drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c - linux/torvalds/linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-only
 /* Copyright (c) 2013-2018, The Linux Foundation. All rights reserved.
  *
  * RMNET Data MAP protocol
  */

 #include <linux/netdevice.h>
 #include <linux/ip.h>
 #include <linux/ipv6.h>
 #include <net/ip6_checksum.h>
 #include "rmnet_config.h"
 #include "rmnet_map.h"
 #include "rmnet_private.h"

 #define RMNET_MAP_DEAGGR_SPACING  64
 #define RMNET_MAP_DEAGGR_HEADROOM (RMNET_MAP_DEAGGR_SPACING / 2)

 static __sum16 *rmnet_map_get_csum_field(unsigned char protocol,
 					 const void *txporthdr)
 {
 	__sum16 *check = NULL;

 	switch (protocol) {
 	case IPPROTO_TCP:
 		check = &(((struct tcphdr *)txporthdr)->check);
 		break;

 	case IPPROTO_UDP:
 		check = &(((struct udphdr *)txporthdr)->check);
 		break;

 	default:
 		check = NULL;
 		break;
 	}

 	return check;
 }

 static int
 rmnet_map_ipv4_dl_csum_trailer(struct sk_buff *skb,
 			       struct rmnet_map_dl_csum_trailer *csum_trailer,
 			       struct rmnet_priv *priv)
 {
 	__sum16 *csum_field, csum_temp, pseudo_csum, hdr_csum, ip_payload_csum;
 	u16 csum_value, csum_value_final;
 	struct iphdr *ip4h;
 	void *txporthdr;
 	__be16 addend;

 	ip4h = (struct iphdr *)(skb->data);
 	if ((ntohs(ip4h->frag_off) & IP_MF) ||
 	    ((ntohs(ip4h->frag_off) & IP_OFFSET) > 0)) {
 		priv->stats.csum_fragmented_pkt++;
 		return -EOPNOTSUPP;
 	}

 	txporthdr = skb->data + ip4h->ihl * 4;

 	csum_field = rmnet_map_get_csum_field(ip4h->protocol, txporthdr);

 	if (!csum_field) {
 		priv->stats.csum_err_invalid_transport++;
 		return -EPROTONOSUPPORT;
 	}

 	/* RFC 768 - Skip IPv4 UDP packets where sender checksum field is 0 */
 	if (*csum_field == 0 && ip4h->protocol == IPPROTO_UDP) {
 		priv->stats.csum_skipped++;
 		return 0;
 	}

 	csum_value = ~ntohs(csum_trailer->csum_value);
 	hdr_csum = ~ip_fast_csum(ip4h, (int)ip4h->ihl);
 	ip_payload_csum = csum16_sub((__force __sum16)csum_value,
 				     (__force __be16)hdr_csum);

 	pseudo_csum = ~csum_tcpudp_magic(ip4h->saddr, ip4h->daddr,
 					 ntohs(ip4h->tot_len) - ip4h->ihl * 4,
 					 ip4h->protocol, 0);
 	addend = (__force __be16)ntohs((__force __be16)pseudo_csum);
 	pseudo_csum = csum16_add(ip_payload_csum, addend);

 	addend = (__force __be16)ntohs((__force __be16)*csum_field);
 	csum_temp = ~csum16_sub(pseudo_csum, addend);
 	csum_value_final = (__force u16)csum_temp;

 	if (unlikely(csum_value_final == 0)) {
 		switch (ip4h->protocol) {
 		case IPPROTO_UDP:
 			/* RFC 768 - DL4 1's complement rule for UDP csum 0 */
 			csum_value_final = ~csum_value_final;
 			break;

 		case IPPROTO_TCP:
 			/* DL4 Non-RFC compliant TCP checksum found */
 			if (*csum_field == (__force __sum16)0xFFFF)
 				csum_value_final = ~csum_value_final;
 			break;
 		}
 	}

 	if (csum_value_final == ntohs((__force __be16)*csum_field)) {
 		priv->stats.csum_ok++;
 		return 0;
 	} else {
 		priv->stats.csum_validation_failed++;
 		return -EINVAL;
 	}
 }

