/* Add encapsulation header.
 *
 * The IP header will be moved forward to make space for the encapsulation
 * header.
 */
static int xfrm4_transport_output(struct xfrm_state *x, struct sk_buff *skb)
{
	struct iphdr *iph = ip_hdr(skb);
	int ihl = iph->ihl * 4;

#if IS_ENABLED(CONFIG_RALINK_HWCRYPTO)
	if (x->type->proto == IPPROTO_ESP) {
		int header_len = 0;

		if (x->props.mode == XFRM_MODE_TUNNEL)
			header_len += sizeof(struct iphdr);

		if (x->encap) {
			struct xfrm_encap_tmpl *encap = x->encap;

			header_len += sizeof(struct udphdr);
			if (encap->encap_type == UDP_ENCAP_ESPINUDP_NON_IKE)
				header_len += 2 * sizeof(u32);
		}

		skb_set_network_header(skb, -header_len);
	} else
#endif
	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 + ihl;
	__skb_pull(skb, ihl);
	memmove(skb_network_header(skb), iph, ihl);
	return 0;
}

/*
 * Verify that our various assumptions about sk_buffs and the conditions
 * under which TSO will be attempted hold true.  Return the protocol number.
 */
static __be16 efx_tso_check_protocol(struct sk_buff *skb)
{
	__be16 protocol = skb->protocol;

	EFX_BUG_ON_PARANOID(((struct ethhdr *)skb->data)->h_proto !=
			    protocol);
	if (protocol == htons(ETH_P_8021Q)) {
		/* Find the encapsulated protocol; reset network header
		 * and transport header based on that. */
		struct vlan_ethhdr *veh = (struct vlan_ethhdr *)skb->data;
		protocol = veh->h_vlan_encapsulated_proto;
		skb_set_network_header(skb, sizeof(*veh));
		if (protocol == htons(ETH_P_IP))
			skb_set_transport_header(skb, sizeof(*veh) +
						 4 * ip_hdr(skb)->ihl);
		else if (protocol == htons(ETH_P_IPV6))
			skb_set_transport_header(skb, sizeof(*veh) +
						 sizeof(struct ipv6hdr));
	}

	if (protocol == htons(ETH_P_IP)) {
		EFX_BUG_ON_PARANOID(ip_hdr(skb)->protocol != IPPROTO_TCP);
	} else {
		EFX_BUG_ON_PARANOID(protocol != htons(ETH_P_IPV6));
		EFX_BUG_ON_PARANOID(ipv6_hdr(skb)->nexthdr != NEXTHDR_TCP);
	}
	EFX_BUG_ON_PARANOID((PTR_DIFF(tcp_hdr(skb), skb->data)
			     + (tcp_hdr(skb)->doff << 2u)) >
			    skb_headlen(skb));

	return protocol;
}

/* Add encapsulation header.
 *
 * The top IP header will be constructed per RFC 2401.
 */
static int xfrm6_mode_tunnel_output(struct xfrm_state *x, struct sk_buff *skb)
{
	struct dst_entry *dst = skb_dst(skb);
	struct ipv6hdr *top_iph;
	int dsfield;

	skb_set_network_header(skb, -x->props.header_len);
	skb->mac_header = skb->network_header +
			  offsetof(struct ipv6hdr, nexthdr);
	skb->transport_header = skb->network_header + sizeof(*top_iph);
	top_iph = ipv6_hdr(skb);

	top_iph->version = 6;

	memcpy(top_iph->flow_lbl, XFRM_MODE_SKB_CB(skb)->flow_lbl,
	       sizeof(top_iph->flow_lbl));
	top_iph->nexthdr = xfrm_af2proto(skb_dst(skb)->ops->family);

	dsfield = XFRM_MODE_SKB_CB(skb)->tos;
	dsfield = INET_ECN_encapsulate(dsfield, dsfield);
	if (x->props.flags & XFRM_STATE_NOECN)
		dsfield &= ~INET_ECN_MASK;
	ipv6_change_dsfield(top_iph, 0, dsfield);
	top_iph->hop_limit = ip6_dst_hoplimit(dst->child);
	ipv6_addr_copy(&top_iph->saddr, (const struct in6_addr *)&x->props.saddr);
	ipv6_addr_copy(&top_iph->daddr, (const struct in6_addr *)&x->id.daddr);
	return 0;
}

