v4.19.13 snapshot.
diff --git a/net/ipv4/xfrm4_mode_tunnel.c b/net/ipv4/xfrm4_mode_tunnel.c
new file mode 100644
index 0000000..2a9764b
--- /dev/null
+++ b/net/ipv4/xfrm4_mode_tunnel.c
@@ -0,0 +1,152 @@
+/*
+ * xfrm4_mode_tunnel.c - Tunnel mode encapsulation for IPv4.
+ *
+ * Copyright (c) 2004-2006 Herbert Xu <herbert@gondor.apana.org.au>
+ */
+
+#include <linux/gfp.h>
+#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 *inner_iph = ipip_hdr(skb);
+
+ if (INET_ECN_is_ce(XFRM_MODE_SKB_CB(skb)->tos))
+ IP_ECN_set_ce(inner_iph);
+}
+
+/* Add encapsulation header.
+ *
+ * The top IP header will be constructed per RFC 2401.
+ */
+static int xfrm4_mode_tunnel_output(struct xfrm_state *x, struct sk_buff *skb)
+{
+ struct dst_entry *dst = skb_dst(skb);
+ struct iphdr *top_iph;
+ int flags;
+
+ skb_set_inner_network_header(skb, skb_network_offset(skb));
+ skb_set_inner_transport_header(skb, skb_transport_offset(skb));
+
+ skb_set_network_header(skb, -x->props.header_len);
+ skb->mac_header = skb->network_header +
+ offsetof(struct iphdr, protocol);
+ skb->transport_header = skb->network_header + sizeof(*top_iph);
+ top_iph = ip_hdr(skb);
+
+ top_iph->ihl = 5;
+ top_iph->version = 4;
+
+ top_iph->protocol = xfrm_af2proto(skb_dst(skb)->ops->family);
+
+ /* DS disclosing depends on XFRM_SA_XFLAG_DONT_ENCAP_DSCP */
+ if (x->props.extra_flags & XFRM_SA_XFLAG_DONT_ENCAP_DSCP)
+ top_iph->tos = 0;
+ else
+ top_iph->tos = XFRM_MODE_SKB_CB(skb)->tos;
+ top_iph->tos = INET_ECN_encapsulate(top_iph->tos,
+ XFRM_MODE_SKB_CB(skb)->tos);
+
+ flags = x->props.flags;
+ if (flags & XFRM_STATE_NOECN)
+ IP_ECN_clear(top_iph);
+
+ top_iph->frag_off = (flags & XFRM_STATE_NOPMTUDISC) ?
+ 0 : (XFRM_MODE_SKB_CB(skb)->frag_off & htons(IP_DF));
+
+ top_iph->ttl = ip4_dst_hoplimit(xfrm_dst_child(dst));
+
+ top_iph->saddr = x->props.saddr.a4;
+ top_iph->daddr = x->id.daddr.a4;
+ ip_select_ident(dev_net(dst->dev), skb, NULL);
+
+ return 0;
+}
+
+static int xfrm4_mode_tunnel_input(struct xfrm_state *x, struct sk_buff *skb)
+{
+ int err = -EINVAL;
+
+ if (XFRM_MODE_SKB_CB(skb)->protocol != IPPROTO_IPIP)
+ goto out;
+
+ if (!pskb_may_pull(skb, sizeof(struct iphdr)))
+ goto out;
+
+ err = skb_unclone(skb, GFP_ATOMIC);
+ if (err)
+ goto out;
+
+ if (x->props.flags & XFRM_STATE_DECAP_DSCP)
+ ipv4_copy_dscp(XFRM_MODE_SKB_CB(skb)->tos, ipip_hdr(skb));
+ if (!(x->props.flags & XFRM_STATE_NOECN))
+ ipip_ecn_decapsulate(skb);
+
+ skb_reset_network_header(skb);
+ skb_mac_header_rebuild(skb);
+ if (skb->mac_len)
+ eth_hdr(skb)->h_proto = skb->protocol;
+
+ err = 0;
+
+out:
+ return err;
+}
+
+static struct sk_buff *xfrm4_mode_tunnel_gso_segment(struct xfrm_state *x,
+ struct sk_buff *skb,
+ netdev_features_t features)
+{
+ __skb_push(skb, skb->mac_len);
+ return skb_mac_gso_segment(skb, features);
+}
+
+static void xfrm4_mode_tunnel_xmit(struct xfrm_state *x, struct sk_buff *skb)
+{
+ struct xfrm_offload *xo = xfrm_offload(skb);
+
+ if (xo->flags & XFRM_GSO_SEGMENT)
+ skb->transport_header = skb->network_header +
+ sizeof(struct iphdr);
+
+ skb_reset_mac_len(skb);
+ pskb_pull(skb, skb->mac_len + x->props.header_len);
+}
+
+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,
+ .xmit = xfrm4_mode_tunnel_xmit,
+ .owner = THIS_MODULE,
+ .encap = XFRM_MODE_TUNNEL,
+ .flags = XFRM_MODE_FLAG_TUNNEL,
+};
+
+static int __init xfrm4_mode_tunnel_init(void)
+{
+ return xfrm_register_mode(&xfrm4_tunnel_mode, AF_INET);
+}
+
+static void __exit xfrm4_mode_tunnel_exit(void)
+{
+ int err;
+
+ err = xfrm_unregister_mode(&xfrm4_tunnel_mode, AF_INET);
+ BUG_ON(err);
+}
+
+module_init(xfrm4_mode_tunnel_init);
+module_exit(xfrm4_mode_tunnel_exit);
+MODULE_LICENSE("GPL");
+MODULE_ALIAS_XFRM_MODE(AF_INET, XFRM_MODE_TUNNEL);