From c7232c9979cba684c50b64c513c4a83c9aa70563 Mon Sep 17 00:00:00 2001 From: Patrick McHardy Date: Sun, 26 Aug 2012 19:14:06 +0200 Subject: netfilter: add protocol independent NAT core Convert the IPv4 NAT implementation to a protocol independent core and address family specific modules. Signed-off-by: Patrick McHardy --- net/ipv4/netfilter/nf_nat_l3proto_ipv4.c | 281 +++++++++++++++++++++++++++++++ 1 file changed, 281 insertions(+) create mode 100644 net/ipv4/netfilter/nf_nat_l3proto_ipv4.c (limited to 'net/ipv4/netfilter/nf_nat_l3proto_ipv4.c') diff --git a/net/ipv4/netfilter/nf_nat_l3proto_ipv4.c b/net/ipv4/netfilter/nf_nat_l3proto_ipv4.c new file mode 100644 index 000000000000..d8b2e14efddc --- /dev/null +++ b/net/ipv4/netfilter/nf_nat_l3proto_ipv4.c @@ -0,0 +1,281 @@ +/* + * (C) 1999-2001 Paul `Rusty' Russell + * (C) 2002-2006 Netfilter Core Team + * (C) 2011 Patrick McHardy + * + * 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 +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#include +#include +#include +#include +#include + +static const struct nf_nat_l3proto nf_nat_l3proto_ipv4; + +#ifdef CONFIG_XFRM +static void nf_nat_ipv4_decode_session(struct sk_buff *skb, + const struct nf_conn *ct, + enum ip_conntrack_dir dir, + unsigned long statusbit, + struct flowi *fl) +{ + const struct nf_conntrack_tuple *t = &ct->tuplehash[dir].tuple; + struct flowi4 *fl4 = &fl->u.ip4; + + if (ct->status & statusbit) { + fl4->daddr = t->dst.u3.ip; + if (t->dst.protonum == IPPROTO_TCP || + t->dst.protonum == IPPROTO_UDP || + t->dst.protonum == IPPROTO_UDPLITE || + t->dst.protonum == IPPROTO_DCCP || + t->dst.protonum == IPPROTO_SCTP) + fl4->fl4_dport = t->dst.u.all; + } + + statusbit ^= IPS_NAT_MASK; + + if (ct->status & statusbit) { + fl4->saddr = t->src.u3.ip; + if (t->dst.protonum == IPPROTO_TCP || + t->dst.protonum == IPPROTO_UDP || + t->dst.protonum == IPPROTO_UDPLITE || + t->dst.protonum == IPPROTO_DCCP || + t->dst.protonum == IPPROTO_SCTP) + fl4->fl4_sport = t->src.u.all; + } +} +#endif /* CONFIG_XFRM */ + +static bool nf_nat_ipv4_in_range(const struct nf_conntrack_tuple *t, + const struct nf_nat_range *range) +{ + return ntohl(t->src.u3.ip) >= ntohl(range->min_addr.ip) && + ntohl(t->src.u3.ip) <= ntohl(range->max_addr.ip); +} + +static u32 nf_nat_ipv4_secure_port(const struct nf_conntrack_tuple *t, + __be16 dport) +{ + return secure_ipv4_port_ephemeral(t->src.u3.ip, t->dst.u3.ip, dport); +} + +static bool nf_nat_ipv4_manip_pkt(struct sk_buff *skb, + unsigned int iphdroff, + const struct nf_nat_l4proto *l4proto, + const struct nf_conntrack_tuple *target, + enum nf_nat_manip_type maniptype) +{ + struct iphdr *iph; + unsigned int hdroff; + + if (!skb_make_writable(skb, iphdroff + sizeof(*iph))) + return false; + + iph = (void *)skb->data + iphdroff; + hdroff = iphdroff + iph->ihl * 4; + + if (!l4proto->manip_pkt(skb, &nf_nat_l3proto_ipv4, iphdroff, hdroff, + target, maniptype)) + return false; + iph = (void *)skb->data + iphdroff; + + if (maniptype == NF_NAT_MANIP_SRC) { + csum_replace4(&iph->check, iph->saddr, target->src.u3.ip); + iph->saddr = target->src.u3.ip; + } else { + csum_replace4(&iph->check, iph->daddr, target->dst.u3.ip); + iph->daddr = target->dst.u3.ip; + } + return true; +} + +static void nf_nat_ipv4_csum_update(struct sk_buff *skb, + unsigned int iphdroff, __sum16 *check, + const struct nf_conntrack_tuple *t, + enum nf_nat_manip_type maniptype) +{ + struct iphdr *iph = (struct iphdr *)(skb->data + iphdroff); + __be32 oldip, newip; + + if (maniptype == NF_NAT_MANIP_SRC) { + oldip = iph->saddr; + newip = t->src.u3.ip; + } else { + oldip = iph->daddr; + newip = t->dst.u3.ip; + } + inet_proto_csum_replace4(check, skb, oldip, newip, 1); +} + +static void nf_nat_ipv4_csum_recalc(struct sk_buff *skb, + u8 proto, void *data, __sum16 *check, + int datalen, int oldlen) +{ + const struct iphdr *iph = ip_hdr(skb); + struct rtable *rt = skb_rtable(skb); + + if (skb->ip_summed != CHECKSUM_PARTIAL) { + if (!