[NETFILTER]: nf_nat: add FTP NAT helper port

Add FTP NAT helper.

Split out from Jozsef's big nf_nat patch with a few small fixes by myself.

Signed-off-by: Jozsef Kadlecsik <kadlec@blackhole.kfki.hu>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

4 files changed, 210 insertions, 19 deletions

diff --git a/net/ipv4/netfilter/Kconfig b/net/ipv4/netfilter/Kconfig
index 01789aeaeb5f..52f876db68f4 100644
--- a/net/ipv4/netfilter/Kconfig
+++ b/net/ipv4/netfilter/Kconfig
@@ -477,20 +477,29 @@ config IP_NF_NAT_SNMP_BASIC
 
           To compile it as a module, choose M here.  If unsure, say N.
 
+# If they want FTP, set to $CONFIG_IP_NF_NAT (m or y),
+# or $CONFIG_IP_NF_FTP (m or y), whichever is weaker.
+# From kconfig-language.txt:
+#
+#           <expr> '&&' <expr>                   (6)
+#
+# (6) Returns the result of min(/expr/, /expr/).
+config IP_NF_NAT_FTP
+        tristate
+        depends on IP_NF_IPTABLES && IP_NF_CONNTRACK && IP_NF_NAT
+        default IP_NF_NAT && IP_NF_FTP
+
+config NF_NAT_FTP
+        tristate
+        depends on IP_NF_IPTABLES && NF_CONNTRACK && NF_NAT
+        default NF_NAT && NF_CONNTRACK_FTP
+
 config IP_NF_NAT_IRC
         tristate
         depends on IP_NF_IPTABLES!=n && IP_NF_CONNTRACK!=n && IP_NF_NAT!=n
         default IP_NF_NAT if IP_NF_IRC=y
         default m if IP_NF_IRC=m
 
-# If they want FTP, set to $CONFIG_IP_NF_NAT (m or y), 
-# or $CONFIG_IP_NF_FTP (m or y), whichever is weaker.  Argh.
-config IP_NF_NAT_FTP
-        tristate
-        depends on IP_NF_IPTABLES!=n && IP_NF_CONNTRACK!=n && IP_NF_NAT!=n
-        default IP_NF_NAT if IP_NF_FTP=y
-        default m if IP_NF_FTP=m
-
 config IP_NF_NAT_TFTP
         tristate
         depends on IP_NF_IPTABLES!=n && IP_NF_CONNTRACK!=n && IP_NF_NAT!=n
diff --git a/net/ipv4/netfilter/Makefile b/net/ipv4/netfilter/Makefile
index ec31690764ac..c0c6194bb275 100644
--- a/net/ipv4/netfilter/Makefile
+++ b/net/ipv4/netfilter/Makefile
@@ -40,7 +40,7 @@ obj-$(CONFIG_IP_NF_IRC) += ip_conntrack_irc.o
 obj-$(CONFIG_IP_NF_SIP) += ip_conntrack_sip.o
 obj-$(CONFIG_IP_NF_NETBIOS_NS) += ip_conntrack_netbios_ns.o
 
-# NAT helpers 
+# NAT helpers (ip_conntrack)
 obj-$(CONFIG_IP_NF_NAT_H323) += ip_nat_h323.o
 obj-$(CONFIG_IP_NF_NAT_PPTP) += ip_nat_pptp.o
 obj-$(CONFIG_IP_NF_NAT_AMANDA) += ip_nat_amanda.o
@@ -49,6 +49,9 @@ obj-$(CONFIG_IP_NF_NAT_FTP) += ip_nat_ftp.o
 obj-$(CONFIG_IP_NF_NAT_IRC) += ip_nat_irc.o
 obj-$(CONFIG_IP_NF_NAT_SIP) += ip_nat_sip.o
 
+# NAT helpers (nf_conntrack)
+obj-$(CONFIG_NF_NAT_FTP) += nf_nat_ftp.o
+
 # generic IP tables 
 obj-$(CONFIG_IP_NF_IPTABLES) += ip_tables.o
 