/*
 * We need to grow the skb to accommodate the expanssion of the ipcomp packet.
 *
 * The following comment comes from the skb_decompress() which does the
 * same...
 *
 * We have no way of knowing the exact length of the resulting
 * decompressed output before we have actually done the decompression.
 * For now, we guess that the packet will not be bigger than the
 * attached ipsec device's mtu or 16260, whichever is biggest.
 * This may be wrong, since the sender's mtu may be bigger yet.
 * XXX This must be dealt with later XXX
 */
static int ipsec_ocf_ipcomp_copy_expand(struct ipsec_rcv_state *irs)
{
	struct sk_buff *nskb;
	unsigned grow_to, grow_by;
	ptrdiff_t ptr_delta;

	if (!irs->skb)
		return IPSEC_RCV_IPCOMPFAILED;

	if (irs->skb->dev) {
		grow_to = irs->skb->dev->mtu <
			  16260 ? 16260 : irs->skb->dev->mtu;
	} else {
		int tot_len;
		if (lsw_ip_hdr_version(irs) == 6)
			tot_len = ntohs(lsw_ip6_hdr(irs)->payload_len) +
				  sizeof(struct ipv6hdr);
		else
			tot_len = ntohs(lsw_ip4_hdr(irs)->tot_len);
		grow_to = 65520 - tot_len;
	}
	grow_by = grow_to - irs->skb->len;
	grow_by -= skb_headroom(irs->skb);
	grow_by -= skb_tailroom(irs->skb);

	/* it's big enough */
	if (!grow_by)
		return IPSEC_RCV_OK;

	nskb = skb_copy_expand(irs->skb, skb_headroom(irs->skb),
			       skb_tailroom(irs->skb) + grow_by, GFP_ATOMIC);
	if (!nskb)
		return IPSEC_RCV_ERRMEMALLOC;

	memcpy(nskb->head, irs->skb->head, skb_headroom(irs->skb));

	skb_set_network_header(nskb,
			       ipsec_skb_offset(irs->skb,
						skb_network_header(irs->skb)));
	skb_set_transport_header(nskb,
				 ipsec_skb_offset(irs->skb,
						  skb_transport_header(
							  irs->skb)));

	/* update all irs pointers */
	ptr_delta = nskb->data - irs->skb->data;
	irs->authenticator = (void*)((char*)irs->authenticator + ptr_delta);
	irs->iph           = (void*)((char*)irs->iph           + ptr_delta);

	/* flip in the large one */
	irs->pre_ipcomp_skb = irs->skb;
	irs->skb = nskb;

	/* move the tail up to the end to let OCF know how big the buffer is */
	if (grow_by > (irs->skb->end - irs->skb->tail))
		grow_by = irs->skb->end - irs->skb->tail;
	skb_put(irs->skb, grow_by);

	return IPSEC_RCV_OK;
}

/* UPSTACK: MASTER FUNCTION CALLED BY L2 */
int mhost_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt, struct net_device *orig_dev)
{
    struct mhost_proto *mp;
    struct l3_hdr *hdr;
    
    // printk(KERN_INFO "mhost_rcv called\n");
    
    /* error-checking here */
    
    skb_set_network_header(skb, 0);
    
    /* address family MUST be first member of L3 header 
     * so that we can quickly perform a table lookup on it.*/
    hdr = (struct l3_hdr *) skb_network_header(skb);
    mp = mhost_proto_for_family(hdr->family);

    /* ...and pass it up the stack! */
    if (mp && mp->rcv) {
        mp->rcv(skb, dev, orig_dev);
        return 0;
    }
    
    printk(KERN_INFO "error: no L3 handler registered! family=%x\n", hdr->family);
    return -EAFNOSUPPORT;
}

/* remove VLAN header from packet and update csum accordingly. */
static int __pop_vlan_tci(struct sk_buff *skb, __be16 *current_tci)
{
	struct vlan_hdr *vhdr;
	int err;

	err = make_writable(skb, VLAN_ETH_HLEN);
	if (unlikely(err))
		return err;

	if (skb->ip_summed == CHECKSUM_COMPLETE)
		skb->csum = csum_sub(skb->csum, csum_partial(skb->data
					+ (2 * ETH_ALEN), VLAN_HLEN, 0));

	vhdr = (struct vlan_hdr *)(skb->data + ETH_HLEN);
	*current_tci = vhdr->h_vlan_TCI;

	memmove(skb->data + VLAN_HLEN, skb->data, 2 * ETH_ALEN);
	__skb_pull(skb, VLAN_HLEN);

	vlan_set_encap_proto(skb, vhdr);
	skb->mac_header += VLAN_HLEN;
	if (skb_network_offset(skb) < ETH_HLEN)
		skb_set_network_header(skb, ETH_HLEN);
	skb_reset_mac_len(skb);

	return 0;
}

static int push_mpls(struct sk_buff *skb, struct sw_flow_key *key,
		     const struct ovs_action_push_mpls *mpls)
{
	struct mpls_shim_hdr *new_mpls_lse;

