[NETFILTER]: nf_conntrack/nf_nat: add TFTP helper port

Add IPv4 and IPv6 capable nf_conntrack port of the TFTP conntrack/NAT helper.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

7 files changed, 249 insertions, 0 deletions

diff --git a/include/linux/netfilter/nf_conntrack_tftp.h b/include/linux/netfilter/nf_conntrack_tftp.h
new file mode 100644
index 000000000000..0d79b7ae051f
--- /dev/null
+++ b/include/linux/netfilter/nf_conntrack_tftp.h
@@ -0,0 +1,20 @@
+#ifndef _NF_CONNTRACK_TFTP_H
+#define _NF_CONNTRACK_TFTP_H
+
+#define TFTP_PORT 69
+
+struct tftphdr {
+        __be16 opcode;
+};
+
+#define TFTP_OPCODE_READ        1
+#define TFTP_OPCODE_WRITE       2
+#define TFTP_OPCODE_DATA        3
+#define TFTP_OPCODE_ACK         4
+#define TFTP_OPCODE_ERROR       5
+
+extern unsigned int (*nf_nat_tftp_hook)(struct sk_buff **pskb,
+                                        enum ip_conntrack_info ctinfo,
+                                        struct nf_conntrack_expect *exp);
+
+#endif /* _NF_CONNTRACK_TFTP_H */
diff --git a/net/ipv4/netfilter/Kconfig b/net/ipv4/netfilter/Kconfig
index 83e83f553ccb..1c0018b6bea4 100644
--- a/net/ipv4/netfilter/Kconfig
+++ b/net/ipv4/netfilter/Kconfig
@@ -515,6 +515,11 @@ config IP_NF_NAT_TFTP
         default IP_NF_NAT if IP_NF_TFTP=y
         default m if IP_NF_TFTP=m
 
+config NF_NAT_TFTP
+        tristate
+        depends on IP_NF_IPTABLES && NF_CONNTRACK && NF_NAT
+        default NF_NAT && NF_CONNTRACK_TFTP
+
 config IP_NF_NAT_AMANDA
         tristate
         depends on IP_NF_IPTABLES!=n && IP_NF_CONNTRACK!=n && IP_NF_NAT!=n
diff --git a/net/ipv4/netfilter/Makefile b/net/ipv4/netfilter/Makefile
index 167b65e89aca..3ca0af0ed5f0 100644
--- a/net/ipv4/netfilter/Makefile
+++ b/net/ipv4/netfilter/Makefile
@@ -56,6 +56,7 @@ obj-$(CONFIG_NF_NAT_H323) += nf_nat_h323.o
 obj-$(CONFIG_NF_NAT_IRC) += nf_nat_irc.o
 obj-$(CONFIG_NF_NAT_PPTP) += nf_nat_pptp.o
 obj-$(CONFIG_NF_NAT_SIP) += nf_nat_sip.o
+obj-$(CONFIG_NF_NAT_TFTP) += nf_nat_tftp.o
 
 # NAT protocols (nf_nat)
 obj-$(CONFIG_NF_NAT_PROTO_GRE) += nf_nat_proto_gre.o
diff --git a/net/ipv4/netfilter/nf_nat_tftp.c b/net/ipv4/netfilter/nf_nat_tftp.c
new file mode 100644
index 000000000000..2566b79de224
--- /dev/null
+++ b/net/ipv4/netfilter/nf_nat_tftp.c
@@ -0,0 +1,52 @@
+/* (C) 2001-2002 Magnus Boden <mb@ozaba.mine.nu>
+ *
+ * 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/module.h>
+#include <linux/moduleparam.h>
+#include <linux/udp.h>
+
+#include <net/netfilter/nf_nat_helper.h>
+#include <net/netfilter/nf_nat_rule.h>
+#include <net/netfilter/nf_conntrack_helper.h>
+#include <net/netfilter/nf_conntrack_expect.h>
+#include <linux/netfilter/nf_conntrack_tftp.h>
+
+MODULE_AUTHOR("Magnus Boden <mb@ozaba.mine.nu>");
+MODULE_DESCRIPTION("TFTP NAT helper");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("ip_nat_tftp");
+
+static unsigned int help(struct sk_buff **pskb,
+                         enum ip_conntrack_info ctinfo,
+                         struct nf_conntrack_expect *exp)
+{
+        struct nf_conn *ct = exp->master;
+
+        exp->saved_proto.udp.port
+                = ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.udp.port;
+        exp->dir = IP_CT_DIR_REPLY;
+        exp->expectfn = nf_nat_follow_master;
+        if (nf_conntrack_expect_related(exp) != 0)
+                return NF_DROP;
+        return NF_ACCEPT;
+}
+
+static void __exit nf_nat_tftp_fini(void)
+{
+        rcu_assign_pointer(nf_nat_tftp_hook, NULL);
+        synchronize_rcu();
+}
+
+static int __init nf_nat_tftp_init(void)
+{
+        BUG_ON(rcu_dereference(nf_nat_tftp_hook));
+        rcu_assign_pointer(nf_nat_tftp_hook, help);
+        return 0;
+}
+
+module_init(nf_nat_tftp_init);
+module_exit(nf_nat_tftp_fini);
diff --git a/net/netfilter/Kconfig b/net/netfilter/Kconfig
index e73891194b31..e0deac17df12 100644
--- a/net/netfilter/Kconfig
+++ b/net/netfilter/Kconfig
@@ -248,6 +248,17 @@ config NF_CONNTRACK_SIP
 
