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Subject[patch v2.3 3/4] IPVS: make FTP work with full NAT support
From
From:	Hannes Eder <heder@google.com>

Use nf_conntrack/nf_nat code to do the packet mangling and the TCP
sequence adjusting. The function 'ip_vs_skb_replace' is now dead
code, so it is removed.

To SNAT FTP, use something like:

% iptables -t nat -A POSTROUTING -m ipvs --vaddr 192.168.100.30/32 \
> --vport 21 -j SNAT --to-source 192.168.10.10

and for the data connections in passive mode:

% iptables -t nat -A POSTROUTING -m ipvs --vaddr 192.168.100.30/32 \
> --vportctl 21 -j SNAT --to-source 192.168.10.10

using '-m state --state RELATED' would also works.

Make sure the kernel modules ip_vs_ftp, nf_conntrack_ftp, and
nf_nat_ftp are loaded.

[ up-port and minor fixes by Simon Horman <horms@verge.net.au> ]
Signed-off-by: Hannes Eder <heder@google.com>
Signed-off-by: Simon Horman <horms@verge.net.au>

---
include/net/ip_vs.h | 2
net/netfilter/ipvs/Kconfig | 2
net/netfilter/ipvs/ip_vs_app.c | 43 ----------
net/netfilter/ipvs/ip_vs_core.c | 1
net/netfilter/ipvs/ip_vs_ftp.c | 164 ++++++++++++++++++++++++++++++++++++---
5 files changed, 153 insertions(+), 59 deletions(-)
v2.1
* Up-port

v2.2
* No change

v2.3
* Up-port
* Use %pI4 instead of NIPQUAD
* Drop buf_len = snprintf() change - its a separate, cosmetic, fix

Index: nf-next-2.6/include/net/ip_vs.h
===================================================================
--- nf-next-2.6.orig/include/net/ip_vs.h 2010-07-04 20:30:19.000000000 +0900
+++ nf-next-2.6/include/net/ip_vs.h 2010-07-04 20:32:06.000000000 +0900
@@ -736,8 +736,6 @@ extern void ip_vs_app_inc_put(struct ip_

extern int ip_vs_app_pkt_out(struct ip_vs_conn *, struct sk_buff *skb);
extern int ip_vs_app_pkt_in(struct ip_vs_conn *, struct sk_buff *skb);
-extern int ip_vs_skb_replace(struct sk_buff *skb, gfp_t pri,
- char *o_buf, int o_len, char *n_buf, int n_len);
extern int ip_vs_app_init(void);
extern void ip_vs_app_cleanup(void);

Index: nf-next-2.6/net/netfilter/ipvs/Kconfig
===================================================================
--- nf-next-2.6.orig/net/netfilter/ipvs/Kconfig 2010-07-04 20:32:05.000000000 +0900
+++ nf-next-2.6/net/netfilter/ipvs/Kconfig 2010-07-04 20:32:06.000000000 +0900
@@ -238,7 +238,7 @@ comment 'IPVS application helper'

config IP_VS_FTP
tristate "FTP protocol helper"
- depends on IP_VS_PROTO_TCP
+ depends on IP_VS_PROTO_TCP && NF_NAT
---help---
FTP is a protocol that transfers IP address and/or port number in
the payload. In the virtual server via Network Address Translation,
Index: nf-next-2.6/net/netfilter/ipvs/ip_vs_app.c
===================================================================
--- nf-next-2.6.orig/net/netfilter/ipvs/ip_vs_app.c 2010-07-04 20:30:19.000000000 +0900
+++ nf-next-2.6/net/netfilter/ipvs/ip_vs_app.c 2010-07-04 20:32:06.000000000 +0900
@@ -569,49 +569,6 @@ static const struct file_operations ip_v
};
#endif