	/* Networking stack do not allow simultaneous Tunnel and MPLS GSO. */
	if (skb->encapsulation)
		return -ENOTSUPP;

	if (skb_cow_head(skb, MPLS_HLEN) < 0)
		return -ENOMEM;

	if (!skb->inner_protocol) {
		skb_set_inner_network_header(skb, skb->mac_len);
		skb_set_inner_protocol(skb, skb->protocol);
	}

	skb_push(skb, MPLS_HLEN);
	memmove(skb_mac_header(skb) - MPLS_HLEN, skb_mac_header(skb),
		skb->mac_len);
	skb_reset_mac_header(skb);
	skb_set_network_header(skb, skb->mac_len);

	new_mpls_lse = mpls_hdr(skb);
	new_mpls_lse->label_stack_entry = mpls->mpls_lse;

	skb_postpush_rcsum(skb, new_mpls_lse, MPLS_HLEN);

	if (ovs_key_mac_proto(key) == MAC_PROTO_ETHERNET)
		update_ethertype(skb, eth_hdr(skb), mpls->mpls_ethertype);
	skb->protocol = mpls->mpls_ethertype;

	invalidate_flow_key(key);
	return 0;
}

static int pop_mpls(struct sk_buff *skb, struct sw_flow_key *key,
		    const __be16 ethertype)
{
	int err;

	err = skb_ensure_writable(skb, skb->mac_len + MPLS_HLEN);
	if (unlikely(err))
		return err;

	skb_postpull_rcsum(skb, mpls_hdr(skb), MPLS_HLEN);

	memmove(skb_mac_header(skb) + MPLS_HLEN, skb_mac_header(skb),
		skb->mac_len);

	__skb_pull(skb, MPLS_HLEN);
	skb_reset_mac_header(skb);
	skb_set_network_header(skb, skb->mac_len);

	if (ovs_key_mac_proto(key) == MAC_PROTO_ETHERNET) {
		struct ethhdr *hdr;

		/* mpls_hdr() is used to locate the ethertype field correctly in the
		 * presence of VLAN tags.
		 */
		hdr = (struct ethhdr *)((void *)mpls_hdr(skb) - ETH_HLEN);
		update_ethertype(skb, hdr, ethertype);
	}
	if (eth_p_mpls(skb->protocol))
		skb->protocol = ethertype;

	invalidate_flow_key(key);
	return 0;
}

static void sc_send_8023(struct sk_buff *skb, struct net_device *dev)
{
	struct ethhdr *eh;

	if (unlikely(!pskb_may_pull(skb, ETH_HLEN)))
		return;

	/* drop conntrack reference */
	nf_reset(skb);

	/* detach skb from CAPWAP */
	skb_orphan(skb);
	secpath_reset(skb);

	/* drop any routing info */
	skb_dst_drop(skb);

	skb->dev = dev;
	skb_reset_mac_header(skb);
	eh = eth_hdr(skb);
	if (likely(eth_proto_is_802_3(eh->h_proto)))
		skb->protocol = eh->h_proto;
	else
		skb->protocol = htons(ETH_P_802_2);
	skb_set_network_header(skb, ETH_HLEN);

	/* Force the device to verify it. */
	skb->ip_summed = CHECKSUM_NONE;

	dev_queue_xmit(skb);
}

/*
 * Probably needs some error checks and locking, not sure...
 */
static netdev_tx_t mpc_send_packet(struct sk_buff *skb,
					 struct net_device *dev)
{
	struct mpoa_client *mpc;
	struct ethhdr *eth;
	int i = 0;

	mpc = find_mpc_by_lec(dev); /* this should NEVER fail */
	if (mpc == NULL) {
		pr_info("(%s) no MPC found\n", dev->name);
		goto non_ip;
	}

	eth = (struct ethhdr *)skb->data;
	if (eth->h_proto != htons(ETH_P_IP))
		goto non_ip; /* Multi-Protocol Over ATM :-) */