 #if IS_ENABLED(CONFIG_IPV6)
 static int
 rmnet_map_ipv6_dl_csum_trailer(struct sk_buff *skb,
 			       struct rmnet_map_dl_csum_trailer *csum_trailer,
 			       struct rmnet_priv *priv)
 {
 	__sum16 *csum_field, ip6_payload_csum, pseudo_csum, csum_temp;
 	u16 csum_value, csum_value_final;
 	__be16 ip6_hdr_csum, addend;
 	struct ipv6hdr *ip6h;
 	void *txporthdr;
 	u32 length;

 	ip6h = (struct ipv6hdr *)(skb->data);

 	txporthdr = skb->data + sizeof(struct ipv6hdr);
 	csum_field = rmnet_map_get_csum_field(ip6h->nexthdr, txporthdr);

 	if (!csum_field) {
 		priv->stats.csum_err_invalid_transport++;
 		return -EPROTONOSUPPORT;
 	}

 	csum_value = ~ntohs(csum_trailer->csum_value);
 	ip6_hdr_csum = (__force __be16)
 			~ntohs((__force __be16)ip_compute_csum(ip6h,
 			       (int)(txporthdr - (void *)(skb->data))));
 	ip6_payload_csum = csum16_sub((__force __sum16)csum_value,
 				      ip6_hdr_csum);

 	length = (ip6h->nexthdr == IPPROTO_UDP) ?
 		 ntohs(((struct udphdr *)txporthdr)->len) :
 		 ntohs(ip6h->payload_len);
 	pseudo_csum = ~(csum_ipv6_magic(&ip6h->saddr, &ip6h->daddr,
 			     length, ip6h->nexthdr, 0));
 	addend = (__force __be16)ntohs((__force __be16)pseudo_csum);
 	pseudo_csum = csum16_add(ip6_payload_csum, addend);

 	addend = (__force __be16)ntohs((__force __be16)*csum_field);
 	csum_temp = ~csum16_sub(pseudo_csum, addend);
 	csum_value_final = (__force u16)csum_temp;

 	if (unlikely(csum_value_final == 0)) {
 		switch (ip6h->nexthdr) {
 		case IPPROTO_UDP:
 			/* RFC 2460 section 8.1
 			 * DL6 One's complement rule for UDP checksum 0
 			 */
 			csum_value_final = ~csum_value_final;
 			break;

 		case IPPROTO_TCP:
 			/* DL6 Non-RFC compliant TCP checksum found */
 			if (*csum_field == (__force __sum16)0xFFFF)
 				csum_value_final = ~csum_value_final;
 			break;
 		}
 	}

 	if (csum_value_final == ntohs((__force __be16)*csum_field)) {
 		priv->stats.csum_ok++;
 		return 0;
 	} else {
 		priv->stats.csum_validation_failed++;
 		return -EINVAL;
 	}
 }
 #endif

 static void rmnet_map_complement_ipv4_txporthdr_csum_field(void *iphdr)
 {
 	struct iphdr *ip4h = (struct iphdr *)iphdr;
 	void *txphdr;
 	u16 *csum;

 	txphdr = iphdr + ip4h->ihl * 4;

 	if (ip4h->protocol == IPPROTO_TCP || ip4h->protocol == IPPROTO_UDP) {
 		csum = (u16 *)rmnet_map_get_csum_field(ip4h->protocol, txphdr);
 		*csum = ~(*csum);
 	}
 }

 static void
 rmnet_map_ipv4_ul_csum_header(void *iphdr,
 			      struct rmnet_map_ul_csum_header *ul_header,
 			      struct sk_buff *skb)
 {
 	struct iphdr *ip4h = (struct iphdr *)iphdr;
 	__be16 *hdr = (__be16 *)ul_header, offset;

 	offset = htons((__force u16)(skb_transport_header(skb) -
 				     (unsigned char *)iphdr));
 	ul_header->csum_start_offset = offset;
 	ul_header->csum_insert_offset = skb->csum_offset;
 	ul_header->csum_enabled = 1;
 	if (ip4h->protocol == IPPROTO_UDP)
 		ul_header->udp_ind = 1;
 	else
 		ul_header->udp_ind = 0;

