11da177e4SLinus Torvalds /* module that allows mangling of the arp payload */ 21da177e4SLinus Torvalds #include <linux/module.h> 31da177e4SLinus Torvalds #include <linux/netfilter_arp/arpt_mangle.h> 41da177e4SLinus Torvalds #include <net/sock.h> 51da177e4SLinus Torvalds 61da177e4SLinus Torvalds MODULE_LICENSE("GPL"); 71da177e4SLinus Torvalds MODULE_AUTHOR("Bart De Schuymer <bdschuym@pandora.be>"); 81da177e4SLinus Torvalds MODULE_DESCRIPTION("arptables arp payload mangle target"); 91da177e4SLinus Torvalds 101da177e4SLinus Torvalds static unsigned int 11c4986734SPatrick McHardy target(struct sk_buff **pskb, 12c4986734SPatrick McHardy const struct net_device *in, const struct net_device *out, 13c4986734SPatrick McHardy unsigned int hooknum, const struct xt_target *target, 14*fe1cb108SPatrick McHardy const void *targinfo) 151da177e4SLinus Torvalds { 161da177e4SLinus Torvalds const struct arpt_mangle *mangle = targinfo; 171da177e4SLinus Torvalds struct arphdr *arp; 181da177e4SLinus Torvalds unsigned char *arpptr; 191da177e4SLinus Torvalds int pln, hln; 201da177e4SLinus Torvalds 211da177e4SLinus Torvalds if (skb_shared(*pskb) || skb_cloned(*pskb)) { 221da177e4SLinus Torvalds struct sk_buff *nskb; 231da177e4SLinus Torvalds 241da177e4SLinus Torvalds nskb = skb_copy(*pskb, GFP_ATOMIC); 251da177e4SLinus Torvalds if (!nskb) 261da177e4SLinus Torvalds return NF_DROP; 271da177e4SLinus Torvalds if ((*pskb)->sk) 281da177e4SLinus Torvalds skb_set_owner_w(nskb, (*pskb)->sk); 291da177e4SLinus Torvalds kfree_skb(*pskb); 301da177e4SLinus Torvalds *pskb = nskb; 311da177e4SLinus Torvalds } 321da177e4SLinus Torvalds 331da177e4SLinus Torvalds arp = (*pskb)->nh.arph; 341da177e4SLinus Torvalds arpptr = (*pskb)->nh.raw + sizeof(*arp); 351da177e4SLinus Torvalds pln = arp->ar_pln; 361da177e4SLinus Torvalds hln = arp->ar_hln; 371da177e4SLinus Torvalds /* We assume that pln and hln were checked in the match */ 381da177e4SLinus Torvalds if (mangle->flags & ARPT_MANGLE_SDEV) { 391da177e4SLinus Torvalds if (ARPT_DEV_ADDR_LEN_MAX < hln || 401da177e4SLinus Torvalds (arpptr + hln > (**pskb).tail)) 411da177e4SLinus Torvalds return NF_DROP; 421da177e4SLinus Torvalds memcpy(arpptr, mangle->src_devaddr, hln); 431da177e4SLinus Torvalds } 441da177e4SLinus Torvalds arpptr += hln; 451da177e4SLinus Torvalds if (mangle->flags & ARPT_MANGLE_SIP) { 461da177e4SLinus Torvalds if (ARPT_MANGLE_ADDR_LEN_MAX < pln || 471da177e4SLinus Torvalds (arpptr + pln > (**pskb).tail)) 481da177e4SLinus Torvalds return NF_DROP; 491da177e4SLinus Torvalds memcpy(arpptr, &mangle->u_s.src_ip, pln); 501da177e4SLinus Torvalds } 511da177e4SLinus Torvalds arpptr += pln; 521da177e4SLinus Torvalds if (mangle->flags & ARPT_MANGLE_TDEV) { 531da177e4SLinus Torvalds if (ARPT_DEV_ADDR_LEN_MAX < hln || 541da177e4SLinus Torvalds (arpptr + hln > (**pskb).tail)) 551da177e4SLinus Torvalds return NF_DROP; 561da177e4SLinus Torvalds memcpy(arpptr, mangle->tgt_devaddr, hln); 571da177e4SLinus Torvalds } 581da177e4SLinus Torvalds arpptr += hln; 591da177e4SLinus Torvalds if (mangle->flags & ARPT_MANGLE_TIP) { 601da177e4SLinus Torvalds if (ARPT_MANGLE_ADDR_LEN_MAX < pln || 611da177e4SLinus Torvalds (arpptr + pln > (**pskb).tail)) 621da177e4SLinus Torvalds return NF_DROP; 631da177e4SLinus Torvalds memcpy(arpptr, &mangle->u_t.tgt_ip, pln); 641da177e4SLinus Torvalds } 651da177e4SLinus Torvalds return mangle->target; 661da177e4SLinus Torvalds } 671da177e4SLinus Torvalds 681da177e4SLinus Torvalds static int 69c4986734SPatrick McHardy checkentry(const char *tablename, const void *e, const struct xt_target *target, 70c4986734SPatrick McHardy void *targinfo, unsigned int targinfosize, unsigned int hook_mask) 711da177e4SLinus Torvalds { 721da177e4SLinus Torvalds const struct arpt_mangle *mangle = targinfo; 731da177e4SLinus Torvalds 741da177e4SLinus Torvalds if (mangle->flags & ~ARPT_MANGLE_MASK || 751da177e4SLinus Torvalds !(mangle->flags & ARPT_MANGLE_MASK)) 761da177e4SLinus Torvalds return 0; 771da177e4SLinus Torvalds 781da177e4SLinus Torvalds if (mangle->target != NF_DROP && mangle->target != NF_ACCEPT && 791da177e4SLinus Torvalds mangle->target != ARPT_CONTINUE) 801da177e4SLinus Torvalds return 0; 811da177e4SLinus Torvalds return 1; 821da177e4SLinus Torvalds } 831da177e4SLinus Torvalds 84aa83c1abSPatrick McHardy static struct arpt_target arpt_mangle_reg = { 851da177e4SLinus Torvalds .name = "mangle", 861da177e4SLinus Torvalds .target = target, 87aa83c1abSPatrick McHardy .targetsize = sizeof(struct arpt_mangle), 881da177e4SLinus Torvalds .checkentry = checkentry, 891da177e4SLinus Torvalds .me = THIS_MODULE, 901da177e4SLinus Torvalds }; 911da177e4SLinus Torvalds 9265b4b4e8SAndrew Morton static int __init arpt_mangle_init(void) 931da177e4SLinus Torvalds { 941da177e4SLinus Torvalds if (arpt_register_target(&arpt_mangle_reg)) 951da177e4SLinus Torvalds return -EINVAL; 961da177e4SLinus Torvalds 971da177e4SLinus Torvalds return 0; 981da177e4SLinus Torvalds } 991da177e4SLinus Torvalds 10065b4b4e8SAndrew Morton static void __exit arpt_mangle_fini(void) 1011da177e4SLinus Torvalds { 1021da177e4SLinus Torvalds arpt_unregister_target(&arpt_mangle_reg); 1031da177e4SLinus Torvalds } 1041da177e4SLinus Torvalds 10565b4b4e8SAndrew Morton module_init(arpt_mangle_init); 10665b4b4e8SAndrew Morton module_exit(arpt_mangle_fini); 107