-
-/*
- * Replace a segment of data with a new segment
- */
-int ip_vs_skb_replace(struct sk_buff *skb, gfp_t pri,
- char *o_buf, int o_len, char *n_buf, int n_len)
-{
- int diff;
- int o_offset;
- int o_left;
-
- EnterFunction(9);
-
- diff = n_len - o_len;
- o_offset = o_buf - (char *)skb->data;
- /* The length of left data after o_buf+o_len in the skb data */
- o_left = skb->len - (o_offset + o_len);
-
- if (diff <= 0) {
- memmove(o_buf + n_len, o_buf + o_len, o_left);
- memcpy(o_buf, n_buf, n_len);
- skb_trim(skb, skb->len + diff);
- } else if (diff <= skb_tailroom(skb)) {
- skb_put(skb, diff);
- memmove(o_buf + n_len, o_buf + o_len, o_left);
- memcpy(o_buf, n_buf, n_len);
- } else {
- if (pskb_expand_head(skb, skb_headroom(skb), diff, pri))
- return -ENOMEM;
- skb_put(skb, diff);
- memmove(skb->data + o_offset + n_len,
- skb->data + o_offset + o_len, o_left);
- skb_copy_to_linear_data_offset(skb, o_offset, n_buf, n_len);
- }
-
- /* must update the iph total length here */
- ip_hdr(skb)->tot_len = htons(skb->len);
-
- LeaveFunction(9);
- return 0;
-}
-
-
int __init ip_vs_app_init(void)
{
/* we will replace it with proc_net_ipvs_create() soon */
Index: nf-next-2.6/net/netfilter/ipvs/ip_vs_core.c
===================================================================
--- nf-next-2.6.orig/net/netfilter/ipvs/ip_vs_core.c 2010-07-04 20:32:05.000000000 +0900
+++ nf-next-2.6/net/netfilter/ipvs/ip_vs_core.c 2010-07-04 20:32:06.000000000 +0900
@@ -54,7 +54,6 @@

EXPORT_SYMBOL(register_ip_vs_scheduler);
EXPORT_SYMBOL(unregister_ip_vs_scheduler);
-EXPORT_SYMBOL(ip_vs_skb_replace);
EXPORT_SYMBOL(ip_vs_proto_name);
EXPORT_SYMBOL(ip_vs_conn_new);
EXPORT_SYMBOL(ip_vs_conn_in_get);
Index: nf-next-2.6/net/netfilter/ipvs/ip_vs_ftp.c
===================================================================
--- nf-next-2.6.orig/net/netfilter/ipvs/ip_vs_ftp.c 2010-07-04 20:30:19.000000000 +0900
+++ nf-next-2.6/net/netfilter/ipvs/ip_vs_ftp.c 2010-07-04 20:32:06.000000000 +0900
@@ -20,6 +20,17 @@
*
* Author: Wouter Gadeyne
*
+ *
+ * Code for ip_vs_expect_related and ip_vs_expect_callback is taken from
+ * http://www.ssi.bg/~ja/nfct/:
+ *
+ * ip_vs_nfct.c: Netfilter connection tracking support for IPVS
+ *
+ * Portions Copyright (C) 2001-2002
+ * Antefacto Ltd, 181 Parnell St, Dublin 1, Ireland.
+ *
+ * Portions Copyright (C) 2003-2008
+ * Julian Anastasov
*/

#define KMSG_COMPONENT "IPVS"
@@ -32,6 +43,9 @@
#include <linux/in.h>
#include <linux/ip.h>
#include <linux/netfilter.h>
+#include <net/netfilter/nf_conntrack.h>
+#include <net/netfilter/nf_conntrack_expect.h>
+#include <net/netfilter/nf_nat_helper.h>
#include <linux/gfp.h>
#include <net/protocol.h>
#include <net/tcp.h>
@@ -43,6 +57,16 @@
#define SERVER_STRING "227 Entering Passive Mode ("
#define CLIENT_STRING "PORT "

+#define FMT_TUPLE "%pI4:%u->%pI4:%u/%u"
+#define ARG_TUPLE(T) (T)->src.u3.ip, ntohs((T)->src.u.all), \
+ (T)->dst.u3.ip, ntohs((T)->dst.u.all), \
+ (T)->dst.protonum
+
+#define FMT_CONN "%pI4:%u->%pI4:%u->%pI4:%u/%u:%u"
+#define ARG_CONN(C) (C)->caddr, ntohs((C)->cport), \
+ (C)->vaddr, ntohs((C)->vport), \
+ (C)->daddr, ntohs((C)->dport), \
+ (C)->protocol, (C)->state