 	/* Changing remaining fields to network order */
 	hdr++;
 	*hdr = htons((__force u16)*hdr);

 	skb->ip_summed = CHECKSUM_NONE;

 	rmnet_map_complement_ipv4_txporthdr_csum_field(iphdr);
 }

 #if IS_ENABLED(CONFIG_IPV6)
 static void rmnet_map_complement_ipv6_txporthdr_csum_field(void *ip6hdr)
 {
 	struct ipv6hdr *ip6h = (struct ipv6hdr *)ip6hdr;
 	void *txphdr;
 	u16 *csum;

 	txphdr = ip6hdr + sizeof(struct ipv6hdr);

 	if (ip6h->nexthdr == IPPROTO_TCP || ip6h->nexthdr == IPPROTO_UDP) {
 		csum = (u16 *)rmnet_map_get_csum_field(ip6h->nexthdr, txphdr);
 		*csum = ~(*csum);
 	}
 }

 static void
 rmnet_map_ipv6_ul_csum_header(void *ip6hdr,
 			      struct rmnet_map_ul_csum_header *ul_header,
 			      struct sk_buff *skb)
 {
 	struct ipv6hdr *ip6h = (struct ipv6hdr *)ip6hdr;
 	__be16 *hdr = (__be16 *)ul_header, offset;

 	offset = htons((__force u16)(skb_transport_header(skb) -
 				     (unsigned char *)ip6hdr));
 	ul_header->csum_start_offset = offset;
 	ul_header->csum_insert_offset = skb->csum_offset;
 	ul_header->csum_enabled = 1;

 	if (ip6h->nexthdr == IPPROTO_UDP)
 		ul_header->udp_ind = 1;
 	else
 		ul_header->udp_ind = 0;

 	/* Changing remaining fields to network order */
 	hdr++;
 	*hdr = htons((__force u16)*hdr);

 	skb->ip_summed = CHECKSUM_NONE;

 	rmnet_map_complement_ipv6_txporthdr_csum_field(ip6hdr);
 }
 #endif

 /* Adds MAP header to front of skb->data
  * Padding is calculated and set appropriately in MAP header. Mux ID is
  * initialized to 0.
  */
 struct rmnet_map_header *rmnet_map_add_map_header(struct sk_buff *skb,
 						  int hdrlen, int pad)
 {
 	struct rmnet_map_header *map_header;
 	u32 padding, map_datalen;
 	u8 *padbytes;

 	map_datalen = skb->len - hdrlen;
 	map_header = (struct rmnet_map_header *)
 			skb_push(skb, sizeof(struct rmnet_map_header));
 	memset(map_header, 0, sizeof(struct rmnet_map_header));

 	if (pad == RMNET_MAP_NO_PAD_BYTES) {
 		map_header->pkt_len = htons(map_datalen);
 		return map_header;
 	}

 	padding = ALIGN(map_datalen, 4) - map_datalen;

 	if (padding == 0)
 		goto done;

 	if (skb_tailroom(skb) < padding)
 		return NULL;

 	padbytes = (u8 *)skb_put(skb, padding);
 	memset(padbytes, 0, padding);

 done:
 	map_header->pkt_len = htons(map_datalen + padding);
 	map_header->pad_len = padding & 0x3F;

 	return map_header;
 }

 /* Deaggregates a single packet
  * A whole new buffer is allocated for each portion of an aggregated frame.
  * Caller should keep calling deaggregate() on the source skb until 0 is
  * returned, indicating that there are no more packets to deaggregate. Caller
  * is responsible for freeing the original skb.
  */
 struct sk_buff *rmnet_map_deaggregate(struct sk_buff *skb,
 				      struct rmnet_port *port)
 {
 	struct rmnet_map_header *maph;
 	struct sk_buff *skbn;
 	u32 packet_len;

 	if (skb->len == 0)
 		return NULL;

 	maph = (struct rmnet_map_header *)skb->data;
 	packet_len = ntohs(maph->pkt_len) + sizeof(struct rmnet_map_header);

 	if (port->data_format & RMNET_FLAGS_INGRESS_MAP_CKSUMV4)
 		packet_len += sizeof(struct rmnet_map_dl_csum_trailer);

 	if (((int)skb->len - (int)packet_len) < 0)
 		return NULL;

