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- /* (C) 1999-2001 Paul `Rusty' Russell
- * (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>
- *
- * 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 <linux/types.h>
- #include <linux/init.h>
- #include <linux/random.h>
- #include <linux/ip.h>
- #include <linux/tcp.h>
- #include <linux/netfilter.h>
- #include <linux/netfilter/nfnetlink_conntrack.h>
- #include <net/netfilter/nf_nat.h>
- #include <net/netfilter/nf_nat_rule.h>
- #include <net/netfilter/nf_nat_protocol.h>
- #include <net/netfilter/nf_nat_core.h>
- static int
- tcp_in_range(const struct nf_conntrack_tuple *tuple,
- enum nf_nat_manip_type maniptype,
- const union nf_conntrack_man_proto *min,
- const union nf_conntrack_man_proto *max)
- {
- __be16 port;
- if (maniptype == IP_NAT_MANIP_SRC)
- port = tuple->src.u.tcp.port;
- else
- port = tuple->dst.u.tcp.port;
- return ntohs(port) >= ntohs(min->tcp.port) &&
- ntohs(port) <= ntohs(max->tcp.port);
- }
- static int
- tcp_unique_tuple(struct nf_conntrack_tuple *tuple,
- const struct nf_nat_range *range,
- enum nf_nat_manip_type maniptype,
- const struct nf_conn *ct)
- {
- static u_int16_t port;
- __be16 *portptr;
- unsigned int range_size, min, i;
- if (maniptype == IP_NAT_MANIP_SRC)
- portptr = &tuple->src.u.tcp.port;
- else
- portptr = &tuple->dst.u.tcp.port;
- /* If no range specified... */
- if (!(range->flags & IP_NAT_RANGE_PROTO_SPECIFIED)) {
- /* If it's dst rewrite, can't change port */
- if (maniptype == IP_NAT_MANIP_DST)
- return 0;
- /* Map privileged onto privileged. */
- if (ntohs(*portptr) < 1024) {
- /* Loose convention: >> 512 is credential passing */
- if (ntohs(*portptr)<512) {
- min = 1;
- range_size = 511 - min + 1;
- } else {
- min = 600;
- range_size = 1023 - min + 1;
- }
- } else {
- min = 1024;
- range_size = 65535 - 1024 + 1;
- }
- } else {
- min = ntohs(range->min.tcp.port);
- range_size = ntohs(range->max.tcp.port) - min + 1;
- }
- if (range->flags & IP_NAT_RANGE_PROTO_RANDOM)
- port = net_random();
- for (i = 0; i < range_size; i++, port++) {
- *portptr = htons(min + port % range_size);
- if (!nf_nat_used_tuple(tuple, ct))
- return 1;
- }
- return 0;
- }
- static int
- tcp_manip_pkt(struct sk_buff **pskb,
- unsigned int iphdroff,
- const struct nf_conntrack_tuple *tuple,
- enum nf_nat_manip_type maniptype)
- {
- struct iphdr *iph = (struct iphdr *)((*pskb)->data + iphdroff);
- struct tcphdr *hdr;
- unsigned int hdroff = iphdroff + iph->ihl*4;
- __be32 oldip, newip;
- __be16 *portptr, newport, oldport;
- int hdrsize = 8; /* TCP connection tracking guarantees this much */
- /* this could be a inner header returned in icmp packet; in such
- cases we cannot update the checksum field since it is outside of
- the 8 bytes of transport layer headers we are guaranteed */
- if ((*pskb)->len >= hdroff + sizeof(struct tcphdr))
- hdrsize = sizeof(struct tcphdr);
- if (!skb_make_writable(pskb, hdroff + hdrsize))
- return 0;
- iph = (struct iphdr *)((*pskb)->data + iphdroff);
- hdr = (struct tcphdr *)((*pskb)->data + hdroff);
- if (maniptype == IP_NAT_MANIP_SRC) {
- /* Get rid of src ip and src pt */
- oldip = iph->saddr;
- newip = tuple->src.u3.ip;
- newport = tuple->src.u.tcp.port;
- portptr = &hdr->source;
- } else {
- /* Get rid of dst ip and dst pt */
- oldip = iph->daddr;
- newip = tuple->dst.u3.ip;
- newport = tuple->dst.u.tcp.port;
- portptr = &hdr->dest;
- }
- oldport = *portptr;
- *portptr = newport;
- if (hdrsize < sizeof(*hdr))
- return 1;
- nf_proto_csum_replace4(&hdr->check, *pskb, oldip, newip, 1);
- nf_proto_csum_replace2(&hdr->check, *pskb, oldport, newport, 0);
- return 1;
- }
- struct nf_nat_protocol nf_nat_protocol_tcp = {
- .name = "TCP",
- .protonum = IPPROTO_TCP,
- .me = THIS_MODULE,
- .manip_pkt = tcp_manip_pkt,
- .in_range = tcp_in_range,
- .unique_tuple = tcp_unique_tuple,
- #if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
- .range_to_nfattr = nf_nat_port_range_to_nfattr,
- .nfattr_to_range = nf_nat_port_nfattr_to_range,
- #endif
- };
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