           To compile it as a module, choose M here.  If unsure, say N.
 
+config NF_CONNTRACK_TFTP
+        tristate "TFTP protocol support (EXPERIMENTAL)"
+        depends on EXPERIMENTAL && NF_CONNTRACK
+        help
+          TFTP connection tracking helper, this is required depending
+          on how restrictive your ruleset is.
+          If you are using a tftp client behind -j SNAT or -j MASQUERADING
+          you will need this.
+
+          To compile it as a module, choose M here.  If unsure, say N.
+
 config NF_CT_NETLINK
         tristate 'Connection tracking netlink interface (EXPERIMENTAL)'
         depends on EXPERIMENTAL && NF_CONNTRACK && NETFILTER_NETLINK
diff --git a/net/netfilter/Makefile b/net/netfilter/Makefile
index 86da21700aa3..5dc5574f7e99 100644
--- a/net/netfilter/Makefile
+++ b/net/netfilter/Makefile
@@ -30,6 +30,7 @@ obj-$(CONFIG_NF_CONNTRACK_IRC) += nf_conntrack_irc.o
 obj-$(CONFIG_NF_CONNTRACK_NETBIOS_NS) += nf_conntrack_netbios_ns.o
 obj-$(CONFIG_NF_CONNTRACK_PPTP) += nf_conntrack_pptp.o
 obj-$(CONFIG_NF_CONNTRACK_SIP) += nf_conntrack_sip.o
+obj-$(CONFIG_NF_CONNTRACK_TFTP) += nf_conntrack_tftp.o
 