 	/* Some hardware can send us empty frames. Catch them */
 	if (ntohs(maph->pkt_len) == 0)
 		return NULL;

 	skbn = alloc_skb(packet_len + RMNET_MAP_DEAGGR_SPACING, GFP_ATOMIC);
 	if (!skbn)
 		return NULL;

 	skb_reserve(skbn, RMNET_MAP_DEAGGR_HEADROOM);
 	skb_put(skbn, packet_len);
 	memcpy(skbn->data, skb->data, packet_len);
 	skb_pull(skb, packet_len);

 	return skbn;
 }

 /* Validates packet checksums. Function takes a pointer to
  * the beginning of a buffer which contains the IP payload +
  * padding + checksum trailer.
  * Only IPv4 and IPv6 are supported along with TCP & UDP.
  * Fragmented or tunneled packets are not supported.
  */
 int rmnet_map_checksum_downlink_packet(struct sk_buff *skb, u16 len)
 {
 	struct rmnet_priv *priv = netdev_priv(skb->dev);
 	struct rmnet_map_dl_csum_trailer *csum_trailer;

 	if (unlikely(!(skb->dev->features & NETIF_F_RXCSUM))) {
 		priv->stats.csum_sw++;
 		return -EOPNOTSUPP;
 	}

 	csum_trailer = (struct rmnet_map_dl_csum_trailer *)(skb->data + len);

 	if (!csum_trailer->valid) {
 		priv->stats.csum_valid_unset++;
 		return -EINVAL;
 	}

 	if (skb->protocol == htons(ETH_P_IP)) {
 		return rmnet_map_ipv4_dl_csum_trailer(skb, csum_trailer, priv);
 	} else if (skb->protocol == htons(ETH_P_IPV6)) {
 #if IS_ENABLED(CONFIG_IPV6)
 		return rmnet_map_ipv6_dl_csum_trailer(skb, csum_trailer, priv);
 #else
 		priv->stats.csum_err_invalid_ip_version++;
 		return -EPROTONOSUPPORT;
 #endif
 	} else {
 		priv->stats.csum_err_invalid_ip_version++;
 		return -EPROTONOSUPPORT;
 	}

 	return 0;
 }

 /* Generates UL checksum meta info header for IPv4 and IPv6 over TCP and UDP
  * packets that are supported for UL checksum offload.
  */
 void rmnet_map_checksum_uplink_packet(struct sk_buff *skb,
 				      struct net_device *orig_dev)
 {
 	struct rmnet_priv *priv = netdev_priv(orig_dev);
 	struct rmnet_map_ul_csum_header *ul_header;
 	void *iphdr;

 	ul_header = (struct rmnet_map_ul_csum_header *)
 		    skb_push(skb, sizeof(struct rmnet_map_ul_csum_header));

 	if (unlikely(!(orig_dev->features &
 		     (NETIF_F_IP_CSUM | NETIF_F_IPV6_CSUM))))
 		goto sw_csum;

 	if (skb->ip_summed == CHECKSUM_PARTIAL) {
 		iphdr = (char *)ul_header +
 			sizeof(struct rmnet_map_ul_csum_header);

 		if (skb->protocol == htons(ETH_P_IP)) {
 			rmnet_map_ipv4_ul_csum_header(iphdr, ul_header, skb);
 			return;
 		} else if (skb->protocol == htons(ETH_P_IPV6)) {
 #if IS_ENABLED(CONFIG_IPV6)
 			rmnet_map_ipv6_ul_csum_header(iphdr, ul_header, skb);
 			return;
 #else
 			priv->stats.csum_err_invalid_ip_version++;
 			goto sw_csum;
 #endif
 		} else {
 			priv->stats.csum_err_invalid_ip_version++;
 		}
 	}

 sw_csum:
 	ul_header->csum_start_offset = 0;
 	ul_header->csum_insert_offset = 0;
 	ul_header->csum_enabled = 0;
 	ul_header->udp_ind = 0;

 	priv->stats.csum_sw++;
 }
	// SPDX-License-Identifier: GPL-2.0-only
	/* Copyright (c) 2013-2018, The Linux Foundation. All rights reserved.
	*
	* RMNET Data MAP protocol
	*/

