xfrm: remove input indirection from xfrm_mode

No need for any indirection or abstraction here, both functions
are pretty much the same and quite small, they also have no external
dependencies.

xfrm_prepare_input can then be made static.

With allmodconfig build, size increase of vmlinux is 25 byte:

Before:
   text   data     bss     dec      filename
15730207  6936924 4046908 26714039  vmlinux

After:
15730208  6936948 4046908 26714064 vmlinux

v2: Fix INET_XFRM_MODE_TRANSPORT name in is-enabled test (Sabrina Dubroca)
    change copied comment to refer to transport and network header,
    not skb->{h,nh}, which don't exist anymore. (Sabrina)
    make xfrm_prepare_input static (Eyal Birger)
Signed-off-by: Florian Westphal <fw@strlen.de>
Reviewed-by: Sabrina Dubroca <sd@queasysnail.net>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

include/net/xfrm.h

@@ -436,16 +436,6 @@ struct xfrm_mode {
 	 */
 	int (*input2)(struct xfrm_state *x, struct sk_buff *skb);
 
-	/*
-	 * This is the actual input entry point.
-	 *
-	 * For transport mode and equivalent this would be identical to
-	 * input2 (which does not need to be set).  While tunnel mode
-	 * and equivalent would set this to the tunnel encapsulation function
-	 * xfrm4_prepare_input that would in turn call input2.
-	 */
-	int (*input)(struct xfrm_state *x, struct sk_buff *skb);
-
 	/*
 	 * Add encapsulation header.
 	 *
@@ -1606,7 +1596,6 @@ int xfrm_init_replay(struct xfrm_state *x);
 int xfrm_state_mtu(struct xfrm_state *x, int mtu);
 int __xfrm_init_state(struct xfrm_state *x, bool init_replay, bool offload);
 int xfrm_init_state(struct xfrm_state *x);
-int xfrm_prepare_input(struct xfrm_state *x, struct sk_buff *skb);
 int xfrm_input(struct sk_buff *skb, int nexthdr, __be32 spi, int encap_type);
 int xfrm_input_resume(struct sk_buff *skb, int nexthdr);
 int xfrm_trans_queue(struct sk_buff *skb,

net/ipv4/xfrm4_mode_beet.c

@@ -128,7 +128,6 @@ static int xfrm4_beet_input(struct xfrm_state *x, struct sk_buff *skb)
 
 static struct xfrm_mode xfrm4_beet_mode = {
 	.input2 = xfrm4_beet_input,
-	.input = xfrm_prepare_input,
 	.output2 = xfrm4_beet_output,
 	.output = xfrm4_prepare_output,
 	.owner = THIS_MODULE,

net/ipv4/xfrm4_mode_transport.c

@@ -35,28 +35,6 @@ static int xfrm4_transport_output(struct xfrm_state *x, struct sk_buff *skb)
 	return 0;
 }
 
-/* Remove encapsulation header.
- *
- * The IP header will be moved over the top of the encapsulation header.
- *
- * On entry, skb->h shall point to where the IP header should be and skb->nh
- * shall be set to where the IP header currently is.  skb->data shall point
- * to the start of the payload.
- */
-static int xfrm4_transport_input(struct xfrm_state *x, struct sk_buff *skb)
-{
-	int ihl = skb->data - skb_transport_header(skb);
-
-	if (skb->transport_header != skb->network_header) {
-		memmove(skb_transport_header(skb),
-			skb_network_header(skb), ihl);
-		skb->network_header = skb->transport_header;
-	}
-	ip_hdr(skb)->tot_len = htons(skb->len + ihl);
-	skb_reset_transport_header(skb);
-	return 0;
-}
-
 static struct sk_buff *xfrm4_transport_gso_segment(struct xfrm_state *x,
 						   struct sk_buff *skb,
 						   netdev_features_t features)
@@ -87,7 +65,6 @@ static void xfrm4_transport_xmit(struct xfrm_state *x, struct sk_buff *skb)
 }
 
 static struct xfrm_mode xfrm4_transport_mode = {
-	.input = xfrm4_transport_input,
 	.output = xfrm4_transport_output,
 	.gso_segment = xfrm4_transport_gso_segment,
 	.xmit = xfrm4_transport_xmit,

net/ipv4/xfrm4_mode_tunnel.c

@@ -123,7 +123,6 @@ static void xfrm4_mode_tunnel_xmit(struct xfrm_state *x, struct sk_buff *skb)
 
 static struct xfrm_mode xfrm4_tunnel_mode = {
 	.input2 = xfrm4_mode_tunnel_input,
-	.input = xfrm_prepare_input,
 	.output2 = xfrm4_mode_tunnel_output,
 	.output = xfrm4_prepare_output,
 	.gso_segment = xfrm4_mode_tunnel_gso_segment,

net/ipv6/xfrm6_mode_beet.c

@@ -104,7 +104,6 @@ static int xfrm6_beet_input(struct xfrm_state *x, struct sk_buff *skb)
 
 static struct xfrm_mode xfrm6_beet_mode = {
 	.input2 = xfrm6_beet_input,
-	.input = xfrm_prepare_input,
 	.output2 = xfrm6_beet_output,
 	.output = xfrm6_prepare_output,
 	.owner = THIS_MODULE,

net/ipv6/xfrm6_mode_transport.c

@@ -40,29 +40,6 @@ static int xfrm6_transport_output(struct xfrm_state *x, struct sk_buff *skb)
 	return 0;
 }
 
