1// SPDX-License-Identifier: GPL-2.0-or-later
2#include <linux/skbuff.h>
3#include <linux/sctp.h>
4#include <net/gso.h>
5#include <net/gro.h>
6
7/**
8 * skb_eth_gso_segment - segmentation handler for ethernet protocols.
9 * @skb: buffer to segment
10 * @features: features for the output path (see dev->features)
11 * @type: Ethernet Protocol ID
12 */
13struct sk_buff *skb_eth_gso_segment(struct sk_buff *skb,
14 netdev_features_t features, __be16 type)
15{
16 struct sk_buff *segs = ERR_PTR(error: -EPROTONOSUPPORT);
17 struct packet_offload *ptype;
18
19 rcu_read_lock();
20 list_for_each_entry_rcu(ptype, &net_hotdata.offload_base, list) {
21 if (ptype->type == type && ptype->callbacks.gso_segment) {
22 segs = ptype->callbacks.gso_segment(skb, features);
23 break;
24 }
25 }
26 rcu_read_unlock();
27
28 return segs;
29}
30EXPORT_SYMBOL(skb_eth_gso_segment);
31
32/**
33 * skb_mac_gso_segment - mac layer segmentation handler.
34 * @skb: buffer to segment
35 * @features: features for the output path (see dev->features)
36 */
37struct sk_buff *skb_mac_gso_segment(struct sk_buff *skb,
38 netdev_features_t features)
39{
40 struct sk_buff *segs = ERR_PTR(error: -EPROTONOSUPPORT);
41 struct packet_offload *ptype;
42 int vlan_depth = skb->mac_len;
43 __be16 type = skb_network_protocol(skb, depth: &vlan_depth);
44
45 if (unlikely(!type))
46 return ERR_PTR(error: -EINVAL);
47
48 __skb_pull(skb, len: vlan_depth);
49
50 rcu_read_lock();
51 list_for_each_entry_rcu(ptype, &net_hotdata.offload_base, list) {
52 if (ptype->type == type && ptype->callbacks.gso_segment) {
53 segs = ptype->callbacks.gso_segment(skb, features);
54 break;
55 }
56 }
57 rcu_read_unlock();
58
59 __skb_push(skb, len: skb->data - skb_mac_header(skb));
60
61 return segs;
62}
63EXPORT_SYMBOL(skb_mac_gso_segment);
64/* openvswitch calls this on rx path, so we need a different check.
65 */
66static bool skb_needs_check(const struct sk_buff *skb, bool tx_path)
67{
68 if (tx_path)
69 return skb->ip_summed != CHECKSUM_PARTIAL &&
70 skb->ip_summed != CHECKSUM_UNNECESSARY;
71
72 return skb->ip_summed == CHECKSUM_NONE;
73}
74
75/**
76 * __skb_gso_segment - Perform segmentation on skb.
77 * @skb: buffer to segment
78 * @features: features for the output path (see dev->features)
79 * @tx_path: whether it is called in TX path
80 *
81 * This function segments the given skb and returns a list of segments.
82 *
83 * It may return NULL if the skb requires no segmentation. This is
84 * only possible when GSO is used for verifying header integrity.
85 *
86 * Segmentation preserves SKB_GSO_CB_OFFSET bytes of previous skb cb.
87 */
88struct sk_buff *__skb_gso_segment(struct sk_buff *skb,
89 netdev_features_t features, bool tx_path)
90{
91 struct sk_buff *segs;
92
93 if (unlikely(skb_needs_check(skb, tx_path))) {
94 int err;
95
96 /* We're going to init ->check field in TCP or UDP header */
97 err = skb_cow_head(skb, headroom: 0);
98 if (err < 0)
99 return ERR_PTR(error: err);
100 }
101
102 /* Only report GSO partial support if it will enable us to
103 * support segmentation on this frame without needing additional
104 * work.
105 */
106 if (features & NETIF_F_GSO_PARTIAL) {
107 netdev_features_t partial_features = NETIF_F_GSO_ROBUST;
108 struct net_device *dev = skb->dev;
109
110 partial_features |= dev->features & dev->gso_partial_features;
111 if (!skb_gso_ok(skb, features: features | partial_features))
112 features &= ~NETIF_F_GSO_PARTIAL;
113 }
114
115 BUILD_BUG_ON(SKB_GSO_CB_OFFSET +
116 sizeof(*SKB_GSO_CB(skb)) > sizeof(skb->cb));
117
118 SKB_GSO_CB(skb)->mac_offset = skb_headroom(skb);
119 SKB_GSO_CB(skb)->encap_level = 0;
120
121 skb_reset_mac_header(skb);
122 skb_reset_mac_len(skb);
123
124 segs = skb_mac_gso_segment(skb, features);
125
126 if (segs != skb && unlikely(skb_needs_check(skb, tx_path) && !IS_ERR(segs)))
127 skb_warn_bad_offload(skb);
128
129 return segs;
130}
131EXPORT_SYMBOL(__skb_gso_segment);
132
133/**
134 * skb_gso_transport_seglen - Return length of individual segments of a gso packet
135 *
136 * @skb: GSO skb
137 *
138 * skb_gso_transport_seglen is used to determine the real size of the
139 * individual segments, including Layer4 headers (TCP/UDP).
140 *
141 * The MAC/L2 or network (IP, IPv6) headers are not accounted for.
