1/*
2 * IPV4 GSO/GRO offload support
3 * Linux INET implementation
4 *
5 * This program is free software; you can redistribute it and/or
6 * modify it under the terms of the GNU General Public License
7 * as published by the Free Software Foundation; either version
8 * 2 of the License, or (at your option) any later version.
9 *
10 * GRE GSO support
11 */
12
13#include <linux/skbuff.h>
14#include <linux/init.h>
15#include <net/protocol.h>
16#include <net/gre.h>
17
18static struct sk_buff *gre_gso_segment(struct sk_buff *skb,
19 netdev_features_t features)
20{
21 int tnl_hlen = skb_inner_mac_header(skb) - skb_transport_header(skb);
22 struct sk_buff *segs = ERR_PTR(-EINVAL);
23 u16 mac_offset = skb->mac_header;
24 __be16 protocol = skb->protocol;
25 u16 mac_len = skb->mac_len;
26 int gre_offset, outer_hlen;
27 bool need_csum, gso_partial;
28
29 if (!skb->encapsulation)
30 goto out;
31
32 if (unlikely(tnl_hlen < sizeof(struct gre_base_hdr)))
33 goto out;
34
35 if (unlikely(!pskb_may_pull(skb, tnl_hlen)))
36 goto out;
37
38 /* setup inner skb. */
39 skb->encapsulation = 0;
40 SKB_GSO_CB(skb)->encap_level = 0;
41 __skb_pull(skb, tnl_hlen);
42 skb_reset_mac_header(skb);
43 skb_set_network_header(skb, skb_inner_network_offset(skb));
44 skb->mac_len = skb_inner_network_offset(skb);
45 skb->protocol = skb->inner_protocol;
46
47 need_csum = !!(skb_shinfo(skb)->gso_type & SKB_GSO_GRE_CSUM);
48 skb->encap_hdr_csum = need_csum;
49
50 features &= skb->dev->hw_enc_features;
51
52 /* segment inner packet. */
53 segs = skb_mac_gso_segment(skb, features);
54 if (IS_ERR_OR_NULL(segs)) {
55 skb_gso_error_unwind(skb, protocol, tnl_hlen, mac_offset,
56 mac_len);
57 goto out;
58 }
59
60 gso_partial = !!(skb_shinfo(segs)->gso_type & SKB_GSO_PARTIAL);
61
62 outer_hlen = skb_tnl_header_len(skb);
63 gre_offset = outer_hlen - tnl_hlen;
64 skb = segs;
65 do {
66 struct gre_base_hdr *greh;
67 __sum16 *pcsum;
68
69 /* Set up inner headers if we are offloading inner checksum */
70 if (skb->ip_summed == CHECKSUM_PARTIAL) {
71 skb_reset_inner_headers(skb);
72 skb->encapsulation = 1;
73 }
74
75 skb->mac_len = mac_len;
76 skb->protocol = protocol;
77
78 __skb_push(skb, outer_hlen);
79 skb_reset_mac_header(skb);
80 skb_set_network_header(skb, mac_len);
81 skb_set_transport_header(skb, gre_offset);
82
83 if (!need_csum)
84 continue;
85
86 greh = (struct gre_base_hdr *)skb_transport_header(skb);
87 pcsum = (__sum16 *)(greh + 1);
88
89 if (gso_partial && skb_is_gso(skb)) {
90 unsigned int partial_adj;
91
92 /* Adjust checksum to account for the fact that
93 * the partial checksum is based on actual size
94 * whereas headers should be based on MSS size.
95 */
96 partial_adj = skb->len + skb_headroom(skb) -
97 SKB_GSO_CB(skb)->data_offset -
98 skb_shinfo(skb)->gso_size;
99 *pcsum = ~csum_fold((__force __wsum)htonl(partial_adj));
100 } else {
101 *pcsum = 0;
102 }
103
104 *(pcsum + 1) = 0;
105 *pcsum = gso_make_checksum(skb, 0);
106 } while ((skb = skb->next));
107out:
108 return segs;
109}
110
111static struct sk_buff *gre_gro_receive(struct list_head *head,
112 struct sk_buff *skb)
113{
114 struct sk_buff *pp = NULL;
115 struct sk_buff *p;
116 const struct gre_base_hdr *greh;
117 unsigned int hlen, grehlen;
118 unsigned int off;
119 int flush = 1;
120 struct packet_offload *ptype;
121 __be16 type;
122
123 if (NAPI_GRO_CB(skb)->encap_mark)
124 goto out;
125
126 NAPI_GRO_CB(skb)->encap_mark = 1;
127
128 off = skb_gro_offset(skb);
129 hlen = off + sizeof(*greh);
130 greh = skb_gro_header_fast(skb, off);
131 if (skb_gro_header_hard(skb, hlen)) {
132 greh = skb_gro_header_slow(skb, hlen, off);
133 if (unlikely(!greh))
134 goto out;
135 }
136
137 /* Only support version 0 and K (key), C (csum) flags. Note that
138 * although the support for the S (seq#) flag can be added easily
139 * for GRO, this is problematic for GSO hence can not be enabled
140 * here because a GRO pkt may end up in the forwarding path, thus
141 * requiring GSO support to break it up correctly.
