/* * Stateless NAT actions * * Copyright (c) 2007 Herbert Xu <herbert@gondor.apana.org.au> * * This program is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License as published by the Free * Software Foundation; either version 2 of the License, or (at your option) * any later version. */ #include <linux/errno.h> #include <linux/init.h> #include <linux/kernel.h> #include <linux/module.h> #include <linux/netfilter.h> #include <linux/rtnetlink.h> #include <linux/skbuff.h> #include <linux/slab.h> #include <linux/spinlock.h> #include <linux/string.h> #include <linux/tc_act/tc_nat.h> #include <net/act_api.h> #include <net/icmp.h> #include <net/ip.h> #include <net/netlink.h> #include <net/tc_act/tc_nat.h> #include <net/tcp.h> #include <net/udp.h> #define NAT_TAB_MASK 15 static struct tcf_common *tcf_nat_ht[NAT_TAB_MASK + 1]; static u32 nat_idx_gen; static DEFINE_RWLOCK(nat_lock); static struct tcf_hashinfo nat_hash_info = { .htab = tcf_nat_ht, .hmask = NAT_TAB_MASK, .lock = &nat_lock, }; static const struct nla_policy nat_policy[TCA_NAT_MAX + 1] = { [TCA_NAT_PARMS] = { .len = sizeof(struct tc_nat) }, }; static int tcf_nat_init(struct nlattr *nla, struct nlattr *est, struct tc_action *a, int ovr, int bind) { struct nlattr *tb[TCA_NAT_MAX + 1]; struct tc_nat *parm; int ret = 0, err; struct tcf_nat *p; struct tcf_common *pc; if (nla == NULL) return -EINVAL; err = nla_parse_nested(tb, TCA_NAT_MAX, nla, nat_policy); if (err < 0) return err; if (tb[TCA_NAT_PARMS] == NULL) return -EINVAL; parm = nla_data(tb[TCA_NAT_PARMS]); pc = tcf_hash_check(parm->index, a, bind, &nat_hash_info); if (!pc) { pc = tcf_hash_create(parm->index, est, a, sizeof(*p), bind, &nat_idx_gen, &nat_hash_info); if (unlikely(!pc)) return -ENOMEM; p = to_tcf_nat(pc); ret = ACT_P_CREATED; } else { p = to_tcf_nat(pc); if (!ovr) { tcf_hash_release(pc, bind, &nat_hash_info); return -EEXIST; } } spin_lock_bh(&p->tcf_lock); p->old_addr = parm->old_addr; p->new_addr = parm->new_addr; p->mask = parm->mask; p->flags = parm->flags; p->tcf_action = parm->action; spin_unlock_bh(&p->tcf_lock); if (ret == ACT_P_CREATED) tcf_hash_insert(pc, &nat_hash_info); return ret; } static int tcf_nat_cleanup(struct tc_action *a, int bind) { struct tcf_nat *p = a->priv; return tcf_hash_release(&p->common, bind, &nat_hash_info); } static int tcf_nat(struct sk_buff *skb, struct tc_action *a, struct tcf_result *res) { struct tcf_nat *p = a->priv; struct iphdr *iph; __be32 old_addr; __be32 new_addr; __be32 mask; __be32 addr; int egress; int action; int ihl; spin_lock(&p->tcf_lock); p->tcf_tm.lastuse = jiffies; old_addr = p->old_addr; new_addr = p->new_addr; mask = p->mask; egress = p->flags & TCA_NAT_FLAG_EGRESS; action = p->tcf_action; p->tcf_bstats.bytes += qdisc_pkt_len(skb); p->tcf_bstats.packets++; spin_unlock(&p->tcf_lock); if (unlikely(action == TC_ACT_SHOT)) goto drop; if (!pskb_may_pull(skb, sizeof(*iph))) goto drop; iph = ip_hdr(skb); if (egress) addr = iph->saddr; else addr = iph->daddr; if (!((old_addr ^ addr) & mask)) { if (skb_cloned(skb) && !skb_clone_writable(skb, sizeof(*iph)) && pskb_expand_head(skb, 0, 0, GFP_ATOMIC)) goto drop; new_addr &= mask; new_addr |= addr & ~mask; /* Rewrite IP header */ iph = ip_hdr(skb); if (egress) iph->saddr = new_addr; else iph->daddr = new_addr; csum_replace4(&iph->check, addr, new_addr); } ihl = iph->ihl * 4; /* It would be nice to share code with stateful NAT. */ switch (iph->frag_off & htons(IP_OFFSET) ? 