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	struct sk_buff *segs = ERR_PTR(-EINVAL);
22	netdev_features_t enc_features;
23	int ghl;
24	struct gre_base_hdr *greh;
25	u16 mac_offset = skb->mac_header;
26	int mac_len = skb->mac_len;
27	__be16 protocol = skb->protocol;
28	int tnl_hlen;
29	bool csum;
30
31	if (unlikely(skb_shinfo(skb)->gso_type &
32				~(SKB_GSO_TCPV4 |
33				  SKB_GSO_TCPV6 |
34				  SKB_GSO_UDP |
35				  SKB_GSO_DODGY |
36				  SKB_GSO_TCP_ECN |
37				  SKB_GSO_GRE |
38				  SKB_GSO_GRE_CSUM |
39				  SKB_GSO_IPIP |
40				  SKB_GSO_SIT)))
41		goto out;
42
43	if (!skb->encapsulation)
44		goto out;
45
46	if (unlikely(!pskb_may_pull(skb, sizeof(*greh))))
47		goto out;
48
49	greh = (struct gre_base_hdr *)skb_transport_header(skb);
50
51	ghl = skb_inner_mac_header(skb) - skb_transport_header(skb);
52	if (unlikely(ghl < sizeof(*greh)))
53		goto out;
54
55	csum = !!(greh->flags & GRE_CSUM);
56	if (csum)
57		skb->encap_hdr_csum = 1;
58
59	/* setup inner skb. */
60	skb->protocol = greh->protocol;
61	skb->encapsulation = 0;
62
63	if (unlikely(!pskb_may_pull(skb, ghl)))
64		goto out;
65
66	__skb_pull(skb, ghl);
67	skb_reset_mac_header(skb);
68	skb_set_network_header(skb, skb_inner_network_offset(skb));
69	skb->mac_len = skb_inner_network_offset(skb);
70
71	/* segment inner packet. */
72	enc_features = skb->dev->hw_enc_features & features;
73	segs = skb_mac_gso_segment(skb, enc_features);
74	if (IS_ERR_OR_NULL(segs)) {
75		skb_gso_error_unwind(skb, protocol, ghl, mac_offset, mac_len);
76		goto out;
77	}
78
79	skb = segs;
80	tnl_hlen = skb_tnl_header_len(skb);
81	do {
82		__skb_push(skb, ghl);
83		if (csum) {
84			__be32 *pcsum;
85
86			if (skb_has_shared_frag(skb)) {
87				int err;
88
89				err = __skb_linearize(skb);
90				if (err) {
91					kfree_skb_list(segs);
92					segs = ERR_PTR(err);
93					goto out;
94				}
95			}
96
97			skb_reset_transport_header(skb);
98
99			greh = (struct gre_base_hdr *)
100			    skb_transport_header(skb);
101			pcsum = (__be32 *)(greh + 1);
102			*pcsum = 0;
103			*(__sum16 *)pcsum = gso_make_checksum(skb, 0);
104		}
105		__skb_push(skb, tnl_hlen - ghl);
106
107		skb_reset_inner_headers(skb);
108		skb->encapsulation = 1;
109
110		skb_reset_mac_header(skb);
111		skb_set_network_header(skb, mac_len);
112		skb->mac_len = mac_len;
113		skb->protocol = protocol;
114	} while ((skb = skb->next));
115out:
116	return segs;
117}
118
119static struct sk_buff **gre_gro_receive(struct sk_buff **head,
120					struct sk_buff *skb)
121{
122	struct sk_buff **pp = NULL;
123	struct sk_buff *p;
124	const struct gre_base_hdr *greh;
125	unsigned int hlen, grehlen;
126	unsigned int off;
127	int flush = 1;
128	struct packet_offload *ptype;
129	__be16 type;
130
131	off = skb_gro_offset(skb);
132	hlen = off + sizeof(*greh);
133	greh = skb_gro_header_fast(skb, off);
134	if (skb_gro_header_hard(skb, hlen)) {
135		greh = skb_gro_header_slow(skb, hlen, off);
136		if (unlikely(!greh))
137			goto out;
138	}
139
140	/* Only support version 0 and K (key), C (csum) flags. Note that
141	 * although the support for the S (seq#) flag can be added easily
142	 * for GRO, this is problematic for GSO hence can not be enabled
143	 * here because a GRO pkt may end up in the forwarding path, thus
144	 * requiring GSO support to break it up correctly.
