net/ipv4/gre_offload.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-or-later
 /*
  *	IPV4 GSO/GRO offload support
  *	Linux INET implementation
  *
  *	GRE GSO support
  */

 #include <linux/skbuff.h>
 #include <linux/init.h>
 #include <net/protocol.h>
 #include <net/gre.h>

 static struct sk_buff *gre_gso_segment(struct sk_buff *skb,
 				       netdev_features_t features)
 {
 	int tnl_hlen = skb_inner_mac_header(skb) - skb_transport_header(skb);
 	bool need_csum, offload_csum, gso_partial, need_ipsec;
 	struct sk_buff *segs = ERR_PTR(-EINVAL);
 	u16 mac_offset = skb->mac_header;
 	__be16 protocol = skb->protocol;
 	u16 mac_len = skb->mac_len;
 	int gre_offset, outer_hlen;

 	if (!skb->encapsulation)
 		goto out;

 	if (unlikely(tnl_hlen < sizeof(struct gre_base_hdr)))
 		goto out;

 	if (unlikely(!pskb_may_pull(skb, tnl_hlen)))
 		goto out;

 	/* setup inner skb. */
 	skb->encapsulation = 0;
 	SKB_GSO_CB(skb)->encap_level = 0;
 	__skb_pull(skb, tnl_hlen);
 	skb_reset_mac_header(skb);
 	skb_set_network_header(skb, skb_inner_network_offset(skb));
 	skb->mac_len = skb_inner_network_offset(skb);
 	skb->protocol = skb->inner_protocol;

 	need_csum = !!(skb_shinfo(skb)->gso_type & SKB_GSO_GRE_CSUM);
 	skb->encap_hdr_csum = need_csum;

 	features &= skb->dev->hw_enc_features;
 	if (need_csum)
 		features &= ~NETIF_F_SCTP_CRC;

 	need_ipsec = skb_dst(skb) && dst_xfrm(skb_dst(skb));
 	/* Try to offload checksum if possible */
 	offload_csum = !!(need_csum && !need_ipsec &&
 			  (skb->dev->features & NETIF_F_HW_CSUM));

 	/* segment inner packet. */
 	segs = skb_mac_gso_segment(skb, features);
 	if (IS_ERR_OR_NULL(segs)) {
 		skb_gso_error_unwind(skb, protocol, tnl_hlen, mac_offset,
 				     mac_len);
 		goto out;
 	}

 	gso_partial = !!(skb_shinfo(segs)->gso_type & SKB_GSO_PARTIAL);

 	outer_hlen = skb_tnl_header_len(skb);
 	gre_offset = outer_hlen - tnl_hlen;
 	skb = segs;
 	do {
 		struct gre_base_hdr *greh;
 		__sum16 *pcsum;

 		/* Set up inner headers if we are offloading inner checksum */
 		if (skb->ip_summed == CHECKSUM_PARTIAL) {
 			skb_reset_inner_headers(skb);
 			skb->encapsulation = 1;
 		}

 		skb->mac_len = mac_len;
 		skb->protocol = protocol;

 		__skb_push(skb, outer_hlen);
 		skb_reset_mac_header(skb);
 		skb_set_network_header(skb, mac_len);
 		skb_set_transport_header(skb, gre_offset);

 		if (!need_csum)
 			continue;

 		greh = (struct gre_base_hdr *)skb_transport_header(skb);
 		pcsum = (__sum16 *)(greh + 1);

 		if (gso_partial && skb_is_gso(skb)) {
 			unsigned int partial_adj;

 			/* Adjust checksum to account for the fact that
 			 * the partial checksum is based on actual size
 			 * whereas headers should be based on MSS size.
 			 */
 			partial_adj = skb->len + skb_headroom(skb) -
 				      SKB_GSO_CB(skb)->data_offset -
 				      skb_shinfo(skb)->gso_size;
 			*pcsum = ~csum_fold((__force __wsum)htonl(partial_adj));
 		} else {
 			*pcsum = 0;
 		}