0 : iph->protocol) { case IPPROTO_TCP: { struct tcphdr *tcph; if (!pskb_may_pull(skb, ihl + sizeof(*tcph)) || (skb_cloned(skb) && !skb_clone_writable(skb, ihl + sizeof(*tcph)) && pskb_expand_head(skb, 0, 0, GFP_ATOMIC))) goto drop; tcph = (void *)(skb_network_header(skb) + ihl); inet_proto_csum_replace4(&tcph->check, skb, addr, new_addr, 1); break; } case IPPROTO_UDP: { struct udphdr *udph; if (!pskb_may_pull(skb, ihl + sizeof(*udph)) || (skb_cloned(skb) && !skb_clone_writable(skb, ihl + sizeof(*udph)) && pskb_expand_head(skb, 0, 0, GFP_ATOMIC))) goto drop; udph = (void *)(skb_network_header(skb) + ihl); if (udph->check || skb->ip_summed == CHECKSUM_PARTIAL) { inet_proto_csum_replace4(&udph->check, skb, addr, new_addr, 1); if (!udph->check) udph->check = CSUM_MANGLED_0; } break; } case IPPROTO_ICMP: { struct icmphdr *icmph; if (!pskb_may_pull(skb, ihl + sizeof(*icmph) + sizeof(*iph))) goto drop; icmph = (void *)(skb_network_header(skb) + ihl); if ((icmph->type != ICMP_DEST_UNREACH) && (icmph->type != ICMP_TIME_EXCEEDED) && (icmph->type != ICMP_PARAMETERPROB)) break; iph = (void *)(icmph + 1); if (egress) addr = iph->daddr; else addr = iph->saddr; if ((old_addr ^ addr) & mask) break; if (skb_cloned(skb) && !skb_clone_writable(skb, ihl + sizeof(*icmph) + sizeof(*iph)) && pskb_expand_head(skb, 0, 0, GFP_ATOMIC)) goto drop; icmph = (void *)(skb_network_header(skb) + ihl); iph = (void *)(icmph + 1); new_addr &= mask; new_addr |= addr & ~mask; /* XXX Fix up the inner checksums. */ if (egress) iph->daddr = new_addr; else iph->saddr = new_addr; inet_proto_csum_replace4(&icmph->checksum, skb, addr, new_addr, 1); break; } default: break; } return action; drop: spin_lock(&p->tcf_lock); p->tcf_qstats.drops++; spin_unlock(&p->tcf_lock); return TC_ACT_SHOT; } static int tcf_nat_dump(struct sk_buff *skb, struct tc_action *a, int bind, int ref) { unsigned char *b = skb_tail_pointer(skb); struct tcf_nat *p = a->priv; struct tc_nat *opt; struct tcf_t t; int s; s = sizeof(*opt); /* netlink spinlocks held above us - must use ATOMIC */ opt = kzalloc(s, GFP_ATOMIC); if (unlikely(!opt)) return -ENOBUFS; opt->old_addr = p->old_addr; opt->new_addr = p->new_addr; opt->mask = p->mask; opt->flags = p->flags; opt->index = p->tcf_index; opt->action = p->tcf_action; opt->refcnt = p->tcf_refcnt - ref; opt->bindcnt = p->tcf_bindcnt - bind; NLA_PUT(skb, TCA_NAT_PARMS, s, opt); t.install = jiffies_to_clock_t(jiffies - p->tcf_tm.install); t.lastuse = jiffies_to_clock_t(jiffies - p->tcf_tm.lastuse); t.expires = jiffies_to_clock_t(p->tcf_tm.expires); NLA_PUT(skb, TCA_NAT_TM, sizeof(t), &t); kfree(opt); return skb->len; nla_put_failure: nlmsg_trim(skb, b); kfree(opt); return -1; } static struct tc_action_ops act_nat_ops = { .kind = "nat", .hinfo = &nat_hash_info, .type = TCA_ACT_NAT, .capab = TCA_CAP_NONE, .owner = THIS_MODULE, .act = tcf_nat, .dump = tcf_nat_dump, .cleanup = tcf_nat_cleanup, .lookup = tcf_hash_search, .init = tcf_nat_init, .walk = tcf_generic_walker }; MODULE_DESCRIPTION("Stateless NAT actions"); MODULE_LICENSE("GPL"); static int __init nat_init_module(void) { return tcf_register_action(&act_nat_ops); } static void __exit nat_cleanup_module(void) { tcf_unregister_action(&act_nat_ops); } module_init(nat_init_module); module_exit(nat_cleanup_module);