1/* SPDX-License-Identifier: GPL-2.0-or-later */
  2
  3#ifndef _NET_GSO_H
  4#define _NET_GSO_H
  5
  6#include <linux/skbuff.h>
  7
  8/* Keeps track of mac header offset relative to skb->head.
  9 * It is useful for TSO of Tunneling protocol. e.g. GRE.
 10 * For non-tunnel skb it points to skb_mac_header() and for
 11 * tunnel skb it points to outer mac header.
 12 * Keeps track of level of encapsulation of network headers.
 13 */
 14struct skb_gso_cb {
 15	union {
 16		int	mac_offset;
 17		int	data_offset;
 18	};
 19	int	encap_level;
 20	__wsum	csum;
 21	__u16	csum_start;
 22};
 23#define SKB_GSO_CB_OFFSET	32
 24#define SKB_GSO_CB(skb) ((struct skb_gso_cb *)((skb)->cb + SKB_GSO_CB_OFFSET))
 25
 26static inline int skb_tnl_header_len(const struct sk_buff *inner_skb)
 27{
 28	return (skb_mac_header(inner_skb) - inner_skb->head) -
 29		SKB_GSO_CB(inner_skb)->mac_offset;
 30}
 31
 32static inline int gso_pskb_expand_head(struct sk_buff *skb, int extra)
 33{
 34	int new_headroom, headroom;
 35	int ret;
 36
 37	headroom = skb_headroom(skb);
 38	ret = pskb_expand_head(skb, extra, 0, GFP_ATOMIC);
 39	if (ret)
 40		return ret;
 41
 42	new_headroom = skb_headroom(skb);
 43	SKB_GSO_CB(skb)->mac_offset += (new_headroom - headroom);
 44	return 0;
 45}
 46
 47static inline void gso_reset_checksum(struct sk_buff *skb, __wsum res)
 48{
 49	/* Do not update partial checksums if remote checksum is enabled. */
 50	if (skb->remcsum_offload)
 51		return;
 52
 53	SKB_GSO_CB(skb)->csum = res;
 54	SKB_GSO_CB(skb)->csum_start = skb_checksum_start(skb) - skb->head;
 55}
 56
 57/* Compute the checksum for a gso segment. First compute the checksum value
 58 * from the start of transport header to SKB_GSO_CB(skb)->csum_start, and
 59 * then add in skb->csum (checksum from csum_start to end of packet).
 60 * skb->csum and csum_start are then updated to reflect the checksum of the
 61 * resultant packet starting from the transport header-- the resultant checksum
 62 * is in the res argument (i.e. normally zero or ~ of checksum of a pseudo
 63 * header.
 64 */
 65static inline __sum16 gso_make_checksum(struct sk_buff *skb, __wsum res)
 66{
 67	unsigned char *csum_start = skb_transport_header(skb);
 68	int plen = (skb->head + SKB_GSO_CB(skb)->csum_start) - csum_start;
 69	__wsum partial = SKB_GSO_CB(skb)->csum;
 70
 71	SKB_GSO_CB(skb)->csum = res;
 72	SKB_GSO_CB(skb)->csum_start = csum_start - skb->head;
 73
 74	return csum_fold(csum_partial(csum_start, plen, partial));
 75}
 76
 77struct sk_buff *__skb_gso_segment(struct sk_buff *skb,
 78				  netdev_features_t features, bool tx_path);
 79
 80static inline struct sk_buff *skb_gso_segment(struct sk_buff *skb,
 81					      netdev_features_t features)
 82{
 83	return __skb_gso_segment(skb, features, true);
 84}
 85
 86struct sk_buff *skb_eth_gso_segment(struct sk_buff *skb,
 87				    netdev_features_t features, __be16 type);
 88
 89struct sk_buff *skb_mac_gso_segment(struct sk_buff *skb,
 90				    netdev_features_t features);
 91
 92bool skb_gso_validate_network_len(const struct sk_buff *skb, unsigned int mtu);
 93
 94bool skb_gso_validate_mac_len(const struct sk_buff *skb, unsigned int len);
 95
 96static inline void skb_gso_error_unwind(struct sk_buff *skb, __be16 protocol,
 97					int pulled_hlen, u16 mac_offset,
 98					int mac_len)
 99{
100	skb->protocol = protocol;
101	skb->encapsulation = 1;
102	skb_push(skb, pulled_hlen);
103	skb_reset_transport_header(skb);
104	skb->mac_header = mac_offset;
105	skb->network_header = skb->mac_header + mac_len;
106	skb->mac_len = mac_len;
107}
108
109#endif /* _NET_GSO_H */