[IPSEC] xfrm: Abstract out encapsulation modes

This patch adds the structure xfrm_mode.  It is meant to represent
the operations carried out by transport/tunnel modes.

By doing this we allow additional encapsulation modes to be added
without clogging up the xfrm_input/xfrm_output paths.

Candidate modes include 4-to-6 tunnel mode, 6-to-4 tunnel mode, and
BEET modes.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

7 files changed, 224 insertions, 86 deletions

diff --git a/net/ipv6/Kconfig b/net/ipv6/Kconfig
index f8a107ab5592..e923d4dea418 100644
--- a/net/ipv6/Kconfig
+++ b/net/ipv6/Kconfig
@@ -106,6 +106,26 @@ config INET6_TUNNEL
         tristate
         default n
 
+config INET6_XFRM_MODE_TRANSPORT
+        tristate "IPv6: IPsec transport mode"
+        depends on IPV6
+        default IPV6
+        select XFRM
+        ---help---
+          Support for IPsec transport mode.
+
+          If unsure, say Y.
+
+config INET6_XFRM_MODE_TUNNEL
+        tristate "IPv6: IPsec tunnel mode"
+        depends on IPV6
+        default IPV6
+        select XFRM
+        ---help---
+          Support for IPsec tunnel mode.
+
+          If unsure, say Y.
+
 config IPV6_TUNNEL
         tristate "IPv6: IPv6-in-IPv6 tunnel"
         select INET6_TUNNEL
diff --git a/net/ipv6/Makefile b/net/ipv6/Makefile
index a760b0988fbb..386e0a626948 100644
--- a/net/ipv6/Makefile
+++ b/net/ipv6/Makefile
@@ -20,6 +20,8 @@ obj-$(CONFIG_INET6_ESP) += esp6.o
 obj-$(CONFIG_INET6_IPCOMP) += ipcomp6.o
 obj-$(CONFIG_INET6_XFRM_TUNNEL) += xfrm6_tunnel.o
 obj-$(CONFIG_INET6_TUNNEL) += tunnel6.o
+obj-$(CONFIG_INET6_XFRM_MODE_TRANSPORT) += xfrm6_mode_transport.o
+obj-$(CONFIG_INET6_XFRM_MODE_TUNNEL) += xfrm6_mode_tunnel.o
 obj-$(CONFIG_NETFILTER) += netfilter/
 
 obj-$(CONFIG_IPV6_TUNNEL) += ip6_tunnel.o
diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index e46048974f37..416f6e428a0a 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -39,6 +39,7 @@
 #include <linux/in6.h>
 #include <linux/tcp.h>
 #include <linux/route.h>
+#include <linux/module.h>
 
 #include <linux/netfilter.h>
 #include <linux/netfilter_ipv6.h>
@@ -488,6 +489,7 @@ int ip6_find_1stfragopt(struct sk_buff *skb, u8 **nexthdr)
 
         return offset;
 }
+EXPORT_SYMBOL_GPL(ip6_find_1stfragopt);
 
 static int ip6_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *))
 {
diff --git a/net/ipv6/xfrm6_input.c b/net/ipv6/xfrm6_input.c
index 00cfdee18dca..0405d74ff910 100644
--- a/net/ipv6/xfrm6_input.c
+++ b/net/ipv6/xfrm6_input.c
@@ -13,21 +13,9 @@
 #include <linux/string.h>
 #include <linux/netfilter.h>
 #include <linux/netfilter_ipv6.h>
-#include <net/dsfield.h>
-#include <net/inet_ecn.h>
-#include <net/ip.h>
 #include <net/ipv6.h>
 #include <net/xfrm.h>
 
-static inline void ipip6_ecn_decapsulate(struct sk_buff *skb)
-{
-        struct ipv6hdr *outer_iph = skb->nh.ipv6h;
-        struct ipv6hdr *inner_iph = skb->h.ipv6h;
-
-        if (INET_ECN_is_ce(ipv6_get_dsfield(outer_iph)))
-                IP6_ECN_set_ce(inner_iph);
-}
-
 int xfrm6_rcv_spi(struct sk_buff *skb, u32 spi)
 {
         int err;
@@ -81,21 +69,10 @@ int xfrm6_rcv_spi(struct sk_buff *skb, u32 spi)
 
                 xfrm_vec[xfrm_nr++] = x;
 
