2eb0f624b7
This is a patch proposal to support shifted ranges in portmaps. (i.e. tcp/udp incoming port 5000-5100 on WAN redirected to LAN 192.168.1.5:2000-2100) Currently DNAT only works for single port or identical port ranges. (i.e. ports 5000-5100 on WAN interface redirected to a LAN host while original destination port is not altered) When different port ranges are configured, either 'random' mode should be used, or else all incoming connections are mapped onto the first port in the redirect range. (in described example WAN:5000-5100 will all be mapped to 192.168.1.5:2000) This patch introduces a new mode indicated by flag NF_NAT_RANGE_PROTO_OFFSET which uses a base port value to calculate an offset with the destination port present in the incoming stream. That offset is then applied as index within the redirect port range (index modulo rangewidth to handle range overflow). In described example the base port would be 5000. An incoming stream with destination port 5004 would result in an offset value 4 which means that the NAT'ed stream will be using destination port 2004. Other possibilities include deterministic mapping of larger or multiple ranges to a smaller range : WAN:5000-5999 -> LAN:5000-5099 (maps WAN port 5*xx to port 51xx) This patch does not change any current behavior. It just adds new NAT proto range functionality which must be selected via the specific flag when intended to use. A patch for iptables (libipt_DNAT.c + libip6t_DNAT.c) will also be proposed which makes this functionality immediately available. Signed-off-by: Thierry Du Tre <thierry@dtsystems.be> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
78 lines
2 KiB
C
78 lines
2 KiB
C
/*
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* Copyright (c) 2008 Patrick McHardy <kaber@trash.net>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#include <linux/types.h>
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#include <linux/sctp.h>
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#include <net/sctp/checksum.h>
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#include <net/netfilter/nf_nat_l4proto.h>
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static u_int16_t nf_sctp_port_rover;
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static void
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sctp_unique_tuple(const struct nf_nat_l3proto *l3proto,
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struct nf_conntrack_tuple *tuple,
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const struct nf_nat_range2 *range,
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enum nf_nat_manip_type maniptype,
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const struct nf_conn *ct)
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{
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nf_nat_l4proto_unique_tuple(l3proto, tuple, range, maniptype, ct,
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&nf_sctp_port_rover);
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}
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static bool
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sctp_manip_pkt(struct sk_buff *skb,
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const struct nf_nat_l3proto *l3proto,
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unsigned int iphdroff, unsigned int hdroff,
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const struct nf_conntrack_tuple *tuple,
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enum nf_nat_manip_type maniptype)
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{
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struct sctphdr *hdr;
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int hdrsize = 8;
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/* This could be an inner header returned in imcp packet; in such
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* cases we cannot update the checksum field since it is outside
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* of the 8 bytes of transport layer headers we are guaranteed.
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*/
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if (skb->len >= hdroff + sizeof(*hdr))
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hdrsize = sizeof(*hdr);
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if (!skb_make_writable(skb, hdroff + hdrsize))
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return false;
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hdr = (struct sctphdr *)(skb->data + hdroff);
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if (maniptype == NF_NAT_MANIP_SRC) {
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/* Get rid of src port */
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hdr->source = tuple->src.u.sctp.port;
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} else {
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/* Get rid of dst port */
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hdr->dest = tuple->dst.u.sctp.port;
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}
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if (hdrsize < sizeof(*hdr))
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return true;
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if (skb->ip_summed != CHECKSUM_PARTIAL) {
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hdr->checksum = sctp_compute_cksum(skb, hdroff);
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skb->ip_summed = CHECKSUM_NONE;
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}
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return true;
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}
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const struct nf_nat_l4proto nf_nat_l4proto_sctp = {
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.l4proto = IPPROTO_SCTP,
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.manip_pkt = sctp_manip_pkt,
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.in_range = nf_nat_l4proto_in_range,
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.unique_tuple = sctp_unique_tuple,
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#if IS_ENABLED(CONFIG_NF_CT_NETLINK)
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.nlattr_to_range = nf_nat_l4proto_nlattr_to_range,
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#endif
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};
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