| 1 | /* Amanda extension for TCP NAT alteration. |
| 2 | * (C) 2002 by Brian J. Murrell <netfilter@interlinx.bc.ca> |
| 3 | * based on a copy of HW's ip_nat_irc.c as well as other modules |
| 4 | * (C) 2006-2012 Patrick McHardy <kaber@trash.net> |
| 5 | * |
| 6 | * This program is free software; you can redistribute it and/or |
| 7 | * modify it under the terms of the GNU General Public License |
| 8 | * as published by the Free Software Foundation; either version |
| 9 | * 2 of the License, or (at your option) any later version. |
| 10 | */ |
| 11 | |
| 12 | #include <linux/kernel.h> |
| 13 | #include <linux/module.h> |
| 14 | #include <linux/skbuff.h> |
| 15 | #include <linux/udp.h> |
| 16 | |
| 17 | #include <net/netfilter/nf_conntrack_helper.h> |
| 18 | #include <net/netfilter/nf_conntrack_expect.h> |
| 19 | #include <net/netfilter/nf_nat_helper.h> |
| 20 | #include <linux/netfilter/nf_conntrack_amanda.h> |
| 21 | |
| 22 | MODULE_AUTHOR("Brian J. Murrell <netfilter@interlinx.bc.ca>"); |
| 23 | MODULE_DESCRIPTION("Amanda NAT helper"); |
| 24 | MODULE_LICENSE("GPL"); |
| 25 | MODULE_ALIAS("ip_nat_amanda"); |
| 26 | |
| 27 | static unsigned int help(struct sk_buff *skb, |
| 28 | enum ip_conntrack_info ctinfo, |
| 29 | unsigned int protoff, |
| 30 | unsigned int matchoff, |
| 31 | unsigned int matchlen, |
| 32 | struct nf_conntrack_expect *exp) |
| 33 | { |
| 34 | char buffer[sizeof("65535")]; |
| 35 | u_int16_t port; |
| 36 | unsigned int ret; |
| 37 | |
| 38 | /* Connection comes from client. */ |
| 39 | exp->saved_proto.tcp.port = exp->tuple.dst.u.tcp.port; |
| 40 | exp->dir = IP_CT_DIR_ORIGINAL; |
| 41 | |
| 42 | /* When you see the packet, we need to NAT it the same as the |
| 43 | * this one (ie. same IP: it will be TCP and master is UDP). */ |
| 44 | exp->expectfn = nf_nat_follow_master; |
| 45 | |
| 46 | /* Try to get same port: if not, try to change it. */ |
| 47 | for (port = ntohs(exp->saved_proto.tcp.port); port != 0; port++) { |
| 48 | int res; |
| 49 | |
| 50 | exp->tuple.dst.u.tcp.port = htons(port); |
| 51 | res = nf_ct_expect_related(exp); |
| 52 | if (res == 0) |
| 53 | break; |
| 54 | else if (res != -EBUSY) { |
| 55 | port = 0; |
| 56 | break; |
| 57 | } |
| 58 | } |
| 59 | |
| 60 | if (port == 0) { |
| 61 | nf_ct_helper_log(skb, exp->master, "all ports in use"); |
| 62 | return NF_DROP; |
| 63 | } |
| 64 | |
| 65 | sprintf(buffer, "%u", port); |
| 66 | ret = nf_nat_mangle_udp_packet(skb, exp->master, ctinfo, |
| 67 | protoff, matchoff, matchlen, |
| 68 | buffer, strlen(buffer)); |
| 69 | if (ret != NF_ACCEPT) { |
| 70 | nf_ct_helper_log(skb, exp->master, "cannot mangle packet"); |
| 71 | nf_ct_unexpect_related(exp); |
| 72 | } |
| 73 | return ret; |
| 74 | } |
| 75 | |
| 76 | static void __exit nf_nat_amanda_fini(void) |
| 77 | { |
| 78 | RCU_INIT_POINTER(nf_nat_amanda_hook, NULL); |
| 79 | synchronize_rcu(); |
| 80 | } |
| 81 | |
| 82 | static int __init nf_nat_amanda_init(void) |
| 83 | { |
| 84 | BUG_ON(nf_nat_amanda_hook != NULL); |
| 85 | RCU_INIT_POINTER(nf_nat_amanda_hook, help); |
| 86 | return 0; |
| 87 | } |
| 88 | |
| 89 | module_init(nf_nat_amanda_init); |
| 90 | module_exit(nf_nat_amanda_fini); |