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[patch v2.8 3/4] IPVS: make FTP work with full NAT support

To: lvs-devel@xxxxxxxxxxxxxxx, netdev@xxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, netfilter@xxxxxxxxxxxxxxx, netfilter-devel@xxxxxxxxxxxxxxx
Subject: [patch v2.8 3/4] IPVS: make FTP work with full NAT support
Cc: Malcolm Turnbull <malcolm@xxxxxxxxxxxxxxxx>, Mark Brooks <mark@xxxxxxxxxxxxxxxx>, Wensong Zhang <wensong@xxxxxxxxxxxx>, Julius Volz <julius.volz@xxxxxxxxx>, Patrick McHardy <kaber@xxxxxxxxx>, "David S. Miller" <davem@xxxxxxxxxxxxx>, Hannes Eder <heder@xxxxxxxxxx>, Jan Engelhardt <jengelh@xxxxxxxxxx>
From: Simon Horman <horms@xxxxxxxxxxxx>
Date: Thu, 22 Jul 2010 16:35:50 +0900
From:   Hannes Eder <heder@xxxxxxxxxx>

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@xxxxxxxxxxxx> ]
Signed-off-by: Hannes Eder <heder@xxxxxxxxxx>
Signed-off-by: Simon Horman <horms@xxxxxxxxxxxx>

--- 

 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  |  174 ++++++++++++++++++++++++++++++++++++---
 5 files changed, 164 insertions(+), 58 deletions(-)

v2.6
* pointer arguments for %pI4

v2.5
* Use nf_ct_is_untracked(ct) instead of nf_ct_is_untracked(),
  the latter is blatantly incorrect
* Return 0 (and thus drop the packet) if mangling wasn't attempted

v2.4
As suggested by Patrick McHardy
* Use nf_conntrack_untracked() instead of &nf_conntrack_untracked
* Fix ip_vs_ftp_out logic
  - Don't call nf_nat_mangle_tcp_packet() unless ct is valid and tracked
  - Only call ip_vs_expect_relatedi() if  nf_nat_mangle_tcp_packet()
    succeeds
  - Note that packets are dropped if mangling fails
Other
* Drop unrelated cosmetic change to sizing of buf in ip_vs_ftp_out()

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

v2.2
* No change

v2.1
* Up-port

Index: nf-next-2.6/include/net/ip_vs.h
===================================================================
--- nf-next-2.6.orig/include/net/ip_vs.h        2010-07-11 17:30:19.000000000 
+0900
+++ nf-next-2.6/include/net/ip_vs.h     2010-07-11 17:33:33.000000000 +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 2010-07-11 17:33:06.000000000 
+0900
+++ nf-next-2.6/net/netfilter/ipvs/Kconfig      2010-07-11 17:33:33.000000000 
+0900
@@ -235,7 +235,7 @@ 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     2010-07-11 
17:30:19.000000000 +0900
+++ nf-next-2.6/net/netfilter/ipvs/ip_vs_app.c  2010-07-11 17:33:33.000000000 
+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    2010-07-11 
17:33:06.000000000 +0900
+++ nf-next-2.6/net/netfilter/ipvs/ip_vs_core.c 2010-07-11 17:33:33.000000000 
+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     2010-07-11 
17:30:19.000000000 +0900
+++ nf-next-2.6/net/netfilter/ipvs/ip_vs_ftp.c  2010-07-11 18:01:58.000000000 
+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.ip), ntohs((C)->cport), \
+                       &((C)->vaddr.ip), ntohs((C)->vport), \
+                       &((C)->daddr.ip), 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
@@ -149,7 +286,9 @@ static int ip_vs_ftp_out(struct ip_vs_ap
        struct ip_vs_conn *n_cp;
        char buf[24];           /* xxx.xxx.xxx.xxx,ppp,ppp\000 */
        unsigned buf_len;
-       int ret;
+       int ret = 0;
+       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 +358,26 @@ static int ip_vs_ftp_out(struct ip_vs_ap
 
                buf_len = strlen(buf);
 
+               ct = nf_ct_get(skb, &ctinfo);
+               if (ct && !nf_ct_is_untracked(ct)) {
+                       /* If mangling fails this function will return 0
+                        * which will cause the packet to be dropped.
+                        * Mangling can only fail under memory pressure,
+                        * hopefully it will succeed on the retransmitted
+                        * packet.
+                        */
+                       ret = nf_nat_mangle_tcp_packet(skb, ct, ctinfo,
+                                                      start-data, end-start,
+                                                      buf, buf_len);
+                       if (ret)
+                               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 +409,7 @@ 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 +496,11 @@ 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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