include/net/gso.h

   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  */
  14 struct 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
  26 static 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
  32 static 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
  47 static 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  */
  65 static 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
  77 struct sk_buff *__skb_gso_segment(struct sk_buff *skb,
  78                                   netdev_features_t features, bool tx_path);
  79
  80 static 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
  86 struct sk_buff *skb_eth_gso_segment(struct sk_buff *skb,
  87                                     netdev_features_t features, __be16 type);
  88
  89 struct sk_buff *skb_mac_gso_segment(struct sk_buff *skb,
  90                                     netdev_features_t features);
  91
  92 bool skb_gso_validate_network_len(const struct sk_buff *skb, unsigned int mtu);
  93
  94 bool skb_gso_validate_mac_len(const struct sk_buff *skb, unsigned int len);
  95
  96 static 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 */