diff options
author | Harald Welte <laforge@netfilter.org> | 2006-01-12 21:30:04 (GMT) |
---|---|---|
committer | David S. Miller <davem@sunset.davemloft.net> | 2006-01-12 22:06:43 (GMT) |
commit | 2e4e6a17af35be359cc8f1c924f8f198fbd478cc (patch) | |
tree | cb4b5438dcf9ff9d57518a26124308bcbfffd214 /net/netfilter/xt_tcpmss.c | |
parent | 880b005f294454d989783d0984dc554dfe3c8214 (diff) | |
download | linux-2e4e6a17af35be359cc8f1c924f8f198fbd478cc.tar.xz |
[NETFILTER] x_tables: Abstraction layer for {ip,ip6,arp}_tables
This monster-patch tries to do the best job for unifying the data
structures and backend interfaces for the three evil clones ip_tables,
ip6_tables and arp_tables. In an ideal world we would never have
allowed this kind of copy+paste programming... but well, our world
isn't (yet?) ideal.
o introduce a new x_tables module
o {ip,arp,ip6}_tables depend on this x_tables module
o registration functions for tables, matches and targets are only
wrappers around x_tables provided functions
o all matches/targets that are used from ip_tables and ip6_tables
are now implemented as xt_FOOBAR.c files and provide module aliases
to ipt_FOOBAR and ip6t_FOOBAR
o header files for xt_matches are in include/linux/netfilter/,
include/linux/netfilter_{ipv4,ipv6} contains compatibility wrappers
around the xt_FOOBAR.h headers
Based on this patchset we're going to further unify the code,
gradually getting rid of all the layer 3 specific assumptions.
Signed-off-by: Harald Welte <laforge@netfilter.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/netfilter/xt_tcpmss.c')
-rw-r--r-- | net/netfilter/xt_tcpmss.c | 172 |
1 files changed, 172 insertions, 0 deletions
diff --git a/net/netfilter/xt_tcpmss.c b/net/netfilter/xt_tcpmss.c new file mode 100644 index 0000000..acf7f53 --- /dev/null +++ b/net/netfilter/xt_tcpmss.c @@ -0,0 +1,172 @@ +/* Kernel module to match TCP MSS values. */ + +/* Copyright (C) 2000 Marc Boucher <marc@mbsi.ca> + * Portions (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 <net/tcp.h> + +#include <linux/netfilter/xt_tcpmss.h> +#include <linux/netfilter/x_tables.h> + +#include <linux/netfilter_ipv4/ip_tables.h> +#include <linux/netfilter_ipv6/ip6_tables.h> + +#define TH_SYN 0x02 + +MODULE_LICENSE("GPL"); +MODULE_AUTHOR("Marc Boucher <marc@mbsi.ca>"); +MODULE_DESCRIPTION("iptables TCP MSS match module"); +MODULE_ALIAS("ipt_tcpmss"); + +/* 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, + unsigned int protoff, + 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, protoff, 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, protoff + 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, + unsigned int protoff, + int *hotdrop) +{ + const struct xt_tcpmss_match_info *info = matchinfo; + + return mssoption_match(info->mss_min, info->mss_max, skb, protoff, + info->invert, hotdrop); +} + +static int +checkentry(const char *tablename, + const void *ipinfo, + void *matchinfo, + unsigned int matchsize, + unsigned int hook_mask) +{ + const struct ipt_ip *ip = ipinfo; + if (matchsize != XT_ALIGN(sizeof(struct xt_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 int +checkentry6(const char *tablename, + const void *ipinfo, + void *matchinfo, + unsigned int matchsize, + unsigned int hook_mask) +{ + const struct ip6t_ip6 *ip = ipinfo; + + if (matchsize != XT_ALIGN(sizeof(struct xt_tcpmss_match_info))) + return 0; + + /* Must specify -p tcp */ + if (ip->proto != IPPROTO_TCP || (ip->invflags & XT_INV_PROTO)) { + printk("tcpmss: Only works on TCP packets\n"); + return 0; + } + + return 1; +} + +static struct xt_match tcpmss_match = { + .name = "tcpmss", + .match = &match, + .checkentry = &checkentry, + .me = THIS_MODULE, +}; + +static struct xt_match tcpmss6_match = { + .name = "tcpmss", + .match = &match, + .checkentry = &checkentry6, + .me = THIS_MODULE, +}; + + +static int __init init(void) +{ + int ret; + ret = xt_register_match(AF_INET, &tcpmss_match); + if (ret) + return ret; + + ret = xt_register_match(AF_INET6, &tcpmss6_match); + if (ret) + xt_unregister_match(AF_INET, &tcpmss_match); + + return ret; +} + +static void __exit fini(void) +{ + xt_unregister_match(AF_INET6, &tcpmss6_match); + xt_unregister_match(AF_INET, &tcpmss_match); +} + +module_init(init); +module_exit(fini); |