[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>

6 files changed, 219 insertions, 84 deletions

diff --git a/net/ipv4/Kconfig b/net/ipv4/Kconfig
index e40f75322377..35eb70b1448d 100644
--- a/net/ipv4/Kconfig
+++ b/net/ipv4/Kconfig
@@ -414,6 +414,24 @@ config INET_TUNNEL
         tristate
         default n
 
+config INET_XFRM_MODE_TRANSPORT
+        tristate "IP: IPsec transport mode"
+        default y
+        select XFRM
+        ---help---
+          Support for IPsec transport mode.
+
+          If unsure, say Y.
+
+config INET_XFRM_MODE_TUNNEL
+        tristate "IP: IPsec tunnel mode"
+        default y
+        select XFRM
+        ---help---
+          Support for IPsec tunnel mode.
+
+          If unsure, say Y.
+
 config INET_DIAG
         tristate "INET: socket monitoring interface"
         default y
diff --git a/net/ipv4/Makefile b/net/ipv4/Makefile
index 9ef50a0b9d2c..4cc94482eacc 100644
--- a/net/ipv4/Makefile
+++ b/net/ipv4/Makefile
@@ -24,6 +24,8 @@ obj-$(CONFIG_INET_ESP) += esp4.o
 obj-$(CONFIG_INET_IPCOMP) += ipcomp.o
 obj-$(CONFIG_INET_XFRM_TUNNEL) += xfrm4_tunnel.o
 obj-$(CONFIG_INET_TUNNEL) += tunnel4.o
+obj-$(CONFIG_INET_XFRM_MODE_TRANSPORT) += xfrm4_mode_transport.o
+obj-$(CONFIG_INET_XFRM_MODE_TUNNEL) += xfrm4_mode_tunnel.o
 obj-$(CONFIG_IP_PNP) += ipconfig.o
 obj-$(CONFIG_IP_ROUTE_MULTIPATH_RR) += multipath_rr.o
 obj-$(CONFIG_IP_ROUTE_MULTIPATH_RANDOM) += multipath_random.o
diff --git a/net/ipv4/xfrm4_input.c b/net/ipv4/xfrm4_input.c
index 3e174c83bfe7..817ed84511a6 100644
--- a/net/ipv4/xfrm4_input.c
+++ b/net/ipv4/xfrm4_input.c
@@ -13,7 +13,6 @@
 #include <linux/string.h>
 #include <linux/netfilter.h>
 #include <linux/netfilter_ipv4.h>
-#include <net/inet_ecn.h>
 #include <net/ip.h>
 #include <net/xfrm.h>
 
@@ -24,15 +23,6 @@ int xfrm4_rcv(struct sk_buff *skb)
 
 EXPORT_SYMBOL(xfrm4_rcv);
 
-static inline void ipip_ecn_decapsulate(struct sk_buff *skb)
-{
-        struct iphdr *outer_iph = skb->nh.iph;
-        struct iphdr *inner_iph = skb->h.ipiph;
-
-        if (INET_ECN_is_ce(outer_iph->tos))
-                IP_ECN_set_ce(inner_iph);
-}
-
 static int xfrm4_parse_spi(struct sk_buff *skb, u8 nexthdr, u32 *spi, u32 *seq)
 {
         switch (nexthdr) {
@@ -113,24 +103,10 @@ int xfrm4_rcv_encap(struct sk_buff *skb, __u16 encap_type)
 
                 xfrm_vec[xfrm_nr++] = x;
 
-                iph = skb->nh.iph;
+                if (x->mode->input(x, skb))
+                        goto drop;
 
