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