[UDP]: Cleanup UDP encapsulation code

This cleanup fell out after adding L2TP support where a new encap_rcv
funcptr was added to struct udp_sock. Have XFRM use the new encap_rcv
funcptr, which allows us to move the XFRM encap code from udp.c into
xfrm4_input.c.

Make xfrm4_rcv_encap() static since it is no longer called externally.

Signed-off-by: James Chapman <jchapman@katalix.com>
Acked-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 106 insertions, 8 deletions

diff --git a/net/ipv4/xfrm4_input.c b/net/ipv4/xfrm4_input.c
index fa1902dc81b8..2fa108245413 100644
--- a/net/ipv4/xfrm4_input.c
+++ b/net/ipv4/xfrm4_input.c
@@ -16,13 +16,6 @@
 #include <net/ip.h>
 #include <net/xfrm.h>
 
-int xfrm4_rcv(struct sk_buff *skb)
-{
-        return xfrm4_rcv_encap(skb, 0);
-}
-
-EXPORT_SYMBOL(xfrm4_rcv);
-
 static int xfrm4_parse_spi(struct sk_buff *skb, u8 nexthdr, __be32 *spi, __be32 *seq)
 {
         switch (nexthdr) {
@@ -53,7 +46,7 @@ drop:
 }
 #endif
 
-int xfrm4_rcv_encap(struct sk_buff *skb, __u16 encap_type)
+static int xfrm4_rcv_encap(struct sk_buff *skb, __u16 encap_type)
 {
         __be32 spi, seq;
         struct xfrm_state *xfrm_vec[XFRM_MAX_DEPTH];
@@ -167,3 +160,108 @@ drop:
         kfree_skb(skb);
         return 0;
 }
+
+/* If it's a keepalive packet, then just eat it.
+ * If it's an encapsulated packet, then pass it to the
+ * IPsec xfrm input.
+ * Returns 0 if skb passed to xfrm or was dropped.
+ * Returns >0 if skb should be passed to UDP.
+ * Returns <0 if skb should be resubmitted (-ret is protocol)
+ */
+int xfrm4_udp_encap_rcv(struct sock *sk, struct sk_buff *skb)
+{
+        struct udp_sock *up = udp_sk(sk);
+        struct udphdr *uh;
+        struct iphdr *iph;
+        int iphlen, len;
+        int ret;
+
+        __u8 *udpdata;
+        __be32 *udpdata32;
+        __u16 encap_type = up->encap_type;
+
+        /* if this is not encapsulated socket, then just return now */
+        if (!encap_type)
+                return 1;
+
+        /* If this is a paged skb, make sure we pull up
+         * whatever data we need to look at. */
+        len = skb->len - sizeof(struct udphdr);
+        if (!pskb_may_pull(skb, sizeof(struct udphdr) + min(len, 8)))
+                return 1;
+
+        /* Now we can get the pointers */
+        uh = udp_hdr(skb);
+        udpdata = (__u8 *)uh + sizeof(struct udphdr);
+        udpdata32 = (__be32 *)udpdata;
+
+        switch (encap_type) {
+        default:
+        case UDP_ENCAP_ESPINUDP:
+                /* Check if this is a keepalive packet.  If so, eat it. */
+                if (len == 1 && udpdata[0] == 0xff) {
+                        goto drop;
+                } else if (len > sizeof(struct ip_esp_hdr) && udpdata32[0] != 0) {
+                        /* ESP Packet without Non-ESP header */
+                        len = sizeof(struct udphdr);
+                } else
+                        /* Must be an IKE packet.. pass it through */
+                        return 1;
+                break;
+        case UDP_ENCAP_ESPINUDP_NON_IKE:
+                /* Check if this is a keepalive packet.  If so, eat it. */
+                if (len == 1 && udpdata[0] == 0xff) {
+                        goto drop;
+                } else if (len > 2 * sizeof(u32) + sizeof(struct ip_esp_hdr) &&
+                           udpdata32[0] == 0 && udpdata32[1] == 0) {
+
+                        /* ESP Packet with Non-IKE marker */
+                        len = sizeof(struct udphdr) + 2 * sizeof(u32);
+                } else
+                        /* Must be an IKE packet.. pass it through */
+                        return 1;
+                break;
+        }
+
+        /* At this point we are sure that this is an ESPinUDP packet,
+         * so we need to remove 'len' bytes from the packet (the UDP
+         * header and optional ESP marker bytes) and then modify the
+         * protocol to ESP, and then call into the transform receiver.
+         */
+        if (skb_cloned(skb) && pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
+                goto drop;
+
+        /* Now we can update and verify the packet length... */
+        iph = ip_hdr(skb);
+        iphlen = iph->ihl << 2;
+        iph->tot_len = htons(ntohs(iph->tot_len) - len);
+        if (skb->len < iphlen + len) {
+                /* packet is too small!?! */
+                goto drop;
+        }
+
+        /* pull the data buffer up to the ESP header and set the
+         * transport header to point to ESP.  Keep UDP on the stack
+         * for later.
+         */
+        __skb_pull(skb, len);
+        skb_reset_transport_header(skb);
+
+        /* modify the protocol (it's ESP!) */
+        iph->protocol = IPPROTO_ESP;
+
+        /* process ESP */
+        ret = xfrm4_rcv_encap(skb, encap_type);
+        return ret;
+
+drop:
+        kfree_skb(skb);
+        return 0;
+}
+
+int xfrm4_rcv(struct sk_buff *skb)
+{
+        return xfrm4_rcv_encap(skb, 0);
+}
+
+EXPORT_SYMBOL(xfrm4_rcv);