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 /* Number of IPv4/IPv6 GSO handler entries for this packet. */ 23 u8 recursion_counter; 24 }; 25 #define SKB_GSO_CB_OFFSET 32 26 #define SKB_GSO_CB(skb) ((struct skb_gso_cb *)((skb)->cb + SKB_GSO_CB_OFFSET)) 27 28 static inline bool gso_recursion_inc_test(struct sk_buff *skb, 29 unsigned int limit) 30 { 31 return ++SKB_GSO_CB(skb)->recursion_counter > limit; 32 } 33 34 static inline int skb_tnl_header_len(const struct sk_buff *inner_skb) 35 { 36 return (skb_mac_header(inner_skb) - inner_skb->head) - 37 SKB_GSO_CB(inner_skb)->mac_offset; 38 } 39 40 static inline int gso_pskb_expand_head(struct sk_buff *skb, int extra) 41 { 42 int new_headroom, headroom; 43 int ret; 44 45 headroom = skb_headroom(skb); 46 ret = pskb_expand_head(skb, extra, 0, GFP_ATOMIC); 47 if (ret) 48 return ret; 49 50 new_headroom = skb_headroom(skb); 51 SKB_GSO_CB(skb)->mac_offset += (new_headroom - headroom); 52 return 0; 53 } 54 55 static inline void gso_reset_checksum(struct sk_buff *skb, __wsum res) 56 { 57 /* Do not update partial checksums if remote checksum is enabled. */ 58 if (skb->remcsum_offload) 59 return; 60 61 SKB_GSO_CB(skb)->csum = res; 62 SKB_GSO_CB(skb)->csum_start = skb_checksum_start(skb) - skb->head; 63 } 64 65 /* Compute the checksum for a gso segment. First compute the checksum value 66 * from the start of transport header to SKB_GSO_CB(skb)->csum_start, and 67 * then add in skb->csum (checksum from csum_start to end of packet). 68 * skb->csum and csum_start are then updated to reflect the checksum of the 69 * resultant packet starting from the transport header-- the resultant checksum 70 * is in the res argument (i.e. normally zero or ~ of checksum of a pseudo 71 * header. 72 */ 73 static inline __sum16 gso_make_checksum(struct sk_buff *skb, __wsum res) 74 { 75 unsigned char *csum_start = skb_transport_header(skb); 76 int plen = (skb->head + SKB_GSO_CB(skb)->csum_start) - csum_start; 77 __wsum partial = SKB_GSO_CB(skb)->csum; 78 79 SKB_GSO_CB(skb)->csum = res; 80 SKB_GSO_CB(skb)->csum_start = csum_start - skb->head; 81 82 return csum_fold(csum_partial(csum_start, plen, partial)); 83 } 84 85 struct sk_buff *__skb_gso_segment(struct sk_buff *skb, 86 netdev_features_t features, bool tx_path); 87 88 static inline struct sk_buff *skb_gso_segment(struct sk_buff *skb, 89 netdev_features_t features) 90 { 91 return __skb_gso_segment(skb, features, true); 92 } 93 94 struct sk_buff *skb_eth_gso_segment(struct sk_buff *skb, 95 netdev_features_t features, __be16 type); 96 97 struct sk_buff *skb_mac_gso_segment(struct sk_buff *skb, 98 netdev_features_t features); 99 100 bool skb_gso_validate_network_len(const struct sk_buff *skb, unsigned int mtu); 101 102 bool skb_gso_validate_mac_len(const struct sk_buff *skb, unsigned int len); 103 104 static inline void skb_gso_error_unwind(struct sk_buff *skb, __be16 protocol, 105 int pulled_hlen, u16 mac_offset, 106 int mac_len) 107 { 108 skb->protocol = protocol; 109 skb->encapsulation = 1; 110 skb_push(skb, pulled_hlen); 111 skb_reset_transport_header(skb); 112 skb->mac_header = mac_offset; 113 skb->network_header = skb->mac_header + mac_len; 114 skb->mac_len = mac_len; 115 } 116 117 #endif /* _NET_GSO_H */ 118