(rt->rt_flags & RTCF_LOCAL) && + (!skb->dev || skb->dev->features & NETIF_F_V4_CSUM)) { + skb->ip_summed = CHECKSUM_PARTIAL; + skb->csum_start = skb_headroom(skb) + + skb_network_offset(skb) + + ip_hdrlen(skb); + skb->csum_offset = (void *)check - data; + *check = ~csum_tcpudp_magic(iph->saddr, iph->daddr, + datalen, proto, 0); + } else { + *check = 0; + *check = csum_tcpudp_magic(iph->saddr, iph->daddr, + datalen, proto, + csum_partial(data, datalen, + 0)); + if (proto == IPPROTO_UDP && !*check) + *check = CSUM_MANGLED_0; + } + } else + inet_proto_csum_replace2(check, skb, + htons(oldlen), htons(datalen), 1); +} + +static int nf_nat_ipv4_nlattr_to_range(struct nlattr *tb[], + struct nf_nat_range *range) +{ + if (tb[CTA_NAT_V4_MINIP]) { + range->min_addr.ip = nla_get_be32(tb[CTA_NAT_V4_MINIP]); + range->flags |= NF_NAT_RANGE_MAP_IPS; + } + + if (tb[CTA_NAT_V4_MAXIP]) + range->max_addr.ip = nla_get_be32(tb[CTA_NAT_V4_MAXIP]); + else + range->max_addr.ip = range->min_addr.ip; + + return 0; +} + +static const struct nf_nat_l3proto nf_nat_l3proto_ipv4 = { + .l3proto = NFPROTO_IPV4, + .in_range = nf_nat_ipv4_in_range, + .secure_port = nf_nat_ipv4_secure_port, + .manip_pkt = nf_nat_ipv4_manip_pkt, + .csum_update = nf_nat_ipv4_csum_update, + .csum_recalc = nf_nat_ipv4_csum_recalc, + .nlattr_to_range = nf_nat_ipv4_nlattr_to_range, +#ifdef CONFIG_XFRM + .decode_session = nf_nat_ipv4_decode_session, +#endif +}; + +int nf_nat_icmp_reply_translation(struct sk_buff *skb, + struct nf_conn *ct, + enum ip_conntrack_info ctinfo, + unsigned int hooknum) +{ + struct { + struct icmphdr icmp; + struct iphdr ip; + } *inside; + enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo); + enum nf_nat_manip_type manip = HOOK2MANIP(hooknum); + unsigned int hdrlen = ip_hdrlen(skb); + const struct nf_nat_l4proto *l4proto; + struct nf_conntrack_tuple target; + unsigned long statusbit; + + NF_CT_ASSERT(ctinfo == IP_CT_RELATED || ctinfo == IP_CT_RELATED_REPLY); + + if (!skb_make_writable(skb, hdrlen + sizeof(*inside))) + return 0; + if (nf_ip_checksum(skb, hooknum, hdrlen, 0)) + return 0; + + inside = (void *)skb->data + hdrlen; + if (inside->icmp.type == ICMP_REDIRECT) { + if ((ct->status & IPS_NAT_DONE_MASK) != IPS_NAT_DONE_MASK) + return 0; + if (ct->status & IPS_NAT_MASK) + return 0; + } + + if (manip == NF_NAT_MANIP_SRC) + statusbit = IPS_SRC_NAT; + else + statusbit = IPS_DST_NAT; + + /* Invert if this is reply direction */ + if (dir == IP_CT_DIR_REPLY) + statusbit ^= IPS_NAT_MASK; + + if (!(ct->status & statusbit)) + return 1; + + l4proto = __nf_nat_l4proto_find(NFPROTO_IPV4, inside->ip.protocol); + if (!nf_nat_ipv4_manip_pkt(skb, hdrlen + sizeof(inside->icmp), + l4proto, &ct->tuplehash[!dir].tuple, !manip)) + return 0; + + if (skb->ip_summed != CHECKSUM_PARTIAL) { + /* Reloading "inside" here since manip_pkt may reallocate */ + inside = (void *)skb->data + hdrlen; + inside->icmp.checksum = 0; + inside->icmp.checksum = + csum_fold(skb_checksum(skb, hdrlen, + skb->len - hdrlen, 0)); + } + + /* Change outer to look like the reply to an incoming packet */ + nf_ct_invert_tuplepr(&target, &ct->tuplehash[!dir].tuple); + l4proto = __nf_nat_l4proto_find(NFPROTO_IPV4, 0); + if (!nf_nat_ipv4_manip_pkt(skb, 0, l4proto, &target, manip)) + return 0; + + return 1; +} +EXPORT_SYMBOL_GPL(nf_nat_icmp_reply_translation); + +static int __init nf_nat_l3proto_ipv4_init(void) +{ + int err; + + err = nf_nat_l4proto_register(NFPROTO_IPV4, &nf_nat_l4proto_icmp); + if (err < 0) + goto err1; + err = nf_nat_l3proto_register(&nf_nat_l3proto_ipv4); + if (err < 0) + goto err2; + return err; + +err2: + nf_nat_l4proto_unregister(NFPROTO_IPV4, &nf_nat_l4proto_icmp); +err1: + return err; +} + +static void __exit nf_nat_l3proto_ipv4_exit(void) +{ + nf_nat_l3proto_unregister(&nf_nat_l3proto_ipv4); + nf_nat_l4proto_unregister(NFPROTO_IPV4, &nf_nat_l4proto_icmp); +} + +MODULE_LICENSE("GPL"); +MODULE_ALIAS("nf-nat-" __stringify(AF_INET)); + +module_init(nf_nat_l3proto_ipv4_init); +module_exit(nf_nat_l3proto_ipv4_exit); -- cgit v1.2.3