	/* Weed out funny packets (e.g., AF_PACKET or raw). */
	if (skb->len < ETH_HLEN + sizeof(struct iphdr))
		goto non_ip;
	skb_set_network_header(skb, ETH_HLEN);
	if (skb->len < ETH_HLEN + ip_hdr(skb)->ihl * 4 || ip_hdr(skb)->ihl < 5)
		goto non_ip;

	while (i < mpc->number_of_mps_macs) {
		if (!compare_ether_addr(eth->h_dest,
					(mpc->mps_macs + i*ETH_ALEN)))
			if (send_via_shortcut(skb, mpc) == 0) /* try shortcut */
				return NETDEV_TX_OK;
		i++;
	}

non_ip:
	return mpc->old_ops->ndo_start_xmit(skb, dev);
}

int skb_from_pkt(void *pkt, u32 pkt_len, struct sk_buff **skb)
{
	*skb = alloc_skb(LL_MAX_HEADER + pkt_len, GFP_ATOMIC);
	if (!*skb) {
		log_err("Could not allocate a skb.");
		return -ENOMEM;
	}

	skb_reserve(*skb, LL_MAX_HEADER); /* Reserve space for Link Layer data. */
	skb_put(*skb, pkt_len); /* L3 + L4 + payload. */

	skb_set_mac_header(*skb, 0);
	skb_set_network_header(*skb, 0);
	skb_set_transport_header(*skb, net_hdr_size(pkt));

	(*skb)->ip_summed = CHECKSUM_UNNECESSARY;
	switch (get_l3_proto(pkt)) {
	case 6:
		(*skb)->protocol = htons(ETH_P_IPV6);
		break;
	case 4:
		(*skb)->protocol = htons(ETH_P_IP);
		break;
	default:
		log_err("Invalid mode: %u.", get_l3_proto(pkt));
		kfree_skb(*skb);
		return -EINVAL;
	}

	/* Copy packet content to skb. */
	memcpy(skb_network_header(*skb), pkt, pkt_len);

	return 0;
}

int get_rx_buffers(void *priv, void **pkt_priv, void **buffer, int size)
{
	struct net_device *dev = (struct net_device *) priv;
	struct sk_buff *skb = NULL;
	void *ptr = NULL;

	DBG0("[%s] dev:%s\n", __func__, dev->name);
	skb = __dev_alloc_skb(size, GFP_ATOMIC);
	if (skb == NULL) {
		DBG0("%s: unable to alloc skb\n", __func__);
		return -ENOMEM;
	}

	/* TODO skb_reserve(skb, NET_IP_ALIGN); for ethernet mode */
	/* Populate some params now. */
	skb->dev = dev;
	ptr = skb_put(skb, size);

	skb_set_network_header(skb, 0);

	/* done with skb setup, return the buffer pointer. */
	*pkt_priv = skb;
	*buffer = ptr;

	return 0;
}

static inline int ip6_ufo_append_data(struct sock *sk,
			struct sk_buff_head *queue,
			int getfrag(void *from, char *to, int offset, int len,
			int odd, struct sk_buff *skb),
			void *from, int length, int hh_len, int fragheaderlen,
			int exthdrlen, int transhdrlen, int mtu,
			unsigned int flags, const struct flowi6 *fl6)

{
	struct sk_buff *skb;
	int err;

	/* There is support for UDP large send offload by network
	 * device, so create one single skb packet containing complete
	 * udp datagram
	 */
	skb = skb_peek_tail(queue);
	if (!skb) {
		skb = sock_alloc_send_skb(sk,
			hh_len + fragheaderlen + transhdrlen + 20,
			(flags & MSG_DONTWAIT), &err);
		if (!skb)
			return err;

		/* reserve space for Hardware header */
		skb_reserve(skb, hh_len);

		/* create space for UDP/IP header */
		skb_put(skb, fragheaderlen + transhdrlen);

		/* initialize network header pointer */
		skb_set_network_header(skb, exthdrlen);

		/* initialize protocol header pointer */
		skb->transport_header = skb->network_header + fragheaderlen;

		skb->protocol = htons(ETH_P_IPV6);
		skb->csum = 0;

		__skb_queue_tail(queue, skb);
	} else if (skb_is_gso(skb)) {
		goto append;
	}

	skb->ip_summed = CHECKSUM_PARTIAL;
	/* Specify the length of each IPv6 datagram fragment.
	 * It has to be a multiple of 8.
	 */
	skb_shinfo(skb)->gso_size = (mtu - fragheaderlen -
				     sizeof(struct frag_hdr)) & ~7;
	skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
	skb_shinfo(skb)->ip6_frag_id = ipv6_select_ident(sock_net(sk),
							 &fl6->daddr,
							 &fl6->saddr);

append:
	return skb_append_datato_frags(sk, skb, getfrag, from,
				       (length - transhdrlen));
}