+                if (x->mode->input(x, skb))
+                        goto drop;
+
                 if (x->props.mode) { /* XXX */
-                        if (nexthdr != IPPROTO_IPV6)
-                                goto drop;
-                        if (!pskb_may_pull(skb, sizeof(struct ipv6hdr)))
-                                goto drop;
-                        if (skb_cloned(skb) &&
-                            pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
-                                goto drop;
-                        if (x->props.flags & XFRM_STATE_DECAP_DSCP)
-                                ipv6_copy_dscp(skb->nh.ipv6h, skb->h.ipv6h);
-                        if (!(x->props.flags & XFRM_STATE_NOECN))
-                                ipip6_ecn_decapsulate(skb);
-                        skb->mac.raw = memmove(skb->data - skb->mac_len,
-                                               skb->mac.raw, skb->mac_len);
-                        skb->nh.raw = skb->data;
                         decaps = 1;
                         break;
                 }
diff --git a/net/ipv6/xfrm6_mode_transport.c b/net/ipv6/xfrm6_mode_transport.c
new file mode 100644
index 000000000000..5efbbae08ef0
--- /dev/null
+++ b/net/ipv6/xfrm6_mode_transport.c
@@ -0,0 +1,73 @@
+/*
+ * xfrm6_mode_transport.c - Transport mode encapsulation for IPv6.
+ *
+ * Copyright (C) 2002 USAGI/WIDE Project
+ * Copyright (c) 2004-2006 Herbert Xu <herbert@gondor.apana.org.au>
+ */
+
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/skbuff.h>
+#include <linux/stringify.h>
+#include <net/dst.h>
+#include <net/ipv6.h>
+#include <net/xfrm.h>
+
+/* Add encapsulation header.
+ *
+ * The IP header and mutable extension headers will be moved forward to make
+ * space for the encapsulation header.
+ *
+ * On exit, skb->h will be set to the start of the encapsulation header to be
+ * filled in by x->type->output and skb->nh will be set to the nextheader field
+ * of the extension header directly preceding the encapsulation header, or in
+ * its absence, that of the top IP header.  The value of skb->data will always
+ * point to the top IP header.
+ */
+static int xfrm6_transport_output(struct sk_buff *skb)
+{
+        struct xfrm_state *x = skb->dst->xfrm;
+        struct ipv6hdr *iph;
+        u8 *prevhdr;
+        int hdr_len;
+
+        skb_push(skb, x->props.header_len);
+        iph = skb->nh.ipv6h;
+
+        hdr_len = ip6_find_1stfragopt(skb, &prevhdr);
+        skb->nh.raw = prevhdr - x->props.header_len;
+        skb->h.raw = skb->data + hdr_len;
+        memmove(skb->data, iph, hdr_len);
+        return 0;
+}
+
+static int xfrm6_transport_input(struct xfrm_state *x, struct sk_buff *skb)
+{
+        return 0;
+}
+
+static struct xfrm_mode xfrm6_transport_mode = {
+        .input = xfrm6_transport_input,
+        .output = xfrm6_transport_output,
+        .owner = THIS_MODULE,
+        .encap = XFRM_MODE_TRANSPORT,
+};
+
+static int __init xfrm6_transport_init(void)
+{
+        return xfrm_register_mode(&xfrm6_transport_mode, AF_INET6);
+}
+
+static void __exit xfrm6_transport_exit(void)
+{
+        int err;
+
+        err = xfrm_unregister_mode(&xfrm6_transport_mode, AF_INET6);
+        BUG_ON(err);
+}
+
+module_init(xfrm6_transport_init);
+module_exit(xfrm6_transport_exit);
+MODULE_LICENSE("GPL");
+MODULE_ALIAS_XFRM_MODE(AF_INET6, XFRM_MODE_TRANSPORT);
diff --git a/net/ipv6/xfrm6_mode_tunnel.c b/net/ipv6/xfrm6_mode_tunnel.c
new file mode 100644
index 000000000000..8af79be2edca
--- /dev/null
+++ b/net/ipv6/xfrm6_mode_tunnel.c
@@ -0,0 +1,121 @@
+/*
+ * xfrm6_mode_tunnel.c - Tunnel mode encapsulation for IPv6.
+ *
+ * Copyright (C) 2002 USAGI/WIDE Project
+ * Copyright (c) 2004-2006 Herbert Xu <herbert@gondor.apana.org.au>
+ */
+
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/skbuff.h>
+#include <linux/stringify.h>
+#include <net/dsfield.h>
+#include <net/dst.h>
