1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * IPV4 GSO/GRO offload support
4 * Linux INET implementation
5 *
6 * GRE GSO support
7 */
8
9 #include <linux/skbuff.h>
10 #include <linux/init.h>
11 #include <net/protocol.h>
12 #include <net/gre.h>
13 #include <net/gro.h>
14 #include <net/gso.h>
15
gre_gso_segment(struct sk_buff * skb,netdev_features_t features)16 static struct sk_buff *gre_gso_segment(struct sk_buff *skb,
17 netdev_features_t features)
18 {
19 int tnl_hlen = skb_inner_mac_header(skb) - skb_transport_header(skb);
20 bool need_csum, offload_csum, gso_partial, need_ipsec;
21 struct sk_buff *segs = ERR_PTR(-EINVAL);
22 u16 mac_offset = skb->mac_header;
23 __be16 protocol = skb->protocol;
24 u16 mac_len = skb->mac_len;
25 int gre_offset, outer_hlen;
26
27 if (!skb->encapsulation)
28 goto out;
29
30 if (unlikely(tnl_hlen < sizeof(struct gre_base_hdr)))
31 goto out;
32
33 if (unlikely(!pskb_may_pull(skb, tnl_hlen)))
34 goto out;
35
36 /* setup inner skb. */
37 skb->encapsulation = 0;
38 SKB_GSO_CB(skb)->encap_level = 0;
39 __skb_pull(skb, tnl_hlen);
40 skb_reset_mac_header(skb);
41 skb_set_network_header(skb, skb_inner_network_offset(skb));
42 skb->mac_len = skb_inner_network_offset(skb);
43 skb->protocol = skb->inner_protocol;
44
45 need_csum = !!(skb_shinfo(skb)->gso_type & SKB_GSO_GRE_CSUM);
46 skb->encap_hdr_csum = need_csum;
47
48 features &= skb->dev->hw_enc_features;
49 if (need_csum)
50 features &= ~NETIF_F_SCTP_CRC;
51
52 need_ipsec = skb_dst(skb) && dst_xfrm(skb_dst(skb));
53 /* Try to offload checksum if possible */
54 offload_csum = !!(need_csum && !need_ipsec &&
55 (skb->dev->features & NETIF_F_HW_CSUM));
56
57 /* segment inner packet. */
58 segs = skb_mac_gso_segment(skb, features);
59 if (IS_ERR_OR_NULL(segs)) {
60 skb_gso_error_unwind(skb, protocol, tnl_hlen, mac_offset,
61 mac_len);
62 goto out;
63 }
64
65 gso_partial = !!(skb_shinfo(segs)->gso_type & SKB_GSO_PARTIAL);
66
67 outer_hlen = skb_tnl_header_len(skb);
68 gre_offset = outer_hlen - tnl_hlen;
69 skb = segs;
70 do {
71 struct gre_base_hdr *greh;
72 __sum16 *pcsum;
73
74 /* Set up inner headers if we are offloading inner checksum */
75 if (skb->ip_summed == CHECKSUM_PARTIAL) {
76 skb_reset_inner_headers(skb);
77 skb->encapsulation = 1;
78 }
79
80 skb->mac_len = mac_len;
81 skb->protocol = protocol;
82
83 __skb_push(skb, outer_hlen);
84 skb_reset_mac_header(skb);
85 skb_set_network_header(skb, mac_len);
86 skb_set_transport_header(skb, gre_offset);
87
88 if (!need_csum)
89 continue;
90
91 greh = (struct gre_base_hdr *)skb_transport_header(skb);
92 pcsum = (__sum16 *)(greh + 1);
93
94 if (gso_partial && skb_is_gso(skb)) {
95 unsigned int partial_adj;
96
97 /* Adjust checksum to account for the fact that
98 * the partial checksum is based on actual size
99 * whereas headers should be based on MSS size.
100 */
101 partial_adj = skb->len + skb_headroom(skb) -
102 SKB_GSO_CB(skb)->data_offset -
103 skb_shinfo(skb)->gso_size;
104 *pcsum = ~csum_fold((__force __wsum)htonl(partial_adj));
105 } else {
106 *pcsum = 0;
107 }
108
109 *(pcsum + 1) = 0;
110 if (skb->encapsulation || !offload_csum) {
111 *pcsum = gso_make_checksum(skb, 0);
112 } else {
113 skb->ip_summed = CHECKSUM_PARTIAL;
114 skb->csum_start = skb_transport_header(skb) - skb->head;
115 skb->csum_offset = sizeof(*greh);
116 }
117 } while ((skb = skb->next));
118 out:
119 return segs;
120 }
121
gre_gro_receive(struct list_head * head,struct sk_buff * skb)122 static struct sk_buff *gre_gro_receive(struct list_head *head,
123 struct sk_buff *skb)
124 {
125 struct sk_buff *pp = NULL;
126 struct sk_buff *p;
127 const struct gre_base_hdr *greh;
128 unsigned int hlen, grehlen;
129 unsigned int off;
130 int flush = 1;
131 struct packet_offload *ptype;
132 __be16 type;
133
134 if (NAPI_GRO_CB(skb)->encap_mark)
135 goto out;
136
137 NAPI_GRO_CB(skb)->encap_mark = 1;
138
139 off = skb_gro_offset(skb);
140 hlen = off + sizeof(*greh);
141 greh = skb_gro_header(skb, hlen, off);
142 if (unlikely(!greh))
143 goto out;
144
145 /* Only support version 0 and K (key), C (csum) flags. Note that
146 * although the support for the S (seq#) flag can be added easily
147 * for GRO, this is problematic for GSO hence can not be enabled
148 * here because a GRO pkt may end up in the forwarding path, thus
149 * requiring GSO support to break it up correctly.
