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1 /*
2  *	IPV6 GSO/GRO offload support
3  *	Linux INET6 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  *      UDPv6 GSO support
11  */
12 #include <linux/skbuff.h>
13 #include <linux/netdevice.h>
14 #include <net/protocol.h>
15 #include <net/ipv6.h>
16 #include <net/udp.h>
17 #include <net/ip6_checksum.h>
18 #include "ip6_offload.h"
19 
udp6_ufo_fragment(struct sk_buff * skb,netdev_features_t features)20 static struct sk_buff *udp6_ufo_fragment(struct sk_buff *skb,
21 					 netdev_features_t features)
22 {
23 	struct sk_buff *segs = ERR_PTR(-EINVAL);
24 	unsigned int mss;
25 	unsigned int unfrag_ip6hlen, unfrag_len;
26 	struct frag_hdr *fptr;
27 	u8 *packet_start, *prevhdr;
28 	u8 nexthdr;
29 	u8 frag_hdr_sz = sizeof(struct frag_hdr);
30 	__wsum csum;
31 	int tnl_hlen;
32 	int err;
33 
34 	mss = skb_shinfo(skb)->gso_size;
35 	if (unlikely(skb->len <= mss))
36 		goto out;
37 
38 	if (skb_gso_ok(skb, features | NETIF_F_GSO_ROBUST)) {
39 		/* Packet is from an untrusted source, reset gso_segs. */
40 
41 		skb_shinfo(skb)->gso_segs = DIV_ROUND_UP(skb->len, mss);
42 
43 		/* Set the IPv6 fragment id if not set yet */
44 		if (!skb_shinfo(skb)->ip6_frag_id)
45 			ipv6_proxy_select_ident(dev_net(skb->dev), skb);
46 
47 		segs = NULL;
48 		goto out;
49 	}
50 
51 	if (skb->encapsulation && skb_shinfo(skb)->gso_type &
52 	    (SKB_GSO_UDP_TUNNEL|SKB_GSO_UDP_TUNNEL_CSUM))
53 		segs = skb_udp_tunnel_segment(skb, features, true);
54 	else {
55 		const struct ipv6hdr *ipv6h;
56 		struct udphdr *uh;
57 
58 		if (!(skb_shinfo(skb)->gso_type & SKB_GSO_UDP))
59 			goto out;
60 
61 		if (!pskb_may_pull(skb, sizeof(struct udphdr)))
62 			goto out;
63 
64 		/* Do software UFO. Complete and fill in the UDP checksum as HW cannot
65 		 * do checksum of UDP packets sent as multiple IP fragments.
66 		 */
67 
68 		uh = udp_hdr(skb);
69 		ipv6h = ipv6_hdr(skb);
70 
71 		uh->check = 0;
72 		csum = skb_checksum(skb, 0, skb->len, 0);
73 		uh->check = udp_v6_check(skb->len, &ipv6h->saddr,
74 					  &ipv6h->daddr, csum);
75 		if (uh->check == 0)
76 			uh->check = CSUM_MANGLED_0;
77 
78 		skb->ip_summed = CHECKSUM_UNNECESSARY;
79 
80 		/* If there is no outer header we can fake a checksum offload
81 		 * due to the fact that we have already done the checksum in
82 		 * software prior to segmenting the frame.
83 		 */
84 		if (!skb->encap_hdr_csum)
85 			features |= NETIF_F_HW_CSUM;
86 
87 		/* Check if there is enough headroom to insert fragment header. */
88 		tnl_hlen = skb_tnl_header_len(skb);
89 		if (skb->mac_header < (tnl_hlen + frag_hdr_sz)) {
90 			if (gso_pskb_expand_head(skb, tnl_hlen + frag_hdr_sz))
91 				goto out;
92 		}
93 
94 		/* Find the unfragmentable header and shift it left by frag_hdr_sz
95 		 * bytes to insert fragment header.