142 */
143static unsigned int skb_gso_transport_seglen(const struct sk_buff *skb)
144{
145 const struct skb_shared_info *shinfo = skb_shinfo(skb);
146 unsigned int thlen = 0;
147
148 if (skb->encapsulation) {
149 thlen = skb_inner_transport_header(skb) -
150 skb_transport_header(skb);
151
152 if (likely(shinfo->gso_type & (SKB_GSO_TCPV4 | SKB_GSO_TCPV6)))
153 thlen += inner_tcp_hdrlen(skb);
154 } else if (likely(shinfo->gso_type & (SKB_GSO_TCPV4 | SKB_GSO_TCPV6))) {
155 thlen = tcp_hdrlen(skb);
156 } else if (unlikely(skb_is_gso_sctp(skb))) {
157 thlen = sizeof(struct sctphdr);
158 } else if (shinfo->gso_type & SKB_GSO_UDP_L4) {
159 thlen = sizeof(struct udphdr);
160 }
161 /* UFO sets gso_size to the size of the fragmentation
162 * payload, i.e. the size of the L4 (UDP) header is already
163 * accounted for.
164 */
165 return thlen + shinfo->gso_size;
166}
167
168/**
169 * skb_gso_network_seglen - Return length of individual segments of a gso packet
170 *
171 * @skb: GSO skb
172 *
173 * skb_gso_network_seglen is used to determine the real size of the
174 * individual segments, including Layer3 (IP, IPv6) and L4 headers (TCP/UDP).
175 *
176 * The MAC/L2 header is not accounted for.
177 */
178static unsigned int skb_gso_network_seglen(const struct sk_buff *skb)
179{
180 unsigned int hdr_len = skb_transport_header(skb) -
181 skb_network_header(skb);
182
183 return hdr_len + skb_gso_transport_seglen(skb);
184}
185
186/**
187 * skb_gso_mac_seglen - Return length of individual segments of a gso packet
188 *
189 * @skb: GSO skb
190 *
191 * skb_gso_mac_seglen is used to determine the real size of the
192 * individual segments, including MAC/L2, Layer3 (IP, IPv6) and L4
193 * headers (TCP/UDP).
194 */
195static unsigned int skb_gso_mac_seglen(const struct sk_buff *skb)
196{
197 unsigned int hdr_len = skb_transport_header(skb) - skb_mac_header(skb);
198
199 return hdr_len + skb_gso_transport_seglen(skb);
200}
201
202/**
203 * skb_gso_size_check - check the skb size, considering GSO_BY_FRAGS
204 *
205 * There are a couple of instances where we have a GSO skb, and we
206 * want to determine what size it would be after it is segmented.
207 *
208 * We might want to check:
209 * - L3+L4+payload size (e.g. IP forwarding)
210 * - L2+L3+L4+payload size (e.g. sanity check before passing to driver)
211 *
212 * This is a helper to do that correctly considering GSO_BY_FRAGS.
213 *
214 * @skb: GSO skb
215 *
216 * @seg_len: The segmented length (from skb_gso_*_seglen). In the
217 * GSO_BY_FRAGS case this will be [header sizes + GSO_BY_FRAGS].
218 *
219 * @max_len: The maximum permissible length.
220 *
221 * Returns true if the segmented length <= max length.
222 */
223static inline bool skb_gso_size_check(const struct sk_buff *skb,
224 unsigned int seg_len,
225 unsigned int max_len) {
226 const struct skb_shared_info *shinfo = skb_shinfo(skb);
227 const struct sk_buff *iter;
228
229 if (shinfo->gso_size != GSO_BY_FRAGS)
230 return seg_len <= max_len;
231
232 /* Undo this so we can re-use header sizes */
233 seg_len -= GSO_BY_FRAGS;
234
235 skb_walk_frags(skb, iter) {
236 if (seg_len + skb_headlen(skb: iter) > max_len)
237 return false;
238 }
239
240 return true;
241}
242
243/**
244 * skb_gso_validate_network_len - Will a split GSO skb fit into a given MTU?
245 *
246 * @skb: GSO skb
247 * @mtu: MTU to validate against
248 *
249 * skb_gso_validate_network_len validates if a given skb will fit a
250 * wanted MTU once split. It considers L3 headers, L4 headers, and the
251 * payload.
252 */
253bool skb_gso_validate_network_len(const struct sk_buff *skb, unsigned int mtu)
254{
255 return skb_gso_size_check(skb, seg_len: skb_gso_network_seglen(skb), max_len: mtu);
256}
257EXPORT_SYMBOL_GPL(skb_gso_validate_network_len);
258
259/**
260 * skb_gso_validate_mac_len - Will a split GSO skb fit in a given length?
261 *
262 * @skb: GSO skb
263 * @len: length to validate against
264 *
265 * skb_gso_validate_mac_len validates if a given skb will fit a wanted
266 * length once split, including L2, L3 and L4 headers and the payload.
267 */
268bool skb_gso_validate_mac_len(const struct sk_buff *skb, unsigned int len)
269{
270 return skb_gso_size_check(skb, seg_len: skb_gso_mac_seglen(skb), max_len: len);
271}
272EXPORT_SYMBOL_GPL(skb_gso_validate_mac_len);
273
274

source code of linux/net/core/gso.c