	#include <linux/netdevice.h>
	#include <linux/ip.h>
	#include <linux/ipv6.h>
	#include <net/ip6_checksum.h>
	#include "rmnet_config.h"
	#include "rmnet_map.h"
	#include "rmnet_private.h"

	#define RMNET_MAP_DEAGGR_SPACING 64
	#define RMNET_MAP_DEAGGR_HEADROOM (RMNET_MAP_DEAGGR_SPACING / 2)

	static __sum16 *rmnet_map_get_csum_field(unsigned char protocol,
	const void *txporthdr)
	{
	__sum16 *check = NULL;

	switch (protocol) {
	case IPPROTO_TCP:
	check = &(((struct tcphdr *)txporthdr)->check);
	break;

	case IPPROTO_UDP:
	check = &(((struct udphdr *)txporthdr)->check);
	break;

	default:
	check = NULL;
	break;
	}

	return check;
	}

	static int
	rmnet_map_ipv4_dl_csum_trailer(struct sk_buff *skb,
	struct rmnet_map_dl_csum_trailer *csum_trailer,
	struct rmnet_priv *priv)
	{
	__sum16 *csum_field, csum_temp, pseudo_csum, hdr_csum, ip_payload_csum;
	u16 csum_value, csum_value_final;
	struct iphdr *ip4h;
	void *txporthdr;
	__be16 addend;

	ip4h = (struct iphdr *)(skb->data);
	if ((ntohs(ip4h->frag_off) & IP_MF) \|\|
	((ntohs(ip4h->frag_off) & IP_OFFSET) > 0)) {
	priv->stats.csum_fragmented_pkt++;
	return -EOPNOTSUPP;
	}

	txporthdr = skb->data + ip4h->ihl * 4;

	csum_field = rmnet_map_get_csum_field(ip4h->protocol, txporthdr);

	if (!csum_field) {
	priv->stats.csum_err_invalid_transport++;
	return -EPROTONOSUPPORT;
	}

	/* RFC 768 - Skip IPv4 UDP packets where sender checksum field is 0 */
	if (*csum_field == 0 && ip4h->protocol == IPPROTO_UDP) {
	priv->stats.csum_skipped++;
	return 0;
	}

	csum_value = ~ntohs(csum_trailer->csum_value);
	hdr_csum = ~ip_fast_csum(ip4h, (int)ip4h->ihl);
	ip_payload_csum = csum16_sub((__force __sum16)csum_value,
	(__force __be16)hdr_csum);

	pseudo_csum = ~csum_tcpudp_magic(ip4h->saddr, ip4h->daddr,
	ntohs(ip4h->tot_len) - ip4h->ihl * 4,
	ip4h->protocol, 0);
	addend = (__force __be16)ntohs((__force __be16)pseudo_csum);
	pseudo_csum = csum16_add(ip_payload_csum, addend);

	addend = (__force __be16)ntohs((__force __be16)*csum_field);
	csum_temp = ~csum16_sub(pseudo_csum, addend);
	csum_value_final = (__force u16)csum_temp;

	if (unlikely(csum_value_final == 0)) {
	switch (ip4h->protocol) {
	case IPPROTO_UDP:
	/* RFC 768 - DL4 1's complement rule for UDP csum 0 */
	csum_value_final = ~csum_value_final;
	break;

	case IPPROTO_TCP:
	/* DL4 Non-RFC compliant TCP checksum found */
	if (*csum_field == (__force __sum16)0xFFFF)
	csum_value_final = ~csum_value_final;
	break;
	}
	}

	if (csum_value_final == ntohs((__force __be16)*csum_field)) {
	priv->stats.csum_ok++;
	return 0;
	} else {
	priv->stats.csum_validation_failed++;
	return -EINVAL;
	}
	}