diff --git a/net/ipv4/netfilter/nf_nat_ftp.c b/net/ipv4/netfilter/nf_nat_ftp.c
new file mode 100644
index 000000000000..751b59801755
--- /dev/null
+++ b/net/ipv4/netfilter/nf_nat_ftp.c
@@ -0,0 +1,179 @@
+/* FTP extension for TCP NAT alteration. */
+
+/* (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/module.h>
+#include <linux/moduleparam.h>
+#include <linux/ip.h>
+#include <linux/tcp.h>
+#include <linux/netfilter_ipv4.h>
+#include <net/netfilter/nf_nat.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_ftp.h>
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>");
+MODULE_DESCRIPTION("ftp NAT helper");
+MODULE_ALIAS("ip_nat_ftp");
+
+#if 0
+#define DEBUGP printk
+#else
+#define DEBUGP(format, args...)
+#endif
+
+/* FIXME: Time out? --RR */
+
+static int
+mangle_rfc959_packet(struct sk_buff **pskb,
+                     __be32 newip,
+                     u_int16_t port,
+                     unsigned int matchoff,
+                     unsigned int matchlen,
+                     struct nf_conn *ct,
+                     enum ip_conntrack_info ctinfo,
+                     u32 *seq)
+{
+        char buffer[sizeof("nnn,nnn,nnn,nnn,nnn,nnn")];
+
+        sprintf(buffer, "%u,%u,%u,%u,%u,%u",
+                NIPQUAD(newip), port>>8, port&0xFF);
+
+        DEBUGP("calling nf_nat_mangle_tcp_packet\n");
+
+        *seq += strlen(buffer) - matchlen;
+        return nf_nat_mangle_tcp_packet(pskb, ct, ctinfo, matchoff,
+                                        matchlen, buffer, strlen(buffer));
+}
+
+/* |1|132.235.1.2|6275| */
+static int
+mangle_eprt_packet(struct sk_buff **pskb,
+                   __be32 newip,
+                   u_int16_t port,
+                   unsigned int matchoff,
+                   unsigned int matchlen,
+                   struct nf_conn *ct,
+                   enum ip_conntrack_info ctinfo,
+                   u32 *seq)
+{
+        char buffer[sizeof("|1|255.255.255.255|65535|")];
+
+        sprintf(buffer, "|1|%u.%u.%u.%u|%u|", NIPQUAD(newip), port);
+
+        DEBUGP("calling nf_nat_mangle_tcp_packet\n");
+
+        *seq += strlen(buffer) - matchlen;
+        return nf_nat_mangle_tcp_packet(pskb, ct, ctinfo, matchoff,
+                                        matchlen, buffer, strlen(buffer));
+}
+
+/* |1|132.235.1.2|6275| */
+static int
+mangle_epsv_packet(struct sk_buff **pskb,
+                   __be32 newip,
+                   u_int16_t port,
+                   unsigned int matchoff,
+                   unsigned int matchlen,
+                   struct nf_conn *ct,
+                   enum ip_conntrack_info ctinfo,
+                   u32 *seq)
+{
+        char buffer[sizeof("|||65535|")];
+
+        sprintf(buffer, "|||%u|", port);
+
+        DEBUGP("calling nf_nat_mangle_tcp_packet\n");
+
+        *seq += strlen(buffer) - matchlen;
+        return nf_nat_mangle_tcp_packet(pskb, ct, ctinfo, matchoff,
+                                        matchlen, buffer, strlen(buffer));
+}
+
+static int (*mangle[])(struct sk_buff **, __be32, u_int16_t,
+                       unsigned int, unsigned int, struct nf_conn *,
+                       enum ip_conntrack_info, u32 *seq)
+= {
+        [NF_CT_FTP_PORT] = mangle_rfc959_packet,
+        [NF_CT_FTP_PASV] = mangle_rfc959_packet,
+        [NF_CT_FTP_EPRT] = mangle_eprt_packet,
+        [NF_CT_FTP_EPSV] = mangle_epsv_packet
+};
+
+/* So, this packet has hit the connection tracking matching code.
+   Mangle it, and change the expectation to match the new version. */
+static unsigned int nf_nat_ftp(struct sk_buff **pskb,
+                               enum ip_conntrack_info ctinfo,
+                               enum nf_ct_ftp_type type,
+                               unsigned int matchoff,
+                               unsigned int matchlen,
+                               struct nf_conntrack_expect *exp,
+                               u32 *seq)
+{
+        __be32 newip;
+        u_int16_t port;
+        int dir = CTINFO2DIR(ctinfo);
+        struct nf_conn *ct = exp->master;
+
+        DEBUGP("FTP_NAT: type %i, off %u len %u\n", type, matchoff, matchlen);
+
+        /* Connection will come from wherever this packet goes, hence !dir */
+        newip = ct->tuplehash[!dir].tuple.dst.u3.ip;
+        exp->saved_proto.tcp.port = exp->tuple.dst.u.tcp.port;
+        exp->dir = !dir;
+
+        /* When you see the packet, we need to NAT it the same as the
+         * this one. */
+        exp->expectfn = nf_nat_follow_master;
+
+        /* Try to get same port: if not, try to change it. */
+        for (port = ntohs(exp->saved_proto.tcp.port); port != 0; port++) {
+                exp->tuple.dst.u.tcp.port = htons(port);
+                if (nf_conntrack_expect_related(exp) == 0)
+                        break;
+        }
+
+        if (port == 0)
+                return NF_DROP;
+
+        if (!mangle[type](pskb, newip, port, matchoff, matchlen, ct, ctinfo,
+                          seq)) {
+                nf_conntrack_unexpect_related(exp);
+                return NF_DROP;
+        }
+        return NF_ACCEPT;
+}
+
+static void __exit nf_nat_ftp_fini(void)
+{
+        rcu_assign_pointer(nf_nat_ftp_hook, NULL);
+        synchronize_rcu();
+}
+
+static int __init nf_nat_ftp_init(void)
+{
+        BUG_ON(rcu_dereference(nf_nat_ftp_hook));
+        rcu_assign_pointer(nf_nat_ftp_hook, nf_nat_ftp);
+        return 0;
+}
+
+/* Prior to 2.6.11, we had a ports param.  No longer, but don't break users. */
+static int warn_set(const char *val, struct kernel_param *kp)
+{
+        printk(KERN_INFO KBUILD_MODNAME
+               ": kernel >= 2.6.10 only uses 'ports' for conntrack modules\n");
+        return 0;
+}
+module_param_call(ports, warn_set, NULL, NULL, 0);
+
+module_init(nf_nat_ftp_init);
+module_exit(nf_nat_ftp_fini);
diff --git a/net/netfilter/nf_conntrack_ftp.c b/net/netfilter/nf_conntrack_ftp.c
index e299d657e4fc..92a947168761 100644
--- a/net/netfilter/nf_conntrack_ftp.c
+++ b/net/netfilter/nf_conntrack_ftp.c
@@ -51,7 +51,7 @@ module_param(loose, bool, 0600);
 
