1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * xfrm6_output.c - Common IPsec encapsulation code for IPv6.
4 * Copyright (C) 2002 USAGI/WIDE Project
5 * Copyright (c) 2004 Herbert Xu <herbert@gondor.apana.org.au>
6 */
7
8#include <linux/if_ether.h>
9#include <linux/kernel.h>
10#include <linux/module.h>
11#include <linux/skbuff.h>
12#include <linux/icmpv6.h>
13#include <linux/netfilter_ipv6.h>
14#include <net/dst.h>
15#include <net/ipv6.h>
16#include <net/ip6_route.h>
17#include <net/xfrm.h>
18
19int xfrm6_find_1stfragopt(struct xfrm_state *x, struct sk_buff *skb,
20			  u8 **prevhdr)
21{
22	return ip6_find_1stfragopt(skb, prevhdr);
23}
24EXPORT_SYMBOL(xfrm6_find_1stfragopt);
25
26void xfrm6_local_rxpmtu(struct sk_buff *skb, u32 mtu)
27{
28	struct flowi6 fl6;
29	struct sock *sk = skb->sk;
30
31	fl6.flowi6_oif = sk->sk_bound_dev_if;
32	fl6.daddr = ipv6_hdr(skb)->daddr;
33
34	ipv6_local_rxpmtu(sk, &fl6, mtu);
35}
36
37void xfrm6_local_error(struct sk_buff *skb, u32 mtu)
38{
39	struct flowi6 fl6;
40	const struct ipv6hdr *hdr;
41	struct sock *sk = skb->sk;
42
43	hdr = skb->encapsulation ? inner_ipv6_hdr(skb) : ipv6_hdr(skb);
44	fl6.fl6_dport = inet_sk(sk)->inet_dport;
45	fl6.daddr = hdr->daddr;
46
47	ipv6_local_error(sk, EMSGSIZE, &fl6, mtu);
48}
49
50static int __xfrm6_output_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
51{
52	return xfrm_output(sk, skb);
53}
54
55static int xfrm6_noneed_fragment(struct sk_buff *skb)
56{
57	struct frag_hdr *fh;
58	u8 prevhdr = ipv6_hdr(skb)->nexthdr;
59
60	if (prevhdr != NEXTHDR_FRAGMENT)
61		return 0;
62	fh = (struct frag_hdr *)(skb->data + sizeof(struct ipv6hdr));
63	if (fh->nexthdr == NEXTHDR_ESP || fh->nexthdr == NEXTHDR_AUTH)
64		return 1;
65	return 0;
66}
67
68static int __xfrm6_output(struct net *net, struct sock *sk, struct sk_buff *skb)
69{
70	struct dst_entry *dst = skb_dst(skb);
71	struct xfrm_state *x = dst->xfrm;
72	unsigned int mtu;
73	bool toobig;
74
75#ifdef CONFIG_NETFILTER
76	if (!x) {
77		IP6CB(skb)->flags |= IP6SKB_REROUTED;
78		return dst_output(net, sk, skb);
79	}
80#endif
81
82	if (x->props.mode != XFRM_MODE_TUNNEL)
83		goto skip_frag;
84
85	if (skb->protocol == htons(ETH_P_IPV6))
86		mtu = ip6_skb_dst_mtu(skb);
87	else
88		mtu = dst_mtu(skb_dst(skb));
89
90	toobig = skb->len > mtu && !skb_is_gso(skb);
91
92	if (toobig && xfrm6_local_dontfrag(skb->sk)) {
93		xfrm6_local_rxpmtu(skb, mtu);
94		kfree_skb(skb);
95		return -EMSGSIZE;
96	} else if (toobig && xfrm6_noneed_fragment(skb)) {
97		skb->ignore_df = 1;
98		goto skip_frag;
99	} else if (!skb->ignore_df && toobig && skb->sk) {
100		xfrm_local_error(skb, mtu);
101		kfree_skb(skb);
102		return -EMSGSIZE;
103	}
104
105	if (toobig || dst_allfrag(skb_dst(skb)))
106		return ip6_fragment(net, sk, skb,
107				    __xfrm6_output_finish);
108
109skip_frag:
110	return xfrm_output(sk, skb);
111}
112
113int xfrm6_output(struct net *net, struct sock *sk, struct sk_buff *skb)
114{
115	return NF_HOOK_COND(NFPROTO_IPV6, NF_INET_POST_ROUTING,
116			    net, sk, skb,  skb->dev, skb_dst(skb)->dev,
117			    __xfrm6_output,
118			    !(IP6CB(skb)->flags & IP6SKB_REROUTED));
119}
120