                 if (x->props.mode) {
-                        if (iph->protocol != IPPROTO_IPIP)
-                                goto drop;
-                        if (!pskb_may_pull(skb, sizeof(struct iphdr)))
-                                goto drop;
-                        if (skb_cloned(skb) &&
-                            pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
-                                goto drop;
-                        if (x->props.flags & XFRM_STATE_DECAP_DSCP)
-                                ipv4_copy_dscp(iph, skb->h.ipiph);
-                        if (!(x->props.flags & XFRM_STATE_NOECN))
-                                ipip_ecn_decapsulate(skb);
-                        skb->mac.raw = memmove(skb->data - skb->mac_len,
-                                               skb->mac.raw, skb->mac_len);
-                        skb->nh.raw = skb->data;
-                        memset(&(IPCB(skb)->opt), 0, sizeof(struct ip_options));
                         decaps = 1;
                         break;
                 }
diff --git a/net/ipv4/xfrm4_mode_transport.c b/net/ipv4/xfrm4_mode_transport.c
new file mode 100644
index 000000000000..e46d9a4ccc55
--- /dev/null
+++ b/net/ipv4/xfrm4_mode_transport.c
@@ -0,0 +1,69 @@
+/*
+ * xfrm4_mode_transport.c - Transport mode encapsulation for IPv4.
+ *
+ * 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/ip.h>
+#include <net/xfrm.h>
+
+/* Add encapsulation header.
+ *
+ * The IP header will be moved forward to make space for the encapsulation
+ * header.
+ *
+ * On exit, skb->h will be set to the start of the payload to be processed
+ * by x->type->output and skb->nh will be set to the top IP header.
+ */
+static int xfrm4_transport_output(struct sk_buff *skb)
+{
+        struct xfrm_state *x;
+        struct iphdr *iph;
+        int ihl;
+
+        iph = skb->nh.iph;
+        skb->h.ipiph = iph;
+
+        ihl = iph->ihl * 4;
+        skb->h.raw += ihl;
+
+        x = skb->dst->xfrm;
+        skb->nh.raw = memmove(skb_push(skb, x->props.header_len), iph, ihl);
+        return 0;
+}
+
+static int xfrm4_transport_input(struct xfrm_state *x, struct sk_buff *skb)
+{
+        return 0;
+}
+
+static struct xfrm_mode xfrm4_transport_mode = {
+        .input = xfrm4_transport_input,
+        .output = xfrm4_transport_output,
+        .owner = THIS_MODULE,
+        .encap = XFRM_MODE_TRANSPORT,
+};
+
+static int __init xfrm4_transport_init(void)
+{
+        return xfrm_register_mode(&xfrm4_transport_mode, AF_INET);
+}
+
+static void __exit xfrm4_transport_exit(void)
+{
+        int err;
+
+        err = xfrm_unregister_mode(&xfrm4_transport_mode, AF_INET);
+        BUG_ON(err);
+}
+
+module_init(xfrm4_transport_init);
+module_exit(xfrm4_transport_exit);
+MODULE_LICENSE("GPL");
+MODULE_ALIAS_XFRM_MODE(AF_INET, XFRM_MODE_TRANSPORT);
diff --git a/net/ipv4/xfrm4_mode_tunnel.c b/net/ipv4/xfrm4_mode_tunnel.c
new file mode 100644
index 000000000000..f8d880beb12f
--- /dev/null
+++ b/net/ipv4/xfrm4_mode_tunnel.c
@@ -0,0 +1,125 @@
+/*
+ * xfrm4_mode_tunnel.c - Tunnel mode encapsulation for IPv4.
+ *
+ * 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/inet_ecn.h>
+#include <net/ip.h>
+#include <net/xfrm.h>
+
+static inline void ipip_ecn_decapsulate(struct sk_buff *skb)
+{
+        struct iphdr *outer_iph = skb->nh.iph;
+        struct iphdr *inner_iph = skb->h.ipiph;
+
+        if (INET_ECN_is_ce(outer_iph->tos))
+                IP_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:
+ *      tot_len
+ *      check
+ *
+ * On exit, skb->h will be set to the start of the payload to be processed
+ * by x->type->output and skb->nh will be set to the top IP header.
+ */
+static int xfrm4_tunnel_output(struct sk_buff *skb)
+{
+        struct dst_entry *dst = skb->dst;
+        struct xfrm_state *x = dst->xfrm;
+        struct iphdr *iph, *top_iph;
+        int flags;
+
+        iph = skb->nh.iph;
+        skb->h.ipiph = iph;
+
+        skb->nh.raw = skb_push(skb, x->props.header_len);
+        top_iph = skb->nh.iph;
+
+        top_iph->ihl = 5;
+        top_iph->version = 4;
+
+        /* DS disclosed */
+        top_iph->tos = INET_ECN_encapsulate(iph->tos, iph->tos);
+
+        flags = x->props.flags;
+        if (flags & XFRM_STATE_NOECN)
+                IP_ECN_clear(top_iph);
+
+        top_iph->frag_off = (flags & XFRM_STATE_NOPMTUDISC) ?
+                0 : (iph->frag_off & htons(IP_DF));
+        if (!top_iph->frag_off)
+                __ip_select_ident(top_iph, dst->child, 0);
+
+        top_iph->ttl = dst_metric(dst->child, RTAX_HOPLIMIT);
+
+        top_iph->saddr = x->props.saddr.a4;
+        top_iph->daddr = x->id.daddr.a4;
+        top_iph->protocol = IPPROTO_IPIP;
+
+        memset(&(IPCB(skb)->opt), 0, sizeof(struct ip_options));
+        return 0;
+}
+
+static int xfrm4_tunnel_input(struct xfrm_state *x, struct sk_buff *skb)
+{
+        struct iphdr *iph = skb->nh.iph;
+        int err = -EINVAL;
+
+        if (iph->protocol != IPPROTO_IPIP)
+                goto out;
+        if (!pskb_may_pull(skb, sizeof(struct iphdr)))
+                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)
+                ipv4_copy_dscp(iph, skb->h.ipiph);
+        if (!(x->props.flags & XFRM_STATE_NOECN))
+                ipip_ecn_decapsulate(skb);
+        skb->mac.raw = memmove(skb->data - skb->mac_len,
+                               skb->mac.raw, skb->mac_len);
+        skb->nh.raw = skb->data;
+        memset(&(IPCB(skb)->opt), 0, sizeof(struct ip_options));
+        err = 0;
+
+out:
+        return err;
+}
+
+static struct xfrm_mode xfrm4_tunnel_mode = {
+        .input = xfrm4_tunnel_input,
+        .output = xfrm4_tunnel_output,
+        .owner = THIS_MODULE,
+        .encap = XFRM_MODE_TUNNEL,
+};
+
+static int __init xfrm4_tunnel_init(void)
+{
+        return xfrm_register_mode(&xfrm4_tunnel_mode, AF_INET);
+}
+
+static void __exit xfrm4_tunnel_exit(void)
+{
+        int err;
+
+        err = xfrm_unregister_mode(&xfrm4_tunnel_mode, AF_INET);
+        BUG_ON(err);
+}
+
+module_init(xfrm4_tunnel_init);
+module_exit(xfrm4_tunnel_exit);
+MODULE_LICENSE("GPL");
+MODULE_ALIAS_XFRM_MODE(AF_INET, XFRM_MODE_TUNNEL);
diff --git a/net/ipv4/xfrm4_output.c b/net/ipv4/xfrm4_output.c
index 4ef8efaf6a67..ac9d91d4bb05 100644
--- a/net/ipv4/xfrm4_output.c
+++ b/net/ipv4/xfrm4_output.c
@@ -12,67 +12,10 @@
 #include <linux/skbuff.h>
 #include <linux/spinlock.h>
 #include <linux/netfilter_ipv4.h>
-#include <net/inet_ecn.h>
 #include <net/ip.h>
 #include <net/xfrm.h>
 #include <net/icmp.h>
 
