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(skb: 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, nhead: extra, ntail: 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: csum_partial(buff: csum_start, len: plen, sum: 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, tx_path: 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, len: 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

source code of linux/include/net/gso.h