 # generic X tables 
 obj-$(CONFIG_NETFILTER_XTABLES) += x_tables.o xt_tcpudp.o
diff --git a/net/netfilter/nf_conntrack_tftp.c b/net/netfilter/nf_conntrack_tftp.c
new file mode 100644
index 000000000000..d46a1263fcb5
--- /dev/null
+++ b/net/netfilter/nf_conntrack_tftp.c
@@ -0,0 +1,159 @@
+/* (C) 2001-2002 Magnus Boden <mb@ozaba.mine.nu>
+ *
+ * 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/module.h>
+#include <linux/moduleparam.h>
+#include <linux/in.h>
+#include <linux/udp.h>
+
+#include <net/netfilter/nf_conntrack.h>
+#include <net/netfilter/nf_conntrack_tuple.h>
+#include <net/netfilter/nf_conntrack_expect.h>
+#include <net/netfilter/nf_conntrack_ecache.h>
+#include <net/netfilter/nf_conntrack_helper.h>
+#include <linux/netfilter/nf_conntrack_tftp.h>
+
+MODULE_AUTHOR("Magnus Boden <mb@ozaba.mine.nu>");
+MODULE_DESCRIPTION("TFTP connection tracking helper");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("ip_conntrack_tftp");
+
+#define MAX_PORTS 8
+static unsigned short ports[MAX_PORTS];
+static int ports_c;
+module_param_array(ports, ushort, &ports_c, 0400);
+MODULE_PARM_DESC(ports, "Port numbers of TFTP servers");
+
+#if 0
+#define DEBUGP(format, args...) printk("%s:%s:" format, \
+                                       __FILE__, __FUNCTION__ , ## args)
+#else
+#define DEBUGP(format, args...)
+#endif
+
+unsigned int (*nf_nat_tftp_hook)(struct sk_buff **pskb,
+                                 enum ip_conntrack_info ctinfo,
+                                 struct nf_conntrack_expect *exp) __read_mostly;
+EXPORT_SYMBOL_GPL(nf_nat_tftp_hook);
+
+static int tftp_help(struct sk_buff **pskb,
+                     unsigned int protoff,
+                     struct nf_conn *ct,
+                     enum ip_conntrack_info ctinfo)
+{
+        struct tftphdr _tftph, *tfh;
+        struct nf_conntrack_expect *exp;
+        struct nf_conntrack_tuple *tuple;
+        unsigned int ret = NF_ACCEPT;
+        int family = ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.l3num;
+        typeof(nf_nat_tftp_hook) nf_nat_tftp;
+
+        tfh = skb_header_pointer(*pskb, protoff + sizeof(struct udphdr),
+                                 sizeof(_tftph), &_tftph);
+        if (tfh == NULL)
+                return NF_ACCEPT;
+
+        switch (ntohs(tfh->opcode)) {
+        case TFTP_OPCODE_READ:
+        case TFTP_OPCODE_WRITE:
+                /* RRQ and WRQ works the same way */
+                DEBUGP("");
+                NF_CT_DUMP_TUPLE(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple);
+                NF_CT_DUMP_TUPLE(&ct->tuplehash[IP_CT_DIR_REPLY].tuple);
+
+                exp = nf_conntrack_expect_alloc(ct);
+                if (exp == NULL)
+                        return NF_DROP;
+                tuple = &ct->tuplehash[IP_CT_DIR_REPLY].tuple;
+                nf_conntrack_expect_init(exp, family,
+                                         &tuple->src.u3, &tuple->dst.u3,
+                                         IPPROTO_UDP,
+                                         NULL, &tuple->dst.u.udp.port);
+
+                DEBUGP("expect: ");
+                NF_CT_DUMP_TUPLE(&exp->tuple);
+                NF_CT_DUMP_TUPLE(&exp->mask);
+
+                nf_nat_tftp = rcu_dereference(nf_nat_tftp_hook);
+                if (nf_nat_tftp && ct->status & IPS_NAT_MASK)
+                        ret = nf_nat_tftp(pskb, ctinfo, exp);
+                else if (nf_conntrack_expect_related(exp) != 0)
+                        ret = NF_DROP;
+                nf_conntrack_expect_put(exp);
+                break;
+        case TFTP_OPCODE_DATA:
+        case TFTP_OPCODE_ACK:
+                DEBUGP("Data/ACK opcode\n");
+                break;
+        case TFTP_OPCODE_ERROR:
+                DEBUGP("Error opcode\n");
+                break;
+        default:
+                DEBUGP("Unknown opcode\n");
+        }
+        return ret;
+}
+
+static struct nf_conntrack_helper tftp[MAX_PORTS][2] __read_mostly;
+static char tftp_names[MAX_PORTS][2][sizeof("tftp-65535")] __read_mostly;
+
+static void nf_conntrack_tftp_fini(void)
+{
+        int i, j;
+
+        for (i = 0; i < ports_c; i++) {
+                for (j = 0; j < 2; j++)
+                        nf_conntrack_helper_unregister(&tftp[i][j]);
+        }
+}
+
+static int __init nf_conntrack_tftp_init(void)
+{
+        int i, j, ret;
+        char *tmpname;
+
+        if (ports_c == 0)
+                ports[ports_c++] = TFTP_PORT;
+
+        for (i = 0; i < ports_c; i++) {
+                memset(&tftp[i], 0, sizeof(tftp[i]));
+
+                tftp[i][0].tuple.src.l3num = AF_INET;
+                tftp[i][1].tuple.src.l3num = AF_INET6;
+                for (j = 0; j < 2; j++) {
+                        tftp[i][j].tuple.dst.protonum = IPPROTO_UDP;
+                        tftp[i][j].tuple.src.u.udp.port = htons(ports[i]);
+                        tftp[i][j].mask.src.l3num = 0xFFFF;
+                        tftp[i][j].mask.dst.protonum = 0xFF;
+                        tftp[i][j].mask.src.u.udp.port = htons(0xFFFF);
+                        tftp[i][j].max_expected = 1;
+                        tftp[i][j].timeout = 5 * 60; /* 5 minutes */
+                        tftp[i][j].me = THIS_MODULE;
+                        tftp[i][j].help = tftp_help;
+
+                        tmpname = &tftp_names[i][j][0];
+                        if (ports[i] == TFTP_PORT)
+                                sprintf(tmpname, "tftp");
+                        else
+                                sprintf(tmpname, "tftp-%u", i);
+                        tftp[i][j].name = tmpname;
+
+                        ret = nf_conntrack_helper_register(&tftp[i][j]);
+                        if (ret) {
+                                printk("nf_ct_tftp: failed to register helper "
+                                       "for pf: %u port: %u\n",
+                                        tftp[i][j].tuple.src.l3num, ports[i]);
+                                nf_conntrack_tftp_fini();
+                                return ret;
+                        }
+                }
+        }
+        return 0;
+}
+
+module_init(nf_conntrack_tftp_init);
+module_exit(nf_conntrack_tftp_fini);