/* Add encapsulation header.
 *
 * The IP header will be moved forward to make space for the encapsulation
 * header.
 */
static int xfrm4_transport_output(struct xfrm_state *x, struct sk_buff *skb)
{
	struct iphdr *iph = ip_hdr(skb);
	int ihl = iph->ihl * 4;

	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 + ihl;
	__skb_pull(skb, ihl);
	memmove(skb_network_header(skb), iph, ihl);
	return 0;
}

netdev_tx_t trailer_xmit(struct sk_buff *skb, struct net_device *dev)
{
	struct dsa_slave_priv *p = netdev_priv(dev);
	struct sk_buff *nskb;
	int padlen;
	u8 *trailer;

	dev->stats.tx_packets++;
	dev->stats.tx_bytes += skb->len;

	/*
	 * We have to make sure that the trailer ends up as the very
	 * last 4 bytes of the packet.  This means that we have to pad
	 * the packet to the minimum ethernet frame size, if necessary,
	 * before adding the trailer.
	 */
	padlen = 0;
	if (skb->len < 60)
		padlen = 60 - skb->len;

	nskb = alloc_skb(NET_IP_ALIGN + skb->len + padlen + 4, GFP_ATOMIC);
	if (nskb == NULL) {
		kfree_skb(skb);
		return NETDEV_TX_OK;
	}
	skb_reserve(nskb, NET_IP_ALIGN);

	skb_reset_mac_header(nskb);
	skb_set_network_header(nskb, skb_network_header(skb) - skb->head);
	skb_set_transport_header(nskb, skb_transport_header(skb) - skb->head);
	skb_copy_and_csum_dev(skb, skb_put(nskb, skb->len));
	kfree_skb(skb);

	if (padlen) {
		u8 *pad = skb_put(nskb, padlen);
		memset(pad, 0, padlen);
	}

	trailer = skb_put(nskb, 4);
	trailer[0] = 0x80;
	trailer[1] = 1 << p->port;
	trailer[2] = 0x10;
	trailer[3] = 0x00;

	nskb->protocol = htons(ETH_P_TRAILER);

	nskb->dev = p->parent->dst->master_netdev;
	dev_queue_xmit(nskb);

	return NETDEV_TX_OK;
}

/**
 * batadv_send_skb_packet() - send an already prepared packet
 * @skb: the packet to send
 * @hard_iface: the interface to use to send the broadcast packet
 * @dst_addr: the payload destination
 *
 * Send out an already prepared packet to the given neighbor or broadcast it
 * using the specified interface. Either hard_iface or neigh_node must be not
 * NULL.
 * If neigh_node is NULL, then the packet is broadcasted using hard_iface,
 * otherwise it is sent as unicast to the given neighbor.
 *
 * Regardless of the return value, the skb is consumed.
 *
 * Return: A negative errno code is returned on a failure. A success does not
 * guarantee the frame will be transmitted as it may be dropped due
 * to congestion or traffic shaping.
 */
int batadv_send_skb_packet(struct sk_buff *skb,
			   struct batadv_hard_iface *hard_iface,
			   const u8 *dst_addr)
{
	struct batadv_priv *bat_priv;
	struct ethhdr *ethhdr;
	int ret;

	bat_priv = netdev_priv(hard_iface->soft_iface);

	if (hard_iface->if_status != BATADV_IF_ACTIVE)
		goto send_skb_err;

	if (unlikely(!hard_iface->net_dev))
		goto send_skb_err;

	if (!(hard_iface->net_dev->flags & IFF_UP)) {
		pr_warn("Interface %s is not up - can't send packet via that interface!\n",
			hard_iface->net_dev->name);
		goto send_skb_err;
	}

	/* push to the ethernet header. */
	if (batadv_skb_head_push(skb, ETH_HLEN) < 0)
		goto send_skb_err;

	skb_reset_mac_header(skb);

	ethhdr = eth_hdr(skb);
	ether_addr_copy(ethhdr->h_source, hard_iface->net_dev->dev_addr);
	ether_addr_copy(ethhdr->h_dest, dst_addr);
	ethhdr->h_proto = htons(ETH_P_BATMAN);

	skb_set_network_header(skb, ETH_HLEN);
	skb->protocol = htons(ETH_P_BATMAN);

	skb->dev = hard_iface->net_dev;