/*
* List of ports (up to IP_VS_APP_MAX_PORTS) to be handled by helper
@@ -123,6 +147,119 @@ static int ip_vs_ftp_get_addrport(char *
return 1;
}

+/*
+ * Called from init_conntrack() as expectfn handler.
+ */
+static void
+ip_vs_expect_callback(struct nf_conn *ct,
+ struct nf_conntrack_expect *exp)
+{
+ struct nf_conntrack_tuple *orig, new_reply;
+ struct ip_vs_conn *cp;
+
+ if (exp->tuple.src.l3num != PF_INET)
+ return;
+
+ /*
+ * We assume that no NF locks are held before this callback.
+ * ip_vs_conn_out_get and ip_vs_conn_in_get should match their
+ * expectations even if they use wildcard values, now we provide the
+ * actual values from the newly created original conntrack direction.
+ * The conntrack is confirmed when packet reaches IPVS hooks.
+ */
+
+ /* RS->CLIENT */
+ orig = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
+ cp = ip_vs_conn_out_get(exp->tuple.src.l3num, orig->dst.protonum,
+ &orig->src.u3, orig->src.u.tcp.port,
+ &orig->dst.u3, orig->dst.u.tcp.port);
+ if (cp) {
+ /* Change reply CLIENT->RS to CLIENT->VS */
+ new_reply = ct->tuplehash[IP_CT_DIR_REPLY].tuple;
+ IP_VS_DBG(7, "%s(): ct=%p, status=0x%lX, tuples=" FMT_TUPLE ", "
+ FMT_TUPLE ", found inout cp=" FMT_CONN "\n",
+ __func__, ct, ct->status,
+ ARG_TUPLE(orig), ARG_TUPLE(&new_reply),
+ ARG_CONN(cp));
+ new_reply.dst.u3 = cp->vaddr;
+ new_reply.dst.u.tcp.port = cp->vport;
+ IP_VS_DBG(7, "%s(): ct=%p, new tuples=" FMT_TUPLE ", " FMT_TUPLE
+ ", inout cp=" FMT_CONN "\n",
+ __func__, ct,
+ ARG_TUPLE(orig), ARG_TUPLE(&new_reply),
+ ARG_CONN(cp));
+ goto alter;
+ }
+
+ /* CLIENT->VS */
+ cp = ip_vs_conn_in_get(exp->tuple.src.l3num, orig->dst.protonum,
+ &orig->src.u3, orig->src.u.tcp.port,
+ &orig->dst.u3, orig->dst.u.tcp.port);
+ if (cp) {
+ /* Change reply VS->CLIENT to RS->CLIENT */
+ new_reply = ct->tuplehash[IP_CT_DIR_REPLY].tuple;
+ IP_VS_DBG(7, "%s(): ct=%p, status=0x%lX, tuples=" FMT_TUPLE ", "
+ FMT_TUPLE ", found outin cp=" FMT_CONN "\n",
+ __func__, ct, ct->status,
+ ARG_TUPLE(orig), ARG_TUPLE(&new_reply),
+ ARG_CONN(cp));
+ new_reply.src.u3 = cp->daddr;
+ new_reply.src.u.tcp.port = cp->dport;
+ IP_VS_DBG(7, "%s(): ct=%p, new tuples=" FMT_TUPLE ", "
+ FMT_TUPLE ", outin cp=" FMT_CONN "\n",
+ __func__, ct,
+ ARG_TUPLE(orig), ARG_TUPLE(&new_reply),
+ ARG_CONN(cp));
+ goto alter;
+ }
+
+ IP_VS_DBG(7, "%s(): ct=%p, status=0x%lX, tuple=" FMT_TUPLE
+ " - unknown expect\n",
+ __func__, ct, ct->status, ARG_TUPLE(orig));
+ return;
+
+alter:
+ /* Never alter conntrack for non-NAT conns */
+ if (IP_VS_FWD_METHOD(cp) == IP_VS_CONN_F_MASQ)
+ nf_conntrack_alter_reply(ct, &new_reply);
+ ip_vs_conn_put(cp);
+ return;
+}
+
+/*
+ * Create NF conntrack expectation with wildcard (optional) source port.
+ * Then the default callback function will alter the reply and will confirm
+ * the conntrack entry when the first packet comes.
+ */
+static void
+ip_vs_expect_related(struct sk_buff *skb, struct nf_conn *ct,
+ struct ip_vs_conn *cp, u_int8_t proto,
+ const __be16 *port, int from_rs)
+{
+ struct nf_conntrack_expect *exp;
+
+ BUG_ON(!ct || ct == &nf_conntrack_untracked);
+
+ exp = nf_ct_expect_alloc(ct);
+ if (!exp)
+ return;
+
+ if (from_rs)
+ nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT,
+ nf_ct_l3num(ct), &cp->daddr, &cp->caddr,
+ proto, port, &cp->cport);
+ else
+ nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT,
+ nf_ct_l3num(ct), &cp->caddr, &cp->vaddr,
+ proto, port, &cp->vport);
+
+ exp->expectfn = ip_vs_expect_callback;
+
+ IP_VS_DBG(7, "%s(): ct=%p, expect tuple=" FMT_TUPLE "\n",
+ __func__, ct, ARG_TUPLE(&exp->tuple));
+ nf_ct_expect_related(exp);
+ nf_ct_expect_put(exp);
+}