96 		 */
97 		err = ip6_find_1stfragopt(skb, &prevhdr);
98 		if (err < 0)
99 			return ERR_PTR(err);
100 		unfrag_ip6hlen = err;
101 		nexthdr = *prevhdr;
102 		*prevhdr = NEXTHDR_FRAGMENT;
103 		unfrag_len = (skb_network_header(skb) - skb_mac_header(skb)) +
104 			     unfrag_ip6hlen + tnl_hlen;
105 		packet_start = (u8 *) skb->head + SKB_GSO_CB(skb)->mac_offset;
106 		memmove(packet_start-frag_hdr_sz, packet_start, unfrag_len);
107 
108 		SKB_GSO_CB(skb)->mac_offset -= frag_hdr_sz;
109 		skb->mac_header -= frag_hdr_sz;
110 		skb->network_header -= frag_hdr_sz;
111 
112 		fptr = (struct frag_hdr *)(skb_network_header(skb) + unfrag_ip6hlen);
113 		fptr->nexthdr = nexthdr;
114 		fptr->reserved = 0;
115 		if (!skb_shinfo(skb)->ip6_frag_id)
116 			ipv6_proxy_select_ident(dev_net(skb->dev), skb);
117 		fptr->identification = skb_shinfo(skb)->ip6_frag_id;
118 
119 		/* Fragment the skb. ipv6 header and the remaining fields of the
120 		 * fragment header are updated in ipv6_gso_segment()
121 		 */
122 		segs = skb_segment(skb, features);
123 	}
124 
125 out:
126 	return segs;
127 }
128 
udp6_gro_receive(struct sk_buff ** head,struct sk_buff * skb)129 static struct sk_buff **udp6_gro_receive(struct sk_buff **head,
130 					 struct sk_buff *skb)
131 {
132 	struct udphdr *uh = udp_gro_udphdr(skb);
133 
134 	if (unlikely(!uh))
135 		goto flush;
136 
137 	/* Don't bother verifying checksum if we're going to flush anyway. */
138 	if (NAPI_GRO_CB(skb)->flush)
139 		goto skip;
140 
141 	if (skb_gro_checksum_validate_zero_check(skb, IPPROTO_UDP, uh->check,
142 						 ip6_gro_compute_pseudo))
143 		goto flush;
144 	else if (uh->check)
145 		skb_gro_checksum_try_convert(skb, IPPROTO_UDP, uh->check,
146 					     ip6_gro_compute_pseudo);
147 
148 skip:
149 	NAPI_GRO_CB(skb)->is_ipv6 = 1;
150 	return udp_gro_receive(head, skb, uh, udp6_lib_lookup_skb);
151 
152 flush:
153 	NAPI_GRO_CB(skb)->flush = 1;
154 	return NULL;
155 }
156 
udp6_gro_complete(struct sk_buff * skb,int nhoff)157 static int udp6_gro_complete(struct sk_buff *skb, int nhoff)
158 {
159 	const struct ipv6hdr *ipv6h = ipv6_hdr(skb);
160 	struct udphdr *uh = (struct udphdr *)(skb->data + nhoff);
161 
162 	if (uh->check) {
163 		skb_shinfo(skb)->gso_type |= SKB_GSO_UDP_TUNNEL_CSUM;
164 		uh->check = ~udp_v6_check(skb->len - nhoff, &ipv6h->saddr,
165 					  &ipv6h->daddr, 0);
166 	} else {
167 		skb_shinfo(skb)->gso_type |= SKB_GSO_UDP_TUNNEL;
168 	}
169 
170 	return udp_gro_complete(skb, nhoff, udp6_lib_lookup_skb);
171 }
172 
173 static const struct net_offload udpv6_offload = {
174 	.callbacks = {
175 		.gso_segment	=	udp6_ufo_fragment,
176 		.gro_receive	=	udp6_gro_receive,
177 		.gro_complete	=	udp6_gro_complete,
178 	},
179 };
180 
udpv6_offload_init(void)181 int udpv6_offload_init(void)
182 {
183 	return inet6_add_offload(&udpv6_offload, IPPROTO_UDP);
184 }
185 
udpv6_offload_exit(void)186 int udpv6_offload_exit(void)
187 {
188 	return inet6_del_offload(&udpv6_offload, IPPROTO_UDP);
189 }
190