 		*(pcsum + 1) = 0;
 		if (skb->encapsulation || !offload_csum) {
 			*pcsum = gso_make_checksum(skb, 0);
 		} else {
 			skb->ip_summed = CHECKSUM_PARTIAL;
 			skb->csum_start = skb_transport_header(skb) - skb->head;
 			skb->csum_offset = sizeof(*greh);
 		}
 	} while ((skb = skb->next));
 out:
 	return segs;
 }

 static struct sk_buff *gre_gro_receive(struct list_head *head,
 				       struct sk_buff *skb)
 {
 	struct sk_buff *pp = NULL;
 	struct sk_buff *p;
 	const struct gre_base_hdr *greh;
 	unsigned int hlen, grehlen;
 	unsigned int off;
 	int flush = 1;
 	struct packet_offload *ptype;
 	__be16 type;

 	if (NAPI_GRO_CB(skb)->encap_mark)
 		goto out;

 	NAPI_GRO_CB(skb)->encap_mark = 1;

 	off = skb_gro_offset(skb);
 	hlen = off + sizeof(*greh);
 	greh = skb_gro_header_fast(skb, off);
 	if (skb_gro_header_hard(skb, hlen)) {
 		greh = skb_gro_header_slow(skb, hlen, off);
 		if (unlikely(!greh))
 			goto out;
 	}

 	/* Only support version 0 and K (key), C (csum) flags. Note that
 	 * although the support for the S (seq#) flag can be added easily
 	 * for GRO, this is problematic for GSO hence can not be enabled
 	 * here because a GRO pkt may end up in the forwarding path, thus
 	 * requiring GSO support to break it up correctly.
 	 */
 	if ((greh->flags & ~(GRE_KEY|GRE_CSUM)) != 0)
 		goto out;

 	/* We can only support GRE_CSUM if we can track the location of
 	 * the GRE header.  In the case of FOU/GUE we cannot because the
 	 * outer UDP header displaces the GRE header leaving us in a state
 	 * of limbo.
 	 */
 	if ((greh->flags & GRE_CSUM) && NAPI_GRO_CB(skb)->is_fou)
 		goto out;

 	type = greh->protocol;

 	rcu_read_lock();
 	ptype = gro_find_receive_by_type(type);
 	if (!ptype)
 		goto out_unlock;

 	grehlen = GRE_HEADER_SECTION;

 	if (greh->flags & GRE_KEY)
 		grehlen += GRE_HEADER_SECTION;

 	if (greh->flags & GRE_CSUM)
 		grehlen += GRE_HEADER_SECTION;

 	hlen = off + grehlen;
 	if (skb_gro_header_hard(skb, hlen)) {
 		greh = skb_gro_header_slow(skb, hlen, off);
 		if (unlikely(!greh))
 			goto out_unlock;
 	}

 	/* Don't bother verifying checksum if we're going to flush anyway. */
 	if ((greh->flags & GRE_CSUM) && !NAPI_GRO_CB(skb)->flush) {
 		if (skb_gro_checksum_simple_validate(skb))
 			goto out_unlock;

 		skb_gro_checksum_try_convert(skb, IPPROTO_GRE,
 					     null_compute_pseudo);
 	}

 	list_for_each_entry(p, head, list) {
 		const struct gre_base_hdr *greh2;

 		if (!NAPI_GRO_CB(p)->same_flow)
 			continue;

 		/* The following checks are needed to ensure only pkts
 		 * from the same tunnel are considered for aggregation.
 		 * The criteria for "the same tunnel" includes:
 		 * 1) same version (we only support version 0 here)
 		 * 2) same protocol (we only support ETH_P_IP for now)
 		 * 3) same set of flags
 		 * 4) same key if the key field is present.
 		 */
 		greh2 = (struct gre_base_hdr *)(p->data + off);

 		if (greh2->flags != greh->flags ||
 		    greh2->protocol != greh->protocol) {
 			NAPI_GRO_CB(p)->same_flow = 0;
 			continue;
 		}
 		if (greh->flags & GRE_KEY) {
 			/* compare keys */
 			if (*(__be32 *)(greh2+1) != *(__be32 *)(greh+1)) {
 				NAPI_GRO_CB(p)->same_flow = 0;
 				continue;
 			}
 		}
 	}

 	skb_gro_pull(skb, grehlen);