	#if IS_ENABLED(CONFIG_IPV6)
	static int
	rmnet_map_ipv6_dl_csum_trailer(struct sk_buff *skb,
	struct rmnet_map_dl_csum_trailer *csum_trailer,
	struct rmnet_priv *priv)
	{
	__sum16 *csum_field, ip6_payload_csum, pseudo_csum, csum_temp;
	u16 csum_value, csum_value_final;
	__be16 ip6_hdr_csum, addend;
	struct ipv6hdr *ip6h;
	void *txporthdr;
	u32 length;

	ip6h = (struct ipv6hdr *)(skb->data);

	txporthdr = skb->data + sizeof(struct ipv6hdr);
	csum_field = rmnet_map_get_csum_field(ip6h->nexthdr, txporthdr);

	if (!csum_field) {
	priv->stats.csum_err_invalid_transport++;
	return -EPROTONOSUPPORT;
	}

	csum_value = ~ntohs(csum_trailer->csum_value);
	ip6_hdr_csum = (__force __be16)
	~ntohs((__force __be16)ip_compute_csum(ip6h,
	(int)(txporthdr - (void *)(skb->data))));
	ip6_payload_csum = csum16_sub((__force __sum16)csum_value,
	ip6_hdr_csum);

	length = (ip6h->nexthdr == IPPROTO_UDP) ?
	ntohs(((struct udphdr *)txporthdr)->len) :
	ntohs(ip6h->payload_len);
	pseudo_csum = ~(csum_ipv6_magic(&ip6h->saddr, &ip6h->daddr,
	length, ip6h->nexthdr, 0));
	addend = (__force __be16)ntohs((__force __be16)pseudo_csum);
	pseudo_csum = csum16_add(ip6_payload_csum, addend);

	addend = (__force __be16)ntohs((__force __be16)*csum_field);
	csum_temp = ~csum16_sub(pseudo_csum, addend);
	csum_value_final = (__force u16)csum_temp;

	if (unlikely(csum_value_final == 0)) {
	switch (ip6h->nexthdr) {
	case IPPROTO_UDP:
	/* RFC 2460 section 8.1
	* DL6 One's complement rule for UDP checksum 0
	*/
	csum_value_final = ~csum_value_final;
	break;

	case IPPROTO_TCP:
	/* DL6 Non-RFC compliant TCP checksum found */
	if (*csum_field == (__force __sum16)0xFFFF)
	csum_value_final = ~csum_value_final;
	break;
	}
	}

	if (csum_value_final == ntohs((__force __be16)*csum_field)) {
	priv->stats.csum_ok++;
	return 0;
	} else {
	priv->stats.csum_validation_failed++;
	return -EINVAL;
	}
	}
	#endif

	static void rmnet_map_complement_ipv4_txporthdr_csum_field(void *iphdr)
	{
	struct iphdr ip4h = (struct iphdr )iphdr;
	void *txphdr;
	u16 *csum;

	txphdr = iphdr + ip4h->ihl * 4;

	if (ip4h->protocol == IPPROTO_TCP \|\| ip4h->protocol == IPPROTO_UDP) {
	csum = (u16 *)rmnet_map_get_csum_field(ip4h->protocol, txphdr);
	csum = ~(csum);
	}
	}

	static void
	rmnet_map_ipv4_ul_csum_header(void *iphdr,
	struct rmnet_map_ul_csum_header *ul_header,
	struct sk_buff *skb)
	{
	struct iphdr ip4h = (struct iphdr )iphdr;
	__be16 hdr = (__be16 )ul_header, offset;

	offset = htons((__force u16)(skb_transport_header(skb) -
	(unsigned char *)iphdr));
	ul_header->csum_start_offset = offset;
	ul_header->csum_insert_offset = skb->csum_offset;
	ul_header->csum_enabled = 1;
	if (ip4h->protocol == IPPROTO_UDP)
	ul_header->udp_ind = 1;
	else
	ul_header->udp_ind = 0;