+#include <net/inet_ecn.h>
+#include <net/ipv6.h>
+#include <net/xfrm.h>
+
+static inline void ipip6_ecn_decapsulate(struct sk_buff *skb)
+{
+        struct ipv6hdr *outer_iph = skb->nh.ipv6h;
+        struct ipv6hdr *inner_iph = skb->h.ipv6h;
+
+        if (INET_ECN_is_ce(ipv6_get_dsfield(outer_iph)))
+                IP6_ECN_set_ce(inner_iph);
+}
+
+/* Add encapsulation header.
+ *
+ * The top IP header will be constructed per RFC 2401.  The following fields
+ * in it shall be filled in by x->type->output:
+ *      payload_len
+ *
+ * On exit, skb->h will be set to the start of the encapsulation header to be
+ * filled in by x->type->output and skb->nh will be set to the nextheader field
+ * of the extension header directly preceding the encapsulation header, or in
+ * its absence, that of the top IP header.  The value of skb->data will always
+ * point to the top IP header.
+ */
+static int xfrm6_tunnel_output(struct sk_buff *skb)
+{
+        struct dst_entry *dst = skb->dst;
+        struct xfrm_state *x = dst->xfrm;
+        struct ipv6hdr *iph, *top_iph;
+        int dsfield;
+
+        skb_push(skb, x->props.header_len);
+        iph = skb->nh.ipv6h;
+
+        skb->nh.raw = skb->data;
+        top_iph = skb->nh.ipv6h;
+        skb->nh.raw = &top_iph->nexthdr;
+        skb->h.ipv6h = top_iph + 1;
+
+        top_iph->version = 6;
+        top_iph->priority = iph->priority;
+        top_iph->flow_lbl[0] = iph->flow_lbl[0];
+        top_iph->flow_lbl[1] = iph->flow_lbl[1];
+        top_iph->flow_lbl[2] = iph->flow_lbl[2];
+        dsfield = ipv6_get_dsfield(top_iph);
+        dsfield = INET_ECN_encapsulate(dsfield, dsfield);
+        if (x->props.flags & XFRM_STATE_NOECN)
+                dsfield &= ~INET_ECN_MASK;
+        ipv6_change_dsfield(top_iph, 0, dsfield);
+        top_iph->nexthdr = IPPROTO_IPV6; 
+        top_iph->hop_limit = dst_metric(dst->child, RTAX_HOPLIMIT);
+        ipv6_addr_copy(&top_iph->saddr, (struct in6_addr *)&x->props.saddr);
+        ipv6_addr_copy(&top_iph->daddr, (struct in6_addr *)&x->id.daddr);
+        return 0;
+}
+
+static int xfrm6_tunnel_input(struct xfrm_state *x, struct sk_buff *skb)
+{
+        int err = -EINVAL;
+
+        if (skb->nh.raw[IP6CB(skb)->nhoff] != IPPROTO_IPV6)
+                goto out;
+        if (!pskb_may_pull(skb, sizeof(struct ipv6hdr)))
+                goto out;
+
+        if (skb_cloned(skb) &&
+            (err = pskb_expand_head(skb, 0, 0, GFP_ATOMIC)))
+                goto out;
+
+        if (x->props.flags & XFRM_STATE_DECAP_DSCP)
+                ipv6_copy_dscp(skb->nh.ipv6h, skb->h.ipv6h);
+        if (!(x->props.flags & XFRM_STATE_NOECN))
+                ipip6_ecn_decapsulate(skb);
+        skb->mac.raw = memmove(skb->data - skb->mac_len,
+                               skb->mac.raw, skb->mac_len);
+        skb->nh.raw = skb->data;
+        err = 0;
+
+out:
+        return err;
+}
+
+static struct xfrm_mode xfrm6_tunnel_mode = {
+        .input = xfrm6_tunnel_input,
+        .output = xfrm6_tunnel_output,
+        .owner = THIS_MODULE,
+        .encap = XFRM_MODE_TUNNEL,
+};
+
+static int __init xfrm6_tunnel_init(void)
+{
+        return xfrm_register_mode(&xfrm6_tunnel_mode, AF_INET6);
+}
+
+static void __exit xfrm6_tunnel_exit(void)
+{
+        int err;
+
+        err = xfrm_unregister_mode(&xfrm6_tunnel_mode, AF_INET6);
+        BUG_ON(err);
+}
+
+module_init(xfrm6_tunnel_init);
+module_exit(xfrm6_tunnel_exit);
+MODULE_LICENSE("GPL");
+MODULE_ALIAS_XFRM_MODE(AF_INET6, XFRM_MODE_TUNNEL);
diff --git a/net/ipv6/xfrm6_output.c b/net/ipv6/xfrm6_output.c
index 80242172a5df..16e84254a252 100644
--- a/net/ipv6/xfrm6_output.c
+++ b/net/ipv6/xfrm6_output.c
@@ -14,68 +14,9 @@
 #include <linux/spinlock.h>
 #include <linux/icmpv6.h>
 #include <linux/netfilter_ipv6.h>
-#include <net/dsfield.h>
-#include <net/inet_ecn.h>
 #include <net/ipv6.h>
 #include <net/xfrm.h>
 
