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1 /*
2  * xfrm_output.c - Common IPsec encapsulation code.
3  *
4  * Copyright (c) 2007 Herbert Xu <herbert@gondor.apana.org.au>
5  *
6  * This program is free software; you can redistribute it and/or
7  * modify it under the terms of the GNU General Public License
8  * as published by the Free Software Foundation; either version
9  * 2 of the License, or (at your option) any later version.
10  */
11 
12 #include <linux/errno.h>
13 #include <linux/module.h>
14 #include <linux/netdevice.h>
15 #include <linux/netfilter.h>
16 #include <linux/skbuff.h>
17 #include <linux/slab.h>
18 #include <linux/spinlock.h>
19 #include <net/dst.h>
20 #include <net/xfrm.h>
21 
22 static int xfrm_output2(struct net *net, struct sock *sk, struct sk_buff *skb);
23 
xfrm_skb_check_space(struct sk_buff * skb)24 static int xfrm_skb_check_space(struct sk_buff *skb)
25 {
26 	struct dst_entry *dst = skb_dst(skb);
27 	int nhead = dst->header_len + LL_RESERVED_SPACE(dst->dev)
28 		- skb_headroom(skb);
29 	int ntail = dst->dev->needed_tailroom - skb_tailroom(skb);
30 
31 	if (nhead <= 0) {
32 		if (ntail <= 0)
33 			return 0;
34 		nhead = 0;
35 	} else if (ntail < 0)
36 		ntail = 0;
37 
38 	return pskb_expand_head(skb, nhead, ntail, GFP_ATOMIC);
39 }
40 
41 /* Children define the path of the packet through the
42  * Linux networking.  Thus, destinations are stackable.
43  */
44 
skb_dst_pop(struct sk_buff * skb)45 static struct dst_entry *skb_dst_pop(struct sk_buff *skb)
46 {
47 	struct dst_entry *child = dst_clone(skb_dst(skb)->child);
48 
49 	skb_dst_drop(skb);
50 	return child;
51 }
52 
xfrm_output_one(struct sk_buff * skb,int err)53 static int xfrm_output_one(struct sk_buff *skb, int err)
54 {
55 	struct dst_entry *dst = skb_dst(skb);
56 	struct xfrm_state *x = dst->xfrm;
57 	struct net *net = xs_net(x);
58 
59 	if (err <= 0)
60 		goto resume;
61 
62 	do {
63 		err = xfrm_skb_check_space(skb);
64 		if (err) {
65 			XFRM_INC_STATS(net, LINUX_MIB_XFRMOUTERROR);
66 			goto error_nolock;
67 		}
68 
69 		if (x->props.output_mark)
70 			skb->mark = x->props.output_mark;
71 
72 		err = x->outer_mode->output(x, skb);
73 		if (err) {
74 			XFRM_INC_STATS(net, LINUX_MIB_XFRMOUTSTATEMODEERROR);
75 			goto error_nolock;
76 		}
77 
78 		spin_lock_bh(&x->lock);
79 
80 		if (unlikely(x->km.state != XFRM_STATE_VALID)) {
81 			XFRM_INC_STATS(net, LINUX_MIB_XFRMOUTSTATEINVALID);
82 			err = -EINVAL;
83 			goto error;
84 		}
85 
86 		err = xfrm_state_check_expire(x);
87 		if (err) {
88 			XFRM_INC_STATS(net, LINUX_MIB_XFRMOUTSTATEEXPIRED);
89 			goto error;
90 		}
91 
92 		err = x->repl->overflow(x, skb);
93 		if (err) {
94 			XFRM_INC_STATS(net, LINUX_MIB_XFRMOUTSTATESEQERROR);
95 			goto error;
96 		}
97 
98 		x->curlft.bytes += skb->len;
99 		x->curlft.packets++;
100 
101 		spin_unlock_bh(&x->lock);
102 
103 		skb_dst_force(skb);
104 
105 		/* Inner headers are invalid now. */
106 		skb->encapsulation = 0;
107 
108 		err = x->type->output(x, skb);
109 		if (err == -EINPROGRESS)
110 			goto out;
111 
112 resume:
113 		if (err) {
114 			XFRM_INC_STATS(net, LINUX_MIB_XFRMOUTSTATEPROTOERROR);
115 			goto error_nolock;
116 		}
117 
118 		dst = skb_dst_pop(skb);
119 		if (!dst) {
120 			XFRM_INC_STATS(net, LINUX_MIB_XFRMOUTERROR);
121 			err = -EHOSTUNREACH;
122 			goto error_nolock;
123 		}
124 		skb_dst_set(skb, dst);
125 		x = dst->xfrm;
126 	} while (x && !(x->outer_mode->flags & XFRM_MODE_FLAG_TUNNEL));
127 
128 	return 0;
129 
130 error:
131 	spin_unlock_bh(&x->lock);
132 error_nolock:
133 	kfree_skb(skb);
134 out:
135 	return err;
136 }
137 
xfrm_output_resume(struct sk_buff * skb,int err)138 int xfrm_output_resume(struct sk_buff *skb, int err)
139 {
140 	struct net *net = xs_net(skb_dst(skb)->xfrm);
141 
142 	while (likely((err = xfrm_output_one(skb, err)) == 0)) {
143 		nf_reset(skb);
144 
145 		err = skb_dst(skb)->ops->local_out(net, skb->sk, skb);
146 		if (unlikely(err != 1))
147 			goto out;
148 
149 		if (!skb_dst(skb)->xfrm)
150 			return dst_output(net, skb->sk, skb);
151 
152 		err = nf_hook(skb_dst(skb)->ops->family,
153 			      NF_INET_POST_ROUTING, net, skb->sk, skb,
154 			      NULL, skb_dst(skb)->dev, xfrm_output2);
155 		if (unlikely(err != 1))
156 			goto out;
157 	}
158 
159 	if (err == -EINPROGRESS)
160 		err = 0;
161 
162 out:
163 	return err;
164 }
165 EXPORT_SYMBOL_GPL(xfrm_output_resume);
166 
xfrm_output2(struct net * net,struct sock * sk,struct sk_buff * skb)167 static int xfrm_output2(struct net *net, struct sock *sk, struct sk_buff *skb)
168 {
169 	return xfrm_output_resume(skb, 1);
170 }
171 
xfrm_output_gso(struct net * net,struct sock * sk,struct sk_buff * skb)172 static int xfrm_output_gso(struct net *net, struct sock *sk, struct sk_buff *skb)
173 {
174 	struct sk_buff *segs;
175 
176 	BUILD_BUG_ON(sizeof(*IPCB(skb)) > SKB_SGO_CB_OFFSET);
177 	BUILD_BUG_ON(sizeof(*IP6CB(skb)) > SKB_SGO_CB_OFFSET);
178 	segs = skb_gso_segment(skb, 0);
179 	kfree_skb(skb);
180 	if (IS_ERR(segs))
181 		return PTR_ERR(segs);
182 	if (segs == NULL)
183 		return -EINVAL;
184 
185 	do {
186 		struct sk_buff *nskb = segs->next;
187 		int err;
188 
189 		segs->next = NULL;
190 		err = xfrm_output2(net, sk, segs);
191 
192 		if (unlikely(err)) {
193 			kfree_skb_list(nskb);
194 			return err;
195 		}
196 
197 		segs = nskb;
198 	} while (segs);
199 
200 	return 0;
201 }
202 
xfrm_output(struct sock * sk,struct sk_buff * skb)203 int xfrm_output(struct sock *sk, struct sk_buff *skb)
204 {
205 	struct net *net = dev_net(skb_dst(skb)->dev);
206 	int err;
207 
208 	if (skb_is_gso(skb))
209 		return xfrm_output_gso(net, sk, skb);
210 
211 	if (skb->ip_summed == CHECKSUM_PARTIAL) {
212 		err = skb_checksum_help(skb);
213 		if (err) {
214 			XFRM_INC_STATS(net, LINUX_MIB_XFRMOUTERROR);
215 			kfree_skb(skb);
216 			return err;
217 		}
218 	}
219 
220 	return xfrm_output2(net, sk, skb);
221 }
222 EXPORT_SYMBOL_GPL(xfrm_output);
223 
xfrm_inner_extract_output(struct xfrm_state * x,struct sk_buff * skb)224 int xfrm_inner_extract_output(struct xfrm_state *x, struct sk_buff *skb)
225 {
226 	struct xfrm_mode *inner_mode;
227 	if (x->sel.family == AF_UNSPEC)
228 		inner_mode = xfrm_ip2inner_mode(x,
229 				xfrm_af2proto(skb_dst(skb)->ops->family));
230 	else
231 		inner_mode = x->inner_mode;
232 
233 	if (inner_mode == NULL)
234 		return -EAFNOSUPPORT;
235 	return inner_mode->afinfo->extract_output(x, skb);
236 }
237 EXPORT_SYMBOL_GPL(xfrm_inner_extract_output);
238 
xfrm_local_error(struct sk_buff * skb,int mtu)239 void xfrm_local_error(struct sk_buff *skb, int mtu)
240 {
241 	unsigned int proto;
242 	struct xfrm_state_afinfo *afinfo;
243 
244 	if (skb->protocol == htons(ETH_P_IP))
245 		proto = AF_INET;
246 	else if (skb->protocol == htons(ETH_P_IPV6))
247 		proto = AF_INET6;
248 	else
249 		return;
250 
251 	afinfo = xfrm_state_get_afinfo(proto);
252 	if (!afinfo)
253 		return;
254 
255 	afinfo->local_error(skb, mtu);
256 	xfrm_state_put_afinfo(afinfo);
257 }
258 EXPORT_SYMBOL_GPL(xfrm_local_error);
259