142 */
143 if ((greh->flags & ~(GRE_KEY|GRE_CSUM)) != 0)
144 goto out;
145
146 /* We can only support GRE_CSUM if we can track the location of
147 * the GRE header. In the case of FOU/GUE we cannot because the
148 * outer UDP header displaces the GRE header leaving us in a state
149 * of limbo.
150 */
151 if ((greh->flags & GRE_CSUM) && NAPI_GRO_CB(skb)->is_fou)
152 goto out;
153
154 type = greh->protocol;
155
156 rcu_read_lock();
157 ptype = gro_find_receive_by_type(type);
158 if (!ptype)
159 goto out_unlock;
160
161 grehlen = GRE_HEADER_SECTION;
162
163 if (greh->flags & GRE_KEY)
164 grehlen += GRE_HEADER_SECTION;
165
166 if (greh->flags & GRE_CSUM)
167 grehlen += GRE_HEADER_SECTION;
168
169 hlen = off + grehlen;
170 if (skb_gro_header_hard(skb, hlen)) {
171 greh = skb_gro_header_slow(skb, hlen, off);
172 if (unlikely(!greh))
173 goto out_unlock;
174 }
175
176 /* Don't bother verifying checksum if we're going to flush anyway. */
177 if ((greh->flags & GRE_CSUM) && !NAPI_GRO_CB(skb)->flush) {
178 if (skb_gro_checksum_simple_validate(skb))
179 goto out_unlock;
180
181 skb_gro_checksum_try_convert(skb, IPPROTO_GRE, 0,
182 null_compute_pseudo);
183 }
184
185 list_for_each_entry(p, head, list) {
186 const struct gre_base_hdr *greh2;
187
188 if (!NAPI_GRO_CB(p)->same_flow)
189 continue;
190
191 /* The following checks are needed to ensure only pkts
192 * from the same tunnel are considered for aggregation.
193 * The criteria for "the same tunnel" includes:
194 * 1) same version (we only support version 0 here)
195 * 2) same protocol (we only support ETH_P_IP for now)
196 * 3) same set of flags
197 * 4) same key if the key field is present.
198 */
199 greh2 = (struct gre_base_hdr *)(p->data + off);
200
201 if (greh2->flags != greh->flags ||
202 greh2->protocol != greh->protocol) {
203 NAPI_GRO_CB(p)->same_flow = 0;
204 continue;
205 }
206 if (greh->flags & GRE_KEY) {
207 /* compare keys */
208 if (*(__be32 *)(greh2+1) != *(__be32 *)(greh+1)) {
209 NAPI_GRO_CB(p)->same_flow = 0;
210 continue;
211 }
212 }
213 }
214
215 skb_gro_pull(skb, grehlen);
216
217 /* Adjusted NAPI_GRO_CB(skb)->csum after skb_gro_pull()*/
218 skb_gro_postpull_rcsum(skb, greh, grehlen);
219
220 pp = call_gro_receive(ptype->callbacks.gro_receive, head, skb);
221 flush = 0;
222
223out_unlock:
224 rcu_read_unlock();
225out:
226 skb_gro_flush_final(skb, pp, flush);
227
228 return pp;
229}
230
231static int gre_gro_complete(struct sk_buff *skb, int nhoff)
232{
233 struct gre_base_hdr *greh = (struct gre_base_hdr *)(skb->data + nhoff);
234 struct packet_offload *ptype;
235 unsigned int grehlen = sizeof(*greh);
236 int err = -ENOENT;
237 __be16 type;
238
239 skb->encapsulation = 1;
240 skb_shinfo(skb)->gso_type = SKB_GSO_GRE;
241
242 type = greh->protocol;
243 if (greh->flags & GRE_KEY)
244 grehlen += GRE_HEADER_SECTION;
245
246 if (greh->flags & GRE_CSUM)
247 grehlen += GRE_HEADER_SECTION;
248
249 rcu_read_lock();
250 ptype = gro_find_complete_by_type(type);
251 if (ptype)
252 err = ptype->callbacks.gro_complete(skb, nhoff + grehlen);
253
254 rcu_read_unlock();
255
256 skb_set_inner_mac_header(skb, nhoff + grehlen);
257
258 return err;
259}
260
261static const struct net_offload gre_offload = {
262 .callbacks = {
263 .gso_segment = gre_gso_segment,
264 .gro_receive = gre_gro_receive,
265 .gro_complete = gre_gro_complete,
266 },
267};
268
269static int __init gre_offload_init(void)
270{
271 int err;
272
273 err = inet_add_offload(&gre_offload, IPPROTO_GRE);
274#if IS_ENABLED(CONFIG_IPV6)
275 if (err)
276 return err;
277
278 err = inet6_add_offload(&gre_offload, IPPROTO_GRE);
279 if (err)
280 inet_del_offload(&gre_offload, IPPROTO_GRE);
281#endif
282
283 return err;
284}
285device_initcall(gre_offload_init);
286