145	 */
146	if ((greh->flags & ~(GRE_KEY|GRE_CSUM)) != 0)
147		goto out;
148
149	type = greh->protocol;
150
151	rcu_read_lock();
152	ptype = gro_find_receive_by_type(type);
153	if (!ptype)
154		goto out_unlock;
155
156	grehlen = GRE_HEADER_SECTION;
157
158	if (greh->flags & GRE_KEY)
159		grehlen += GRE_HEADER_SECTION;
160
161	if (greh->flags & GRE_CSUM)
162		grehlen += GRE_HEADER_SECTION;
163
164	hlen = off + grehlen;
165	if (skb_gro_header_hard(skb, hlen)) {
166		greh = skb_gro_header_slow(skb, hlen, off);
167		if (unlikely(!greh))
168			goto out_unlock;
169	}
170
171	/* Don't bother verifying checksum if we're going to flush anyway. */
172	if ((greh->flags & GRE_CSUM) && !NAPI_GRO_CB(skb)->flush) {
173		if (skb_gro_checksum_simple_validate(skb))
174			goto out_unlock;
175
176		skb_gro_checksum_try_convert(skb, IPPROTO_GRE, 0,
177					     null_compute_pseudo);
178	}
179
180	flush = 0;
181
182	for (p = *head; p; p = p->next) {
183		const struct gre_base_hdr *greh2;
184
185		if (!NAPI_GRO_CB(p)->same_flow)
186			continue;
187
188		/* The following checks are needed to ensure only pkts
189		 * from the same tunnel are considered for aggregation.
190		 * The criteria for "the same tunnel" includes:
191		 * 1) same version (we only support version 0 here)
192		 * 2) same protocol (we only support ETH_P_IP for now)
193		 * 3) same set of flags
194		 * 4) same key if the key field is present.
195		 */
196		greh2 = (struct gre_base_hdr *)(p->data + off);
197
198		if (greh2->flags != greh->flags ||
199		    greh2->protocol != greh->protocol) {
200			NAPI_GRO_CB(p)->same_flow = 0;
201			continue;
202		}
203		if (greh->flags & GRE_KEY) {
204			/* compare keys */
205			if (*(__be32 *)(greh2+1) != *(__be32 *)(greh+1)) {
206				NAPI_GRO_CB(p)->same_flow = 0;
207				continue;
208			}
209		}
210	}
211
212	skb_gro_pull(skb, grehlen);
213
214	/* Adjusted NAPI_GRO_CB(skb)->csum after skb_gro_pull()*/
215	skb_gro_postpull_rcsum(skb, greh, grehlen);
216
217	pp = ptype->callbacks.gro_receive(head, skb);
218
219out_unlock:
220	rcu_read_unlock();
221out:
222	NAPI_GRO_CB(skb)->flush |= flush;
223
224	return pp;
225}
226
227static int gre_gro_complete(struct sk_buff *skb, int nhoff)
228{
229	struct gre_base_hdr *greh = (struct gre_base_hdr *)(skb->data + nhoff);
230	struct packet_offload *ptype;
231	unsigned int grehlen = sizeof(*greh);
232	int err = -ENOENT;
233	__be16 type;
234
235	skb->encapsulation = 1;
236	skb_shinfo(skb)->gso_type = SKB_GSO_GRE;
237
238	type = greh->protocol;
239	if (greh->flags & GRE_KEY)
240		grehlen += GRE_HEADER_SECTION;
241
242	if (greh->flags & GRE_CSUM)
243		grehlen += GRE_HEADER_SECTION;
244
245	rcu_read_lock();
246	ptype = gro_find_complete_by_type(type);
247	if (ptype)
248		err = ptype->callbacks.gro_complete(skb, nhoff + grehlen);
249
250	rcu_read_unlock();
251
252	skb_set_inner_mac_header(skb, nhoff + grehlen);
253
254	return err;
255}
256
257static const struct net_offload gre_offload = {
258	.callbacks = {
259		.gso_segment = gre_gso_segment,
260		.gro_receive = gre_gro_receive,
261		.gro_complete = gre_gro_complete,
262	},
263};
264
265static int __init gre_offload_init(void)
266{
267	return inet_add_offload(&gre_offload, IPPROTO_GRE);
268}
269device_initcall(gre_offload_init);
270