xref: /linux/net/ipv4/gre_offload.c (revision c4ee0af3fa0dc65f690fc908f02b8355f9576ea0)
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 <net/protocol.h>
15 #include <net/gre.h>
16 
17 static int gre_gso_send_check(struct sk_buff *skb)
18 {
19 	if (!skb->encapsulation)
20 		return -EINVAL;
21 	return 0;
22 }
23 
24 static struct sk_buff *gre_gso_segment(struct sk_buff *skb,
25 				       netdev_features_t features)
26 {
27 	struct sk_buff *segs = ERR_PTR(-EINVAL);
28 	netdev_features_t enc_features;
29 	int ghl = GRE_HEADER_SECTION;
30 	struct gre_base_hdr *greh;
31 	int mac_len = skb->mac_len;
32 	__be16 protocol = skb->protocol;
33 	int tnl_hlen;
34 	bool csum;
35 
36 	if (unlikely(skb_shinfo(skb)->gso_type &
37 				~(SKB_GSO_TCPV4 |
38 				  SKB_GSO_TCPV6 |
39 				  SKB_GSO_UDP |
40 				  SKB_GSO_DODGY |
41 				  SKB_GSO_TCP_ECN |
42 				  SKB_GSO_GRE |
43 				  SKB_GSO_IPIP)))
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 	if (greh->flags & GRE_KEY)
52 		ghl += GRE_HEADER_SECTION;
53 	if (greh->flags & GRE_SEQ)
54 		ghl += GRE_HEADER_SECTION;
55 	if (greh->flags & GRE_CSUM) {
56 		ghl += GRE_HEADER_SECTION;
57 		csum = true;
58 	} else
59 		csum = false;
60 
61 	/* setup inner skb. */
62 	skb->protocol = greh->protocol;
63 	skb->encapsulation = 0;
64 
65 	if (unlikely(!pskb_may_pull(skb, ghl)))
66 		goto out;
67 
68 	__skb_pull(skb, ghl);
69 	skb_reset_mac_header(skb);
70 	skb_set_network_header(skb, skb_inner_network_offset(skb));
71 	skb->mac_len = skb_inner_network_offset(skb);
72 
73 	/* segment inner packet. */
74 	enc_features = skb->dev->hw_enc_features & netif_skb_features(skb);
75 	segs = skb_mac_gso_segment(skb, enc_features);
76 	if (!segs || IS_ERR(segs))
77 		goto out;
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 			greh = (struct gre_base_hdr *)(skb->data);
98 			pcsum = (__be32 *)(greh + 1);
99 			*pcsum = 0;
100 			*(__sum16 *)pcsum = csum_fold(skb_checksum(skb, 0, skb->len, 0));
101 		}
102 		__skb_push(skb, tnl_hlen - ghl);
103 
104 		skb_reset_inner_headers(skb);
105 		skb->encapsulation = 1;
106 
107 		skb_reset_mac_header(skb);
108 		skb_set_network_header(skb, mac_len);
109 		skb->mac_len = mac_len;
110 		skb->protocol = protocol;
111 	} while ((skb = skb->next));
112 out:
113 	return segs;
114 }
115 
116 static const struct net_offload gre_offload = {
117 	.callbacks = {
118 		.gso_send_check = gre_gso_send_check,
119 		.gso_segment = gre_gso_segment,
120 	},
121 };
122 
123 int __init gre_offload_init(void)
124 {
125 	return inet_add_offload(&gre_offload, IPPROTO_GRE);
126 }
127 
128 void __exit gre_offload_exit(void)
129 {
130 	inet_del_offload(&gre_offload, IPPROTO_GRE);
131 }
132