	/* Changing remaining fields to network order */
	hdr++;
	hdr = htons((__force u16)hdr);

	skb->ip_summed = CHECKSUM_NONE;

	rmnet_map_complement_ipv4_txporthdr_csum_field(iphdr);
	}

	#if IS_ENABLED(CONFIG_IPV6)
	static void rmnet_map_complement_ipv6_txporthdr_csum_field(void *ip6hdr)
	{
	struct ipv6hdr ip6h = (struct ipv6hdr )ip6hdr;
	void *txphdr;
	u16 *csum;

	txphdr = ip6hdr + sizeof(struct ipv6hdr);

	if (ip6h->nexthdr == IPPROTO_TCP \|\| ip6h->nexthdr == IPPROTO_UDP) {
	csum = (u16 *)rmnet_map_get_csum_field(ip6h->nexthdr, txphdr);
	csum = ~(csum);
	}
	}

	static void
	rmnet_map_ipv6_ul_csum_header(void *ip6hdr,
	struct rmnet_map_ul_csum_header *ul_header,
	struct sk_buff *skb)
	{
	struct ipv6hdr ip6h = (struct ipv6hdr )ip6hdr;
	__be16 hdr = (__be16 )ul_header, offset;

	offset = htons((__force u16)(skb_transport_header(skb) -
	(unsigned char *)ip6hdr));
	ul_header->csum_start_offset = offset;
	ul_header->csum_insert_offset = skb->csum_offset;
	ul_header->csum_enabled = 1;

	if (ip6h->nexthdr == IPPROTO_UDP)
	ul_header->udp_ind = 1;
	else
	ul_header->udp_ind = 0;

	/* Changing remaining fields to network order */
	hdr++;
	hdr = htons((__force u16)hdr);

	skb->ip_summed = CHECKSUM_NONE;

	rmnet_map_complement_ipv6_txporthdr_csum_field(ip6hdr);
	}
	#endif

	/* Adds MAP header to front of skb->data
	* Padding is calculated and set appropriately in MAP header. Mux ID is
	* initialized to 0.
	*/
	struct rmnet_map_header rmnet_map_add_map_header(struct sk_buff skb,
	int hdrlen, int pad)
	{
	struct rmnet_map_header *map_header;
	u32 padding, map_datalen;
	u8 *padbytes;

	map_datalen = skb->len - hdrlen;
	map_header = (struct rmnet_map_header *)
	skb_push(skb, sizeof(struct rmnet_map_header));
	memset(map_header, 0, sizeof(struct rmnet_map_header));

	if (pad == RMNET_MAP_NO_PAD_BYTES) {
	map_header->pkt_len = htons(map_datalen);
	return map_header;
	}

	padding = ALIGN(map_datalen, 4) - map_datalen;

	if (padding == 0)
	goto done;

	if (skb_tailroom(skb) < padding)
	return NULL;

	padbytes = (u8 *)skb_put(skb, padding);
	memset(padbytes, 0, padding);

	done:
	map_header->pkt_len = htons(map_datalen + padding);
	map_header->pad_len = padding & 0x3F;

	return map_header;
	}

	/* Deaggregates a single packet
	* A whole new buffer is allocated for each portion of an aggregated frame.
	* Caller should keep calling deaggregate() on the source skb until 0 is
	* returned, indicating that there are no more packets to deaggregate. Caller
	* is responsible for freeing the original skb.
	*/
	struct sk_buff rmnet_map_deaggregate(struct sk_buff skb,
	struct rmnet_port *port)
	{
	struct rmnet_map_header *maph;
	struct sk_buff *skbn;
	u32 packet_len;

	if (skb->len == 0)
	return NULL;

	maph = (struct rmnet_map_header *)skb->data;
	packet_len = ntohs(maph->pkt_len) + sizeof(struct rmnet_map_header);

	if (port->data_format & RMNET_FLAGS_INGRESS_MAP_CKSUMV4)
	packet_len += sizeof(struct rmnet_map_dl_csum_trailer);

	if (((int)skb->len - (int)packet_len) < 0)
	return NULL;