-/* Add encapsulation header.
- *
- * In transport mode, the IP header 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:
- *      tot_len
- *      check
- *
- * On exit, skb->h will be set to the start of the payload to be processed
- * by x->type->output and skb->nh will be set to the top IP header.
- */
-static void xfrm4_encap(struct sk_buff *skb)
-{
-        struct dst_entry *dst = skb->dst;
-        struct xfrm_state *x = dst->xfrm;
-        struct iphdr *iph, *top_iph;
-        int flags;
-
-        iph = skb->nh.iph;
-        skb->h.ipiph = iph;
-
-        skb->nh.raw = skb_push(skb, x->props.header_len);
-        top_iph = skb->nh.iph;
-
-        if (!x->props.mode) {
-                skb->h.raw += iph->ihl*4;
-                memmove(top_iph, iph, iph->ihl*4);
-                return;
-        }
-
-        top_iph->ihl = 5;
-        top_iph->version = 4;
-
-        /* DS disclosed */
-        top_iph->tos = INET_ECN_encapsulate(iph->tos, iph->tos);
-
-        flags = x->props.flags;
-        if (flags & XFRM_STATE_NOECN)
-                IP_ECN_clear(top_iph);
-
-        top_iph->frag_off = (flags & XFRM_STATE_NOPMTUDISC) ?
-                0 : (iph->frag_off & htons(IP_DF));
-        if (!top_iph->frag_off)
-                __ip_select_ident(top_iph, dst->child, 0);
-
-        top_iph->ttl = dst_metric(dst->child, RTAX_HOPLIMIT);
-
-        top_iph->saddr = x->props.saddr.a4;
-        top_iph->daddr = x->id.daddr.a4;
-        top_iph->protocol = IPPROTO_IPIP;
-
-        memset(&(IPCB(skb)->opt), 0, sizeof(struct ip_options));
-}
-
 static int xfrm4_tunnel_check_size(struct sk_buff *skb)
 {
         int mtu, ret = 0;
@@ -121,7 +64,9 @@ static int xfrm4_output_one(struct sk_buff *skb)
                 if (err)
                         goto error;
 
-                xfrm4_encap(skb);
+                err = x->mode->output(skb);
+                if (err)
+                        goto error;
 
                 err = x->type->output(x, skb);
                 if (err)