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 */
110