	/* Some hardware can send us empty frames. Catch them */
	if (ntohs(maph->pkt_len) == 0)
	return NULL;

	skbn = alloc_skb(packet_len + RMNET_MAP_DEAGGR_SPACING, GFP_ATOMIC);
	if (!skbn)
	return NULL;

	skb_reserve(skbn, RMNET_MAP_DEAGGR_HEADROOM);
	skb_put(skbn, packet_len);
	memcpy(skbn->data, skb->data, packet_len);
	skb_pull(skb, packet_len);

	return skbn;
	}

	/* Validates packet checksums. Function takes a pointer to
	* the beginning of a buffer which contains the IP payload +
	* padding + checksum trailer.
	* Only IPv4 and IPv6 are supported along with TCP & UDP.
	* Fragmented or tunneled packets are not supported.
	*/
	int rmnet_map_checksum_downlink_packet(struct sk_buff *skb, u16 len)
	{
	struct rmnet_priv *priv = netdev_priv(skb->dev);
	struct rmnet_map_dl_csum_trailer *csum_trailer;

	if (unlikely(!(skb->dev->features & NETIF_F_RXCSUM))) {
	priv->stats.csum_sw++;
	return -EOPNOTSUPP;
	}

	csum_trailer = (struct rmnet_map_dl_csum_trailer *)(skb->data + len);

	if (!csum_trailer->valid) {
	priv->stats.csum_valid_unset++;
	return -EINVAL;
	}

	if (skb->protocol == htons(ETH_P_IP)) {
	return rmnet_map_ipv4_dl_csum_trailer(skb, csum_trailer, priv);
	} else if (skb->protocol == htons(ETH_P_IPV6)) {
	#if IS_ENABLED(CONFIG_IPV6)
	return rmnet_map_ipv6_dl_csum_trailer(skb, csum_trailer, priv);
	#else
	priv->stats.csum_err_invalid_ip_version++;
	return -EPROTONOSUPPORT;
	#endif
	} else {
	priv->stats.csum_err_invalid_ip_version++;
	return -EPROTONOSUPPORT;
	}

	return 0;
	}

	/* Generates UL checksum meta info header for IPv4 and IPv6 over TCP and UDP
	* packets that are supported for UL checksum offload.
	*/
	void rmnet_map_checksum_uplink_packet(struct sk_buff *skb,
	struct net_device *orig_dev)
	{
	struct rmnet_priv *priv = netdev_priv(orig_dev);
	struct rmnet_map_ul_csum_header *ul_header;
	void *iphdr;

	ul_header = (struct rmnet_map_ul_csum_header *)
	skb_push(skb, sizeof(struct rmnet_map_ul_csum_header));

	if (unlikely(!(orig_dev->features &
	(NETIF_F_IP_CSUM \| NETIF_F_IPV6_CSUM))))
	goto sw_csum;

	if (skb->ip_summed == CHECKSUM_PARTIAL) {
	iphdr = (char *)ul_header +
	sizeof(struct rmnet_map_ul_csum_header);

	if (skb->protocol == htons(ETH_P_IP)) {
	rmnet_map_ipv4_ul_csum_header(iphdr, ul_header, skb);
	return;
	} else if (skb->protocol == htons(ETH_P_IPV6)) {
	#if IS_ENABLED(CONFIG_IPV6)
	rmnet_map_ipv6_ul_csum_header(iphdr, ul_header, skb);
	return;
	#else
	priv->stats.csum_err_invalid_ip_version++;
	goto sw_csum;
	#endif
	} else {
	priv->stats.csum_err_invalid_ip_version++;
	}
	}

	sw_csum:
	ul_header->csum_start_offset = 0;
	ul_header->csum_insert_offset = 0;
	ul_header->csum_enabled = 0;
	ul_header->udp_ind = 0;

	priv->stats.csum_sw++;
	}