-/* Remove encapsulation header.
- *
- * The IP header will be moved over the top of the encapsulation header.
- *
- * On entry, skb->h shall point to where the IP header should be and skb->nh
- * shall be set to where the IP header currently is.  skb->data shall point
- * to the start of the payload.
- */
-static int xfrm6_transport_input(struct xfrm_state *x, struct sk_buff *skb)
-{
-	int ihl = skb->data - skb_transport_header(skb);
-
-	if (skb->transport_header != skb->network_header) {
-		memmove(skb_transport_header(skb),
-			skb_network_header(skb), ihl);
-		skb->network_header = skb->transport_header;
-	}
-	ipv6_hdr(skb)->payload_len = htons(skb->len + ihl -
-					   sizeof(struct ipv6hdr));
-	skb_reset_transport_header(skb);
-	return 0;
-}
-
 static struct sk_buff *xfrm4_transport_gso_segment(struct xfrm_state *x,
 						   struct sk_buff *skb,
 						   netdev_features_t features)
@@ -92,9 +69,7 @@ static void xfrm6_transport_xmit(struct xfrm_state *x, struct sk_buff *skb)
 	}
 }
 
-
 static struct xfrm_mode xfrm6_transport_mode = {
-	.input = xfrm6_transport_input,
 	.output = xfrm6_transport_output,
 	.gso_segment = xfrm4_transport_gso_segment,
 	.xmit = xfrm6_transport_xmit,

net/ipv6/xfrm6_mode_tunnel.c

@@ -122,7 +122,6 @@ static void xfrm6_mode_tunnel_xmit(struct xfrm_state *x, struct sk_buff *skb)
 
 static struct xfrm_mode xfrm6_tunnel_mode = {
 	.input2 = xfrm6_mode_tunnel_input,
-	.input = xfrm_prepare_input,
 	.output2 = xfrm6_mode_tunnel_output,
 	.output = xfrm6_prepare_output,
 	.gso_segment = xfrm6_mode_tunnel_gso_segment,

net/xfrm/xfrm_input.c

@@ -166,7 +166,7 @@ int xfrm_parse_spi(struct sk_buff *skb, u8 nexthdr, __be32 *spi, __be32 *seq)
 }
 EXPORT_SYMBOL(xfrm_parse_spi);
 
-int xfrm_prepare_input(struct xfrm_state *x, struct sk_buff *skb)
+static int xfrm_prepare_input(struct xfrm_state *x, struct sk_buff *skb)
 {
 	struct xfrm_mode *inner_mode = x->inner_mode;
 	int err;
@@ -184,7 +184,76 @@ int xfrm_prepare_input(struct xfrm_state *x, struct sk_buff *skb)
 	skb->protocol = inner_mode->afinfo->eth_proto;
 	return inner_mode->input2(x, skb);
 }
-EXPORT_SYMBOL(xfrm_prepare_input);
+
+/* Remove encapsulation header.
+ *
+ * The IP header will be moved over the top of the encapsulation header.
+ *
+ * On entry, skb_transport_header() shall point to where the IP header
+ * should be and skb_network_header() shall be set to where the IP header
+ * currently is.  skb->data shall point to the start of the payload.
+ */
+static int xfrm4_transport_input(struct xfrm_state *x, struct sk_buff *skb)
+{
+#if IS_ENABLED(CONFIG_INET_XFRM_MODE_TRANSPORT)
+	int ihl = skb->data - skb_transport_header(skb);
+
+	if (skb->transport_header != skb->network_header) {
+		memmove(skb_transport_header(skb),
+			skb_network_header(skb), ihl);
+		skb->network_header = skb->transport_header;
+	}
+	ip_hdr(skb)->tot_len = htons(skb->len + ihl);
+	skb_reset_transport_header(skb);
+	return 0;
+#else
+	return -EOPNOTSUPP;
+#endif
+}
+
+static int xfrm6_transport_input(struct xfrm_state *x, struct sk_buff *skb)
+{
+#if IS_ENABLED(CONFIG_INET6_XFRM_MODE_TRANSPORT)
+	int ihl = skb->data - skb_transport_header(skb);
+
+	if (skb->transport_header != skb->network_header) {
+		memmove(skb_transport_header(skb),
+			skb_network_header(skb), ihl);
+		skb->network_header = skb->transport_header;
+	}
+	ipv6_hdr(skb)->payload_len = htons(skb->len + ihl -
+					   sizeof(struct ipv6hdr));
+	skb_reset_transport_header(skb);
+	return 0;
+#else
+	return -EOPNOTSUPP;
+#endif
+}
+
+static int xfrm_inner_mode_input(struct xfrm_state *x,
+				 const struct xfrm_mode *inner_mode,
+				 struct sk_buff *skb)
+{
+	switch (inner_mode->encap) {
+	case XFRM_MODE_BEET:
+	case XFRM_MODE_TUNNEL:
+		return xfrm_prepare_input(x, skb);
+	case XFRM_MODE_TRANSPORT:
+		if (inner_mode->family == AF_INET)
+			return xfrm4_transport_input(x, skb);
+		if (inner_mode->family == AF_INET6)
+			return xfrm6_transport_input(x, skb);
+		break;
+	case XFRM_MODE_ROUTEOPTIMIZATION:
+		WARN_ON_ONCE(1);
+		break;
+	default:
+		WARN_ON_ONCE(1);
+		break;
+	}
+
+	return -EOPNOTSUPP;
+}
 
 int xfrm_input(struct sk_buff *skb, int nexthdr, __be32 spi, int encap_type)
 {
@@ -410,7 +479,7 @@ int xfrm_input(struct sk_buff *skb, int nexthdr, __be32 spi, int encap_type)
 			}
 		}
 
-		if (inner_mode->input(x, skb)) {
+		if (xfrm_inner_mode_input(x, inner_mode, skb)) {
 			XFRM_INC_STATS(net, LINUX_MIB_XFRMINSTATEMODEERROR);
 			goto drop;
 		}