 	/* Adjusted NAPI_GRO_CB(skb)->csum after skb_gro_pull()*/
 	skb_gro_postpull_rcsum(skb, greh, grehlen);

 	pp = call_gro_receive(ptype->callbacks.gro_receive, head, skb);
 	flush = 0;

 out_unlock:
 	rcu_read_unlock();
 out:
 	skb_gro_flush_final(skb, pp, flush);

 	return pp;
 }

 static int gre_gro_complete(struct sk_buff *skb, int nhoff)
 {
 	struct gre_base_hdr *greh = (struct gre_base_hdr *)(skb->data + nhoff);
 	struct packet_offload *ptype;
 	unsigned int grehlen = sizeof(*greh);
 	int err = -ENOENT;
 	__be16 type;

 	skb->encapsulation = 1;
 	skb_shinfo(skb)->gso_type = SKB_GSO_GRE;

 	type = greh->protocol;
 	if (greh->flags & GRE_KEY)
 		grehlen += GRE_HEADER_SECTION;

 	if (greh->flags & GRE_CSUM)
 		grehlen += GRE_HEADER_SECTION;

 	rcu_read_lock();
 	ptype = gro_find_complete_by_type(type);
 	if (ptype)
 		err = ptype->callbacks.gro_complete(skb, nhoff + grehlen);

 	rcu_read_unlock();

 	skb_set_inner_mac_header(skb, nhoff + grehlen);

 	return err;
 }

 static const struct net_offload gre_offload = {
 	.callbacks = {
 		.gso_segment = gre_gso_segment,
 		.gro_receive = gre_gro_receive,
 		.gro_complete = gre_gro_complete,
 	},
 };

 static int __init gre_offload_init(void)
 {
 	int err;

 	err = inet_add_offload(&gre_offload, IPPROTO_GRE);
 #if IS_ENABLED(CONFIG_IPV6)
 	if (err)
 		return err;

 	err = inet6_add_offload(&gre_offload, IPPROTO_GRE);
 	if (err)
 		inet_del_offload(&gre_offload, IPPROTO_GRE);
 #endif

 	return err;
 }
 device_initcall(gre_offload_init);
	// SPDX-License-Identifier: GPL-2.0-or-later
	/*
	* IPV4 GSO/GRO offload support
	* Linux INET implementation
	*
	* GRE GSO support
	*/

	#include <linux/skbuff.h>
	#include <linux/init.h>
	#include <net/protocol.h>
	#include <net/gre.h>

	static struct sk_buff gre_gso_segment(struct sk_buff skb,
	netdev_features_t features)
	{
	int tnl_hlen = skb_inner_mac_header(skb) - skb_transport_header(skb);
	bool need_csum, offload_csum, gso_partial, need_ipsec;
	struct sk_buff *segs = ERR_PTR(-EINVAL);
	u16 mac_offset = skb->mac_header;
	__be16 protocol = skb->protocol;
	u16 mac_len = skb->mac_len;
	int gre_offset, outer_hlen;

	if (!skb->encapsulation)
	goto out;

	if (unlikely(tnl_hlen < sizeof(struct gre_base_hdr)))
	goto out;

	if (unlikely(!pskb_may_pull(skb, tnl_hlen)))
	goto out;

	/* setup inner skb. */
	skb->encapsulation = 0;
	SKB_GSO_CB(skb)->encap_level = 0;
	__skb_pull(skb, tnl_hlen);
	skb_reset_mac_header(skb);
	skb_set_network_header(skb, skb_inner_network_offset(skb));
	skb->mac_len = skb_inner_network_offset(skb);
	skb->protocol = skb->inner_protocol;

	need_csum = !!(skb_shinfo(skb)->gso_type & SKB_GSO_GRE_CSUM);
	skb->encap_hdr_csum = need_csum;

	features &= skb->dev->hw_enc_features;
	if (need_csum)
	features &= ~NETIF_F_SCTP_CRC;

	need_ipsec = skb_dst(skb) && dst_xfrm(skb_dst(skb));
	/* Try to offload checksum if possible */
	offload_csum = !!(need_csum && !need_ipsec &&
	(skb->dev->features & NETIF_F_HW_CSUM));