 unsigned int (*nf_nat_ftp_hook)(struct sk_buff **pskb,
                                 enum ip_conntrack_info ctinfo,
-                                enum ip_ct_ftp_type type,
+                                enum nf_ct_ftp_type type,
                                 unsigned int matchoff,
                                 unsigned int matchlen,
                                 struct nf_conntrack_expect *exp,
@@ -74,7 +74,7 @@ static struct ftp_search {
         size_t plen;
         char skip;
         char term;
-        enum ip_ct_ftp_type ftptype;
+        enum nf_ct_ftp_type ftptype;
         int (*getnum)(const char *, size_t, struct nf_conntrack_man *, char);
 } search[IP_CT_DIR_MAX][2] = {
         [IP_CT_DIR_ORIGINAL] = {
@@ -83,7 +83,7 @@ static struct ftp_search {
                         .plen           = sizeof("PORT") - 1,
                         .skip           = ' ',
                         .term           = '\r',
-                        .ftptype        = IP_CT_FTP_PORT,
+                        .ftptype        = NF_CT_FTP_PORT,
                         .getnum         = try_rfc959,
                 },
                 {
@@ -91,7 +91,7 @@ static struct ftp_search {
                         .plen           = sizeof("EPRT") - 1,
                         .skip           = ' ',
                         .term           = '\r',
-                        .ftptype        = IP_CT_FTP_EPRT,
+                        .ftptype        = NF_CT_FTP_EPRT,
                         .getnum         = try_eprt,
                 },
         },
@@ -101,7 +101,7 @@ static struct ftp_search {
                         .plen           = sizeof("227 ") - 1,
                         .skip           = '(',
                         .term           = ')',
-                        .ftptype        = IP_CT_FTP_PASV,
+                        .ftptype        = NF_CT_FTP_PASV,
                         .getnum         = try_rfc959,
                 },
                 {
@@ -109,7 +109,7 @@ static struct ftp_search {
                         .plen           = sizeof("229 ") - 1,
                         .skip           = '(',
                         .term           = ')',
-                        .ftptype        = IP_CT_FTP_EPSV,
+                        .ftptype        = NF_CT_FTP_EPSV,
                         .getnum         = try_epsv_response,
                 },
         },
@@ -320,7 +320,7 @@ static int find_pattern(const char *data, size_t dlen,
 }
 
 /* Look up to see if we're just after a \n. */
-static int find_nl_seq(u32 seq, const struct ip_ct_ftp_master *info, int dir)
+static int find_nl_seq(u32 seq, const struct nf_ct_ftp_master *info, int dir)
 {
         unsigned int i;
 
@@ -331,7 +331,7 @@ static int find_nl_seq(u32 seq, const struct ip_ct_ftp_master *info, int dir)
 }
 
 /* We don't update if it's older than what we have. */
-static void update_nl_seq(u32 nl_seq, struct ip_ct_ftp_master *info, int dir,
+static void update_nl_seq(u32 nl_seq, struct nf_ct_ftp_master *info, int dir,
                           struct sk_buff *skb)
 {
         unsigned int i, oldest = NUM_SEQ_TO_REMEMBER;
@@ -367,7 +367,7 @@ static int help(struct sk_buff **pskb,
         u32 seq;
         int dir = CTINFO2DIR(ctinfo);
         unsigned int matchlen, matchoff;
-        struct ip_ct_ftp_master *ct_ftp_info = &nfct_help(ct)->help.ct_ftp_info;
+        struct nf_ct_ftp_master *ct_ftp_info = &nfct_help(ct)->help.ct_ftp_info;
         struct nf_conntrack_expect *exp;
         struct nf_conntrack_man cmd = {};
         unsigned int i;
@@ -523,7 +523,7 @@ static int help(struct sk_buff **pskb,
         /* Now, NAT might want to mangle the packet, and register the
          * (possibly changed) expectation itself. */
         nf_nat_ftp = rcu_dereference(nf_nat_ftp_hook);
-        if (nf_nat_ftp)
+        if (nf_nat_ftp && ct->status & IPS_NAT_MASK)
                 ret = nf_nat_ftp(pskb, ctinfo, search[dir][i].ftptype,
                                  matchoff, matchlen, exp, &seq);
         else {