// SPDX-License-Identifier: GPL-2.0-or-later

  /*
   *	MPLS GSO Support
   *
   *	Authors: Simon Horman (horms@verge.net.au)
   *

   *	Based on: GSO portions of net/ipv4/gre.c
   */
  
  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  
  #include <linux/err.h>
  #include <linux/module.h>
  #include <linux/netdev_features.h>
  #include <linux/netdevice.h>
  #include <linux/skbuff.h>
  
  static struct sk_buff *mpls_gso_segment(struct sk_buff *skb,
  				       netdev_features_t features)
  {
  	struct sk_buff *segs = ERR_PTR(-EINVAL);

  	u16 mac_offset = skb->mac_header;

  	netdev_features_t mpls_features;

  	u16 mac_len = skb->mac_len;

  	__be16 mpls_protocol;

  	unsigned int mpls_hlen;
  
  	skb_reset_network_header(skb);
  	mpls_hlen = skb_inner_network_header(skb) - skb_network_header(skb);
  	if (unlikely(!pskb_may_pull(skb, mpls_hlen)))
  		goto out;

  	/* Setup inner SKB. */
  	mpls_protocol = skb->protocol;
  	skb->protocol = skb->inner_protocol;

  	__skb_pull(skb, mpls_hlen);
  
  	skb->mac_len = 0;
  	skb_reset_mac_header(skb);

  
  	/* Segment inner packet. */

  	mpls_features = skb->dev->mpls_features & features;

  	segs = skb_mac_gso_segment(skb, mpls_features);

  	if (IS_ERR_OR_NULL(segs)) {
  		skb_gso_error_unwind(skb, mpls_protocol, mpls_hlen, mac_offset,
  				     mac_len);
  		goto out;
  	}
  	skb = segs;
  
  	mpls_hlen += mac_len;
  	do {
  		skb->mac_len = mac_len;
  		skb->protocol = mpls_protocol;

  		skb_reset_inner_network_header(skb);

  		__skb_push(skb, mpls_hlen);

  		skb_reset_mac_header(skb);
  		skb_set_network_header(skb, mac_len);
  	} while ((skb = skb->next));

  out:

  	return segs;
  }

  static struct packet_offload mpls_mc_offload __read_mostly = {

  	.type = cpu_to_be16(ETH_P_MPLS_MC),

  	.priority = 15,

  	.callbacks = {

  		.gso_segment    =	mpls_gso_segment,
  	},
  };

  static struct packet_offload mpls_uc_offload __read_mostly = {

  	.type = cpu_to_be16(ETH_P_MPLS_UC),

  	.priority = 15,

  	.callbacks = {

  		.gso_segment    =	mpls_gso_segment,
  	},
  };
  
  static int __init mpls_gso_init(void)
  {
  	pr_info("MPLS GSO support
  ");
  
  	dev_add_offload(&mpls_uc_offload);
  	dev_add_offload(&mpls_mc_offload);
  
  	return 0;
  }
  
  static void __exit mpls_gso_exit(void)
  {
  	dev_remove_offload(&mpls_uc_offload);
  	dev_remove_offload(&mpls_mc_offload);
  }
  
  module_init(mpls_gso_init);
  module_exit(mpls_gso_exit);
  
  MODULE_DESCRIPTION("MPLS GSO support");
  MODULE_AUTHOR("Simon Horman (horms@verge.net.au)");
  MODULE_LICENSE("GPL");