150 */
151 if ((greh->flags & ~(GRE_KEY|GRE_CSUM)) != 0)
152 goto out;
153
154 /* We can only support GRE_CSUM if we can track the location of
155 * the GRE header. In the case of FOU/GUE we cannot because the
156 * outer UDP header displaces the GRE header leaving us in a state
157 * of limbo.
158 */
159 if ((greh->flags & GRE_CSUM) && NAPI_GRO_CB(skb)->is_fou)
160 goto out;
161
162 type = greh->protocol;
163
164 ptype = gro_find_receive_by_type(type);
165 if (!ptype)
166 goto out;
167
168 grehlen = GRE_HEADER_SECTION;
169
170 if (greh->flags & GRE_KEY)
171 grehlen += GRE_HEADER_SECTION;
172
173 if (greh->flags & GRE_CSUM)
174 grehlen += GRE_HEADER_SECTION;
175
176 hlen = off + grehlen;
177 if (skb_gro_header_hard(skb, hlen)) {
178 greh = skb_gro_header_slow(skb, hlen, off);
179 if (unlikely(!greh))
180 goto out;
181 }
182
183 /* Don't bother verifying checksum if we're going to flush anyway. */
184 if ((greh->flags & GRE_CSUM) && !NAPI_GRO_CB(skb)->flush) {
185 if (skb_gro_checksum_simple_validate(skb))
186 goto out;
187
188 skb_gro_checksum_try_convert(skb, IPPROTO_GRE,
189 null_compute_pseudo);
190 }
191
192 list_for_each_entry(p, head, list) {
193 const struct gre_base_hdr *greh2;
194
195 if (!NAPI_GRO_CB(p)->same_flow)
196 continue;
197
198 /* The following checks are needed to ensure only pkts
199 * from the same tunnel are considered for aggregation.
200 * The criteria for "the same tunnel" includes:
201 * 1) same version (we only support version 0 here)
202 * 2) same protocol (we only support ETH_P_IP for now)
203 * 3) same set of flags
204 * 4) same key if the key field is present.
205 */
206 greh2 = (struct gre_base_hdr *)(p->data + off);
207
208 if (greh2->flags != greh->flags ||
209 greh2->protocol != greh->protocol) {
210 NAPI_GRO_CB(p)->same_flow = 0;
211 continue;
212 }
213 if (greh->flags & GRE_KEY) {
214 /* compare keys */
215 if (*(__be32 *)(greh2+1) != *(__be32 *)(greh+1)) {
216 NAPI_GRO_CB(p)->same_flow = 0;
217 continue;
218 }
219 }
220 }
221
222 skb_gro_pull(skb, grehlen);
223
224 /* Adjusted NAPI_GRO_CB(skb)->csum after skb_gro_pull()*/
225 skb_gro_postpull_rcsum(skb, greh, grehlen);
226
227 pp = call_gro_receive(ptype->callbacks.gro_receive, head, skb);
228 flush = 0;
229
230 out:
231 skb_gro_flush_final(skb, pp, flush);
232
233 return pp;
234 }
235
gre_gro_complete(struct sk_buff * skb,int nhoff)236 static int gre_gro_complete(struct sk_buff *skb, int nhoff)
237 {
238 struct gre_base_hdr *greh = (struct gre_base_hdr *)(skb->data + nhoff);
239 struct packet_offload *ptype;
240 unsigned int grehlen = sizeof(*greh);
241 int err = -ENOENT;
242 __be16 type;
243
244 skb->encapsulation = 1;
245 skb_shinfo(skb)->gso_type = SKB_GSO_GRE;
246
247 type = greh->protocol;
248 if (greh->flags & GRE_KEY)
249 grehlen += GRE_HEADER_SECTION;
250
251 if (greh->flags & GRE_CSUM)
252 grehlen += GRE_HEADER_SECTION;
253
254 ptype = gro_find_complete_by_type(type);
255 if (ptype)
256 err = ptype->callbacks.gro_complete(skb, nhoff + grehlen);
257
258 skb_set_inner_mac_header(skb, nhoff + grehlen);
259
260 return err;
261 }
262
263 static const struct net_offload gre_offload = {
264 .callbacks = {
265 .gso_segment = gre_gso_segment,
266 .gro_receive = gre_gro_receive,
267 .gro_complete = gre_gro_complete,
268 },
269 };
270
gre_offload_init(void)271 static int __init gre_offload_init(void)
272 {
273 int err;
274
275 err = inet_add_offload(&gre_offload, IPPROTO_GRE);
276 #if IS_ENABLED(CONFIG_IPV6)
277 if (err)
278 return err;
279
280 err = inet6_add_offload(&gre_offload, IPPROTO_GRE);
281 if (err)
282 inet_del_offload(&gre_offload, IPPROTO_GRE);
283 #endif
284
285 return err;
286 }
287 device_initcall(gre_offload_init);
288