	/* segment inner packet. */
	segs = skb_mac_gso_segment(skb, features);
	if (IS_ERR_OR_NULL(segs)) {
	skb_gso_error_unwind(skb, protocol, tnl_hlen, mac_offset,
	mac_len);
	goto out;
	}

	gso_partial = !!(skb_shinfo(segs)->gso_type & SKB_GSO_PARTIAL);

	outer_hlen = skb_tnl_header_len(skb);
	gre_offset = outer_hlen - tnl_hlen;
	skb = segs;
	do {
	struct gre_base_hdr *greh;
	__sum16 *pcsum;

	/* Set up inner headers if we are offloading inner checksum */
	if (skb->ip_summed == CHECKSUM_PARTIAL) {
	skb_reset_inner_headers(skb);
	skb->encapsulation = 1;
	}

	skb->mac_len = mac_len;
	skb->protocol = protocol;

	__skb_push(skb, outer_hlen);
	skb_reset_mac_header(skb);
	skb_set_network_header(skb, mac_len);
	skb_set_transport_header(skb, gre_offset);

	if (!need_csum)
	continue;

	greh = (struct gre_base_hdr *)skb_transport_header(skb);
	pcsum = (__sum16 *)(greh + 1);

	if (gso_partial && skb_is_gso(skb)) {
	unsigned int partial_adj;

	/* Adjust checksum to account for the fact that
	* the partial checksum is based on actual size
	* whereas headers should be based on MSS size.
	*/
	partial_adj = skb->len + skb_headroom(skb) -
	SKB_GSO_CB(skb)->data_offset -
	skb_shinfo(skb)->gso_size;
	*pcsum = ~csum_fold((__force __wsum)htonl(partial_adj));
	} else {
	*pcsum = 0;
	}

	*(pcsum + 1) = 0;
	if (skb->encapsulation \|\| !offload_csum) {
	*pcsum = gso_make_checksum(skb, 0);
	} else {
	skb->ip_summed = CHECKSUM_PARTIAL;
	skb->csum_start = skb_transport_header(skb) - skb->head;
	skb->csum_offset = sizeof(*greh);
	}
	} while ((skb = skb->next));
	out:
	return segs;
	}

	static struct sk_buff gre_gro_receive(struct list_head head,
	struct sk_buff *skb)
	{
	struct sk_buff *pp = NULL;
	struct sk_buff *p;
	const struct gre_base_hdr *greh;
	unsigned int hlen, grehlen;
	unsigned int off;
	int flush = 1;
	struct packet_offload *ptype;
	__be16 type;

	if (NAPI_GRO_CB(skb)->encap_mark)
	goto out;

	NAPI_GRO_CB(skb)->encap_mark = 1;

	off = skb_gro_offset(skb);
	hlen = off + sizeof(*greh);
	greh = skb_gro_header_fast(skb, off);
	if (skb_gro_header_hard(skb, hlen)) {
	greh = skb_gro_header_slow(skb, hlen, off);
	if (unlikely(!greh))
	goto out;
	}

	/* Only support version 0 and K (key), C (csum) flags. Note that
	* although the support for the S (seq#) flag can be added easily
	* for GRO, this is problematic for GSO hence can not be enabled
	* here because a GRO pkt may end up in the forwarding path, thus
	* requiring GSO support to break it up correctly.
	*/
	if ((greh->flags & ~(GRE_KEY\|GRE_CSUM)) != 0)
	goto out;