	/* Save a clone of the skb to use when decoding coded packets */
	batadv_nc_skb_store_for_decoding(bat_priv, skb);

	/* dev_queue_xmit() returns a negative result on error.	 However on
	 * congestion and traffic shaping, it drops and returns NET_XMIT_DROP
	 * (which is > 0). This will not be treated as an error.
	 */
	ret = dev_queue_xmit(skb);
	return net_xmit_eval(ret);
send_skb_err:
	kfree_skb(skb);
	return NET_XMIT_DROP;
}

static int ztdeth_transmit(void *pvt, unsigned char *msg, int msglen)
{
	struct ztdeth *z;
	struct sk_buff *skb;
	struct ztdeth_header *zh;
	unsigned long flags;
	struct net_device *dev;
	unsigned char addr[ETH_ALEN];
	unsigned short subaddr; /* Network byte order */

	spin_lock_irqsave(&zlock, flags);
	z = pvt;
	if (z->dev) {
		/* Copy fields to local variables to remove spinlock ASAP */
		dev = z->dev;
		memcpy(addr, z->addr, sizeof(z->addr));
		subaddr = z->subaddr;
		spin_unlock_irqrestore(&zlock, flags);
		skb = dev_alloc_skb(msglen + dev->hard_header_len + sizeof(struct ztdeth_header) + 32);
		if (skb) {
			/* Reserve header space */
			skb_reserve(skb, dev->hard_header_len + sizeof(struct ztdeth_header));

			/* Copy message body */
			memcpy(skb_put(skb, msglen), msg, msglen);

			/* Throw on header */
			zh = (struct ztdeth_header *)skb_push(skb, sizeof(struct ztdeth_header));
			zh->subaddr = subaddr;

			/* Setup protocol and such */
			skb->protocol = __constant_htons(ETH_P_DAHDI_DETH);
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,22)
			skb_set_network_header(skb, 0);
#else
			skb->nh.raw = skb->data;
#endif
			skb->dev = dev;
#if  LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,24)
			dev_hard_header(skb, dev, ETH_P_DAHDI_DETH, addr, dev->dev_addr, skb->len);
#else
			if (dev->hard_header)
				dev->hard_header(skb, dev, ETH_P_DAHDI_DETH, addr, dev->dev_addr, skb->len);
#endif
			skb_queue_tail(&skbs, skb);
		}
	}
	else
		spin_unlock_irqrestore(&zlock, flags);
	return 0;
}

static void init_skbuff(const struct ipq_packet_msg *ipq_msg, struct sk_buff *skb)
{
    memcpy(skb->head, ipq_msg->payload, ipq_msg->data_len);
    skb->len = skb->data_len = ipq_msg->data_len;

    // Becasue the payload of ipq_msg l3 packet. so there is no mac header
    skb_set_mac_header(skb, ~0U);

    skb_set_network_header(skb, 0);

    struct iphdr *iph = (struct iphdr*)skb_network_header(skb);
    
    skb_set_transport_header(skb, iph->ihl<<2);
    
}

static int xfrm6_transport_output(struct xfrm_state *x, struct sk_buff *skb)
{
	struct ipv6hdr *iph;
	u8 *prevhdr;
	int hdr_len;

	iph = ipv6_hdr(skb);

	hdr_len = x->type->hdr_offset(x, skb, &prevhdr);
	skb_set_mac_header(skb, (prevhdr - x->props.header_len) - skb->data);
	skb_set_network_header(skb, -x->props.header_len);
	skb->transport_header = skb->network_header + hdr_len;
	__skb_pull(skb, hdr_len);
	memmove(ipv6_hdr(skb), iph, hdr_len);
	return 0;
}

/*  Headroom is not adjusted.  Caller should ensure that skb has sufficient
 *  headroom in case the frame is encrypted. */
static void prepare_frame_for_deferred_tx(struct ieee80211_sub_if_data *sdata,
		struct sk_buff *skb)
{
	struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);

	skb_set_mac_header(skb, 0);
	skb_set_network_header(skb, 0);
	skb_set_transport_header(skb, 0);

	/* Send all internal mgmt frames on VO. Accordingly set TID to 7. */
	skb_set_queue_mapping(skb, IEEE80211_AC_VO);
	skb->priority = 7;

	info->control.vif = &sdata->vif;
	info->flags |= IEEE80211_TX_INTFL_NEED_TXPROCESSING;
	ieee80211_set_qos_hdr(sdata, skb);
}