-/* Add encapsulation header.
- *
- * In transport mode, the IP header and mutable extension headers will be moved
- * forward to make space for the encapsulation header.
- *
- * In tunnel mode, the top IP header will be constructed per RFC 2401.
- * The following fields in it shall be filled in by x->type->output:
- *      payload_len
- *
- * On exit, skb->h will be set to the start of the encapsulation header to be
- * filled in by x->type->output and skb->nh will be set to the nextheader field
- * of the extension header directly preceding the encapsulation header, or in
- * its absence, that of the top IP header.  The value of skb->data will always
- * point to the top IP header.
- */
-static void xfrm6_encap(struct sk_buff *skb)
-{
-        struct dst_entry *dst = skb->dst;
-        struct xfrm_state *x = dst->xfrm;
-        struct ipv6hdr *iph, *top_iph;
-        int dsfield;
-
-        skb_push(skb, x->props.header_len);
-        iph = skb->nh.ipv6h;
-
-        if (!x->props.mode) {
-                u8 *prevhdr;
-                int hdr_len;
-
-                hdr_len = ip6_find_1stfragopt(skb, &prevhdr);
-                skb->nh.raw = prevhdr - x->props.header_len;
-                skb->h.raw = skb->data + hdr_len;
-                memmove(skb->data, iph, hdr_len);
-                return;
-        }
-
-        skb->nh.raw = skb->data;
-        top_iph = skb->nh.ipv6h;
-        skb->nh.raw = &top_iph->nexthdr;
-        skb->h.ipv6h = top_iph + 1;
-
-        top_iph->version = 6;
-        top_iph->priority = iph->priority;
-        top_iph->flow_lbl[0] = iph->flow_lbl[0];
-        top_iph->flow_lbl[1] = iph->flow_lbl[1];
-        top_iph->flow_lbl[2] = iph->flow_lbl[2];
-        dsfield = ipv6_get_dsfield(top_iph);
-        dsfield = INET_ECN_encapsulate(dsfield, dsfield);
-        if (x->props.flags & XFRM_STATE_NOECN)
-                dsfield &= ~INET_ECN_MASK;
-        ipv6_change_dsfield(top_iph, 0, dsfield);
-        top_iph->nexthdr = IPPROTO_IPV6; 
-        top_iph->hop_limit = dst_metric(dst->child, RTAX_HOPLIMIT);
-        ipv6_addr_copy(&top_iph->saddr, (struct in6_addr *)&x->props.saddr);
-        ipv6_addr_copy(&top_iph->daddr, (struct in6_addr *)&x->id.daddr);
-}
-
 static int xfrm6_tunnel_check_size(struct sk_buff *skb)
 {
         int mtu, ret = 0;
@@ -118,7 +59,9 @@ static int xfrm6_output_one(struct sk_buff *skb)
                 if (err)
                         goto error;
 
-                xfrm6_encap(skb);
+                err = x->mode->output(skb);
+                if (err)
+                        goto error;
 
                 err = x->type->output(x, skb);
                 if (err)