12e4e6a17SHarald Welte /* Kernel module to match packet length. */ 22e4e6a17SHarald Welte /* (C) 1999-2001 James Morris <jmorros@intercode.com.au> 32e4e6a17SHarald Welte * 42e4e6a17SHarald Welte * This program is free software; you can redistribute it and/or modify 52e4e6a17SHarald Welte * it under the terms of the GNU General Public License version 2 as 62e4e6a17SHarald Welte * published by the Free Software Foundation. 72e4e6a17SHarald Welte */ 82e4e6a17SHarald Welte 92e4e6a17SHarald Welte #include <linux/module.h> 102e4e6a17SHarald Welte #include <linux/skbuff.h> 1137d8dc82SDavid S. Miller #include <linux/ipv6.h> 122e4e6a17SHarald Welte #include <net/ip.h> 132e4e6a17SHarald Welte 142e4e6a17SHarald Welte #include <linux/netfilter/xt_length.h> 152e4e6a17SHarald Welte #include <linux/netfilter/x_tables.h> 162e4e6a17SHarald Welte 172e4e6a17SHarald Welte MODULE_AUTHOR("James Morris <jmorris@intercode.com.au>"); 182e4e6a17SHarald Welte MODULE_DESCRIPTION("IP tables packet length matching module"); 192e4e6a17SHarald Welte MODULE_LICENSE("GPL"); 202e4e6a17SHarald Welte MODULE_ALIAS("ipt_length"); 212e4e6a17SHarald Welte MODULE_ALIAS("ip6t_length"); 222e4e6a17SHarald Welte 232e4e6a17SHarald Welte static int 242e4e6a17SHarald Welte match(const struct sk_buff *skb, 252e4e6a17SHarald Welte const struct net_device *in, 262e4e6a17SHarald Welte const struct net_device *out, 27c4986734SPatrick McHardy const struct xt_match *match, 282e4e6a17SHarald Welte const void *matchinfo, 292e4e6a17SHarald Welte int offset, 302e4e6a17SHarald Welte unsigned int protoff, 312e4e6a17SHarald Welte int *hotdrop) 322e4e6a17SHarald Welte { 332e4e6a17SHarald Welte const struct xt_length_info *info = matchinfo; 342e4e6a17SHarald Welte u_int16_t pktlen = ntohs(skb->nh.iph->tot_len); 352e4e6a17SHarald Welte 362e4e6a17SHarald Welte return (pktlen >= info->min && pktlen <= info->max) ^ info->invert; 372e4e6a17SHarald Welte } 382e4e6a17SHarald Welte 392e4e6a17SHarald Welte static int 402e4e6a17SHarald Welte match6(const struct sk_buff *skb, 412e4e6a17SHarald Welte const struct net_device *in, 422e4e6a17SHarald Welte const struct net_device *out, 43c4986734SPatrick McHardy const struct xt_match *match, 442e4e6a17SHarald Welte const void *matchinfo, 452e4e6a17SHarald Welte int offset, 462e4e6a17SHarald Welte unsigned int protoff, 472e4e6a17SHarald Welte int *hotdrop) 482e4e6a17SHarald Welte { 492e4e6a17SHarald Welte const struct xt_length_info *info = matchinfo; 502e4e6a17SHarald Welte u_int16_t pktlen = ntohs(skb->nh.ipv6h->payload_len) + sizeof(struct ipv6hdr); 512e4e6a17SHarald Welte 522e4e6a17SHarald Welte return (pktlen >= info->min && pktlen <= info->max) ^ info->invert; 532e4e6a17SHarald Welte } 542e4e6a17SHarald Welte 552e4e6a17SHarald Welte static struct xt_match length_match = { 562e4e6a17SHarald Welte .name = "length", 575d04bff0SPatrick McHardy .match = match, 585d04bff0SPatrick McHardy .matchsize = sizeof(struct xt_length_info), 592e4e6a17SHarald Welte .me = THIS_MODULE, 602e4e6a17SHarald Welte }; 615d04bff0SPatrick McHardy 622e4e6a17SHarald Welte static struct xt_match length6_match = { 632e4e6a17SHarald Welte .name = "length", 645d04bff0SPatrick McHardy .match = match6, 655d04bff0SPatrick McHardy .matchsize = sizeof(struct xt_length_info), 662e4e6a17SHarald Welte .me = THIS_MODULE, 672e4e6a17SHarald Welte }; 682e4e6a17SHarald Welte 692e4e6a17SHarald Welte static int __init init(void) 702e4e6a17SHarald Welte { 712e4e6a17SHarald Welte int ret; 722e4e6a17SHarald Welte ret = xt_register_match(AF_INET, &length_match); 732e4e6a17SHarald Welte if (ret) 742e4e6a17SHarald Welte return ret; 752e4e6a17SHarald Welte ret = xt_register_match(AF_INET6, &length6_match); 762e4e6a17SHarald Welte if (ret) 772e4e6a17SHarald Welte xt_unregister_match(AF_INET, &length_match); 782e4e6a17SHarald Welte 792e4e6a17SHarald Welte return ret; 802e4e6a17SHarald Welte } 812e4e6a17SHarald Welte 822e4e6a17SHarald Welte static void __exit fini(void) 832e4e6a17SHarald Welte { 842e4e6a17SHarald Welte xt_unregister_match(AF_INET, &length_match); 852e4e6a17SHarald Welte xt_unregister_match(AF_INET6, &length6_match); 862e4e6a17SHarald Welte } 872e4e6a17SHarald Welte 882e4e6a17SHarald Welte module_init(init); 892e4e6a17SHarald Welte module_exit(fini); 90