/*
* Look at outgoing ftp packets to catch the response to a PASV command
@@ -147,9 +284,11 @@ static int ip_vs_ftp_out(struct ip_vs_ap
union nf_inet_addr from;
__be16 port;
struct ip_vs_conn *n_cp;
- char buf[24]; /* xxx.xxx.xxx.xxx,ppp,ppp\000 */
+ char buf[sizeof("xxx,xxx,xxx,xxx,ppp,ppp")];
unsigned buf_len;
int ret;
+ enum ip_conntrack_info ctinfo;
+ struct nf_conn *ct;

#ifdef CONFIG_IP_VS_IPV6
/* This application helper doesn't work with IPv6 yet,
@@ -219,19 +358,23 @@ static int ip_vs_ftp_out(struct ip_vs_ap

buf_len = strlen(buf);

+ ct = nf_ct_get(skb, &ctinfo);
+ ret = nf_nat_mangle_tcp_packet(skb,
+ ct,
+ ctinfo,
+ start-data,
+ end-start,
+ buf,
+ buf_len);
+
+ if (ct && ct != &nf_conntrack_untracked)
+ ip_vs_expect_related(skb, ct, n_cp,
+ IPPROTO_TCP, NULL, 0);
+
/*
- * Calculate required delta-offset to keep TCP happy
+ * Not setting 'diff' is intentional, otherwise the sequence
+ * would be adjusted twice.
*/
- *diff = buf_len - (end-start);
-
- if (*diff == 0) {
- /* simply replace it with new passive address */
- memcpy(start, buf, buf_len);
- ret = 1;
- } else {
- ret = !ip_vs_skb_replace(skb, GFP_ATOMIC, start,
- end-start, buf, buf_len);
- }

cp->app_data = NULL;
ip_vs_tcp_conn_listen(n_cp);
@@ -263,6 +406,7 @@ static int ip_vs_ftp_in(struct ip_vs_app
union nf_inet_addr to;
__be16 port;
struct ip_vs_conn *n_cp;
+ struct nf_conn *ct;

#ifdef CONFIG_IP_VS_IPV6
/* This application helper doesn't work with IPv6 yet,
@@ -349,6 +493,11 @@ static int ip_vs_ftp_in(struct ip_vs_app
ip_vs_control_add(n_cp, cp);
}

+ ct = (struct nf_conn *)skb->nfct;
+ if (ct && ct != &nf_conntrack_untracked)
+ ip_vs_expect_related(skb, ct, n_cp,
+ IPPROTO_TCP, &n_cp->dport, 1);
+
/*
* Move tunnel to listen state
*/


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