	/* We can only support GRE_CSUM if we can track the location of
	* the GRE header. In the case of FOU/GUE we cannot because the
	* outer UDP header displaces the GRE header leaving us in a state
	* of limbo.
	*/
	if ((greh->flags & GRE_CSUM) && NAPI_GRO_CB(skb)->is_fou)
	goto out;

	type = greh->protocol;

	rcu_read_lock();
	ptype = gro_find_receive_by_type(type);
	if (!ptype)
	goto out_unlock;

	grehlen = GRE_HEADER_SECTION;

	if (greh->flags & GRE_KEY)
	grehlen += GRE_HEADER_SECTION;

	if (greh->flags & GRE_CSUM)
	grehlen += GRE_HEADER_SECTION;

	hlen = off + grehlen;
	if (skb_gro_header_hard(skb, hlen)) {
	greh = skb_gro_header_slow(skb, hlen, off);
	if (unlikely(!greh))
	goto out_unlock;
	}

	/* Don't bother verifying checksum if we're going to flush anyway. */
	if ((greh->flags & GRE_CSUM) && !NAPI_GRO_CB(skb)->flush) {
	if (skb_gro_checksum_simple_validate(skb))
	goto out_unlock;

	skb_gro_checksum_try_convert(skb, IPPROTO_GRE,
	null_compute_pseudo);
	}

	list_for_each_entry(p, head, list) {
	const struct gre_base_hdr *greh2;

	if (!NAPI_GRO_CB(p)->same_flow)
	continue;

	/* The following checks are needed to ensure only pkts
	* from the same tunnel are considered for aggregation.
	* The criteria for "the same tunnel" includes:
	* 1) same version (we only support version 0 here)
	* 2) same protocol (we only support ETH_P_IP for now)
	* 3) same set of flags
	* 4) same key if the key field is present.
	*/
	greh2 = (struct gre_base_hdr *)(p->data + off);

	if (greh2->flags != greh->flags \|\|
	greh2->protocol != greh->protocol) {
	NAPI_GRO_CB(p)->same_flow = 0;
	continue;
	}
	if (greh->flags & GRE_KEY) {
	/* compare keys */
	if ((__be32 )(greh2+1) != (__be32 )(greh+1)) {
	NAPI_GRO_CB(p)->same_flow = 0;
	continue;
	}
	}
	}

	skb_gro_pull(skb, grehlen);

	/* Adjusted NAPI_GRO_CB(skb)->csum after skb_gro_pull()*/
	skb_gro_postpull_rcsum(skb, greh, grehlen);

	pp = call_gro_receive(ptype->callbacks.gro_receive, head, skb);
	flush = 0;

	out_unlock:
	rcu_read_unlock();
	out:
	skb_gro_flush_final(skb, pp, flush);

	return pp;
	}

	static int gre_gro_complete(struct sk_buff *skb, int nhoff)
	{
	struct gre_base_hdr greh = (struct gre_base_hdr )(skb->data + nhoff);
	struct packet_offload *ptype;
	unsigned int grehlen = sizeof(*greh);
	int err = -ENOENT;
	__be16 type;

	skb->encapsulation = 1;
	skb_shinfo(skb)->gso_type = SKB_GSO_GRE;

	type = greh->protocol;
	if (greh->flags & GRE_KEY)
	grehlen += GRE_HEADER_SECTION;

	if (greh->flags & GRE_CSUM)
	grehlen += GRE_HEADER_SECTION;

	rcu_read_lock();
	ptype = gro_find_complete_by_type(type);
	if (ptype)
	err = ptype->callbacks.gro_complete(skb, nhoff + grehlen);

	rcu_read_unlock();

	skb_set_inner_mac_header(skb, nhoff + grehlen);

	return err;
	}

	static const struct net_offload gre_offload = {
	.callbacks = {
	.gso_segment = gre_gso_segment,
	.gro_receive = gre_gro_receive,
	.gro_complete = gre_gro_complete,
	},
	};

	static int __init gre_offload_init(void)
	{
	int err;

	err = inet_add_offload(&gre_offload, IPPROTO_GRE);
	#if IS_ENABLED(CONFIG_IPV6)
	if (err)
	return err;

	err = inet6_add_offload(&gre_offload, IPPROTO_GRE);
	if (err)
	inet_del_offload(&gre_offload, IPPROTO_GRE);
	#endif

	return err;
	}
	device_initcall(gre_offload_init);