlen; + + /* If we don't have the whole header, drop packet. */ + th = skb_header_pointer(skb, skb->nh.iph->ihl * 4, + sizeof(_tcph), &_tcph); + if (th == NULL) + goto dropit; + + /* Malformed. */ + if (th->doff*4 < sizeof(*th)) + goto dropit; + + optlen = th->doff*4 - sizeof(*th); + if (!optlen) + goto out; + + /* Truncated options. */ + op = skb_header_pointer(skb, skb->nh.iph->ihl * 4 + sizeof(*th), + optlen, _opt); + if (op == NULL) + goto dropit; + + for (i = 0; i < optlen; ) { + if (op[i] == TCPOPT_MSS + && (optlen - i) >= TCPOLEN_MSS + && op[i+1] == TCPOLEN_MSS) { + u_int16_t mssval; + + mssval = (op[i+2] << 8) | op[i+3]; + + return (mssval >= min && mssval <= max) ^ invert; + } + if (op[i] < 2) i++; + else i += op[i+1]?:1; + } +out: + return invert; + + dropit: + *hotdrop = 1; + return 0; +} + +static int +match(const struct sk_buff *skb, + const struct net_device *in, + const struct net_device *out, + const void *matchinfo, + int offset, + int *hotdrop) +{ + const struct ipt_tcpmss_match_info *info = matchinfo; + + return mssoption_match(info->mss_min, info->mss_max, skb, + info->invert, hotdrop); +} + +static int +checkentry(const char *tablename, + const struct ipt_ip *ip, + void *matchinfo, + unsigned int matchsize, + unsigned int hook_mask) +{ + if (matchsize != IPT_ALIGN(sizeof(struct ipt_tcpmss_match_info))) + return 0; + + /* Must specify -p tcp */ + if (ip->proto != IPPROTO_TCP || (ip->invflags & IPT_INV_PROTO)) { + printk("tcpmss: Only works on TCP packets\n"); + return 0; + } + + return 1; +} + +static struct ipt_match tcpmss_match = { + .name = "tcpmss", + .match = &match, + .checkentry = &checkentry, + .me = THIS_MODULE, +}; + +static int __init init(void) +{ + return ipt_register_match(&tcpmss_match); +} + +static void __exit fini(void) +{ + ipt_unregister_match(&tcpmss_match); +} + +module_init(init); +module_exit(fini); |