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, 272e4e6a17SHarald Welte const void *matchinfo, 282e4e6a17SHarald Welte int offset, 292e4e6a17SHarald Welte unsigned int protoff, 302e4e6a17SHarald Welte int *hotdrop) 312e4e6a17SHarald Welte { 322e4e6a17SHarald Welte const struct xt_length_info *info = matchinfo; 332e4e6a17SHarald Welte u_int16_t pktlen = ntohs(skb->nh.iph->tot_len); 342e4e6a17SHarald Welte 352e4e6a17SHarald Welte return (pktlen >= info->min && pktlen <= info->max) ^ info->invert; 362e4e6a17SHarald Welte } 372e4e6a17SHarald Welte 382e4e6a17SHarald Welte static int 392e4e6a17SHarald Welte match6(const struct sk_buff *skb, 402e4e6a17SHarald Welte const struct net_device *in, 412e4e6a17SHarald Welte const struct net_device *out, 422e4e6a17SHarald Welte const void *matchinfo, 432e4e6a17SHarald Welte int offset, 442e4e6a17SHarald Welte unsigned int protoff, 452e4e6a17SHarald Welte int *hotdrop) 462e4e6a17SHarald Welte { 472e4e6a17SHarald Welte const struct xt_length_info *info = matchinfo; 482e4e6a17SHarald Welte u_int16_t pktlen = ntohs(skb->nh.ipv6h->payload_len) + sizeof(struct ipv6hdr); 492e4e6a17SHarald Welte 502e4e6a17SHarald Welte return (pktlen >= info->min && pktlen <= info->max) ^ info->invert; 512e4e6a17SHarald Welte } 522e4e6a17SHarald Welte 532e4e6a17SHarald Welte static struct xt_match length_match = { 542e4e6a17SHarald Welte .name = "length", 555d04bff0SPatrick McHardy .match = match, 565d04bff0SPatrick McHardy .matchsize = sizeof(struct xt_length_info), 572e4e6a17SHarald Welte .me = THIS_MODULE, 582e4e6a17SHarald Welte }; 595d04bff0SPatrick McHardy 602e4e6a17SHarald Welte static struct xt_match length6_match = { 612e4e6a17SHarald Welte .name = "length", 625d04bff0SPatrick McHardy .match = match6, 635d04bff0SPatrick McHardy .matchsize = sizeof(struct xt_length_info), 642e4e6a17SHarald Welte .me = THIS_MODULE, 652e4e6a17SHarald Welte }; 662e4e6a17SHarald Welte 672e4e6a17SHarald Welte static int __init init(void) 682e4e6a17SHarald Welte { 692e4e6a17SHarald Welte int ret; 702e4e6a17SHarald Welte ret = xt_register_match(AF_INET, &length_match); 712e4e6a17SHarald Welte if (ret) 722e4e6a17SHarald Welte return ret; 732e4e6a17SHarald Welte ret = xt_register_match(AF_INET6, &length6_match); 742e4e6a17SHarald Welte if (ret) 752e4e6a17SHarald Welte xt_unregister_match(AF_INET, &length_match); 762e4e6a17SHarald Welte 772e4e6a17SHarald Welte return ret; 782e4e6a17SHarald Welte } 792e4e6a17SHarald Welte 802e4e6a17SHarald Welte static void __exit fini(void) 812e4e6a17SHarald Welte { 822e4e6a17SHarald Welte xt_unregister_match(AF_INET, &length_match); 832e4e6a17SHarald Welte xt_unregister_match(AF_INET6, &length6_match); 842e4e6a17SHarald Welte } 852e4e6a17SHarald Welte 862e4e6a17SHarald Welte module_init(init); 872e4e6a17SHarald Welte module_exit(fini); 88